Clin Genet 2015: 87: 401–410 Printed in Singapore. All rights reserved
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd CLINICAL GENETICS doi: 10.1111/cge.12498
Review
The natural history of spinal neurofibromatosis: a critical review of clinical and genetic features Ruggieri M, Polizzi A, Spalice A, Salpietro V, Caltabiano R, D’Orazi V, Pavone P, Pirrone C, Magro G, Platania N, Cavallaro S, Muglia M, Nicita F. The natural history of spinal neurofibromatosis: a critical review of clinical and genetic features. Clin Genet 2015: 87: 401–410. © John Wiley & Sons A/S. Published by John Wiley & Sons Ltd, 2014 Spinal neurofibromatosis (SNF) is a related form of neurofibromatosis 1 (NF1), characterized by bilateral neurofibromas (histologically proven) of all spinal roots (and, eventually, of all the major peripheral nerve branches) with or without other manifestations of classical NF1. By rigorous application of these criteria to the 98 SNF cases published, we developed: (i) a cohort of 49 SNF patients (21 males and 28 females; aged 4–74 years]: 9 SNF families (21/49), 1 mixed SNF/NF1 family (1/49) and 27 of 49 sporadic SNF patients (including 5 unpublished patients in this report); and (ii) a group of 49 non-SNF patients including: (a) 32 patients with neurofibromas of multiple but not all spinal roots (MNFSR): 4 mixed SNF/MNFSR families (6/32); (b) 14 patients with NF1 manifestations without spinal neurofibromas, belonging to SNF (8/49) or MNFSR families (6/32); (c) 3 patients with neurofibromas in one spinal root. In addition to reduced incidence of café-au-lait spots (67% in SNF vs 56% in MNFSR), other NF1 manifestations were less frequent in either cohort. Molecular testing showed common NF1 gene abnormalities in both groups. The risk of developing SNF vs NF1 was increased for missense mutations [p = 0.0001; odds ratio (OR) = 6.16; confidence interval (CI) = 3.14–13.11], which were more frequent in SNF vs MNFSR (p = 0.0271). Conflict of interest
The authors declare no conflict of interest
M. Ruggieria,b , A. Polizzic,d , A. Spalicee , V. Salpietrof , R. Caltabianog , V. D’Orazih , P. Pavonei , C. Pirronej , G. Magrog , N. Plataniak , S. Cavallaroc , M. Muglial and F. Nicitae a Department of Educational Sciences, Chair of Paediatrics , b Centre for Neurocutaneous Disorders, University of Catania, Catania, Italy, c Institute of Neurological Sciences, National Research Council, Catania, Italy, d National Centre for Rare Diseases, Istituto Superiore di Sanità, Rome, Italy, e Child Neurology Division, Department of Paediatrics, Sapienza University of Rome, Rome, Italy, f Unit of Genetics and Pediatric Immunology, Department of Pediatrics, University of Messina, Messina, Italy, g Department ‘G. Ingrassia’, Section of Anatomic Pathology, University of Catania, Catania, Italy, h Department of Surgical Sciences, “Sapienza” University of Rome, Rome, Italy and Unit of Microsurgery and Hand Surgery, Fabia Mater Hospital, Rome, Italy, i Unit of Paediatrics and Paediatric Emergency, University Hospital ‘Policlinico-Vittorio Emanuele’, Catania, Italy, j Branches of Psychology, Department of Educational Sciences, University of Catania, Catania, Italy , k Institute of Neurosurgery, Department of Neurosciences ‘G. Ingrassia’, University of Catania, Catania, Italy, and l Institute of Neurological Sciences, National Research Council, Cosenza, Italy Key words: familial spinal neurofibromatosis – multiple neurofibromas – NF1 – paraspinal neurofibromatosis – spinal neurofibromatosis
Corresponding author: Martino Ruggieri, BA, MD, PhD, Department of Educational Sciences, Chair of Paediatrics, University of Catania, Via Casa Nutrizione, 1, 95124 Catania, Italy. Tel.: +39 095 7466377; fax: +39 095 7466385; e-mail: [email protected]
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Ruggieri et al. Received 10 August 2013, revised and accepted for publication 8 September 2014
Definition and historical background
Spinal neurofibromatosis (SNF) is a distinct clinical entity – a related form of neurofibromatosis 1 (NF1) – characterized by bilateral, histologically proven, neurofibromas of all spinal roots leaving no intact segments, with or without other manifestations of the NF1 diagnostic criteria (1, 2). This form was first recognized in the literature by Pulst et al. in 1991, in eight members of two multi-generation families and named ‘familial spinal neurofibromatosis’ (1). A few years later, in 1997, Poyhonen et al. (2) reported a family in which seven members over three generations were affected with a rare SNF (‘ … a distinct variant of NF1 … ’), named ‘hereditary spinal neurofibromatosis’. Interestingly, while affected members of the two families of Pulst et al. (1) had ‘ . . . . multiple paraspinal neurofibromas on both sides at all levels of multiple (but not all) segments of the spine’, all the (four) affected adults of the family of Pohyonen et al. (2) had ‘ … multiple spinal neurofibromas symmetrically affecting all spinal roots’. Both studies noted, for the first time [irrespective of full (2) or partial (1) spinal root involvement], that these phenotypes were (1, 2): (i) different from the well-established NF1 and NF2 phenotypes, (ii) distinct, in that the predominant feature was multiple (extensive) spinal neurofibromas, and (iii) much more restricted in their manifestations with absence of Lisch nodules and of non-tumour features of NF1 (e.g. learning difficulties and skeletal dysplasia). At the time of the studies (1, 2), linkage with the NF1 gene was recorded in family 1 of Pulst et al. (odds of 97:1) (1) and in the family of Pohyonen et al. (LOD score of 1.763) (2). After these two reports (1, 2), 17 further studies recorded 83 additional (both familiar sporadic) patients for a total of 98 patients labelled under the umbrella term of ‘familial/hereditary spinal neurofibromatosis’ or just ‘spinal neurofibromatosis’ (3–20). The condition has been regarded as a true NF1 variant or subtype, and either linkage to the NF1 locus (1, 2) or mutations in the NF1 gene have been recorded in most reported cases (3, 5–11, 13, 16–20). In addition to its hallmark of multiple neurofibromas of the spinal roots and, major nerve trunks, the phenotype variably included classical NF1 stigmata (e.g. typical pigmentary manifestations, Lisch nodules and cutaneous and nodular neurofibromas) and other NF1-associated manifestations (e.g. scoliosis, long bone dysplasia, optic and non-optic pathway gliomas, plexiform neurofibromas (PNFs), pheochromocytoma and the typical T2 hyperintensities in the brain) (3–20). Besides the classical families with multiple spinal neurofibromas, several sporadic cases have been recorded and, more recently, the phenotypic spectrum has included a set of concordant twins with SNF (16) and individuals with SNF belonging to families with classical NF1 (20). Thus, it was proposed
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to drop the term ‘familial (hereditary) spinal neurofibromatosis’ and to replace it with ‘Spinal neurofibromatosis’ (16, 19, 20) as the condition could simply reflect a typical autosomal dominant pattern of inheritance, therefore one would expect a balance of familial (including twins and cases within classical NF1 families) vs sporadic cases. Rationale of review
By critically reviewing the published reports labelled as (familial/hereditary) spinal neurofibromatosis (1–20), we realized that not all the reported cases presented with involvement of all the 38 spinal roots. In many individuals, the affected status of SNF was assigned to (familial or sporadic) patients with few or multiple neurofibromas involving multiple (but not all) segments of the spine (either unilaterally or bilaterally). In addition, some families included members with classical NF1 and other members with multiple neurofibromas involving all the spinal roots. Other families included some members with involvement of all spinal roots and other members with involvement of multiple but not all spinal roots, irrespective of age. This implies that for some individuals gleaned from these reports, spinal root neurofibromas could reflect more severe of a manifestation of classical NF1 rather than a related or alternate form of NF1. In some other families involvement of all vs multiple but not all spinal roots could merely reflect the phenotypic variability within the spectrum of SNF. Aim and methods of review
Aiming to better define the phenotype of SNF we searched existing databases (i.e. Medline, Scopus and Web of Knowledge) for reports on individuals labelled under the terms ‘familial spinal neurofibromatosis’, ‘hereditary spinal neurofibromatosis’ or ‘spinal neurofibromatosis’. We identified 20 reports (1–20), which included a total of 98 patients with SNF. We rigorously applied the criteria, which define SNF [i.e. the presence of multiple, histologically proven, neurofibromas of all spinal roots, bilaterally (and, eventually, of all the major peripheral nerve branches)], to each of these 98 individuals. Assignment of affected status of SNF, in each of the 98 reported patients, was based on complete phenotype assessment (including skin, ophthalmologic and orthopaedic examination and cognitive profile) and results of brain and spinal magnetic resonance imaging (MRI) studies and biopsies of at least one lesion of the peripheral nervous system. We added to this cohort complete phenotypes and genotype in five unpublished cases followed at our institutions (Table 1).
Spinal neurofibromatosis Table 1. Clinical, laboratory and imaging features of five (unreported) patients affected by spinal neurofibromatosis seen and followed-up at our institutions Patient
1
2
3
4
5
Gender Current age (year) Age of onset (year) Familial (NF1 or SNF) Sporadic Growth parameters (weight, length, HC) Café-au-lait spots Number >6 2 Irregular − − − Limbs, trunk − + −
3 NA Light-brown >3 cm Irregular − − − Limbs, trunk − − −
NA Light-brown >2 Irregular − − − Limbs, trunk − − −
Light-brown >5 Irregular − − − Limbs − − −
Light-brown >4 Irregular − + − Trunk, limb + + −
− −
− −
− −
− −
− −
+ B (all roots) +
+ B (all roots) +
+ B (all roots) +
+ B (all roots) +
+ B (all roots) +
Limbs, trunk Neuropathy LL IQ = 95
Limbs, trunk Neuropathy LL, abdomen IQ = 88
Limbs, trunk Neuropathy UL IQ = 89
Limbs Pain, neuropathy Trunk, limbs IQ = 90
Trunk, limb Pain, paresis LL IQ = 95
Exon 21 p.(Gly848Glu)
Intron 42 c.6427+2T>G
Exon 12a 1733T>G
Exon 37 6757delG
Pending
B, bilateral; F, female; HC, head circumference; IQ, intelligence quotient; LL, lower limbs; M, male; MPNST, malignant peripheral nerve sheet tumour; MRI, magnetic resonance imaging; NBO, neurofibromatosis bright objects (high signal lesions on T2-weighted MRI); NF1, neurofibromatosis type 1; NFs, neurofibromas; NA, not applicable; NS, not specified; OPG, optic pathway glioma; UL, upper limbs.
Results of review Clinical findings and natural history
We assigned affected status of SNF to 49 patients [21 males and 28 females (male:female ratio = 0.72)] aged, at their last follow-up, 4–74 years (Tables S1 and S2, Supporting information). The main clinical and imaging aspects of SNF are illustrated in Figs 1–4. We identified a second cohort, which included 32 patients (22 males and 8 females; aged 7–74 years) with multiple neurofibromas in multiple ‘but not all’ spinal roots (MNFSR) (Table S3). An additional group of 14 patients belonging either to SNF families (8/49; Table S1) or to MNFSR families (6/32; Table S3) were identified who had NF1 stigmata without neurofibromas in spinal root.
Three out of the original 98 patients, labelled as having SNF (1–20), were excluded from present analysis as they had involvement of only one spinal root (patients 406, 894 and 548) (8). We generated an additional table (Table S4) that included data from the five unpublished patients hereby reported (as shown in Table 1) and follow-ups of the four published patients (16, 19) seen at our institutions. Molecular testing
Results of molecular NF1 gene testing, which was performed in 40 of 49 SNF patients and in 25 of 32 MNFSR patients are summarized in Tables S1–S3 and detailed in Tables S5 and S6. We generated an additional table (Table S7) detailing the phenotypic features in SNF patients harbouring NF1 gene deletions.
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Fig. 1. Close view-up of the pigmentary macules recorded in children with spinal neurofibromatosis; note the paler brownish colour and the irregular margins of the macules [the figures show the pigmentary lesions seen in patient 1 (a), patient 2 (b), and patient 3 (c) as reported in Ruggieri et al. (16)].
Overall, molecular NF1 gene testing identified mutations in 37 of 40 (92.5%) SNF patients (including a double mutation) and 24 of 25 (96%) MNFSR. There were whole gene deletions [4/37 (1 familial) and 2/24 (1 familial)], missense [16/37 (5 familial) and 4/24 (2 familial)], splicing [8/37 (3 familial) and 6/24 (3 familial)], nonsense [4/37 (1 familial) and 3/24 (2 familial)] and frameshift mutations [5/37 (1 familial) and 9/24 (3 familial)]. The risk of having SNF vs classical NF1 was increased in individuals harbouring missense mutations [p = 0.0001; odds ratio (OR) = 6.16; confidence interval (CI) = 3.14–13.11], and missense mutations were more frequent in SNF vs MNFSR patients (p = 0.0271) (Appendix S1). Other types of mutations did not have a significant association with any one phenotype. Phenotypic spectrum and natural history Hallmark of disease
The hallmark of SNF is bilateral neurofibromas of all spinal roots (Tables S1 and S2; Fig. 2a,b). This feature characterizes SNF as a related or alternate form of NF1, and not merely as a classical NF1 phenotype manifesting with increased occurrence of spinal neurofibromas or with a concentration of multiple neurofibromas in some segments of the spine. By critical literature review and by personal experience we could easily identify the first cohort of 49 patients with this feature (Table S1; see also Tables 1 and S5) (16, 19). Bilateral involvement of all spinal nerve roots most
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clearly defined the SNF phenotype. Lack of rigorous application of this criterion has perpetuated phenotype designations that are not SNF (Table S3). Relaxing the application of strict criteria requiring neurofibromas of all spinal nerves generated the second cohort, and we identified 32 patients with multiple neurofibromas in multiple (but not all) spinal roots, which we named MNFSR (Table S3). Three individuals, in this cohort had massive involvement of almost all spinal roots (Table S3) (12) and six other individuals, with MNFSR, belonged to four single-generation or multi-generation families with SNF (Tables S1 and S2) (3, 8, 10, 13): such phenotypic variability must be taken into consideration and is likely part of the phenotypic spectrum of SNF. Individuals with MNFSR, unless part of a family with affected members having SNF, should not be regarded as having SNF. Neurofibromas, in SNF, can be localized in the paraspinal segments or may have either intradural or extradural components, or both (so-called dumbbell tumours), with a large extraspinal component causing foraminal enlargement. Histologically they prove to be classical neurofibromas (Fig. 3a,b). The biopsy needs to have enough tissue of high quality to enable the clinical pathologist to make the determination of tumour type, and there is no role of thin needle biopsy. If the diagnosis of NF1 or NF2 cannot be established then a biopsy is indicated to determine if the tumours were neurofibromas or schwannomas. Schwannomas have been recorded, occasionally, along with neurofibromas within the SNF phenotype (Tables S1 and S2) (5).
Spinal neurofibromatosis
Fig. 2. Coronal (a) and sagittal (b, c) T2-weighted magnetic resonance images of the spine in an affected individual with spinal neurofibromatosis reveal multiple, bilateral neurofibromas of the spinal roots that leave no intact segment [patient III-1 in Nicita et al. (19)].
Fig. 3. Coronal (a) and axial (b) T2-weighted magnetic resonance images of the sacral spine and lower limbs showing the extension of the multiple tumours along the lower nerve branches leaving no intact segment (patient 2, Table 1).
The MRI appearance of neurofibromas may start as simple nerve thickening (Table S1) or is that of an ovoid lesions, which show slightly greater signal intensity than skeletal muscle on T1-weighted sequences and high intensity periphery with variable intensity centre on T2-weighted sequences (‘target sign’) (21, 22). On computerized tomography (CT), the paraspinal neurofibromas have low attenuation when compared with the muscle. Intraspinal (intrathecal or extrathecal)
neurofibromas may displace the spinal cord or the nerve roots of the cauda equina to the contralateral side of the canal. When bilateral neurofibromas are present, over time, at a single level, the cord can be compressed into a narrow, central band of tissue that is elongated in the anterior–posterior direction (22). Neurofibromas, presenting as subcutaneous nodular lesions of one or more limbs, are frequent (Fig. 4): these lesions can involve, over time, the entire major (and/or
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Fig. 4. Surgical field in the leg area showing a large mass affecting one of the major nerve branches (a) in a 14-year-old twin girl [case 2 in Ruggieri et al. (16)] with spinal neurofibromatosis; (b) histological analysis of the lesion removed in (a) reveals a myxoid matrix (black arrow) containing neoplastic cells and dense collagen bundles typical of the neurofibroma (hematoxylin and eosin staining, ×200).
less frequently the minor) nerve trunks, leaving no intact segment [this is diagnostically important as differentiates SNF from the mosaic forms of neurofibromatosis (23, 24) and from schwannomatosis (25)]. Less frequently, neurofibromas can develop in or extend to the mediastinal region, the abdomen or the pelvis. Associated involvement of all the major peripheral nerve branches in the four limbs could not always be present (Table S1): for this reason we preferred to leave such phenotypic aspect in brackets, in the definition of SNF, and to add the word ‘eventually’. As stated before, however, we could record subcutaneous neurofibromas (relentlessly involving all the major peripheral nerve branches) in all the nine cases followed-up at our institutions (Tables 1 and S4) (16, 19). Associated NF1-features
lesions and were somewhat closer in size, shape, and colour to the hyperpigmented macules typically encountered in (children but also in adults) with NF2 (26, 27) (Fig. 1a,c). Thus, we proposed (16, 19, 20) that multiple (sometimes fewer than six but also in larger numbers), large, light-brownish café-au-lait spots with irregular margins (as those shown in Fig. 1) seen in children, irrespective of their age, could be a marker of or could raise the suspicion of SNF. Cutaneous neurofibromas. Cutaneous neurofibromas were recorded in 24% of SNF vs 37% of MNFSR patients. Thus, whatever group we consider, these figures are lower than classical NF1 where multiple dermal neurofibromas affect more than 90% of affected individuals. Notably, cutaneous neurofibromas were not seen in the group of SNF patients followed at our Institutions, irrespective of their ages.
Skin manifestations
The spectrum of skin manifestations in SNF may consist in café-au-lait spots and/or freckling in specific places, and cutaneous neurofibromas (Tables S1 and S2). Pigmentary manifestations: café-au-lait spots and freckling. The typical café-au-lait spots in SNF
have been recorded in 67% of the analysed cohort (vs 56% in MNFSR); these were multiple (i.e. >6) in 60% (SNF) vs 83% (MNFSR). Freckling in specific places (mostly distributed over the axillae) was reported in 18% (vs 16% in MNFSR). These data indicate that café-au-lait spots in SNF can be less frequent and freckling much less frequent than in classical NF1, thus generating difficulties in diagnosis unless the involvement of peripheral nervous system is apparent (17). We could not record detailed information regarding the shape and colour of café-au-lait spots in most published reports on SNF (Tables S1 and S2); the description of ‘light-brown’ cafè-au-lait spots was recorded only once previously (2) and only one illustration of a typical skin pigmentary lesion has been published previously (14). In our personal experience (16, 19) (Tables 1 and S4) the café-au-lait macules, within the context of SNF, were paler in colour, larger in size and with less regular margins as compared with the typical NF1 pigmentary
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Lisch nodules
Lisch nodules were seen in 24% of SNF patients and in 33% of MNFSR patients, and if present most patients in either cohort had few Lisch nodules. Of interest, we recorded iris nodules in one of nine patients seen at our institutions (16, 19) (Tables 1 and S4). These figures are low as compared with patients with classical NF1 (approximately 90%) and could reflect a localized phenotype, which is the hallmark of SNF. Lisch nodules are seen in less that 10% of patients with mosaic/segmental NF1 (23, 24, 28, 29). Other NF1-associated features and complications Skeletal involvement. Bone involvement (e.g. long
bone dysplasia, vertebral or chest anomalies, cystic-like lesions in long bones), which is typically encountered in NF1 (30), has been reported only occasionally in SNF. Of interest, even though neurofibromas involve every spinal nerve root, only 18% of SNF patients developed scoliosis, of mild to moderate degree (i.e. with a curvature of 0.5. Overall, the analysis of phenotype in the 16 SNF patients harbouring missense mutations recorded café-au-lait spots in 62% (with only 2/16 patients having >6 macules), freckling and Lisch nodules in 12%, cutaneous neurofibromas in 43% (with only 1/16 having multiple skin tumours), and subcutaneous neurofibromas in 25%. A hallmark of NF1 is the high phenotypic variability between affected individuals, even among members of the same family. The only phenotype–genotype correlations described so far in NF1 are large deletions encompassing the whole NF1 gene (31, 32) and the 3-bp deletion of exon 22. One of the striking characteristics of SNF is the overall paucity of associated NF1-features and in particular the absence or low number of cutaneous neurofibromas (Tables S1, S2 and S4), which is in contrast with the high number of early-onset cutaneous neurofibromas seen in patients with the NF1 micro-deletion syndrome (30, 31). Even though the numbers hereby analysed (Table S5) are too few to draw genotype–phenotype correlations we compared SNF vs severe classical NF1 (i.e. NF1 gene microdeletion syndrome) by outlining the phenotype in the SNF patients who had NF1 gene deletions (Table S7); interestingly, these four SNF deletion patients had few NF1-associated features, including few cutaneous neurofibromas. It must be noted, however, that one patient in this group had dysmorphic features (18) [never encountered in SNF (Tables S1 and S2)] and an additional patient died of MPNST complications (11) (Table S7). The SNF phenotype might derive from cooperation between the NF1 gene and other factors: e.g. modifier genes. Some evidences seem to support such premises including the identification of: (i) similar NF1 gene mutations in both classical NF1 and SNF (Tables S5 and S6), (ii) SNF patients belonging to families with classical NF1 who harboured identical NF1 gene abnormalities (Table S1), and (iii) families with either SNF and MNFSR affected members all harbouring identical NF1 gene abnormalities (Tables S1 and S2). Further genetic studies are needed to clarify these unsolved questions. Natural history of disease First appearance of spinal neurofibromas
Spinal neurofibromas, according to our experience (Tables 1 and S4), usually appear early in life (in some cases as early as the first years of life; Tables S1 and S2) (4, 9, 14, 16). Their detection rate, however, can be low at young ages, as most (if not all) of these lesions can be
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initially asymptomatic, becoming symptomatic later in life (e.g. at or after age 20 or 30 or up to 50 years of age; Table S1), or they can be asymptomatic until older ages. When they are symptomatic early in life, this is usually secondary to massive involvement of both spinal roots and major nerve trunks (4, 9, 14). Age at onset of spinal neurofibromas in SNF ranged from 4 to 52 years and was lower in males (mean = 16; mode = 15) vs females (mean = 26; mode = 24) (Table S1). Interestingly, age at onset of spinal neurofibromas in MNFSR had a wider range from 2 to 60.5 and was higher than SNF, irrespective of gender (males: mean = 31; mode = 31; females: mean = 33.5; mode = 30) (Table S3), thus reflecting the true onset of typical neurofibromas in classical NF1. The initial localization was in one segment (by literature review) or at multiple sites (by literature review and by personal experience) and the lesions could appear as simple nerve thickening (in some recorded cases nerve thickening of all the spinal roots persisted until older ages; Table S1) or be tiny. Over the years the nodules progressed and multiplied over the affected and adjacent root segments and nerve trunks. The diagnosis of SNF, unless the suspected individual belonged to SNF or NF1 families, was usually made by chance because of (Table S1): (i) the appearance of a subcutaneous nodule (a ‘lump’), (ii) the removal of a nodule, which turned out to be a neurofibroma or a PNF, (iii) the presence of café-au-lait spots, (iv) the appearance/progression of pain or motor signs, (v) the occasional detection of NF1-like bone dysplasia, or (vi) the occasional detection of nodules at MRI because of radiological investigation for other reasons. Sometimes, despite the appearance of signs, which should have raised the suspect of a form of neurofibromatosis (e.g. café-au-lait spots, histologically proven neurofibromas), the diagnosis was delayed until the appearance of more severe signs/symptoms (e.g. large neurofibromas, paraparesis) (Table S1). Signs/symptoms at onset and progression of disease
Among the most frequent neurological signs/symptoms recorded at onset or bringing affected individuals to their first referral are sensory deficits (neuropathy), and motor signs (e.g. weakness or limb paresis/paralysis). These can be accompanied by (electric-shock) pain. Due to the predominantly extra-axial location of neurofibromas, an extensive tumour burden may be present in asymptomatic SNF patients. Symptomatic and asymptomatic SNF patients may have cutaneous or, more often, subcutaneous ‘lumps’ (and/or NF1 pigmentary anomalies) noticed earlier than the appearance of first neurological manifestations. Usually, signs and symptoms, relentlessly progress, with the appearance of increasing pain, gait disturbances and paraparesis or, eventually, signs of moderate to severe cord compression due to enlargement of the paraspinal masses. Neurosurgical outcomes may be improved by pre-symptomatic intervention in affected individuals.
Spinal neurofibromatosis We recorded no symptomatology progression in some of the affected individuals seen at our institution (Tables 1 and S4). Recommendations for diagnosis and management and differential diagnosis
The diagnosis of SNF relies on visualization of neurofibromas on imaging (i.e. MRI) involving every nerve root, bilaterally. Irrespective to age, when a given individual present with multiple neurofibromas of many spinal segments, serial imaging studies should be obtained so as to get (eventual) later confirmation of (bilateral) involvement of all spinal roots. It cannot be excluded a priori that MNFSR can transition to SNF over time. Thus, unless the SNF phenotype is overt from the first imaging study, serial imaging studies should always be obtained to confirm diagnosis: serial studies would serve for follow-up in confirmed cases. Other NF1 stigmata may be present, but are often lacking. Café-au-lait spot to a lesser extent than classical NF1, and intertriginous freckling, Lisch nodules and cutaneous neurofibromas are seen in a minority of cases. Thus, the affected status of SNF could be assigned irrespective of the presence or lack of NF1-associated manifestations or complications (33, 34), but requires imaging of the spine. The presence of attenuated NF1 manifestations without cognitive impairment or lack of cutaneous neurofibromas in a pubertal toddler or an older adolescent with NF1 may lead one to perform whole spinal imaging to detect SNF. One important issue is that many of the affected SNF (but also MNFSR) patients have endured several years of symptoms before the diagnosis was suspected: this may be unavoidable if no stigmata of NF1 are evident (17). MRI of the spine, limbs and abdomen (e.g. full body MRI) is pivotal for visualization of the tumours. Brain MRI and ophthalmologic evaluation should be obtained in each patient. Electromyography and nerve conduction velocities could confirm the peripheral nervous system damage and may help in localizing the affected site and the extension of involvement. There is a possibility that someone is referred with a few café-au-lait spots or a few cutaneous (or subcutaneous) neurofibromas or with isolated Lisch nodules. In these cases attention should be paid to the specific features of the pigmentary anomalies and a biopsy might be indicated to determine if a tumour was a neurofibroma, schwannoma or something else. Other specific NF1 features/complications should be carefully checked clinically or by other means (e.g. ultrasonography, x-ray) as dictated by clinical findings. The usual clinical assessment in childhood (32) cannot be relied upon to confirm or refute the diagnosis of SNF (17). We usually recommend MRI of the whole spine and brain when the suspicion of a related form of NF1 (or NF2) is raised (see below). Visualization of tumours on MRI involving every nerve root would lead to an assessment for other manifestations of NF1 or NF2. Likewise, absence of pain would steer one away from the diagnosis of schwannomatosis. Due to the predominantly extra-axial location
of neurofibromas, an extensive tumour burden may be present in asymptomatic SNF patients. Molecular NF1 gene testing should be always obtained. The apparent higher relative-risk for SNF to harbour missense mutations needs future confirmation by larger studies. Neurofibromas in SNF affect massively the spine and their multiplicity and progression, which ultimately leave no intact spinal segment, is important in that these features help in differentiating SNF from similar conditions including 33: (i) classical NF1, whose affected patients have usually a (even massive but) limited number of nerve sheath tumours scattered at multiple (but not all) levels of the spine (unilaterally or bilaterally) (21, 22). The presence/absence of typical NF1 stigmata could also help in differentiating the two phenotypes; (ii) ‘mosaic/segmental NF1’, in which patients have either multiple neurofibromas in localized (small or large) segments of their body or extensive PNFs involving localized regions of their body (23, 24); (iii) classical NF2, whose tumours are schwannomas, which are isointense to neural tissue on T1-weighted images and hyperintense (usually) on T2-weighted images and enhance uniformly after intravenous administration of paramagnetic contrast. In addition to that these patients have different NF2-associated stigmata (e.g. vestibular schwannomas, meningiomas, cataract, and peripheral schwannomas) (21, 22, 26, 27); (iv) ‘multiple isolated neurofibromas’ (35), who usually do not have lesions in all the spinal roots; and (v) ‘schwannomatosis’, who usually have paraspinal nerve sheath tumours (mostly schwannomas but sometimes also some neurofibromas) or schwannomas along the major nerves of all the four limbs and thoracic region but do not (usually) manifest at any stage of the disease a massive involvement of the spinal roots as it occurs in SNF (25). The anatomical lesion (through initial MRI suspicion and later histological confirmation, when needed) will help at least in differentiating between the two major forms of neurofibromatosis (i.e. NF1 vs NF2; in this respect between SNF vs schwannomatosis, even though it must be kept in mind that, rarely, schwannomas can be recorded in the context of SNF; Table S1). The extension of the area(s) involved and the natural history of disease will help in differentiating between the NF1-related forms. It is important to keep in mind that only a minority of cases with SNF could entirely satisfy the NF1 diagnostic criteria (34); in these cases the diagnosis of SNF vs classical NF1 will be based on the presence of the hallmark of disease. Therefore, besides the true familial cases of SNF or the cases of SNF within families with classical NF1 or with MNFSR, and given the wide range of manifestations in SNF, assignment of the affected status to a sporadic case can be achieved on the basis of the solely presence of neurofibromas of all the 38 spinal roots. A new term (MNFSR) introduced in this study could provide an avenue for clinical judgement and the expectation that every spinal nerve root is involved in SNF might be a bit restrictive. However, individuals with multiple spinal root tumours and few café-au-lait spots, without post-pubertal cutaneous neurofibromas,
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Ruggieri et al. and without cognitive impairment should be viewed differently than individuals with classical NF1. Supporting Information Additional supporting information may be found in the online version of this article at the publisher’s web-site.
References 1. Pulst SM, Riccardi VM, Fain P, Korenberg JR. Familial spinal neurofibromatosis: clinical and DNA linkage analysis. Neurology 1991: 41: 1923–1927. 2. Poyhonen M, Leisti EL, Kytola S, Leisti J. Hereditary spinal neurofibromatosis: a rare form of NF1? J Med Genet 1997: 34: 184–187. 3. Ars E, Kruyer H, Gaona A et al. A clinical variant of neurofibromatosis type 1: familial spinal neurofibromatosis with a frameshift mutation in the NF1 gene. Am J Hum Genet 1998: 62: 834–841. 4. Pasqual-Castroviejo I, Pascual-Pascual SI, Viano J, Martinez V. Generalized nerve sheath tumors in neurofibromatosis type 1 (NF1) a case report. Neuropediatrics 2000: 31: 211–213. 5. Kaufmann D, Müller R, Bartelt B et al. Spinal neurofibromatosis without café-au-lait macules in two families with null mutations of the NF1 gene. Am J Hum Genet 2001: 69: 1395–1400. 6. Wimmer K, Muhlbauer M, Eckart M et al. A patient severely affected by spinal neurofibromas carries a recurrent splice site mutation in the NF1 gene. Eur J Hum Genet 2002: 10: 334–338. 7. Messiaen L, Riccardi V, Peltonen J et al. Independent NF1 mutations in two large families with spinal neurofibromatosis. J Med Genet 2003: 40: 122–126. 8. Kluwe L, Tatagiba M, Fünsterer C, Mautner VF. NF1 mutations and clinical spectrum in patients with spinal neurofibromas. J Med Genet 2003: 40: 368–371. 9. Pascual-Castroviejo I, Pascual-Pascual SI, Velazquez-Fragua R, Botella P, Viaño J. Familial spinal neurofibromatosis. Neuropediatrics 2007: 38: 105–108. 10. Upadhyaya M, Spurlock G, Kluwe L et al. The spectrum of somatic and germline NF1 mutations in NF1 patients with spinal neurofibromas. Neurogenetics 2009: 10: 251–263. 11. Fauth C, Kehrer-Sawatzki H, Zatkova A et al. Two sporadic spinal neurofibromatosis patients with malignant peripheral nerve sheath tumour. Eur J Med Genet 2009: 52: 409–414. 12. Tsuji M, Harada S, Ueno Y, Osaka N. Neurological pictures. Familial spinal neurofibromatosis: three generations of identical level symptomatic tumours. J Neurol Neurosurg Psychiatry 2010: 81: 1382. 13. Pizzuti A, Bottillo I, Inzana F et al. Familial spinal neurofibromatosis due to a multiexonic NF1 gene deletion. Neurogenetics 2011: 12: 233–240. 14. Pascual-Castroviejo I, Pascual-Pascual SI, Viaño J, Velazquez-Fragua R, López-Gutierrez JC. Bilateral spinal neurofibromas in patients with neurofibromatosis 1. Brain Dev 2012: 34: 563–569. 15. Nunez-Farias AC, Bortzusky A, Morales PS, Zunino R, del Villar S. Severe spinal neurofibromatosis in a child. J Pediatr 2012: 161: 368. 16. Ruggieri M, Polizzi A, Salpietro V et al. Spinal neurofibromatosis with central nervous system involvement in a set of twin girls and a boy. Further expansion of the phenotype. Neuropediatrics 2013: 44: 239–244.
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17. Burkitt Wright EM, Sach E, Sharif S et al. Can the diagnosis of NF1 be excluded clinically? A lack of pigmentary findings in families with spinal neurofibromatosis demonstrates a limitation of clinical diagnosis. J Med Genet 2013: 50: 606–613. 18. Carman KB, Yakut A, Anlar B, Ayter S. Spinal neurofibromatosis associated with classical neurofibromatosis type 1: genetic characterization of an atypical case. BMJ Case Rep 2013: Feb 14; doi: 10.1136/bcr-2012-008468. 19. Nicita F, Torrente I, Spalice A et al. Spinal neurofibromatosis in a family with classical neurofibromatosis type 1 and novel NF1 gene mutation. J Clin Neurosci 2014: 21 (2): 328–330. 20. Nicita F, Spalice A, Ruggieri M. Spinal neurofibromatosis in children. J Pediatr 2013: 162: 217. 21. Ruggieri M, Upadhyaya M, Di Rocco C, Gabriele A, Pascual-Catroviejo I. Neurofibromatosis type 1 and related disorders. In: Ruggieri M, Pascual-Castroviejo I, Di Rocco C, eds. Neurocutaneous disorders: phakomatoses and hamartoneoplastic syndromes. Wien, New York, NY: Springer-Verlag, 2008: 51–151. 22. Vezina G, Barkovich AJ. The Phakomatoses. In: Barkovich AJ, Raybaud C, eds. Pediatric neuroinaging, 5th edn. Philadelphia, PA: Lippincott Williams and Wilkins, 2012: 569–636. 23. Ruggieri M, Polizzi A. Segmental neurofibromatosis. J Neurosurg 2000: 93: 530–532. 24. Ruggieri M, Huson SM. The clinical and diagnostic implications of mosaicism in the neurofibromatoses. Neurology 2001: 56: 1433–1443. 25. Plotkin SR, Blakeley JO, Evans DG et al. Update from the 2011 International Schwannomatosis Workshop: from genetics to diagnostic criteria. Am J Med Genet A 2013: 161: 405–416. 26. Ruggieri M, Iannetti P, Polizzi A et al. Earliest clinical manifestations and natural history of neurofibromatosis type 2 in childhood: a study of 24 patients. Neuropediatrics 2005: 36: 21–34. 27. Ruggieri M, Gabriele AL, Polizzi A et al. Natural history of neurofibromatosis type 2 (NF2) with onset before the age of 1 year. Neurogenetics 2013: 14: 89–98. 28. Ruggieri M, Pavone P, Polizzi A et al. Ophthalmological manifestations in segmental neurofibromatosis type 1. Br J Ophtalmol 2004: 88: 1429–1433. 29. Nicita F, Iannetti L, Spalice A et al. Unilateral Lisch nodules in a 47-year-old woman without other stigmata of neurofibromatosis type 1: an example of segmental neurofibromatosis? Ophtalmic Genet 2013: 34: 178–179. 30. Ruggieri M, Pavone V, De Luca D, Franzò A, Tiné A, Pavone L. Congenital bone malformations in patients with neurofibromatosis type 1. J Pediatr Orthop 1999: 19: 301–305. 31. Kayes LM, Burke W, Riccardi VM et al. Deletions spanning the neurofibromatosis 1 gene: identification and phenotype of five patients. Am J Hum Genet 1994: 54: 424–436. 32. Mautner VF, Kluwe L, Friedrich RE et al. Clinical characterisation of 29 neurofibromatosis type-1 patients with molecularly ascertained 1.4 Mb type-1 NF1 deletions. J Med Genet 2010: 47: 623–630. 33. Ruggieri M. The different forms of neurofibromatosis. Childs Nerv Syst 1999: 15: 295–308. 34. National Institutes of Health Consensus Development Conference. Neurofibromatosis conference statement. Arch Neurol 1988: 45: 575–578. 35. Blakley P, Louis DN, Short MP, MacCollin M. A clinical study of patients with multiple isolated neurofibromas. J Med Genet 2001: 38: 485–488.
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© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd CLINICAL GENETICS doi: 10.1111/cge.12498
Review
The natural history of spinal neurofibromatosis: a critical review of clinical and genetic features Ruggieri M, Polizzi A, Spalice A, Salpietro V, Caltabiano R, D’Orazi V, Pavone P, Pirrone C, Magro G, Platania N, Cavallaro S, Muglia M, Nicita F. The natural history of spinal neurofibromatosis: a critical review of clinical and genetic features. Clin Genet 2015: 87: 401–410. © John Wiley & Sons A/S. Published by John Wiley & Sons Ltd, 2014 Spinal neurofibromatosis (SNF) is a related form of neurofibromatosis 1 (NF1), characterized by bilateral neurofibromas (histologically proven) of all spinal roots (and, eventually, of all the major peripheral nerve branches) with or without other manifestations of classical NF1. By rigorous application of these criteria to the 98 SNF cases published, we developed: (i) a cohort of 49 SNF patients (21 males and 28 females; aged 4–74 years]: 9 SNF families (21/49), 1 mixed SNF/NF1 family (1/49) and 27 of 49 sporadic SNF patients (including 5 unpublished patients in this report); and (ii) a group of 49 non-SNF patients including: (a) 32 patients with neurofibromas of multiple but not all spinal roots (MNFSR): 4 mixed SNF/MNFSR families (6/32); (b) 14 patients with NF1 manifestations without spinal neurofibromas, belonging to SNF (8/49) or MNFSR families (6/32); (c) 3 patients with neurofibromas in one spinal root. In addition to reduced incidence of café-au-lait spots (67% in SNF vs 56% in MNFSR), other NF1 manifestations were less frequent in either cohort. Molecular testing showed common NF1 gene abnormalities in both groups. The risk of developing SNF vs NF1 was increased for missense mutations [p = 0.0001; odds ratio (OR) = 6.16; confidence interval (CI) = 3.14–13.11], which were more frequent in SNF vs MNFSR (p = 0.0271). Conflict of interest
The authors declare no conflict of interest
M. Ruggieria,b , A. Polizzic,d , A. Spalicee , V. Salpietrof , R. Caltabianog , V. D’Orazih , P. Pavonei , C. Pirronej , G. Magrog , N. Plataniak , S. Cavallaroc , M. Muglial and F. Nicitae a Department of Educational Sciences, Chair of Paediatrics , b Centre for Neurocutaneous Disorders, University of Catania, Catania, Italy, c Institute of Neurological Sciences, National Research Council, Catania, Italy, d National Centre for Rare Diseases, Istituto Superiore di Sanità, Rome, Italy, e Child Neurology Division, Department of Paediatrics, Sapienza University of Rome, Rome, Italy, f Unit of Genetics and Pediatric Immunology, Department of Pediatrics, University of Messina, Messina, Italy, g Department ‘G. Ingrassia’, Section of Anatomic Pathology, University of Catania, Catania, Italy, h Department of Surgical Sciences, “Sapienza” University of Rome, Rome, Italy and Unit of Microsurgery and Hand Surgery, Fabia Mater Hospital, Rome, Italy, i Unit of Paediatrics and Paediatric Emergency, University Hospital ‘Policlinico-Vittorio Emanuele’, Catania, Italy, j Branches of Psychology, Department of Educational Sciences, University of Catania, Catania, Italy , k Institute of Neurosurgery, Department of Neurosciences ‘G. Ingrassia’, University of Catania, Catania, Italy, and l Institute of Neurological Sciences, National Research Council, Cosenza, Italy Key words: familial spinal neurofibromatosis – multiple neurofibromas – NF1 – paraspinal neurofibromatosis – spinal neurofibromatosis
Corresponding author: Martino Ruggieri, BA, MD, PhD, Department of Educational Sciences, Chair of Paediatrics, University of Catania, Via Casa Nutrizione, 1, 95124 Catania, Italy. Tel.: +39 095 7466377; fax: +39 095 7466385; e-mail: [email protected]
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Ruggieri et al. Received 10 August 2013, revised and accepted for publication 8 September 2014
Definition and historical background
Spinal neurofibromatosis (SNF) is a distinct clinical entity – a related form of neurofibromatosis 1 (NF1) – characterized by bilateral, histologically proven, neurofibromas of all spinal roots leaving no intact segments, with or without other manifestations of the NF1 diagnostic criteria (1, 2). This form was first recognized in the literature by Pulst et al. in 1991, in eight members of two multi-generation families and named ‘familial spinal neurofibromatosis’ (1). A few years later, in 1997, Poyhonen et al. (2) reported a family in which seven members over three generations were affected with a rare SNF (‘ … a distinct variant of NF1 … ’), named ‘hereditary spinal neurofibromatosis’. Interestingly, while affected members of the two families of Pulst et al. (1) had ‘ . . . . multiple paraspinal neurofibromas on both sides at all levels of multiple (but not all) segments of the spine’, all the (four) affected adults of the family of Pohyonen et al. (2) had ‘ … multiple spinal neurofibromas symmetrically affecting all spinal roots’. Both studies noted, for the first time [irrespective of full (2) or partial (1) spinal root involvement], that these phenotypes were (1, 2): (i) different from the well-established NF1 and NF2 phenotypes, (ii) distinct, in that the predominant feature was multiple (extensive) spinal neurofibromas, and (iii) much more restricted in their manifestations with absence of Lisch nodules and of non-tumour features of NF1 (e.g. learning difficulties and skeletal dysplasia). At the time of the studies (1, 2), linkage with the NF1 gene was recorded in family 1 of Pulst et al. (odds of 97:1) (1) and in the family of Pohyonen et al. (LOD score of 1.763) (2). After these two reports (1, 2), 17 further studies recorded 83 additional (both familiar sporadic) patients for a total of 98 patients labelled under the umbrella term of ‘familial/hereditary spinal neurofibromatosis’ or just ‘spinal neurofibromatosis’ (3–20). The condition has been regarded as a true NF1 variant or subtype, and either linkage to the NF1 locus (1, 2) or mutations in the NF1 gene have been recorded in most reported cases (3, 5–11, 13, 16–20). In addition to its hallmark of multiple neurofibromas of the spinal roots and, major nerve trunks, the phenotype variably included classical NF1 stigmata (e.g. typical pigmentary manifestations, Lisch nodules and cutaneous and nodular neurofibromas) and other NF1-associated manifestations (e.g. scoliosis, long bone dysplasia, optic and non-optic pathway gliomas, plexiform neurofibromas (PNFs), pheochromocytoma and the typical T2 hyperintensities in the brain) (3–20). Besides the classical families with multiple spinal neurofibromas, several sporadic cases have been recorded and, more recently, the phenotypic spectrum has included a set of concordant twins with SNF (16) and individuals with SNF belonging to families with classical NF1 (20). Thus, it was proposed
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to drop the term ‘familial (hereditary) spinal neurofibromatosis’ and to replace it with ‘Spinal neurofibromatosis’ (16, 19, 20) as the condition could simply reflect a typical autosomal dominant pattern of inheritance, therefore one would expect a balance of familial (including twins and cases within classical NF1 families) vs sporadic cases. Rationale of review
By critically reviewing the published reports labelled as (familial/hereditary) spinal neurofibromatosis (1–20), we realized that not all the reported cases presented with involvement of all the 38 spinal roots. In many individuals, the affected status of SNF was assigned to (familial or sporadic) patients with few or multiple neurofibromas involving multiple (but not all) segments of the spine (either unilaterally or bilaterally). In addition, some families included members with classical NF1 and other members with multiple neurofibromas involving all the spinal roots. Other families included some members with involvement of all spinal roots and other members with involvement of multiple but not all spinal roots, irrespective of age. This implies that for some individuals gleaned from these reports, spinal root neurofibromas could reflect more severe of a manifestation of classical NF1 rather than a related or alternate form of NF1. In some other families involvement of all vs multiple but not all spinal roots could merely reflect the phenotypic variability within the spectrum of SNF. Aim and methods of review
Aiming to better define the phenotype of SNF we searched existing databases (i.e. Medline, Scopus and Web of Knowledge) for reports on individuals labelled under the terms ‘familial spinal neurofibromatosis’, ‘hereditary spinal neurofibromatosis’ or ‘spinal neurofibromatosis’. We identified 20 reports (1–20), which included a total of 98 patients with SNF. We rigorously applied the criteria, which define SNF [i.e. the presence of multiple, histologically proven, neurofibromas of all spinal roots, bilaterally (and, eventually, of all the major peripheral nerve branches)], to each of these 98 individuals. Assignment of affected status of SNF, in each of the 98 reported patients, was based on complete phenotype assessment (including skin, ophthalmologic and orthopaedic examination and cognitive profile) and results of brain and spinal magnetic resonance imaging (MRI) studies and biopsies of at least one lesion of the peripheral nervous system. We added to this cohort complete phenotypes and genotype in five unpublished cases followed at our institutions (Table 1).
Spinal neurofibromatosis Table 1. Clinical, laboratory and imaging features of five (unreported) patients affected by spinal neurofibromatosis seen and followed-up at our institutions Patient
1
2
3
4
5
Gender Current age (year) Age of onset (year) Familial (NF1 or SNF) Sporadic Growth parameters (weight, length, HC) Café-au-lait spots Number >6 2 Irregular − − − Limbs, trunk − + −
3 NA Light-brown >3 cm Irregular − − − Limbs, trunk − − −
NA Light-brown >2 Irregular − − − Limbs, trunk − − −
Light-brown >5 Irregular − − − Limbs − − −
Light-brown >4 Irregular − + − Trunk, limb + + −
− −
− −
− −
− −
− −
+ B (all roots) +
+ B (all roots) +
+ B (all roots) +
+ B (all roots) +
+ B (all roots) +
Limbs, trunk Neuropathy LL IQ = 95
Limbs, trunk Neuropathy LL, abdomen IQ = 88
Limbs, trunk Neuropathy UL IQ = 89
Limbs Pain, neuropathy Trunk, limbs IQ = 90
Trunk, limb Pain, paresis LL IQ = 95
Exon 21 p.(Gly848Glu)
Intron 42 c.6427+2T>G
Exon 12a 1733T>G
Exon 37 6757delG
Pending
B, bilateral; F, female; HC, head circumference; IQ, intelligence quotient; LL, lower limbs; M, male; MPNST, malignant peripheral nerve sheet tumour; MRI, magnetic resonance imaging; NBO, neurofibromatosis bright objects (high signal lesions on T2-weighted MRI); NF1, neurofibromatosis type 1; NFs, neurofibromas; NA, not applicable; NS, not specified; OPG, optic pathway glioma; UL, upper limbs.
Results of review Clinical findings and natural history
We assigned affected status of SNF to 49 patients [21 males and 28 females (male:female ratio = 0.72)] aged, at their last follow-up, 4–74 years (Tables S1 and S2, Supporting information). The main clinical and imaging aspects of SNF are illustrated in Figs 1–4. We identified a second cohort, which included 32 patients (22 males and 8 females; aged 7–74 years) with multiple neurofibromas in multiple ‘but not all’ spinal roots (MNFSR) (Table S3). An additional group of 14 patients belonging either to SNF families (8/49; Table S1) or to MNFSR families (6/32; Table S3) were identified who had NF1 stigmata without neurofibromas in spinal root.
Three out of the original 98 patients, labelled as having SNF (1–20), were excluded from present analysis as they had involvement of only one spinal root (patients 406, 894 and 548) (8). We generated an additional table (Table S4) that included data from the five unpublished patients hereby reported (as shown in Table 1) and follow-ups of the four published patients (16, 19) seen at our institutions. Molecular testing
Results of molecular NF1 gene testing, which was performed in 40 of 49 SNF patients and in 25 of 32 MNFSR patients are summarized in Tables S1–S3 and detailed in Tables S5 and S6. We generated an additional table (Table S7) detailing the phenotypic features in SNF patients harbouring NF1 gene deletions.
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Fig. 1. Close view-up of the pigmentary macules recorded in children with spinal neurofibromatosis; note the paler brownish colour and the irregular margins of the macules [the figures show the pigmentary lesions seen in patient 1 (a), patient 2 (b), and patient 3 (c) as reported in Ruggieri et al. (16)].
Overall, molecular NF1 gene testing identified mutations in 37 of 40 (92.5%) SNF patients (including a double mutation) and 24 of 25 (96%) MNFSR. There were whole gene deletions [4/37 (1 familial) and 2/24 (1 familial)], missense [16/37 (5 familial) and 4/24 (2 familial)], splicing [8/37 (3 familial) and 6/24 (3 familial)], nonsense [4/37 (1 familial) and 3/24 (2 familial)] and frameshift mutations [5/37 (1 familial) and 9/24 (3 familial)]. The risk of having SNF vs classical NF1 was increased in individuals harbouring missense mutations [p = 0.0001; odds ratio (OR) = 6.16; confidence interval (CI) = 3.14–13.11], and missense mutations were more frequent in SNF vs MNFSR patients (p = 0.0271) (Appendix S1). Other types of mutations did not have a significant association with any one phenotype. Phenotypic spectrum and natural history Hallmark of disease
The hallmark of SNF is bilateral neurofibromas of all spinal roots (Tables S1 and S2; Fig. 2a,b). This feature characterizes SNF as a related or alternate form of NF1, and not merely as a classical NF1 phenotype manifesting with increased occurrence of spinal neurofibromas or with a concentration of multiple neurofibromas in some segments of the spine. By critical literature review and by personal experience we could easily identify the first cohort of 49 patients with this feature (Table S1; see also Tables 1 and S5) (16, 19). Bilateral involvement of all spinal nerve roots most
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clearly defined the SNF phenotype. Lack of rigorous application of this criterion has perpetuated phenotype designations that are not SNF (Table S3). Relaxing the application of strict criteria requiring neurofibromas of all spinal nerves generated the second cohort, and we identified 32 patients with multiple neurofibromas in multiple (but not all) spinal roots, which we named MNFSR (Table S3). Three individuals, in this cohort had massive involvement of almost all spinal roots (Table S3) (12) and six other individuals, with MNFSR, belonged to four single-generation or multi-generation families with SNF (Tables S1 and S2) (3, 8, 10, 13): such phenotypic variability must be taken into consideration and is likely part of the phenotypic spectrum of SNF. Individuals with MNFSR, unless part of a family with affected members having SNF, should not be regarded as having SNF. Neurofibromas, in SNF, can be localized in the paraspinal segments or may have either intradural or extradural components, or both (so-called dumbbell tumours), with a large extraspinal component causing foraminal enlargement. Histologically they prove to be classical neurofibromas (Fig. 3a,b). The biopsy needs to have enough tissue of high quality to enable the clinical pathologist to make the determination of tumour type, and there is no role of thin needle biopsy. If the diagnosis of NF1 or NF2 cannot be established then a biopsy is indicated to determine if the tumours were neurofibromas or schwannomas. Schwannomas have been recorded, occasionally, along with neurofibromas within the SNF phenotype (Tables S1 and S2) (5).
Spinal neurofibromatosis
Fig. 2. Coronal (a) and sagittal (b, c) T2-weighted magnetic resonance images of the spine in an affected individual with spinal neurofibromatosis reveal multiple, bilateral neurofibromas of the spinal roots that leave no intact segment [patient III-1 in Nicita et al. (19)].
Fig. 3. Coronal (a) and axial (b) T2-weighted magnetic resonance images of the sacral spine and lower limbs showing the extension of the multiple tumours along the lower nerve branches leaving no intact segment (patient 2, Table 1).
The MRI appearance of neurofibromas may start as simple nerve thickening (Table S1) or is that of an ovoid lesions, which show slightly greater signal intensity than skeletal muscle on T1-weighted sequences and high intensity periphery with variable intensity centre on T2-weighted sequences (‘target sign’) (21, 22). On computerized tomography (CT), the paraspinal neurofibromas have low attenuation when compared with the muscle. Intraspinal (intrathecal or extrathecal)
neurofibromas may displace the spinal cord or the nerve roots of the cauda equina to the contralateral side of the canal. When bilateral neurofibromas are present, over time, at a single level, the cord can be compressed into a narrow, central band of tissue that is elongated in the anterior–posterior direction (22). Neurofibromas, presenting as subcutaneous nodular lesions of one or more limbs, are frequent (Fig. 4): these lesions can involve, over time, the entire major (and/or
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Fig. 4. Surgical field in the leg area showing a large mass affecting one of the major nerve branches (a) in a 14-year-old twin girl [case 2 in Ruggieri et al. (16)] with spinal neurofibromatosis; (b) histological analysis of the lesion removed in (a) reveals a myxoid matrix (black arrow) containing neoplastic cells and dense collagen bundles typical of the neurofibroma (hematoxylin and eosin staining, ×200).
less frequently the minor) nerve trunks, leaving no intact segment [this is diagnostically important as differentiates SNF from the mosaic forms of neurofibromatosis (23, 24) and from schwannomatosis (25)]. Less frequently, neurofibromas can develop in or extend to the mediastinal region, the abdomen or the pelvis. Associated involvement of all the major peripheral nerve branches in the four limbs could not always be present (Table S1): for this reason we preferred to leave such phenotypic aspect in brackets, in the definition of SNF, and to add the word ‘eventually’. As stated before, however, we could record subcutaneous neurofibromas (relentlessly involving all the major peripheral nerve branches) in all the nine cases followed-up at our institutions (Tables 1 and S4) (16, 19). Associated NF1-features
lesions and were somewhat closer in size, shape, and colour to the hyperpigmented macules typically encountered in (children but also in adults) with NF2 (26, 27) (Fig. 1a,c). Thus, we proposed (16, 19, 20) that multiple (sometimes fewer than six but also in larger numbers), large, light-brownish café-au-lait spots with irregular margins (as those shown in Fig. 1) seen in children, irrespective of their age, could be a marker of or could raise the suspicion of SNF. Cutaneous neurofibromas. Cutaneous neurofibromas were recorded in 24% of SNF vs 37% of MNFSR patients. Thus, whatever group we consider, these figures are lower than classical NF1 where multiple dermal neurofibromas affect more than 90% of affected individuals. Notably, cutaneous neurofibromas were not seen in the group of SNF patients followed at our Institutions, irrespective of their ages.
Skin manifestations
The spectrum of skin manifestations in SNF may consist in café-au-lait spots and/or freckling in specific places, and cutaneous neurofibromas (Tables S1 and S2). Pigmentary manifestations: café-au-lait spots and freckling. The typical café-au-lait spots in SNF
have been recorded in 67% of the analysed cohort (vs 56% in MNFSR); these were multiple (i.e. >6) in 60% (SNF) vs 83% (MNFSR). Freckling in specific places (mostly distributed over the axillae) was reported in 18% (vs 16% in MNFSR). These data indicate that café-au-lait spots in SNF can be less frequent and freckling much less frequent than in classical NF1, thus generating difficulties in diagnosis unless the involvement of peripheral nervous system is apparent (17). We could not record detailed information regarding the shape and colour of café-au-lait spots in most published reports on SNF (Tables S1 and S2); the description of ‘light-brown’ cafè-au-lait spots was recorded only once previously (2) and only one illustration of a typical skin pigmentary lesion has been published previously (14). In our personal experience (16, 19) (Tables 1 and S4) the café-au-lait macules, within the context of SNF, were paler in colour, larger in size and with less regular margins as compared with the typical NF1 pigmentary
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Lisch nodules
Lisch nodules were seen in 24% of SNF patients and in 33% of MNFSR patients, and if present most patients in either cohort had few Lisch nodules. Of interest, we recorded iris nodules in one of nine patients seen at our institutions (16, 19) (Tables 1 and S4). These figures are low as compared with patients with classical NF1 (approximately 90%) and could reflect a localized phenotype, which is the hallmark of SNF. Lisch nodules are seen in less that 10% of patients with mosaic/segmental NF1 (23, 24, 28, 29). Other NF1-associated features and complications Skeletal involvement. Bone involvement (e.g. long
bone dysplasia, vertebral or chest anomalies, cystic-like lesions in long bones), which is typically encountered in NF1 (30), has been reported only occasionally in SNF. Of interest, even though neurofibromas involve every spinal nerve root, only 18% of SNF patients developed scoliosis, of mild to moderate degree (i.e. with a curvature of 0.5. Overall, the analysis of phenotype in the 16 SNF patients harbouring missense mutations recorded café-au-lait spots in 62% (with only 2/16 patients having >6 macules), freckling and Lisch nodules in 12%, cutaneous neurofibromas in 43% (with only 1/16 having multiple skin tumours), and subcutaneous neurofibromas in 25%. A hallmark of NF1 is the high phenotypic variability between affected individuals, even among members of the same family. The only phenotype–genotype correlations described so far in NF1 are large deletions encompassing the whole NF1 gene (31, 32) and the 3-bp deletion of exon 22. One of the striking characteristics of SNF is the overall paucity of associated NF1-features and in particular the absence or low number of cutaneous neurofibromas (Tables S1, S2 and S4), which is in contrast with the high number of early-onset cutaneous neurofibromas seen in patients with the NF1 micro-deletion syndrome (30, 31). Even though the numbers hereby analysed (Table S5) are too few to draw genotype–phenotype correlations we compared SNF vs severe classical NF1 (i.e. NF1 gene microdeletion syndrome) by outlining the phenotype in the SNF patients who had NF1 gene deletions (Table S7); interestingly, these four SNF deletion patients had few NF1-associated features, including few cutaneous neurofibromas. It must be noted, however, that one patient in this group had dysmorphic features (18) [never encountered in SNF (Tables S1 and S2)] and an additional patient died of MPNST complications (11) (Table S7). The SNF phenotype might derive from cooperation between the NF1 gene and other factors: e.g. modifier genes. Some evidences seem to support such premises including the identification of: (i) similar NF1 gene mutations in both classical NF1 and SNF (Tables S5 and S6), (ii) SNF patients belonging to families with classical NF1 who harboured identical NF1 gene abnormalities (Table S1), and (iii) families with either SNF and MNFSR affected members all harbouring identical NF1 gene abnormalities (Tables S1 and S2). Further genetic studies are needed to clarify these unsolved questions. Natural history of disease First appearance of spinal neurofibromas
Spinal neurofibromas, according to our experience (Tables 1 and S4), usually appear early in life (in some cases as early as the first years of life; Tables S1 and S2) (4, 9, 14, 16). Their detection rate, however, can be low at young ages, as most (if not all) of these lesions can be
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initially asymptomatic, becoming symptomatic later in life (e.g. at or after age 20 or 30 or up to 50 years of age; Table S1), or they can be asymptomatic until older ages. When they are symptomatic early in life, this is usually secondary to massive involvement of both spinal roots and major nerve trunks (4, 9, 14). Age at onset of spinal neurofibromas in SNF ranged from 4 to 52 years and was lower in males (mean = 16; mode = 15) vs females (mean = 26; mode = 24) (Table S1). Interestingly, age at onset of spinal neurofibromas in MNFSR had a wider range from 2 to 60.5 and was higher than SNF, irrespective of gender (males: mean = 31; mode = 31; females: mean = 33.5; mode = 30) (Table S3), thus reflecting the true onset of typical neurofibromas in classical NF1. The initial localization was in one segment (by literature review) or at multiple sites (by literature review and by personal experience) and the lesions could appear as simple nerve thickening (in some recorded cases nerve thickening of all the spinal roots persisted until older ages; Table S1) or be tiny. Over the years the nodules progressed and multiplied over the affected and adjacent root segments and nerve trunks. The diagnosis of SNF, unless the suspected individual belonged to SNF or NF1 families, was usually made by chance because of (Table S1): (i) the appearance of a subcutaneous nodule (a ‘lump’), (ii) the removal of a nodule, which turned out to be a neurofibroma or a PNF, (iii) the presence of café-au-lait spots, (iv) the appearance/progression of pain or motor signs, (v) the occasional detection of NF1-like bone dysplasia, or (vi) the occasional detection of nodules at MRI because of radiological investigation for other reasons. Sometimes, despite the appearance of signs, which should have raised the suspect of a form of neurofibromatosis (e.g. café-au-lait spots, histologically proven neurofibromas), the diagnosis was delayed until the appearance of more severe signs/symptoms (e.g. large neurofibromas, paraparesis) (Table S1). Signs/symptoms at onset and progression of disease
Among the most frequent neurological signs/symptoms recorded at onset or bringing affected individuals to their first referral are sensory deficits (neuropathy), and motor signs (e.g. weakness or limb paresis/paralysis). These can be accompanied by (electric-shock) pain. Due to the predominantly extra-axial location of neurofibromas, an extensive tumour burden may be present in asymptomatic SNF patients. Symptomatic and asymptomatic SNF patients may have cutaneous or, more often, subcutaneous ‘lumps’ (and/or NF1 pigmentary anomalies) noticed earlier than the appearance of first neurological manifestations. Usually, signs and symptoms, relentlessly progress, with the appearance of increasing pain, gait disturbances and paraparesis or, eventually, signs of moderate to severe cord compression due to enlargement of the paraspinal masses. Neurosurgical outcomes may be improved by pre-symptomatic intervention in affected individuals.
Spinal neurofibromatosis We recorded no symptomatology progression in some of the affected individuals seen at our institution (Tables 1 and S4). Recommendations for diagnosis and management and differential diagnosis
The diagnosis of SNF relies on visualization of neurofibromas on imaging (i.e. MRI) involving every nerve root, bilaterally. Irrespective to age, when a given individual present with multiple neurofibromas of many spinal segments, serial imaging studies should be obtained so as to get (eventual) later confirmation of (bilateral) involvement of all spinal roots. It cannot be excluded a priori that MNFSR can transition to SNF over time. Thus, unless the SNF phenotype is overt from the first imaging study, serial imaging studies should always be obtained to confirm diagnosis: serial studies would serve for follow-up in confirmed cases. Other NF1 stigmata may be present, but are often lacking. Café-au-lait spot to a lesser extent than classical NF1, and intertriginous freckling, Lisch nodules and cutaneous neurofibromas are seen in a minority of cases. Thus, the affected status of SNF could be assigned irrespective of the presence or lack of NF1-associated manifestations or complications (33, 34), but requires imaging of the spine. The presence of attenuated NF1 manifestations without cognitive impairment or lack of cutaneous neurofibromas in a pubertal toddler or an older adolescent with NF1 may lead one to perform whole spinal imaging to detect SNF. One important issue is that many of the affected SNF (but also MNFSR) patients have endured several years of symptoms before the diagnosis was suspected: this may be unavoidable if no stigmata of NF1 are evident (17). MRI of the spine, limbs and abdomen (e.g. full body MRI) is pivotal for visualization of the tumours. Brain MRI and ophthalmologic evaluation should be obtained in each patient. Electromyography and nerve conduction velocities could confirm the peripheral nervous system damage and may help in localizing the affected site and the extension of involvement. There is a possibility that someone is referred with a few café-au-lait spots or a few cutaneous (or subcutaneous) neurofibromas or with isolated Lisch nodules. In these cases attention should be paid to the specific features of the pigmentary anomalies and a biopsy might be indicated to determine if a tumour was a neurofibroma, schwannoma or something else. Other specific NF1 features/complications should be carefully checked clinically or by other means (e.g. ultrasonography, x-ray) as dictated by clinical findings. The usual clinical assessment in childhood (32) cannot be relied upon to confirm or refute the diagnosis of SNF (17). We usually recommend MRI of the whole spine and brain when the suspicion of a related form of NF1 (or NF2) is raised (see below). Visualization of tumours on MRI involving every nerve root would lead to an assessment for other manifestations of NF1 or NF2. Likewise, absence of pain would steer one away from the diagnosis of schwannomatosis. Due to the predominantly extra-axial location
of neurofibromas, an extensive tumour burden may be present in asymptomatic SNF patients. Molecular NF1 gene testing should be always obtained. The apparent higher relative-risk for SNF to harbour missense mutations needs future confirmation by larger studies. Neurofibromas in SNF affect massively the spine and their multiplicity and progression, which ultimately leave no intact spinal segment, is important in that these features help in differentiating SNF from similar conditions including 33: (i) classical NF1, whose affected patients have usually a (even massive but) limited number of nerve sheath tumours scattered at multiple (but not all) levels of the spine (unilaterally or bilaterally) (21, 22). The presence/absence of typical NF1 stigmata could also help in differentiating the two phenotypes; (ii) ‘mosaic/segmental NF1’, in which patients have either multiple neurofibromas in localized (small or large) segments of their body or extensive PNFs involving localized regions of their body (23, 24); (iii) classical NF2, whose tumours are schwannomas, which are isointense to neural tissue on T1-weighted images and hyperintense (usually) on T2-weighted images and enhance uniformly after intravenous administration of paramagnetic contrast. In addition to that these patients have different NF2-associated stigmata (e.g. vestibular schwannomas, meningiomas, cataract, and peripheral schwannomas) (21, 22, 26, 27); (iv) ‘multiple isolated neurofibromas’ (35), who usually do not have lesions in all the spinal roots; and (v) ‘schwannomatosis’, who usually have paraspinal nerve sheath tumours (mostly schwannomas but sometimes also some neurofibromas) or schwannomas along the major nerves of all the four limbs and thoracic region but do not (usually) manifest at any stage of the disease a massive involvement of the spinal roots as it occurs in SNF (25). The anatomical lesion (through initial MRI suspicion and later histological confirmation, when needed) will help at least in differentiating between the two major forms of neurofibromatosis (i.e. NF1 vs NF2; in this respect between SNF vs schwannomatosis, even though it must be kept in mind that, rarely, schwannomas can be recorded in the context of SNF; Table S1). The extension of the area(s) involved and the natural history of disease will help in differentiating between the NF1-related forms. It is important to keep in mind that only a minority of cases with SNF could entirely satisfy the NF1 diagnostic criteria (34); in these cases the diagnosis of SNF vs classical NF1 will be based on the presence of the hallmark of disease. Therefore, besides the true familial cases of SNF or the cases of SNF within families with classical NF1 or with MNFSR, and given the wide range of manifestations in SNF, assignment of the affected status to a sporadic case can be achieved on the basis of the solely presence of neurofibromas of all the 38 spinal roots. A new term (MNFSR) introduced in this study could provide an avenue for clinical judgement and the expectation that every spinal nerve root is involved in SNF might be a bit restrictive. However, individuals with multiple spinal root tumours and few café-au-lait spots, without post-pubertal cutaneous neurofibromas,
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Ruggieri et al. and without cognitive impairment should be viewed differently than individuals with classical NF1. Supporting Information Additional supporting information may be found in the online version of this article at the publisher’s web-site.
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