J Neurosurg 48:470-474, 1978

Intracranial extracerebral brain heterotopia Case report

TOHRU MARUBAYASHI, M . D . , AND YASUHIKO MATSUKADO, M . D .

Department of Neurosurgery, Kumamoto University Medical School, Kumamoto, Japan ~" The authors describe a case of intracranial heterotopic brain located on the medial one-third of the left sphenoid ridge, and enveloped in a huge cystic cavity. The heterotopic brain was resected successfully with satisfactory clinical results. The resected brain was 8 • 4 • 3 cm in diameter, of 7 or 8 months gestational age, and consisted of cerebrum, brain stem, and cerebellum. Anatomical and cytoarchitectural findings of the heterotopic brain are presented. KEy W o R o s hydrocephalus

9 congenital abnormality

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INCE the case reported by Wolbach 14 in 1907, various cases of heterotopia within the central nervous system have been presented. 1-s's-ll In these reports, the heterotopic brain was included within the d u r a 5 or the occipital s c a l p ? The case presented here is particularly interesting because the heterotopic tissue, consisting of cerebrum, brain stem, and cerebellum, was found in the intracranial extracerebral space together with normal brain. Case Report

This 27-day-old baby boy was referred to our department for evaluation of progressive enlargement of the head. H e was delivered at full term; his weight was 3520 gm, height 50.6 cm, and head circumference 39.6 cm. He was placed under careful observation, and his head showed progressive enlargement, 40 cm

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9 heterotopic brain

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at 10 days, 41 cm at 17 days, and 42 cm at 20 days. The fontanels were bulging markedly. Examination. On admission, his physical d e v e l o p m e n t was n o r m a l except for a markedly enlarged head. The head circumference was 42.6 cm; the anterior fontanel measured 3.8 • 3.6 cm in diameter and was tense. The skull was asymmetrical with bulging of the left frontotemporal bone. There were no neurological deficits nor anomalies of the body. Routine laboratory tests were within normal limits. Karyotype was 46 XY. A plain skull film showed widely separated sutures and enlargement of the left cranial vault, which was transilluminated. Pneumoencephalogram showed displacement of the lateral ventricles toward the right, more prominently in the anterior part. Operation. When the infant was 38 days old, a left frontotemporal craniotomy was performed, with a free bone flap. After skin

J. Neurosurg. / Volume 48 / March, 1978

Intracranial extracerebral brain heterotopia

FIG. 1. Schematic illustration of the heterotopic brain and surrounding cyst (dotted line). Inset: Operative view of the heterotopic brain after the removal of the cyst membrane. A = frontal lobe; T = tentorium cerebelli; F = falx; M = middle fossa; b = brain stem of the heterotopic brain; c = cerebrum of the heterotopic brain. incision and reflection of the dura, a thin membrane appeared underneath and was moderately adherent to the dura; a clear fluid was visualized through the membrane. Incision into the cystic membrane showed that the cavity was divided into two compartments by a septal membrane (Fig. 1). The fluid in the cystic cavities was identical with cerebrospinal fluid. The cyst occupied the frontal and anterior temporal fossae and was attached to the occipital lobe with loose arachnoid membrane. The lateral portion of the tentorium cerebelli was well formed; the left cerebral hemisphere was displaced posteromedially, but the cerebrum appeared normal except for a defective left olfactory tract. The septal membrane, which divided the cavity, adhered to the sphenoid ridge and was connected to a solid mass (heterotopic brain) situated on the medial one-third of the sphenoid ridge (Fig. 1). The heterotopic tissue adhered loosely to the brain at the Sylvian fissure. Several small feeding arteries, originating from the left C1, Mx, and A~, supplied the heterotopic brain circulation and J. Neurosurg. / Volume 48 / March, 1978

a few small vessels drained into the Sylvian vein of the normal brain. The heterotopic brain was removed totally and the cystic membrane was stripped out, after which the brain stem, basilar artery, and upper cranial nerves were widely exposed in the enlarged tentorial incisura. Postoperative Course. In the early postoperative stage, the infant developed convulsive seizures, which were controlled by an anticonvulsant. Progressive enlargement of the head was noticed and angiogram revealed an extensive subdural fluid collection. On the 26th day after the initial operation, a subdural-peritoneal shunt was inserted. Thereafter the child did well, and follow-up study for about 2 years showed satisfactory physical development, although mentally he appeared behind for his age. Pathological Examination. The excised heterotopic brain measured 8 • 4 • 3 cm, and weighed 55 gm. It was separated into two globular portions by a narrow peduncle-like structure that measured 1.5 cm in diameter (Fig. 2 A). One of the globular parts seemed 471

T. Marubayashi and Y. Matsukado

FIG. 2. A: Ventral surface of the heterotopic brain (compare with Fig. 1). Cerebrum (c) and brain stem are connected by a peduncle-like structure (p). A cerebellum (cb) and nerve fiber resembling cranial nerve (n) are also seen. X, Y, and Z indicate orientation of three sections (B, C, and D) in sagittal planes, which are presented to show gross anatomy. Klfiver-Barrera, X 1.5.1 = dentate nucleus; 2 = ependymal canal; 3 = cranial nerve; 4 = mammillothalamic tract; 5 = red nucleus; 6--substantia nigra; 7 = neuropilogliomesenchymal dysgenesis; 8 = cerebellum; 9 = heterotopic foliar structure; 10 = olive; 11 = lateral ventricle; 12 = ependymal wall connected to cyst wall; 13 = pyramidal cells of Betz; 14 = cerebral sulcus; 15 = basal ganglia; 16 = fourth ventricle. to be cerebrum and the other appeared grossly like brain stem and cerebellum. At the tip of the lower p a r t , there were two cerebellar hemispheres with folia, but the vermis was not visible. On the basal surface, there was a structure resembling the brain stem and nerve fiber resembling cranial nerve. The cerebrum of the heterotopic brain had few convolutions. The vascular system could not be examined because of its very fine network. The heterotopic brain was fixed by 10% formaldehyde and embedded in paraffin. Multiple sagittal sections were examined histologically with H & E, PAS, P T A H , Kl~ver-Barrera, Woelke, Bodian, Holzer, and van Gieson staining. Correlation of each slice was illustrated in Fig. 2 A. Cyst m e m b r a n e consisted of connective tissue lined with e p e n d y m a l cells on the inner surface. Choroid plexus could be identified in some areas, attached to tissue corresponding 472

to ventricular wall (Fig. 2 C, 12). In the cerebrum of the heterotopic brain there were small slits with a layer of ependymal cells appearing as lateral ventricles (Fig. 2 C, 11). F o r m a t i o n of the cerebral gyri and sulci was not evident. Cytoarchitectural characteristics of the cerebral gray m a t t e r were identified in the heterotopic cerebrum, although the laminar arrangement was not obvious in some places. In the white matter, myelination was so poor that the distinction between the gray and white m a t t e r was difficult in m a n y places. Neuroglial heterotopias in the white m a t t e r were also seen. L a r g e neuronal cells resembling the p y r a m i d a l cell of Betz were demonstrated (Fig. 2 C, 13). Groups of neurons resembling the basal ganglia (Fig. 2 D, 15) were seen. Arachnoid m e m b r a n e and pia m a t e r were a b n o r m a l l y thick, and glial and neuronal elements were intermingled where the arachnoid m e m b r a n e merged into gray matter in some places. This J. Neurosurg. / Volume 48 / March, 1978

Intraeranial extracerebral brain heterotopia

FIG. 3. Photomicrographs of the heterotopic brain. A: Neuropilogliomesenchymal dysgenesis. Thickened pia-arachnoid membrane on left merges into the gray matter and becomes mixed with neuronal elements. H & E, • 20. B: Dentate nucleus of mature appearance. Cells are somewhat spherical, and incomplete folding is seen. H & E, • 50. C: Cerebellum. Stratified external granular cells, and narrow folia with fine vascularity are seen. Purkinje cells are well organized. H & E, X 20. D. Heterotopic foliar structure inside the cerebellum. Granular cells, Purkinje cells, and nerve fibers are mixed together. H & E, • 20. neuropilogliomesenchymal dysgenesis was also found in the brain stem (Figs. 2 B, D, and 3 A). In the brain stem and cerebellum, development of the cytoarchitecture was better than that of cerebrum (Fig. 2 B and Fig. 2 D). The dentate nucleus seemed to be well formed; however, it a p p e a r e d spherical and its foldings were incomplete, indicating immaturity (Fig. 3 B). Neuropilogliomesenchymal dysgenesis was also seen more frequently than in the cerebrum. The cerebellum was most m a t u r e of all, but its folia were narrow, and abundant vessels were seen in it. Thick external granular layers remained (Fig. 3 C). P u r k i n j e cells were well formed. Myelination of axons was better than that of cerebrum, but was still poor. Inside the cerebellum and in the dorsal part of the brain stem were heterotopic folial structures (Fig. 3 D) in which granular cells, mature Purkinje J. Neurosurg. / Volume 48 / March, 1978

cells, and nerve fibers were mixed together. Ependymal canals were formed near the cerebellum and distal part of the brain stem resembling a cerebral aqueduct (Fig. 2 B, 2) and fourth ventricle (Fig. 2 D, 16), but the canals did not connect. In the distal part of the brain stem, a structure like the olivary complex was noted. There were no neoplastic cells or degenerative changes. Discussion Various types of heterotopias of the central nervous system have been reported, such as subependymal cortical heterotopia of the lateral ventricle 1 or fourth ventricle, 2 subpial glial nests, a,4,9 and cerebellar heterotopia in association with trisomy. 1~ In 1969, Moriyasu, et al., 8 recorded a case of encephalochoristoma, which was found in the occipital subcutaneous tissue and was 473

T. Marubayashi and Y. Matsukado connected to the brain through the skull by callosum, cerebellar dysgenesis, and aqueducfatty tissue. Histologically, it contained well tal stenosis. 1,a Neuroradiological and surgical formed cerebral white matter and it was findings indicated that this patient had no differentiated from an occipital enceph- other anomalies in craniocerebral developalocele. Farhat and Hudson 5 recorded a rare ment. Clinical follow-up study of this child case of heterotopic brain encased in its own should be of great interest. dura, arising in the left temporoparietal lobe of a newborn infant. The case described here References is extremely unusual and we have found no 1. Bergeron RT: Radiographic demonstration of similar case reported. The heterotopic brain cortical heterotopia. Acta Radinl (Diagn) was composed of cerebrum, brain stem, and 9:135-139, 1969 cerebellum; in short, it took the form of a cen2. Billings KJ, Danziger FS: Cerebellar heterotral nervous system. topia. Case report. J Nenrosnrg 38:218-220, The developmental stage of this hetero1973 topic brain was considered to be 7 or 8 3. Brun A: Marginal glioneural heterotopias of months gestational age, because there was a the central nervous system. Acta Pathal Microbinl Scand 65:221-233, 1965 thick external granular layer of cerebellum, 4. Cooper IS, Kernohan JW: Heterotopic glial whereas the proliferating zone had disnests in the subarachnoid space: Histoappeared. The dentate nucleus was well pathologic characteristics, mode of origin and developed, but its folding was still inrelation to meningeal gliomas. J Neurnpathol complete. 7 On the contrary, organization of Exp Neurol 10:16-29, 1951 the cerebrum was more delayed, which was as 5. Farhat SM, Hudson JS: Extracerebral brain expected in the infant's normal developmenheterotopia. Case report. J Neurosurg 30: tal stage. It can therefore be concluded from 190-194, 1969 the morphological characteristics that a 6. Lemire KJ, Loeser JD, Leech RW, et al: Norheterotopic brain of about 7- or 8-month mal and Abnormal Development nf the Human Nervous System. Hagerstown, MD: Harper gestational age existed in the intracranial exand Row, 1975, pp 54-69 tracerebral space of this 1-month-old child 7. Lemire K J, Loeser JD, Leech RW, et al: Nortogether with his macroscopically normal mal and Abnormal Development nf the Human brain. The heterotopic brain had no proper Nervous System. Hagerstown, Md: Harper dural covering. and Row, 1975, pp 144-165 With regard to the pathogenesis, Farhat 8. Moriyasu N, Sato K, Nomi M, et al: [A and Hudson s postulated that the glial protrucase of encephalochoristoma.] Brain Nerve sion, which was "punched off TM from the (Tokyo) 21:923-927, 1969 (Jpn) neuraxis, became established within the sub9. Popoff N, Feigin I: Heterotopic central nerarachnoid space, and then the heterotopic vous tissue in subarachnoid space. Arch Pathol 78:533-539, 1964 brain caused the formation of a separate dura. It has been said that the first phase of 10. Rorke LB, Fogelson MH, Riggs HE: Cerebellar heterotopia in infancy. Dev Med the formation of the neural tube is acChild Neurol 10:644-650, 1968 complished up to Stage X I I ? During this 11. Terplan KL, Sandberg AA, Aceto T Jr: Strucstage, some piece of the neural fold could tural anomalies in the cerebellum in associapresumably have separated and migrated. tion with trisomy. JAMA 197:557-568, 1966 The ectopic tissue might have survived in the 12. Willis RA: The Borderland nf Embryology and cerebrospinal fluid, and structural organizaPathology. London: Butterworths, 1958, pp tion taken place up to the 7- or 8-month 306-340 gestational stage. 13. Willis RA: Some unusual developmental heterotopias. Br Med J 3:267-272, I968 Willis 12'~ classified heterotopias into four types: 1) supernumerary or accessory organ; 14. Wolbach SB: Congenital rhabdomyoma of the heart. Report of a case associated with multi2) transference of an accessory organ; 3) disple nests of neuroglia tissue in the meninges of location; and 4) heterotopia or anomalous the spinal cord. J Med Res 16:495-520, 1907 differentiation. From its histological findings, our case can be classified as a supernumerary heterotopic organ. S o m e of the reported cases Address reprint requests to: Tohru were associated with other anomalies of the Marubayashi, M.D., Department of Neurocentral nervous system, such as micro- surgery, Kumamoto University Medical School, encephaly, maldevelopment of the corpus Kumamoto, 860, Japan. 474

J. Neurosurg. / Volume 48 / March, 1978

Intracranial extracerebral brain heterotopia. Case report.

J Neurosurg 48:470-474, 1978 Intracranial extracerebral brain heterotopia Case report TOHRU MARUBAYASHI, M . D . , AND YASUHIKO MATSUKADO, M . D ...
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