:Acta . . Ndurochlrurglca
ActaNeurochir(Wien) (1990) 107:56-60
9 by Spfinger-Verlag 1990
Primary Intraosseous Meningiomas of the Skull Base M. Ammirati*, Sh. Mirzai, and M. Samii Neurosurgical Clinic, Krankenhaus Nordstadt, Hannover, Federal Republic of Germany
Summary Four cases of primary intraosseous meningiomas were seen among 373 cases of intracranial meningiomas operated upon in the Neurosurgical Clinic of the Krankenhaus Nordstadt, Hannover, FRG between January 1978 and December 1988. These 4 cases represent 1% of all intracranial meningiomas. Patients' age ranged between 21 and 66 years; 2 were females and 2 males. Presenting symptoms were localized orbital pain in 1 case, protrusion of the eye in 1 patient, pain in the orbit and forehead and protrusion of the eye in ! patient, and peripheral facial palsy in 1 case. Symptoms lasted between 3 and 10 years. Two tumours were in the bony orbit, 1 in the bony orbit and in the frontal bone and 1 in the temporal bone. All tumours were surgically completely removed. All patients are clinically and computer tomography free of tumour 1 to 8 years after the operation.
Keywords: Ectopic; intraosseous; meningioma; skull base.
Introduction Meningiomas are the most common benign intrac r a n i a l t u m o u r s r e p r e s e n t i n g a p p r o x i m a t e l y 13 to 19 % o f all p r i m a r y i n t r a c r a n i a l n e o p l a s m s 35, 43 W h i l e b o n y i n v a s i o n by i n t r a c r a n i a l m e n i n g i o m a is a well r e c o g nized phenomenon, primary intraosseous growth of a m e n i n g i o m a is a r a r e o c c u r r e n c e 2, 4 W e r e p o r t 4 cases o f p r i m a r y i n t r a o s s e o u s m e n i n giomas collected from among
373 i n t r a c r a n i a l m e n -
for left peripheral facial palsy. Computerized Tomography (CT) scans showed a lesion in the medial anterior portion of the left pyramid with a soft tissue density component (Fig. I, left and center). Magnetic Resonance Imaging confirmed the CT findings (Fig. 1, right). EMG demonstrated complete denervation of the muscles innervated by the left facial nerve. At surgery, via a posterior subtemporal approach, an intraosseous tumour involving the medial anterior portion of the left pyramid and extending into the middle ear was removed, together with a small extradural-extraosseous portion of the tumour abuting on the basal temporal dura which was also resected. Postoperatively the patient was deaf. Pathology showed a meningioma. Postoperative CT scans showed no remnants of the tumour (Fig. 2). The complete facial palsy was treated 8 months later with a temporalis muscle transfer. The patient remains disease free 13 months postoperatively.
Case #2 This 66 year old female had a progressive protrusion of the right eye of 10 years duration. Neurological examination was normal and physical examination showed a 4 mm exophtalmos on the right. CT scans showed a hyperostotic tumour involving the lateral and superior orbital wall on the right side (Fig. 3). A frontotemporal craniotomy was performed and an intraosseous tumour involving the orbital roof without invasion of the orbital cavity or of the frontotemporal dura was completely removed. Acrylic was used to reconstruct the bony defect. Histology showed a meningioma. The postoperative course was uneventful and the patient was discharged home neurologically intact. Postoperative CT scans showed complete tumour removal.
i n g i o m a s o p e r a t e d u p o n in t h e N e u r o s u r g i c a l C l i n i c o f the Krankenhaus Nordstadt, Hannover, FRG between 1978 a n d 1988.
Case Reports Case #1 This 21 year old male had been complaining of left sided facial weakness for the past 9 years. Neurological examination was positive * Dr. Mario Ammirati was a recipient of a fellowship of the Alexander yon Humboldt Foundation, Bonn, Federal Republic of Germany.
Case #3 This 55 year old female complained of pain and protrusion of the right eye as well as of occasional double vision when looking toward the left that had been present for the past 3 years. Neurological examination was negative. Physical examination showed a 2 mm right sided exophtalmos and swelling of the right upper eyelid. CT scans showed an intraosseous tumour involving the lateral and superior wall of the orbit and the anterior portion of the temporal squama on the right (Fig. 4). Through a frontotemporal craniotomy an intraosseous tumour involving the greater and lesser wing of the sphenoid in correspondence of the lateral and superior orbital wall and of the anterior part of the temporal squama was completely
M, Ammirati etaL: Primary lntraosseous Meningiomas of ~he Skull Base
57
Fig. I. CT scans show a bony lesion in the anterior aspect of the left pyramis (left). A soft tissue density mass protruding in the middle fossa from the anterior pyramis is well demonstrated using bone window (center). MRI scan, T2 weighted, shows an hyperintense lesion in the left pyramis (right)
Fig. 2. Postoperative CT scans show completed turnout removal. The tumour caviIy is best appreciated using bone window
Fig. 3. CT scans show an hyperostotic tumour of the lateral and superior orbital wall (left and right)
Fig. 4. CT scans without (left) and with (right) bone window show an hyperostotic turnout involving the greater and lesser wing of the sphenoid on the right side
58
M. Ammirati etal.: Primary Intraosseous Meningiomas of the Skull Base
Fig. 5. CT scans demonstrated an hyperostotic tumour of the lower frontal and of the sphenoid bone (left, center and right)
removed. The frontotemporal dura as well as the orbital cavity were free of tumour. The bony defect was repaired using acrylic.Histology showed a meningionra. Postoperative course was uncomplicated and postoperative CT scans showed no evidence of residual tumour. Case #4
This 49 year old male sought medical attention because of pain in the right eye and right lower forehead for the past 6 years. Neurological examination was negative. CT scans showed an intraosseous tumour involving the lateral and superior orbital wall as well as the right lower frontal bone in correspondence of the frontal sinus (Fig. 5). Through a right frontotemporal craniotomy an intraosseous tumour involving the right frontal sinus, the greater and lesser wing of the sphenoid at the level of the lateral and of the superior orbital wall and of the temporal squama was totally removed. The skull was reconstructed using acrylic. Histology showed a meningioma. Postoperative course was uneventful. Control CT scans, 8 years after the operation, showed no tumour recurrence.
Discussion Meningiomas primarily limited to the bone (intraosseous or intradipolic meningiomas) are rarely seen 21, 41. Since the term meningioma was introduced and popularized by Cushing in 1922 8 there have been sporadic reports of intraosseous meningiomas involving the temporal bone 3, 13, 23, 26, 29, the bony orbit 10, ~9, 33, 34, 42 and other areas of the skull 2, 24, 37, 31, 42. These tumour are extremely rare and no age group is spared: a case was indeed reported in a 7 m o n t h old child s The frequency of intraosseous meningioma is not exactly known. Cushing in his classic m o n o g r a p h on meningiomas did not mention any such case 9 and the frequency of primary intraosseous meningiomas has not been reported in any major neurosurgical series. In our series primary intraosseous meningiomas accounted for 1% (4 out of 373) of intracranial meningiomas; it is interesting that all our cases originated in the skull base, representing 1.8% (4 out of 221) of all skull base meningiomas. In the course of their growth
intraosseous meningiomas m a y eventually thin out and break through the bone (just as subdural meningiomas invade bone by breaking through the dura), adding an extraosseous portion to their main intraosseous tumour and m a y eventually locally infiltrate the dura as shown by our case #1. Their primary intraosseous origin may be inferred from the location of the main tumour mass and from the very limited dural invasion 2, 42. Meningiomas are thought to arise from arachnoidal cap cells and are usually located in the subdural space 17, 40; most often they are, even though at times they are not, attached to the dura 28. Occasionally meningiomas m a y be located exclusively in the substance of the dura or on its outer surface 18. Those meningiomas not associated with dural or subdural meningiomas and not representing metastases of such tumours have to be considered ectopic meningiomas and primary intraosseous meningioma are a subset of these ectopic meningiomas. Ectopic meningiomas are very rare and were first described by Winkler, who in 1904 described a case of a paravertebral subcutaneous meningioma in a 10 year old girl 46. Since then, in addition to the intraosseous localization they have been described in the nose 32, oral cavity 38, parapharyngeal space la, 36, 44 paranasal sinuses is, 2o, 28, 32, salivary gland 12, 47, neck 14, 27, 35, skin and subcutaneous tissue tl, 12, 22, lungs 6, 16, 4s and abdomen as. Several theories have been proposed to explain the origin of ectopic meningiomas. Aoyagi and K y u n o as well as Cushing demonstrated arachnoidal cells accompanying certain cranial nerves at their sites of exit through the skull foramina 1,8. Others postulated the presence of similar cells in the arterial sheaths where vessels pierce the skull 32 or in the periosteum 7'48. These arachnoid cells could explain the origin of those ectopic meningiomas found in relation to cranial and spinal nerves47. Ectopic arachnoidal cells inclusions have been
M. Ammirati etal.: Primary Intraosseous Meningiomas of the Skull Base
invoked to explain the origin of the other ectopic meningiomas 22, 26, 28. At least for temporal bone meningiomas it seems reasonable that the arachnoidal cell clusters found in autopsy specimens of patients without meningiomas, at the level of the internal auditory meatus, jugular foramen, at the geniculate ganglion, at the roof of the Eustachian tube or in association with the greater and lesser superficial petrosal nerve, may represent the cells of origin of temporal bone meningiomas 13, 26
Intraosseous meningiomas usually present with localized pain and/or exostosis. Those tumours located in the temporal bone may present with hearing loss or peripheral facial nerve palsy as shown by our case #1, Skull x-rays usually show an osteoblastic reaction 2, 37, 42 even though osteolytic lesions have been reported 24, 30,39. CT scans as well as brain scans have been reported to be normal while bone scanning using 99 M-Tc diphosphate scan has been reported to be very sensitive 25 CT scan was positive in all of our cases demonstrating very adequately the bony lesions. We believe that a thorough CT examination is essential in the full assessment of all extopic meningiomas in order to detect possible connections with the dura or with the subdurat compartment both at the cranial or spinaI level; cases have been reported where an intracranial connection of an "ectopic meningioma" was initially missed 29 The differential diagnosis include osteoma and solitary osteoblastic metastasis for osteoblastic lesions and metastatic carcinoma, myeloma, eosinophilic granuloma, fibrous dyspasia and osteogenic sarcoma for the rare intra-osseous meningioma presenting as an osteolyric area 30, 4l. Tympanic glomus and epidermoid turnouts must also be included in the differential diagnosis when evaluating temporal bone lesions. Treatment of intraosseous meningioma consists of total tumour removal, if feasible en bloc, followed by cranioplasty if indicated. References I. Aoyagi T, Kyuno K (1912) Ober die endothelialen Zellzapfen in der Dura mater cerebri und ihre Lokalisation in derselben, nebst ihrer Beziehung zur Geschwulstbildungin der Dura mater. Neuroglia 11: l 2. Azar-Kia B, Sarwar M, Allan Marc J, Schechter MM ([974) lntraosseous meningioma. Neuroradiology 6:246-253 3. Buehrle R, Goodman WS, Wortzman G (1972) Meningioma of the temporal bone. Can j Otolaryngol 1:16-20 4. Challa RW, Markesbery WP (1985) Meningiomas, Pathology. In: Wilkins RLH, Rengachary SS (eds) Neurosurgery, McGraw Hill, New York, pp 1613-1622
59
5. Choux M, Gomiez A, Choux R, Vigouroux RP 81975) Diagnostic and therapeutic problems concerning tumours of the vault. Child's brain 1:207-216 6. Chumas JC, Lorelle CA (1982) Pulmonary memng/oma, A lightand electron-microscopic study. Am J Surg Pathol 6:795-801 7. Craig WM, Gogela LJ (1949) Intraorbital meningiomas, a clinicopathologic study. Am J Ophthalmol 32:1663-1680 8. Cushing H (1982) Meningiomas (dural endotheliomas), their source and favoured seats of origin. Brain 45:282-316 9. Cushing H, Eisenhardt L (1962) Meningiomas, their classification, regional behavior, life history, and surgical end results, (ed) 2. New York, Hafner Publishing Company 10. DahImann J (1951) Osteoblastisches Meningiom im Orbitaldach. Fortschr Rontgenstr 74:306-315 11. Daugaard S (1983) Ectopicmeningioma ofafinger. JNeurosurg 58: 778-780, 1983. 12. Farr HW, Gray GF, Vrana M, Panio (1973) Extracranial meningioma. J Surg Oncol 5:411-420 13. Guzowski J, Paparella M, Nageswara K, Hoshin T (1986) Meningiomas of the temporal bone. Laryngoscope 86:114I-1146 14. Hallgrimssom J, Bjornsson A, Gudmundsson G (1970) Meningioma of the neck, Case report. J Neurosurg 32:695-699 15. Ho K-L (1980~ Primary mm~ingioma of the ~asa~ cavit'j and paranasal sinuses. Cancer 46:1442-1447 I6. Kemnitz P. Spormann H, Heinrich P (1982) Meningioma of lung, first report with light and electron microscopic findings. Ultrastruct Pathol 33:359-365 17. Kepes JJ: Presidential address (1986) The histopathology ofmeningiomas, a reflection of origins and expected behavior? J Neuropath Exp Neurol 45:95-107 18. Keps JJ (I 982) Meningiomas: biology, pathology and differential diagnosis. Masson, New York 19. Kobayashi S, Kyoshima K, Nakagawa F, Sugita K, Maruyama Y (1980) Diploic meningioma of the orbital roof. Surg Neurol 13: 277-28l 20. Lee KF, Suh JH, Lee YE, Berry RG (1979) Meningioma of the paranasal sinuses. Neuroradiology 17:165-171 21. Lee W, Tu Y, Liu M (1988) Primary intraosseous malignant meningioma of the skull, Case report. Neurosurgery 23:505-508 22. Lopez DA, Silvers DN, Helwig EB (1974) Cutaneous meningiomas - a clinicopathologic study. Cancer 34:728-744 23. Maniglia AJ (1978) Intra and extracraniaI meningiomas involving the temporal bone. Laryngoscope [Suppl] 12 24. Mc Whorter JM, Ghatak NR, Kelly DL (1976) Extracranial meningioma presenting as Iytic skull lesion. Surg Neurol 5: 223-224 25. Mc Worther (1979) Comment to Pearl GS, Takei Y, Parent AD, Boehm WM: Primary intraosseous meningioma presenting as a solitary osteolytic skull lesion. Neurosurgery 4:269-270 26. Nager GT (1964) Meningiomas involving the temporal bone, clinical and clinical and pathological aspects. C Thomas, Springfield 27. Nager GT, Heroy J, Hoeplinger M (1983) Meningiomas invading the temporal bone with extension to the neck. Am J Otolaryngol 4:297-423 28. New GB, Devine KD (1947) Neurogenic tumors of nose and throat. Arch Otolaryngol 46:163-179 29. Parisier SC, Sore PM, Shugar JMA, Marovitz WF (1978) The evaluation of middle ear meningiomas using computerized axial tomography. Laryngoscope 88:1170-1177
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M. Ammirati et al.: Primary Intraosseous Meningiomas of the Skull Base
30. Pearl GS, Takei Y, Parent AD, Boehm WM (1979) Primary intraosseous meningioma presenting as a solitary osteolytic skull lesion, Case report. Neurosurgery 4:269-270 31. Pendergrass EP, Hope JW (1953) An extracranial meningioma with no apparent intracranial source. Am J Roentgenol 70: 967-970 32. Perzin KH, Pushparaj N (1984) Nonepithelial tumors of the nasal cavity, paranasal sinuses, and nasopharynx. Cancer 54: 1860-1869 33. Pompili A, Caroli F, Cattani F, Iachetti M (1983) Intradiploic meningioma of the orbital roof. Neurosurgery 12:565-568 34. Reale F, Delfini R, Cintorino (l 978) An intradiploic meningioma of the orbital roof, Case report. Ophthalmologica 177:82-87 35. Russell DS, Rubinstein LJ (1984) Pathology of tumours of the nervous system. Edward Arnold, London 36. Shuangshoti S, Netsky MG, Slaughter Fitz-Hugh (1971) Parapharyngeal meningioma with special reference to cell of origin. Ann Otol 80:46~473 37. Siegel GT, Anderson PJ (1966) Extracalvarial meningioma, Case report. J Neurosurg 25:83-86 38. Suzuki H, Gilbert EF, Zimmerman B (1967) Primary extracranial meningioma. Arch Path 84:202-206 39. Taveras JM, Wood EH (1976) Diagnostic neuroradiology, (eds) 2. Williams & Wilkins, Baltimore, pp 1159-1168 40. Turner L (1961) The structure of arachnoid granulations with observations on their physiological and pathological significance. Ann Roy Coll Surg 29:237-264
41. Voorhies RM, Sundaresan N (1985) Tumors of the skull. In: Wilkins RH, Rengachary SS (eds) Neurosurgery. Mc Graw Hill, New York, pp 1984-1001 42. Wagman AD, Weiss EK, Riggs HE (1960) Hyperplasia of the skull associated with intraosseus meningioma in the absence of gross tumor. J Neuropath Exp Neuroi I9:111-115 43. Walker EA, Robins M, Weinfeld FD (1985) Epidemiology of brain tumors. The national survey of intracranial neoplasms. Neurology 35:219-226 44. Whicker JH, Devine KD, Mac Carty CS (1973) Diagnostic and therapeutic problems in extracranial meningiomas. Am J Surg t26:452-457 45. Wilson AJ, Ratliff JL, Lagios MD, Aguilar MJ (1979) Mediastinal meningioma. Am J Surg Path 3:557-562 46. Winkler M (1904) ~ber Psammome der Haut und des Unterhautgewebes. Virochows Arch 178:323-350 47. WolffM, Rankow RM (1971) Meningioma of the parotid gland, An insight into the pathogenesis of extracranial meningiomas. Hum Pathol 2:453-459 48. Zachariae L (1952) A case of extracranial primary meningioma. Acta Path Microbiol Scand 31:57-60
Correspondence and Reprints: Mario Ammirati, M. D., University of California, Los Angeles, Division of Neurosurgcry (74140 CHS), School of Medicine, Center for the Health Sciences, 10833 Le Conte Avenue, Los Angeles, CA 90024-1749, U.S.A.
ActaNeurochir(Wien) (1990) 107:56-60
9 by Spfinger-Verlag 1990
Primary Intraosseous Meningiomas of the Skull Base M. Ammirati*, Sh. Mirzai, and M. Samii Neurosurgical Clinic, Krankenhaus Nordstadt, Hannover, Federal Republic of Germany
Summary Four cases of primary intraosseous meningiomas were seen among 373 cases of intracranial meningiomas operated upon in the Neurosurgical Clinic of the Krankenhaus Nordstadt, Hannover, FRG between January 1978 and December 1988. These 4 cases represent 1% of all intracranial meningiomas. Patients' age ranged between 21 and 66 years; 2 were females and 2 males. Presenting symptoms were localized orbital pain in 1 case, protrusion of the eye in 1 patient, pain in the orbit and forehead and protrusion of the eye in ! patient, and peripheral facial palsy in 1 case. Symptoms lasted between 3 and 10 years. Two tumours were in the bony orbit, 1 in the bony orbit and in the frontal bone and 1 in the temporal bone. All tumours were surgically completely removed. All patients are clinically and computer tomography free of tumour 1 to 8 years after the operation.
Keywords: Ectopic; intraosseous; meningioma; skull base.
Introduction Meningiomas are the most common benign intrac r a n i a l t u m o u r s r e p r e s e n t i n g a p p r o x i m a t e l y 13 to 19 % o f all p r i m a r y i n t r a c r a n i a l n e o p l a s m s 35, 43 W h i l e b o n y i n v a s i o n by i n t r a c r a n i a l m e n i n g i o m a is a well r e c o g nized phenomenon, primary intraosseous growth of a m e n i n g i o m a is a r a r e o c c u r r e n c e 2, 4 W e r e p o r t 4 cases o f p r i m a r y i n t r a o s s e o u s m e n i n giomas collected from among
373 i n t r a c r a n i a l m e n -
for left peripheral facial palsy. Computerized Tomography (CT) scans showed a lesion in the medial anterior portion of the left pyramid with a soft tissue density component (Fig. I, left and center). Magnetic Resonance Imaging confirmed the CT findings (Fig. 1, right). EMG demonstrated complete denervation of the muscles innervated by the left facial nerve. At surgery, via a posterior subtemporal approach, an intraosseous tumour involving the medial anterior portion of the left pyramid and extending into the middle ear was removed, together with a small extradural-extraosseous portion of the tumour abuting on the basal temporal dura which was also resected. Postoperatively the patient was deaf. Pathology showed a meningioma. Postoperative CT scans showed no remnants of the tumour (Fig. 2). The complete facial palsy was treated 8 months later with a temporalis muscle transfer. The patient remains disease free 13 months postoperatively.
Case #2 This 66 year old female had a progressive protrusion of the right eye of 10 years duration. Neurological examination was normal and physical examination showed a 4 mm exophtalmos on the right. CT scans showed a hyperostotic tumour involving the lateral and superior orbital wall on the right side (Fig. 3). A frontotemporal craniotomy was performed and an intraosseous tumour involving the orbital roof without invasion of the orbital cavity or of the frontotemporal dura was completely removed. Acrylic was used to reconstruct the bony defect. Histology showed a meningioma. The postoperative course was uneventful and the patient was discharged home neurologically intact. Postoperative CT scans showed complete tumour removal.
i n g i o m a s o p e r a t e d u p o n in t h e N e u r o s u r g i c a l C l i n i c o f the Krankenhaus Nordstadt, Hannover, FRG between 1978 a n d 1988.
Case Reports Case #1 This 21 year old male had been complaining of left sided facial weakness for the past 9 years. Neurological examination was positive * Dr. Mario Ammirati was a recipient of a fellowship of the Alexander yon Humboldt Foundation, Bonn, Federal Republic of Germany.
Case #3 This 55 year old female complained of pain and protrusion of the right eye as well as of occasional double vision when looking toward the left that had been present for the past 3 years. Neurological examination was negative. Physical examination showed a 2 mm right sided exophtalmos and swelling of the right upper eyelid. CT scans showed an intraosseous tumour involving the lateral and superior wall of the orbit and the anterior portion of the temporal squama on the right (Fig. 4). Through a frontotemporal craniotomy an intraosseous tumour involving the greater and lesser wing of the sphenoid in correspondence of the lateral and superior orbital wall and of the anterior part of the temporal squama was completely
M, Ammirati etaL: Primary lntraosseous Meningiomas of ~he Skull Base
57
Fig. I. CT scans show a bony lesion in the anterior aspect of the left pyramis (left). A soft tissue density mass protruding in the middle fossa from the anterior pyramis is well demonstrated using bone window (center). MRI scan, T2 weighted, shows an hyperintense lesion in the left pyramis (right)
Fig. 2. Postoperative CT scans show completed turnout removal. The tumour caviIy is best appreciated using bone window
Fig. 3. CT scans show an hyperostotic tumour of the lateral and superior orbital wall (left and right)
Fig. 4. CT scans without (left) and with (right) bone window show an hyperostotic turnout involving the greater and lesser wing of the sphenoid on the right side
58
M. Ammirati etal.: Primary Intraosseous Meningiomas of the Skull Base
Fig. 5. CT scans demonstrated an hyperostotic tumour of the lower frontal and of the sphenoid bone (left, center and right)
removed. The frontotemporal dura as well as the orbital cavity were free of tumour. The bony defect was repaired using acrylic.Histology showed a meningionra. Postoperative course was uncomplicated and postoperative CT scans showed no evidence of residual tumour. Case #4
This 49 year old male sought medical attention because of pain in the right eye and right lower forehead for the past 6 years. Neurological examination was negative. CT scans showed an intraosseous tumour involving the lateral and superior orbital wall as well as the right lower frontal bone in correspondence of the frontal sinus (Fig. 5). Through a right frontotemporal craniotomy an intraosseous tumour involving the right frontal sinus, the greater and lesser wing of the sphenoid at the level of the lateral and of the superior orbital wall and of the temporal squama was totally removed. The skull was reconstructed using acrylic. Histology showed a meningioma. Postoperative course was uneventful. Control CT scans, 8 years after the operation, showed no tumour recurrence.
Discussion Meningiomas primarily limited to the bone (intraosseous or intradipolic meningiomas) are rarely seen 21, 41. Since the term meningioma was introduced and popularized by Cushing in 1922 8 there have been sporadic reports of intraosseous meningiomas involving the temporal bone 3, 13, 23, 26, 29, the bony orbit 10, ~9, 33, 34, 42 and other areas of the skull 2, 24, 37, 31, 42. These tumour are extremely rare and no age group is spared: a case was indeed reported in a 7 m o n t h old child s The frequency of intraosseous meningioma is not exactly known. Cushing in his classic m o n o g r a p h on meningiomas did not mention any such case 9 and the frequency of primary intraosseous meningiomas has not been reported in any major neurosurgical series. In our series primary intraosseous meningiomas accounted for 1% (4 out of 373) of intracranial meningiomas; it is interesting that all our cases originated in the skull base, representing 1.8% (4 out of 221) of all skull base meningiomas. In the course of their growth
intraosseous meningiomas m a y eventually thin out and break through the bone (just as subdural meningiomas invade bone by breaking through the dura), adding an extraosseous portion to their main intraosseous tumour and m a y eventually locally infiltrate the dura as shown by our case #1. Their primary intraosseous origin may be inferred from the location of the main tumour mass and from the very limited dural invasion 2, 42. Meningiomas are thought to arise from arachnoidal cap cells and are usually located in the subdural space 17, 40; most often they are, even though at times they are not, attached to the dura 28. Occasionally meningiomas m a y be located exclusively in the substance of the dura or on its outer surface 18. Those meningiomas not associated with dural or subdural meningiomas and not representing metastases of such tumours have to be considered ectopic meningiomas and primary intraosseous meningioma are a subset of these ectopic meningiomas. Ectopic meningiomas are very rare and were first described by Winkler, who in 1904 described a case of a paravertebral subcutaneous meningioma in a 10 year old girl 46. Since then, in addition to the intraosseous localization they have been described in the nose 32, oral cavity 38, parapharyngeal space la, 36, 44 paranasal sinuses is, 2o, 28, 32, salivary gland 12, 47, neck 14, 27, 35, skin and subcutaneous tissue tl, 12, 22, lungs 6, 16, 4s and abdomen as. Several theories have been proposed to explain the origin of ectopic meningiomas. Aoyagi and K y u n o as well as Cushing demonstrated arachnoidal cells accompanying certain cranial nerves at their sites of exit through the skull foramina 1,8. Others postulated the presence of similar cells in the arterial sheaths where vessels pierce the skull 32 or in the periosteum 7'48. These arachnoid cells could explain the origin of those ectopic meningiomas found in relation to cranial and spinal nerves47. Ectopic arachnoidal cells inclusions have been
M. Ammirati etal.: Primary Intraosseous Meningiomas of the Skull Base
invoked to explain the origin of the other ectopic meningiomas 22, 26, 28. At least for temporal bone meningiomas it seems reasonable that the arachnoidal cell clusters found in autopsy specimens of patients without meningiomas, at the level of the internal auditory meatus, jugular foramen, at the geniculate ganglion, at the roof of the Eustachian tube or in association with the greater and lesser superficial petrosal nerve, may represent the cells of origin of temporal bone meningiomas 13, 26
Intraosseous meningiomas usually present with localized pain and/or exostosis. Those tumours located in the temporal bone may present with hearing loss or peripheral facial nerve palsy as shown by our case #1, Skull x-rays usually show an osteoblastic reaction 2, 37, 42 even though osteolytic lesions have been reported 24, 30,39. CT scans as well as brain scans have been reported to be normal while bone scanning using 99 M-Tc diphosphate scan has been reported to be very sensitive 25 CT scan was positive in all of our cases demonstrating very adequately the bony lesions. We believe that a thorough CT examination is essential in the full assessment of all extopic meningiomas in order to detect possible connections with the dura or with the subdurat compartment both at the cranial or spinaI level; cases have been reported where an intracranial connection of an "ectopic meningioma" was initially missed 29 The differential diagnosis include osteoma and solitary osteoblastic metastasis for osteoblastic lesions and metastatic carcinoma, myeloma, eosinophilic granuloma, fibrous dyspasia and osteogenic sarcoma for the rare intra-osseous meningioma presenting as an osteolyric area 30, 4l. Tympanic glomus and epidermoid turnouts must also be included in the differential diagnosis when evaluating temporal bone lesions. Treatment of intraosseous meningioma consists of total tumour removal, if feasible en bloc, followed by cranioplasty if indicated. References I. Aoyagi T, Kyuno K (1912) Ober die endothelialen Zellzapfen in der Dura mater cerebri und ihre Lokalisation in derselben, nebst ihrer Beziehung zur Geschwulstbildungin der Dura mater. Neuroglia 11: l 2. Azar-Kia B, Sarwar M, Allan Marc J, Schechter MM ([974) lntraosseous meningioma. Neuroradiology 6:246-253 3. Buehrle R, Goodman WS, Wortzman G (1972) Meningioma of the temporal bone. Can j Otolaryngol 1:16-20 4. Challa RW, Markesbery WP (1985) Meningiomas, Pathology. In: Wilkins RLH, Rengachary SS (eds) Neurosurgery, McGraw Hill, New York, pp 1613-1622
59
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M. Ammirati et al.: Primary Intraosseous Meningiomas of the Skull Base
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Correspondence and Reprints: Mario Ammirati, M. D., University of California, Los Angeles, Division of Neurosurgcry (74140 CHS), School of Medicine, Center for the Health Sciences, 10833 Le Conte Avenue, Los Angeles, CA 90024-1749, U.S.A.
