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Interhemispheric epithelial cyst
Surg
Neural 1988;30:391-5
Interhemispheric
Epithelial
391
Cyst
Case Report Shigeki
Kameyama,
Masao Watanabe, Departments
M.D., Mizuo Kuroki, M.D., and Hiroshi
of Neurosurgery
M.D., Makoto
Kaneko,
Toyama,
M.D.,
M.D.
and Pathology, Nagaoka Red Cross Hospital, Nagaoka, Japan
Kameyama S, Kuroki M, Toyama M, Watanabe M, Kaneko H. Interhemispheric epithelial cyst. Case report. Surg Neurol 1988; 30:391-5.
We report a rare case of a 54-year-old woman with an interhemispheric epithelial cyst. This will be the first report of an interhemispheric epithelial cyst without caIlosaI agenesis. A partial excision of the cyst wall has led to her recovery with no evidence of recurrence. Ultrastructural studies suggest that the cyst was derived from the primitive neuroepithelium. We discuss the pathogenesis of the interhemispheric epithelial cyst. KEY WORDS: Epithelial cyst; Epndymal cyst; Neuroepithelial cyst; Supratentorial; Interhemispheric; Electron microscopy
Benign intracranial cysts have frequently been found, especially after the advent of computed tomography (CT) scanning. Yet understanding the pathogenesis of these cysts is not so easy as the diagnosis using CT. Serial CT scans with metrizamide CT cisternography truly help to classify these cysts preoperatively concerning their diffusion characteristics. Ultrastructural studies allow a more precise definition than routine neuropathological studies in regard to their origin. Unlike arachnoid cysts, epithelial cysts are less frequently encountered. Intracranial epithelial cysts have been divided into four categories as follows: (a) dermoid and epidermoid cysts; (b) Rathke’s cleft cysts and hypophyseal duct cysts; (c) neurenteric cysts; (d) ependymal cysts and colloid cysts of the third ventricle f 151. Dermoid and epidermoid cysts can arise from the primitive ectoderm. These cysts may be easily diagnosed by routine pathological studies because of the squamous epithelium. Rathke’s cleft cysts and hypophyAddress reprint requests to: Shigeki Kameyama, M.D., Department of Neurosurgery, Brain Research Institute, Niigata University, l-757 Asahimachi-dori, Niigata, 95 1 Japan. Received December 4, 1987; accepted May 26, 1988. 8 1988 by Elsevier Science PublishingCo., Inc.
seal duct cysts rarely arise from the stomodeal ectoderm, which is known to differentiate to Rathke’s cleft derivatives. These cysts are found in the parasellar regions. Neurenteric cysts arising from the endoderm are located in the spinal cord, especially in the ventral portion [ll]. Ependymal cysts are most commonly found near the ventricular system or in the subarachnoid space of the supratentorial portion but rarely in the posterior fossa. In a narrow sense, the nomenclature of intracranial epithelial cysts includes ependymal cysts, epithelial cysts, choroidal epithelial cysts, and neuroepithelial cysts. Hirano et al Cl 1,12 J have proposed the term “neuroepithelial cyst” on the basis of ultrastructural studies showing the features of both primitive ependyma and choroid plexus. In those reported cases of an epithelial cyst, cysts are located in the subarachnoid spaces {1,4,20-26,28,30,32] and in the cerebral hemisphere [2,3,6,8-10,13,14,17-19,29,31], but those located in the parasagittal region [5,13,16,22,32] or interhemispheric fissure [4,20,28,32] are very rare. One case of a noncolloid epithelial cyst in the third ventricle has been reported [27]. All cases of an interhemispheric cyst previously reported have been combined with callosal agenesis [4,20,28,32]. In this article, we present a rare case of an interhemispheric epithelial cyst free of callosal agenesis and review the supratentorial epithelial cysts. We also discuss the pathogenesis of the interhemispheric epithelial cysts.
Case Report A 54-year-old woman had a sudden generalized convulsion followed by left hemiparesis 2 months before admission. The day after the onset, she became alert and her left hemiparesis resolved. On June 25, 1980, she was admitted to the Nagaoka Red Cross Hospital complaining of persistent dullness of the head. Physical and neurological examinations were unremarkable. Roentgenograms of the skull were normal. An electroencephalogram demonstrated sporadic small sharp waves at the bilateral centroparietal leads. A CT 0090-3019/88/53.50
392
Surg Neural 1988;30:391-5
Figure 1. Computed tomography scans showing a large round cyst in the midportion of the interhemispheric fissure above a corpus callosum. (A) Horizontal section; (B) coronalsection. The cyst is not connected with any ventricle.
scan revealed a large, round, low-density area located in the midportion above the corpus callosum (Figure 1). It was interpreted as a cyst located in the interhemispheric fissure. Metrizamide CT cisternography showed no communication between the cyst and either the ventricular system or the interhemispheric cistern. Angiography of the right carotid artery revealed that the pericallosal arteries were bilaterally displaced downward at the body of the corpus callosum, and that the callosomarginal arteries were displaced upward and laterally by an avascular mass. A right frontoparietal craniotomy was performed on July 11, 1980. It revealed that the cyst was located in the interhemispheric subarachnoid space under the falx.
Kameyama et al
The cyst contained cerebrospinal fluid (CSF)-like clear fluid with 30 mg/dL of protein and 49 mg/dL of sugar. The roof of the cyst was removed as far as possible. The corpus callosum appeared intact despite being compressed by the cyst. Histologic examination revealed that the cyst was lined with a single layer of columnar cells (Figure 2). On electron microscopic examination (Figure 3), these cells had sparse and irregular microvilli without surface-coating materials. No cilia were observed. Endoplasmic reticula were scarcely seen, while both mitochondria and free ribosomes were scattered. Abundant cytoplasmic filaments were identified. No secretory materials were identified. The basal surface of the cells was bordered by continuous basement membrane. Basal extracellular space contained collagen fibers. Desmosomes and interdigitations were frequently seen at the border of the adjacent cells. Abundant pinocytotic vesicles were found along the basal surface of the cells. No arachnoid cells or glial tissue were demonstrated on the cyst wall. The patient suffered a left hemiconvulsion immediately after the operation. A postictal left hemiparesis persisted for 1 week. The postoperative CT showed that the cyst was collapsed. Two weeks after the operation, she was discharged without any complications. During the follow-up period until June 1985, she was doing well with no recurrence symptoms. The last CT scan on June 12, 1985, showed the cyst collapsed.
Discussion Computed tomography scanning helps to diagnose benign intracranial cysts and, furthermore, with the aid of
Figure 2. Photomicrograph of the cy_u wall showing a single layer of columnar cells with collagen fibers (toluidine blue stain, x 200).
Interhemispheric
Epithelial Cyst
metrizamide CT cisternography, it enables us to know preoperatively the qualities of the fluid contained and the cyst wall. Although it is generally accepted that it is difficult to distinguish epithelial cysts from arachnoid cysts located almost in the same portion, most epithelial cysts in our reviewed cases proved to have no communication with either subarachnoid cisterns or the ventricular system ~3,5,10,13,14,20,21,24,25,27,29,30], in contrast with arachnoid cysts that had communication with CSF spaces. Therefore, delayed metrizamide CT cisternography may have been useful in revealing these communications 120,291. Epithelial cysts can be classified into ciliated and nonciliated epithelial cysts by routine pathological studies. The nomenclature of these cysts, however, has been confused in the literature in regard to their origin, taking various terms such as “ependymal cyst” {2,5, 6,8,10,13,20,23,26,30], “epithelial cyst” 19,16,17,19, 24,27,29], “choroidal epithelial cyst” 13,143, “neuroepithelial cyst” {4,18,22,28], or “meningo-encephalocele” [25]. In some cases, tufts of choroid plexus were detected on the cyst wall [3,4,22,25,281. Recent electron-microscopic examinations have suggested that these cysts may arise from the primitive neuroec-
Surg Neural 1988;30:391-5
393
Figure 3. An electron micrograph of the epithelial cells lining on the cyst wall. Sparse and irregularmicrovilli are seen and prominent continuous basement membrane is identified on the basal surface of the cells. Desmosomes (arrows) and interdigitations (arrowhead) are seen at the cellular junctions (X20,000).
toderm. Ultrastructural features of these cysts are similar to both ependyma and choroid plexus epithelium E&9,14,24,29]. Hirano and his associates 19,121 have suggested that an origin of epithelial cysts was in a primitive neuroepithelium. In their reports of ultrastructural findings of the cyst wall, both microvilli and continuous basement membrane in the epithelial cells resembled those in choroid plexus epithelium, whereas desmosomes and interdigitations resembled those in ependyma. All of the interhemispheric epithelial cysts previously reported were associated with callosal agenesis [4,20,28,32), and contained choroidal tufts. Only our case did not have callosal agenesis and the cyst did not contain choroidal tufts. In general, it is accepted that the interhemispheric epithelial cysts are attributed to callosal agenesis. Interhemispheric fissure is built by invagination forming primitive choroid plexus and ependyma from the roof plate of the neural tube at 6- to
394
Surg Neural 1988;30:391-5
7-week gestation 177. The sequestration of neuroectoderm in that fissure is probably caused by developmental errors occurring at this time. These ultrastructural findings, therefore, must have assumed the primitive features prior to the differentiation from neuroectoderm. The cyst of our case is thought to have been derived from primitive neuroepithelium. In one case of interhemispheric epithelial cyst combined with callosal agenesis [28], it is speculated that the maldevelopment of diencephalic roof plate could have produced a midline cyst, which in turn could have interfered with callosal growth and midline development. Although most epithelial cysts are located in the areas adjacent to the ventricular system regards to their origin, there have been a few located in the subarachnoid space of the sylvian fissure [23,30,32] or the cerebral convexity [1,22,24,25] that are suggested to have originated from heterotopic glias Cl 51. Clinical manifestations of the onset in adult patients with these epithelial cysts were convulsive seizures [2-4,8,13,16,17,19,22,26,27,30,31], headaches 113, 18,21,23,24,28,32], and hemiparesis {32]. In reviewed cases of infants and children with these cysts [1,4,14,20,25,27,29,32}, all patients were admitted because of an enlarged head. Clinical symptoms and courses were similar to those of intracranial tumors. A peak occurrence of epithelial cysts by age was observed in the third decade. In the overall incidence that we have reviewed, there is no predominance in sex, unlike some of the literature that indicates female predominance [17,24]. A half of these cysts as well as ours contained clear fluid [3,5,9,10,13,14,20,22-25,27,28]. The remainder contained milky [8,17-19,21,22,30,31], greenish gray [16,26], xanthochromic [8,29], or turbid fluid 117,241. In the former cases, including ours, the electron-microscopic studies revealed numerous pinocytotic vesicles to be on the basal border of the lining epithelium [9,14,24]. These cysts could be expanded by the fluid accumulation due to the active transport of pinocytosis in spite of no communication with any CSF spaces 191. In general, partial excision is chosen for the surgical management of symptomatic epithelial cysts. Among reviewed cases, total removal of the cysts was performed in only two cases [10,22]. Fenestration of the cyst into the surrounding subarachnoid space predisposed to recurrence [16,17,19]. Either cyst-ventriculostomy {17-20,251 or a cyst-peritoneal shunt [24,27] is optimal in the treatment of recurrent cases.
We thank Dr. Ryuichi Tanaka, Professor and Director of Department of Neurosurgery, Brain Research Institute, Niigata University, for his encouragement and instructive advice.
Kameyama et al
References 1. Aicardi J, Bauman F. Supratentorial and children. J Neural Neurosurg
extracerebral cysts in infants Psychiatry 1975;38:57-68.
2. Argyopoulos G, Heppner F. Angeborene Zentralbl Neurochir 1970;31:39-41. 3. Azzam choroid 4
NI, Timperley WR. Intracerebral plexus. Case report. J Neurosurg
Ependymzysten
cyst due to ectopic 1981;55:651-3.
Barth PG, Uylings HBM, Stam FC. Interhemispheral neuroepithelial (glioependymal) cysts, associated with agenesis of the corpus callosum and neocortical maldevelopment. A case study. Child’s Brain 1984;11:312-9.
5. Bandari YS. Noncommunicating supratentoriai subarachnoid cysts. J Neural Neurosurg Psychiatry 1972;35:763-70. 6. Bouch DC, Mitchell I, Maloney AFJ. Ependymal lined pataventricular cerebral cysts: a report of three cases. J Neural Neurosurg Psychiatry 1973;36:611-7. 7. Corliss CE. Patten’s human embryology: elements development. New York: McGraw-Hill, 1976:208-10.
of clinical
8. Friede RL., Yasargil MG. Supratentorial intracerebral epithelial (ependymal) cysts: review, case reports, and fine structure. J Neural Neurosurg Psychiatry 1977;40:127-37. NR, 9. Ghatak structure of 1974;41:75-82.
Hirano A, Kasoff SS, Zimmerman an intracerebral epithelial cyst. J
10. Haddad FS, Abla A, Allam C. Ependymal 1982;18:246-9.
HM. Fine Neurosurg
brain cyst. Surg Neural
11. Hirano A, Ghatak NR, Wisoff HS, Zimmerman HM. An epithelial cyst of the spinal cord. An electron microscopic study. Acta Neuropathol (Berl) 1971;18:214-23. 12. Hirano A, Matsui T, Zimmerman HM. The fine structure of epithelial cyst in the central nervous system (in Japanese). No Shinkei Geka 1975;3:639-46. P, Dunsmore RH, Beckett 13. Jakubiak cysts. J Neurosurg 1968;28:129-36.
RS. Suptatentorial
14. Koto A, Horoupian DS, Shulman K. Choroidal case report. J Neurosurg 1977;47:955-60.
brain
epithelial
cyst,
15. Leech RW, Olafson RA. Epithelial cysts of the neuraxis: presentation of three cases and a review of the origins and classification. Arch Path01 Lab Med 1977;101:196-202. 16. List CF, Williams JR. Subdural epithelial cyst in the interhemispheral fissure: report of a case, with some remarks concerning the classification of intracranial epithelial cysts. J Neurosurg 1961;18:690-3. 17. MacGregor BJL, Gawler J, South JR. Intracranial epithelial Report of two cases. J Neurosurg 1976;44:109-15. 18. Markwalder T-M, Markwalder RV, Slongo T. Intracranial neuroepithelial cyst mimicking arachnoid cyst. Surg 1981;16:411-4. T-M, Zimmerman A. Intracerebral 19. Markwalder cyst. Surg Neural 1979;11:195-8. 20.
Morimoto T, Kaneko Ependymal cyst-case 1986;14:351-6.
cysts. ciliated Neural
ciliated epithelial
M, Nishikawa R, Ono T, Basugi N. report (in Japanese). No Shinkei Geka
21. Oro JJ, Ansbacher LE, Levy WJ. Septate bifrontal cyst. Case Report. J Neurosurg 1983;59:344-7.
ependymal
22.
Palma L. Supratentorial neuroepithelial cases. J Neurosurg 1975;42:353-7.
23.
Patrick BS. Ependymal cyst of the Sylvian fissure. Neurosurg 1971;35:751-4.
24.
Pearl GS, Takei Y, Tindall GT, Hoffman JC. Supratentorial subarachnoid epithelial cyst: case report and ultrastructural study. Neurosurgery 1982;11:48-51.
25.
Rand
BO,
Foltz EL, Alvord
cysts.
EC. Intracranial
Report
of two
Case report.
telencephalic
J
me-
Interhemispheric
Epithelial
ningo-encephalocele containing Exp Nemo1 1964;23:293-305. 26.
Surg
Cyst
Neurol
395
1988;30:391-5
choroid
plexus.
J Neuropathol
Schelper RL, Ramzy I, Durr N. Ependymal cyst of the subarachnoid space. Cytologic diagnosis and developmental considerations. Acta Cytol 1985;29:44-8.
27.
Shimizu T, Waga S. Intraventricular noncolloid an infant. Surg Neural 1984;21:185-9.
epithelial
28.
Solt LC, Deck JHN, Bairn RS, TerBrugge K. Interhemispheric cyst of neuroepitheliaf origin in association with partial agenesis of corpus callosum: case report and review of the literature. J Neurosurg 1980;52:399-403.
29. Takeshita M, Miyazaki T, Kubo 0, Kagawa M, Saito Y, Kitamura K. Paraventricular cerebral cyst in an infant. Surg Neural 1982;17:123-6. 30. Tandon PN, Roy S, Elvidge A. Subarachnoid ependymal Report of two cases. J Neurosurg 1972;37:741-5.
cyst.
cyst in 31. Vuia 0. Congenital intracerebral (Stuttg) 1976;19:219-26. 32. Zehnder M. Subarachnoidalcysten rochir 1938;2:100-12.
epithelial
cysts. Neurochirurgia
des Gehirns.
Zentralbl
Neu-
Neural 1988;30:391-5
Interhemispheric
Epithelial
391
Cyst
Case Report Shigeki
Kameyama,
Masao Watanabe, Departments
M.D., Mizuo Kuroki, M.D., and Hiroshi
of Neurosurgery
M.D., Makoto
Kaneko,
Toyama,
M.D.,
M.D.
and Pathology, Nagaoka Red Cross Hospital, Nagaoka, Japan
Kameyama S, Kuroki M, Toyama M, Watanabe M, Kaneko H. Interhemispheric epithelial cyst. Case report. Surg Neurol 1988; 30:391-5.
We report a rare case of a 54-year-old woman with an interhemispheric epithelial cyst. This will be the first report of an interhemispheric epithelial cyst without caIlosaI agenesis. A partial excision of the cyst wall has led to her recovery with no evidence of recurrence. Ultrastructural studies suggest that the cyst was derived from the primitive neuroepithelium. We discuss the pathogenesis of the interhemispheric epithelial cyst. KEY WORDS: Epithelial cyst; Epndymal cyst; Neuroepithelial cyst; Supratentorial; Interhemispheric; Electron microscopy
Benign intracranial cysts have frequently been found, especially after the advent of computed tomography (CT) scanning. Yet understanding the pathogenesis of these cysts is not so easy as the diagnosis using CT. Serial CT scans with metrizamide CT cisternography truly help to classify these cysts preoperatively concerning their diffusion characteristics. Ultrastructural studies allow a more precise definition than routine neuropathological studies in regard to their origin. Unlike arachnoid cysts, epithelial cysts are less frequently encountered. Intracranial epithelial cysts have been divided into four categories as follows: (a) dermoid and epidermoid cysts; (b) Rathke’s cleft cysts and hypophyseal duct cysts; (c) neurenteric cysts; (d) ependymal cysts and colloid cysts of the third ventricle f 151. Dermoid and epidermoid cysts can arise from the primitive ectoderm. These cysts may be easily diagnosed by routine pathological studies because of the squamous epithelium. Rathke’s cleft cysts and hypophyAddress reprint requests to: Shigeki Kameyama, M.D., Department of Neurosurgery, Brain Research Institute, Niigata University, l-757 Asahimachi-dori, Niigata, 95 1 Japan. Received December 4, 1987; accepted May 26, 1988. 8 1988 by Elsevier Science PublishingCo., Inc.
seal duct cysts rarely arise from the stomodeal ectoderm, which is known to differentiate to Rathke’s cleft derivatives. These cysts are found in the parasellar regions. Neurenteric cysts arising from the endoderm are located in the spinal cord, especially in the ventral portion [ll]. Ependymal cysts are most commonly found near the ventricular system or in the subarachnoid space of the supratentorial portion but rarely in the posterior fossa. In a narrow sense, the nomenclature of intracranial epithelial cysts includes ependymal cysts, epithelial cysts, choroidal epithelial cysts, and neuroepithelial cysts. Hirano et al Cl 1,12 J have proposed the term “neuroepithelial cyst” on the basis of ultrastructural studies showing the features of both primitive ependyma and choroid plexus. In those reported cases of an epithelial cyst, cysts are located in the subarachnoid spaces {1,4,20-26,28,30,32] and in the cerebral hemisphere [2,3,6,8-10,13,14,17-19,29,31], but those located in the parasagittal region [5,13,16,22,32] or interhemispheric fissure [4,20,28,32] are very rare. One case of a noncolloid epithelial cyst in the third ventricle has been reported [27]. All cases of an interhemispheric cyst previously reported have been combined with callosal agenesis [4,20,28,32]. In this article, we present a rare case of an interhemispheric epithelial cyst free of callosal agenesis and review the supratentorial epithelial cysts. We also discuss the pathogenesis of the interhemispheric epithelial cysts.
Case Report A 54-year-old woman had a sudden generalized convulsion followed by left hemiparesis 2 months before admission. The day after the onset, she became alert and her left hemiparesis resolved. On June 25, 1980, she was admitted to the Nagaoka Red Cross Hospital complaining of persistent dullness of the head. Physical and neurological examinations were unremarkable. Roentgenograms of the skull were normal. An electroencephalogram demonstrated sporadic small sharp waves at the bilateral centroparietal leads. A CT 0090-3019/88/53.50
392
Surg Neural 1988;30:391-5
Figure 1. Computed tomography scans showing a large round cyst in the midportion of the interhemispheric fissure above a corpus callosum. (A) Horizontal section; (B) coronalsection. The cyst is not connected with any ventricle.
scan revealed a large, round, low-density area located in the midportion above the corpus callosum (Figure 1). It was interpreted as a cyst located in the interhemispheric fissure. Metrizamide CT cisternography showed no communication between the cyst and either the ventricular system or the interhemispheric cistern. Angiography of the right carotid artery revealed that the pericallosal arteries were bilaterally displaced downward at the body of the corpus callosum, and that the callosomarginal arteries were displaced upward and laterally by an avascular mass. A right frontoparietal craniotomy was performed on July 11, 1980. It revealed that the cyst was located in the interhemispheric subarachnoid space under the falx.
Kameyama et al
The cyst contained cerebrospinal fluid (CSF)-like clear fluid with 30 mg/dL of protein and 49 mg/dL of sugar. The roof of the cyst was removed as far as possible. The corpus callosum appeared intact despite being compressed by the cyst. Histologic examination revealed that the cyst was lined with a single layer of columnar cells (Figure 2). On electron microscopic examination (Figure 3), these cells had sparse and irregular microvilli without surface-coating materials. No cilia were observed. Endoplasmic reticula were scarcely seen, while both mitochondria and free ribosomes were scattered. Abundant cytoplasmic filaments were identified. No secretory materials were identified. The basal surface of the cells was bordered by continuous basement membrane. Basal extracellular space contained collagen fibers. Desmosomes and interdigitations were frequently seen at the border of the adjacent cells. Abundant pinocytotic vesicles were found along the basal surface of the cells. No arachnoid cells or glial tissue were demonstrated on the cyst wall. The patient suffered a left hemiconvulsion immediately after the operation. A postictal left hemiparesis persisted for 1 week. The postoperative CT showed that the cyst was collapsed. Two weeks after the operation, she was discharged without any complications. During the follow-up period until June 1985, she was doing well with no recurrence symptoms. The last CT scan on June 12, 1985, showed the cyst collapsed.
Discussion Computed tomography scanning helps to diagnose benign intracranial cysts and, furthermore, with the aid of
Figure 2. Photomicrograph of the cy_u wall showing a single layer of columnar cells with collagen fibers (toluidine blue stain, x 200).
Interhemispheric
Epithelial Cyst
metrizamide CT cisternography, it enables us to know preoperatively the qualities of the fluid contained and the cyst wall. Although it is generally accepted that it is difficult to distinguish epithelial cysts from arachnoid cysts located almost in the same portion, most epithelial cysts in our reviewed cases proved to have no communication with either subarachnoid cisterns or the ventricular system ~3,5,10,13,14,20,21,24,25,27,29,30], in contrast with arachnoid cysts that had communication with CSF spaces. Therefore, delayed metrizamide CT cisternography may have been useful in revealing these communications 120,291. Epithelial cysts can be classified into ciliated and nonciliated epithelial cysts by routine pathological studies. The nomenclature of these cysts, however, has been confused in the literature in regard to their origin, taking various terms such as “ependymal cyst” {2,5, 6,8,10,13,20,23,26,30], “epithelial cyst” 19,16,17,19, 24,27,29], “choroidal epithelial cyst” 13,143, “neuroepithelial cyst” {4,18,22,28], or “meningo-encephalocele” [25]. In some cases, tufts of choroid plexus were detected on the cyst wall [3,4,22,25,281. Recent electron-microscopic examinations have suggested that these cysts may arise from the primitive neuroec-
Surg Neural 1988;30:391-5
393
Figure 3. An electron micrograph of the epithelial cells lining on the cyst wall. Sparse and irregularmicrovilli are seen and prominent continuous basement membrane is identified on the basal surface of the cells. Desmosomes (arrows) and interdigitations (arrowhead) are seen at the cellular junctions (X20,000).
toderm. Ultrastructural features of these cysts are similar to both ependyma and choroid plexus epithelium E&9,14,24,29]. Hirano and his associates 19,121 have suggested that an origin of epithelial cysts was in a primitive neuroepithelium. In their reports of ultrastructural findings of the cyst wall, both microvilli and continuous basement membrane in the epithelial cells resembled those in choroid plexus epithelium, whereas desmosomes and interdigitations resembled those in ependyma. All of the interhemispheric epithelial cysts previously reported were associated with callosal agenesis [4,20,28,32), and contained choroidal tufts. Only our case did not have callosal agenesis and the cyst did not contain choroidal tufts. In general, it is accepted that the interhemispheric epithelial cysts are attributed to callosal agenesis. Interhemispheric fissure is built by invagination forming primitive choroid plexus and ependyma from the roof plate of the neural tube at 6- to
394
Surg Neural 1988;30:391-5
7-week gestation 177. The sequestration of neuroectoderm in that fissure is probably caused by developmental errors occurring at this time. These ultrastructural findings, therefore, must have assumed the primitive features prior to the differentiation from neuroectoderm. The cyst of our case is thought to have been derived from primitive neuroepithelium. In one case of interhemispheric epithelial cyst combined with callosal agenesis [28], it is speculated that the maldevelopment of diencephalic roof plate could have produced a midline cyst, which in turn could have interfered with callosal growth and midline development. Although most epithelial cysts are located in the areas adjacent to the ventricular system regards to their origin, there have been a few located in the subarachnoid space of the sylvian fissure [23,30,32] or the cerebral convexity [1,22,24,25] that are suggested to have originated from heterotopic glias Cl 51. Clinical manifestations of the onset in adult patients with these epithelial cysts were convulsive seizures [2-4,8,13,16,17,19,22,26,27,30,31], headaches 113, 18,21,23,24,28,32], and hemiparesis {32]. In reviewed cases of infants and children with these cysts [1,4,14,20,25,27,29,32}, all patients were admitted because of an enlarged head. Clinical symptoms and courses were similar to those of intracranial tumors. A peak occurrence of epithelial cysts by age was observed in the third decade. In the overall incidence that we have reviewed, there is no predominance in sex, unlike some of the literature that indicates female predominance [17,24]. A half of these cysts as well as ours contained clear fluid [3,5,9,10,13,14,20,22-25,27,28]. The remainder contained milky [8,17-19,21,22,30,31], greenish gray [16,26], xanthochromic [8,29], or turbid fluid 117,241. In the former cases, including ours, the electron-microscopic studies revealed numerous pinocytotic vesicles to be on the basal border of the lining epithelium [9,14,24]. These cysts could be expanded by the fluid accumulation due to the active transport of pinocytosis in spite of no communication with any CSF spaces 191. In general, partial excision is chosen for the surgical management of symptomatic epithelial cysts. Among reviewed cases, total removal of the cysts was performed in only two cases [10,22]. Fenestration of the cyst into the surrounding subarachnoid space predisposed to recurrence [16,17,19]. Either cyst-ventriculostomy {17-20,251 or a cyst-peritoneal shunt [24,27] is optimal in the treatment of recurrent cases.
We thank Dr. Ryuichi Tanaka, Professor and Director of Department of Neurosurgery, Brain Research Institute, Niigata University, for his encouragement and instructive advice.
Kameyama et al
References 1. Aicardi J, Bauman F. Supratentorial and children. J Neural Neurosurg
extracerebral cysts in infants Psychiatry 1975;38:57-68.
2. Argyopoulos G, Heppner F. Angeborene Zentralbl Neurochir 1970;31:39-41. 3. Azzam choroid 4
NI, Timperley WR. Intracerebral plexus. Case report. J Neurosurg
Ependymzysten
cyst due to ectopic 1981;55:651-3.
Barth PG, Uylings HBM, Stam FC. Interhemispheral neuroepithelial (glioependymal) cysts, associated with agenesis of the corpus callosum and neocortical maldevelopment. A case study. Child’s Brain 1984;11:312-9.
5. Bandari YS. Noncommunicating supratentoriai subarachnoid cysts. J Neural Neurosurg Psychiatry 1972;35:763-70. 6. Bouch DC, Mitchell I, Maloney AFJ. Ependymal lined pataventricular cerebral cysts: a report of three cases. J Neural Neurosurg Psychiatry 1973;36:611-7. 7. Corliss CE. Patten’s human embryology: elements development. New York: McGraw-Hill, 1976:208-10.
of clinical
8. Friede RL., Yasargil MG. Supratentorial intracerebral epithelial (ependymal) cysts: review, case reports, and fine structure. J Neural Neurosurg Psychiatry 1977;40:127-37. NR, 9. Ghatak structure of 1974;41:75-82.
Hirano A, Kasoff SS, Zimmerman an intracerebral epithelial cyst. J
10. Haddad FS, Abla A, Allam C. Ependymal 1982;18:246-9.
HM. Fine Neurosurg
brain cyst. Surg Neural
11. Hirano A, Ghatak NR, Wisoff HS, Zimmerman HM. An epithelial cyst of the spinal cord. An electron microscopic study. Acta Neuropathol (Berl) 1971;18:214-23. 12. Hirano A, Matsui T, Zimmerman HM. The fine structure of epithelial cyst in the central nervous system (in Japanese). No Shinkei Geka 1975;3:639-46. P, Dunsmore RH, Beckett 13. Jakubiak cysts. J Neurosurg 1968;28:129-36.
RS. Suptatentorial
14. Koto A, Horoupian DS, Shulman K. Choroidal case report. J Neurosurg 1977;47:955-60.
brain
epithelial
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