J Neurosurg 76:224-230, 1992
Giant interhemispheric cysts associated with agenesis of the corpus callosum KOREAKI Mo~l, M.D.
Department of Neurosurgery, Kochi Medical School, Nankoku City, Japan ~" lnterhemispheric cysts, often associated with agenesis of the corpus caUosum, are rare lesions demonstrating little uniformity of pathogenesis. Four large interhemispheric cystic lesions with several unique features are reviewed. Magnetic resonance imaging clearly showed agenesis of the corpus callosum and was useful in the diagnosis of interhemispheric cysts. The differential diagnosis of these lesions is discussed, along with therapeutic considerations. KEY WORDS 9 cyst, interhemispheric corpus callosum cyst, arachnoid 9 magnetic resonance imaging
IAN~ interhemispheric cysts are rare lesions which, until the advent of magnetic resonance (MR) imaging, were mainly diagnosed by computerized tomography (CT). Various types of cystic lesions occur in the interhemispheric area. Often they are associated with agenesis of the corpus callosum, but there is no uniformity in pathogenesis among previously reported cases. These cysts should be differentiated from one another, as the prognostic and therapeutic implications may differ. Four large interhemispheric cystic lesions presenting at four different institutions prompted this report. Magnetic resonance imaging, which is currently the diagnostic tool of choice, clearly demonstrated agenesis of the corpus callosum and was useful in the differential diagnosis of these lesions.
G
Case Reports
Case 1 This 5-month-old boy was delivered normally at term after an uneventful pregnancy. At birth, he weighed 2950 gm and his head circumference was 34.7 cm. He was subsequently noted to have an enlarged head (97th percentile), which increased progressively thereafter despite otherwise normal development. His head circumference was 41.5 cm at the age of 2 months and 43 cm at 3 months. No history of head injury or high fever was obtained. He was admitted to Osaka City University Hospital in May, 1976. Examination. The anterior fontanel measured 4.5 • 5.0 cm and the head circumference was 45 cm. Infantile reflexes such as the Moro and grasp reflexes 224
9 hydrocephalus
9
were normal. Plain skull films showed suture separation, and pneumoencephalography revealed air filling of the left lateral ventricle. A structure similar to a cavum veli interpositi was demonstrated. A tap of the left lateral ventricle through the left corner of the anterior fontanel was attempted but the needle entered a cyst instead. The cystic fluid was replaced with air. On pathological examination, the fluid was xanthochromic, with a cell count of 89 a protein content of 390 mg/dl, a sugar content of 92 mg/dl, and a chlorine level of 691 mg/dl. Carotid angiograms revealed lateral displacement of the left anterior cerebral artery. Operation. A left frontoparietal craniotomy was performed in May, 1976. Immediately after dural reflection, a large cyst measuring approximately 7 • 5 cm was encountered, filled with xanthochromic fluid. The falx was normally developed and the cyst was located between both cerebral hemispheres. Below the falx, the cingulate gyrus of the fight cerebral hemisphere could be seen, but the corpus callosum was obscured. Due to its size, the cyst's anatomical relationship to the surrounding structures could not be verified. It was resected as extensively as possible. Pathological examination of its wall resulted in a diagnosis of arachnoid cyst.
Postoperative Course. The postoperative course was complicated by meningitis, which resolved in about 1 month. Postoperative cisternography revealed marked reflux of the contrast medium into the right lateral ventricle and stasis for more than 24 hours. Postoperative pneumoventricuiography showed an enlargement of the right lateral ventricle. A ventriculoperitoneal (VP) J. Neurosurg. / Volume 76/February, 1992
Giant cysts with corpus callosum agenesis
FIG. 1. Case 2. Left: Preoperative enhanced computerized tomography (CT) scan showing a huge frontoparietal midline cyst and enlargement of the lateral ventricles. The cyst wall is not enhanced by contrast medium. Right: Postoperative CT scan showing shrinkage of the cyst and a decrease in the size of the lateral ventricles.
shunt was inserted in October, 1976. Postoperative CT scans showed separation of the lateral ventricles with a collapsed interhemispheric cyst between them. The patient has developed relatively well with normal head size but with slight psychomotor retardation.
Case 2 This 21-month-old infant was found to have an enlarged ventricle at the 37th week of gestation. He was delivered by suction at 38 weeks of gestation. At birth, he weighed 3060 gin, his head circumference was 33.7 era, and his Apgar score was 8. He developed normally until 1 year of age, when he was noted to have an enlarged head (97th percentile). Frontal bossing was noted at his 1-year examination and he was referred to the Tottori University Hospital. He was diagnosed as having an interhemispheric cyst associated with hydrocephalus and was referred to the Department of Neurosurgery. Examination. The patient had no neurological abnormality and his developmental milestones were normal. Computerized tomography scans showed a huge midline cystic lesion and enlargement of the lateral ventricles (Fig. 1 left). Magnetic resonance imaging revealed a huge interhemispheric cyst associated with agenesis of the corpus callosum and separating the lateral ventricles. Metrizamide CT cisternography revealed no filling of the cyst or the left lateral ventricle. These findings suggested that the cyst had no communication with the subarachnoid space, and that the left foramen of Monro might be obstructed. Operation. Because of progressive enlargement of the head and increase in cyst size, a craniotomy was performed. The cyst was opened and communications were made between it and the subarachnoid space and the lateral ventricles. The cyst and its wall were resected as extensively as possible. The pathological diagnosis was that of an arachnoid cyst. J. Neurosurg. / Volume 76 /February, 1992
Fl~. 2. Case 3: Preoperative computerized tomography scans, without (left) and with (right) contrast enhancement, showing a huge left frontoparietal parasagittal cyst associated with agenesis of the corpus callosum. The cyst wall is not enhanced by contrast medium.
Postoperative Course. The postoperative course was uneventful and the patient was discharged in good condition. However, ventricular enlargement was noted 2 months later and a VP shunt was placed. Thereafter, his course was uneventful. Follow-up CT scans showed shrinkage of the cyst and a decrease in the size of the lateral ventricles (Fig. 1 right). Case 3 This 44-month-old girl was born at the 40th week of gestation by suction delivery. She was brought for evaluation of a generalized convulsive seizure that occurred during sleep. An electroencephalogram (EEG) showed frequent spikes and waves, predominantly in the right parietal region. She was placed on a course of anticonvulsant medication and was referred to the Takayama Red Cross Hospital because of abnormal CT scans. Examination. On admission, the patient weighed 15 kg and her head circumference measured 52.4 cm (approximately 2 standard deviations above the mean for her age group). On physical examination all other characteristics were found to be within normal limits. Neurologically, no abnormality was found. Her developmental quotient was greater than 85. No evidence of increased intracranial pressure was present. Optic fundi were normal. A huge interhemispheric cystic lesion, slightly off midline to the left and associated with agenesis of the corpus callosum, was revealed by CT (Fig. 2); the cyst wall was not enhanced by an 225
K. M o i l
FIG. 3. Case 3: Preoperative magnetic resonance images, Tt-weighted (left) and T2-weighted (right), showing no enlargement of the left parasagittal cyst.
injection of contrast medium. The cerebral hemispheres were separated laterally and the left lateral ventricle, especially the body and occilzital horn, was markedly enlarged, probably due to obstruction of the left foramen of Monro. The cyst seemed to have no communication with the lateral ventricle or subarachnoid space, and a thin septum was seen within its cavity at the level of the foramen of Monro. Clinical Course. The patient has been followed without surgical intervention. The results of follow-up MR imaging were similar to those of the CT scans obtained 2 months previously (Fig. 3).
Case 4 This 54-year-old man with an unremarkable history and normal psychomotor development consulted a neighborhood doctor, complaining of dull pain in the occipital and neck regions. He was noted to have an abnormal CT scan and was referred to the National Cardiovascular Center. Examination. Neurological findings on admission were unremarkable. Computerized tomography revealed a large cystic lesion with the same density as cerebrospinal fluid in the fight frontal region close to the midline. This was associated with dilatation of the body and occipital horn of the right lateral ventricle, and agenesis of the corpus callosum. The falx was present. The cyst was separated from the frontal horn of the right lateral ventricle by a thin septum. There was slight bulging and thinning of the frontal bone adjacent to the cyst. Asymmetry of the lateral ventricle, the right side being larger than the left, was thought to be due to obstruction of the fight foramen of Monro by the cyst. Metrizamide CT cisternography demonstrated minimal filling ef the ventricle and the cyst. Magnetic resonance images revealed findings similar 1o those of the CT scans. The sagittal images clearly demonstrated agenesis of the corpus callosum (Fig. 4 left). Gray matter could be seen between the lateral border of the cyst and the medial aspect of the right frontal lobe in the coronal images (Fig. 4 right). This finding suggested that the cyst was extra- rather than intra-axial. Right carotid angiograms revealed opacification of the right anterior cerebral artery in the anteroposterior view. The pericallosal artery ran an abnormal course and appeared to be under slight tension. In the lateral view, this artery was seen to course posterosuperiorly over the corpus callosum. Clinical Course. These findings confirmed the presence of an extra-axial mass lesion between the medial aspect of the right frontal lobe and the falx, and agenesis of the corpus callosum. Continuous pressure moni-
FIG. 4. Case 4. Left: Magnetic resonance T~-weightedimages,sagittal view, showing agenesisof the corpus callosum and a huge cyst in the frontal region, Right: Tl-weighted images,coronal view, showinga parasagittal right frontal cyst associated with agenesis of the corpus callosum. The third ventricle is displaced downward. Gray matter is present in the medial aspect of the fight frontal lobe close to the lateral border of the cyst, suggesting that the cyst is extra-axial. 226
J. Neurosurg. / Volume 76/February, 1992
Giant cysts with corpus callosum agenesis (Table I). Because of the broad spectrum of cerebral malformations accompanying a cystic cavity in the dorsal midline, they may be referred to as dorsal cyst malformations. 39,42'43The differential diagnosis of midline cysts is important from both the prognostic and therapeutic points of view. Interhemispheric araehnoid cysts have been reported to be clinically benign? J,44
toting in the lumbar subarachnoid space showed no pressure waves. Chromosomal examination was noncontributory. The patient has been followed without operation, and has remained neurologically intact.
Discussion
Cyst Classification
Intra-Axia[ Cysts
Interhemispheric cysts are congenital and usually present symptoms during childhood, but they may sometimes be diagnosed in adults, 18'34'44 as in Case 4. Various types of cystic lesions occur in the interhemispheric or parasagittal area and they are often associated with agenesis of the corpus callosum. 3"1~ Previously reported cases of agenesis of the corpus callosum with a midline cyst in the supratentorial compartment have variously been referred to as midline porencepha]y, 36"4i agenesis of the corpus callosum with porencephalic cyst, 23diencephalic cyst, 4 primary or secondary interhemispheric cyst, 26 and dorsal cyst of lobar holoprosencephaly. 24 Some cysts communicate freely with the ventricular system. The common radiographic features are agenesis of the corpus callosum, a midline location, and ventricular dilatation. Gross psychomotor retardation has been reported in many patients with such an anomaly. 42 Two morphologically distinct types of cysts occur in the interhemispheric area: extra-axial cysts associated with agenesis of the corpus callosum, and intra-axial cysts. Diagnosis of the cysts with agenesis of the corpus callosum has been made easier with CT and MR imaging. 3~Extra-axial cysts associated with agenesis of the corpus callosum should be differentiated from such intra-axial midline cysts as porencephalic cyst, dorsal cysts of holoprosencephaly, and upward extension of the third ventricle in agenesis of the corpus callosum
"Congenital midline porencephaly," a different clinical entity, 36'4~ is dysgenetic hydrocephalus associated with scalp anomalies and characterized by a symmetrical defect of the bilateral posterior mantle along the midline and alopecia or cephalocele in the parietal midline. The midline cyst is considered to be a variant of the dorsal cyst of lobar holoprosencephaly 24"4aand arises from primary dysgenesis of cerebral midline structures. It is not the result of hydrocephalus. Holoprosencephaly consists of a monoventricle communicating with the dorsal cyst in the midparietal region. The falx and corpus callosum are absent. The patient may have a facial anomaly such as cleft lip and palate. Hydrocephalus seen in holoprosencephaly is considered to be intractable? ~ Simple agenesis of the corpus callosum is easily recognized on sagittal MR images. 7's Dorsal extension of the third ventricle in agenesis of the corpus callosum or "diencephalic cyst ''4 has been demonstrated in coronal CT scans. Agenesis of the corpus callosum by itself does not present clinical symptoms; ~53a however, its association with various congenital anomalies is well k n o w n . 2&13"14'1~25'27"32 Consequently, the presence of agenesis of the corpus callosum may suggest such related anomalies as Dandy-Walker syndrome, Aicardi syndrome, and Chiari II malformationJ 3 The clinical symptoms depend on the nature of the associated malformations. 34
TABLE
1
Differential diagnosis of interhemispheric or parasagittal cysts* Factor nature of cyst location of cyst
Interhemispheric Cyst extra-axial midline or parasagittal
size of cyst large mass effect communicationwith ventricle corpus callosum
+ _+
falx
+
Poreneephalic HoloprosenAgenesisof Cyst cephaly Corpus Callosum intra-axial dorsal cystic dilatation of 3rd ventricle mJdline or par- midline midline asagittal variable small small + + + + +
-
+
hydrocephalus + • _+ asymmetryof lateral ventricle + __ monoventricle anterior cerebral a r t e r y separation, abnormal course abnormalcourse azygous abnormal course deep cerebral vein abnormal course abnormal course dysgenesis abnormalcourse frequently associated anoma- gyralabnormality, neuronal nonspecific facial anomaly Aicardisyndrome,Dandy-Walkersynlies heterolopia drome, Chiari II malformation onset of symptoms early or late early early early, if present neurologicaldeficits minimal severe severe subclinical or severe * Abbreviations: + = feature present; - = feature absent; _+= presence or absence of feature equivocal.
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227
K. Mori
FIG. 5. Magnetic resonance Trweighted image, coronal view, showing a large right parasagittal intra-axial cyst in a 39year-old. Mass effect is minimal and the corpus callosum is present.
Extra-Axial Cysts Interhemispheric extra-axial cysts are subdivided by location into bilateral midline cysts 19 (Case 2 in the present series) and unilateral parasagittal cysts 17'3~ (Cases 1, 3, and 4). Coronal MR imaging is especially useful in differentiating inlerhemispheric extra-axial cysts from intra-axial cysts (Fig. 5). These cysts have no communication with the subarachnoid space or lateral
or third ventricle, as can be confirmed by CT cisternography ~'3~'34'37or cystography. 22 The third ventricle is displaced downward by the cyst and thus one or both foramina of Monro may be obstructed with resultant mono- or biventricular dilatation (Fig. 4 right). Because of the location of the cyst, ventricular dilatation is asymmetrical and marked in the body and occipital horn; a paper-thin mantle is sandwiched between the cyst and the dilated body of the lateral ventricle (Fig. 2). The frontal horn is compressed and displaced laterally (Fig. 4 right). Interhemispheric cysts are unusually large and noncommunicating, and are often associated with agenesis of the corpus callosum (Fig. 6). Associated neurological deficits are minimal. Neuroradiological images mimic those of porencephalic cyst, holoprosencephaly, and agenesis of the corpus callosum. These anomalies should be differentiated clinically (Table 1).
Histopathological Considerations In two of the four cases presented here, surgical fenestration of the cysts was performed and pathological examination led to a diagnosis of arachnoid cyst. As the interhemispheric or parasagittal area is a rather uncommon site for the occurrence of arachnoid cyst, the pathological findings may be variable. Agenesis of
FIG. 6. Schematic illustration showing coronal sections of interhemispheric or parasagittal cysts. 228
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Giant cysts with corpus callosum agenesis the corpus callosum and interhemispheric cysts containing ependyma, choroid plexus, and glial cells have been reported. 3'9'22-29,34.3s,4~These have been histopathologically diagnosed as neuroepithelial or glioependymal cysts. With or without agenesis of the corpus callosum, interhemispheric or parasagittal arachnoid cysts tend to carry a favorable prognosis ~93c44compared with neuroepithelial or glioependymal cysts. Neuroepithelial cysts are often associated with polymicrogyria ~6and nodular neuronal heterotopia. 3 These associated anomalies might be helpful in preoperative differentiation of neuroepithelial or glioependymal cysts from arachnoid cysts. 33 Ependymal cysts may be intraaxial (intracerebral) or extra-axial (subarachnoid) in location.3'9'22
Therapeutic Considerations When the cyst is large but the mass effect is minimal and the patient is neurologically intact, surgical intervention is not indicated, although the patient should be re-examined periodically. There are two principal surgical treatments for arachnoid cysts: membranectomy and cystoperitoneal shunt insertion.~2'2~ Neither method is clearly preferable. In most cases, direct surgery on the cyst has been performed in order to: 1) leave the patient shunt-independent; 28 2) obtain sufficient decompression and communication between the cyst and the subarachnoid space and/or the ventricle; or 3) facilitate inspection of the underlying brain. ~ In patients without hydrocephalus, cyst fenestration is the treatment of choice. At present, we believe that performing a craniotomy solely for diagnostic purposes is not justifiable. Cystoperitoneal shunt insertion, however, has the following advantages: 1) in the case of a huge cyst or one associated with marked hydrocephalus, a shunt avoids extreme brain shift due to sudden decompression; and 2) the shunting operation is less invasive and thus is preferable in aged patients. Insertion of a VP shunt followed by resection of the cyst wall may also give good results, especially in the presence of hydrocephalus. Jo In the group of patients reported here, craniotomy with fenestration of the cyst was found to be inadequate and a shunt was required to treat the hydrocephalus. It is also now well documented in the literature that attempts at fenestration of arachnoid cysts are unsuccessful in the vast majority of cases and that shunting is required subsequently. 6'35 Considering the complications of craniotomy, and the large number of patients who need shunts even after fenestration, shunting may be the preferred initial surgical treatment for interhemispheric arachnoid cysts. Acknowledgments The author thanks Drs. Shuro Nishimura, Tomokatsu Hori, Mitsuaki Takada, and Yasuhiro Yonekawa for reviewing the cases. Gratitude is also expressed to Dr. Patrick O. Eghwrudjakpor, a clinical fellow at the Department of Neu-
J. Neurosurg. / Volume 76/February, 1992
rosurgery, Kochi Medical School, for review of the English text, and Miss Chisato Hiroi for preparing the manuscript.
References 1. Anderson FM, Segall HD, Caton WL: Use of computerized tomography scanning in supratentorial arachnoid cysts. A report on 20 children and four adults. J Neurosurg 50:333-338, 1979 2. Barkovich AJ, Norman D: Anomalies of the corpus callosum: correlation with further anomalies of the brain. AJR 151:171-179, 1988 3. Barth PG, Uylings HBM, Stare FC: Interhemispheral neuroepithelial (glio-ependymal) cysts, associated with agenesis of the corpus eallosum and neocortical maldevelopment. A case study. Childs Brain 11:312-319, 1984 4. Brocklehurst G: Diencephalic cysts. J Neurosurg 38: 47-5 l, 1973 5. Brun A, Probst F: The influence of associated cerebral lesions on the morphology of the acallosal brain. A pathological and encephalographic study. Neuroradioiogy 6: 121-131, 1973 6. Ciricillo SF, Cogan PH, Harsh GR, et al: Intracranial arachnoid cysts in children. A comparison of the effects of fenestration and shunting. J Neurosurg 74:230-235, 1991 7. Curnes JT, Laster DW, Koubek TD, et at: MRI of corpus callosal syndromes. AJNR 7:617-622, 1986 8. Davidson HD, Abraham R, Sleiner RE: Agenesis of the corpus callosum: magnetic resonance imaging. Radiology 155:371-373, 1985 9. Friede RL, Yasargil MG: Supratentorial intracerebral epithelial (ependymal) cysts: review, case reports, and fine structure. ,I Neurol Neurosurg Psychiatry 40:127-137, 1977 10. Fujita K, lshida K, Tamaki N, et at: [Midline arachnoid cyst of the brain.] Neurol Med Chir 23:387-392, 1983 (Jpn) 11. Handa J, Nakano Y, Aii H: CT cisternography with intracranial arachnoid cysts. Snrg Neurol 8:451-454, 1977 12. Harsh GR IV, Edwards MSB, Wilson CB: Intracranial arachnoid cysts in children. ,1 Nearosurg 64:835-842, 1986 13. Jeret JS, Serur D, Wisniewski KE, et ah Clinicopathological findings associated with agenesis of the corpus callosum. Brain Dev 9:255-264, 1987 14. Kendall BE: Dysgenesis of the corpus callosum. Neuroradiology 25:239-256, 1983 15. Loeser JD, Alvord ECJr: Agenesis of the corpus callosum. Brain 91:553-570, 1968 16. Loeser JD, Alvord EC Jr: Clinicopathological correlations in agenesis of the corpus callosum. Neurology 18: 745-756, 1968 17. Mashiyama S, Seki H, Takahashi K, et al: [A big arachnoid cyst from the posterior part of the third ventricle up to the cerebral convexity.] Nerv Syst Child 13:189-193, 1988 (Jpn) 18. Matsuda M, Hirai O, Munemitsu H, etal: [Arachnoid cysts. Report of two adult cases in the interhemispheric fissure and over the cerebral convexity.] Neurol Med Chir 22:71-76, 1982 (Jpn) 19. Menezes AH, Bell WE, Perret GE: Arachnoid cysts in children. Arch Neurol 37:168-172, 1980 20. Mori K: Hydrocephalus - - revision of its definition and classification with special reference to "intractable infantile hydrocephalus." Chiids Nerv Syst 6:198-204, 1990 21. Mori K, Harwood-Nash DC: Anomalies of the Central Nervous System. Neuroradiologyand Neurosurgery.New 229
K. Mori York: Thieme-Stratton, 1985, pp 43-51, 54-65 22. Morimoto T, Kaneko M, Nishikawa R, el al: [Ependymal cyst. Case report.] No Shinkei Geka 14:351-356, 1986 (Jpn) 23. Nixon GW, Ravin CE: Malposition of the attached portion of the falx cerebri and superior sagittal sinus. An indicator of severe cerebral maldevelopment. AJR 122: 44-51, 1974 24. Osaka K, Matsumoto S: Holoprosencephaly in neurosurgical practice. J Neurosurg 48:787-803, 1978 25. Parrish ML, Roessmann U, Levinsohn MW: Agenesis of the corpus callosum: a study of the frequency of associated malformations. Ann Neurol 6:349-354, 1979 26. Probst FP: Congenital defects of the corpus callosum. Morphology and encephalographic appearances. Acta Radiol 331 (Suppl):l-152, 1973 27. Probst FP: The Prosencephalies. Morphology, Neororadiological Appearances and Differential Diagnosis. Berlin: Springer-Verlag, 1979 28. Raffel C, McComb JG: To shunt or to fenestrate: which is the best surgical treatment for arachnoid cysts in pediatric patients? Neurosurgery 23:338-342, 1988 29. Rao KCVG, Gunadi IK, Diaconis JN: Interhemispheric intradural cyst. Case report. J Comput Assist Tomogr 6: 1167-1171, 1982 30. Rothner AD, Duchesneau PM, Weinstein M: Agenesis of the corpus callosum revealed by computerized tomography. Dev Med Child Neurol 18:160-166, 1976 31. Rengachary SS: Parasagittal arachnoid cyst: case report. Neurosurgery 9:70-75, 1981 32. Sarwar M, Virapongse C, Bhimani S, et al: Interhemispheric fissure sign of dysgenesis of the corpus callosum. J Comput Assist Tomogr 8:637-644, 1984 33. Shaw CM, Alvord EC Jr: "Congenital arachnoid" cysts and their differential diagnosis, in Vinken PJ, Bruyn GW (eds): Handbook of Clinical Neurology, Vol 31: Congenital Malformations of the Brain and Skull, Part lI. Amsterdam: North-Holland, 1977, pp 75-135 34. Solt LC, Deck JHN, Bairn RS, et al: Interhemispheric cyst of neuroepithelial origin in association with partial
230
agenesis of the corpus callosum. Case report and review of the literature. J Neurosurg 52:399-403, 1980 35. Stein SC: Intracranial developmental cysts in children: treatment of cystoperitoneal shunting. Neurosurgery 8: 647-650, 1981 36. Stein SC: Pathogenesis of congenital midline porencephaly. Childs Brain 8:406-416, 1981 37. Swett HA, Nixon GW: Agenesis of the corpus callosum with interhemispheric cyst. Radiology 114:641-645, 1975 38. Takahashi A, Higuchi H, Mashiyama S, et al: [Agenesis of the corpus callosum associated with interhemispheric cyst. A case report.] No Shinkei Geka 12:1077-1083, 1984 (Jpn) 39. Utsunomiya H, Hayashi T, Hashimoto T, et al: [Neuroradiological evaluation of dorsal cyst malformation.] Nerv Syst Child 13:329-338, 1988 (Jpn) 40. Utsunomiya H, Hayashi T, Honda E, et al: [A case of interhemispheric glio-ependymal cyst in a newborn infant.] No Shinkei Geka 15:771-776, 1987 (Jpn) 41. Yokota A, Matsukado Y: Congenital midline porencephaly: a new brain malformation associated with scalp anomaly. Childs Brain 5:380-397, 1979 42. Yokota A, Oota T, Matsukado Y: Dorsal cyst malformations. Part I. Clinical study and critical review of the definition of holoprosencephaly. Childs Brain l l: 320-341, 1984 43. Yokota A, Oota T, Matsukado Y, et al: Dorsal cyst malformations. Part 11. Galenic dysgenesis and its embryological considerations. ChUds Brain 11:403-417, 1984 44. Zingesser L, Schechter M, Gonatas N, et al: Agenesis of the corpus callosum associated with an inter-hemispheric arachnoid cyst. Br J Radiol 37:905-909, 1964
Manuscript received January 15, 1991. Accepted in final form July 15, 1991. Address reprint requests to: Koreaki Moil, M.D., Department of Neurosurgery, Kochi Medical School, Kobasu, Okohcho, Nankoku City, Kochi 783, Japan.
J. Neurosurg. / Volume 76 / February, 1992
Giant interhemispheric cysts associated with agenesis of the corpus callosum KOREAKI Mo~l, M.D.
Department of Neurosurgery, Kochi Medical School, Nankoku City, Japan ~" lnterhemispheric cysts, often associated with agenesis of the corpus caUosum, are rare lesions demonstrating little uniformity of pathogenesis. Four large interhemispheric cystic lesions with several unique features are reviewed. Magnetic resonance imaging clearly showed agenesis of the corpus callosum and was useful in the diagnosis of interhemispheric cysts. The differential diagnosis of these lesions is discussed, along with therapeutic considerations. KEY WORDS 9 cyst, interhemispheric corpus callosum cyst, arachnoid 9 magnetic resonance imaging
IAN~ interhemispheric cysts are rare lesions which, until the advent of magnetic resonance (MR) imaging, were mainly diagnosed by computerized tomography (CT). Various types of cystic lesions occur in the interhemispheric area. Often they are associated with agenesis of the corpus callosum, but there is no uniformity in pathogenesis among previously reported cases. These cysts should be differentiated from one another, as the prognostic and therapeutic implications may differ. Four large interhemispheric cystic lesions presenting at four different institutions prompted this report. Magnetic resonance imaging, which is currently the diagnostic tool of choice, clearly demonstrated agenesis of the corpus callosum and was useful in the differential diagnosis of these lesions.
G
Case Reports
Case 1 This 5-month-old boy was delivered normally at term after an uneventful pregnancy. At birth, he weighed 2950 gm and his head circumference was 34.7 cm. He was subsequently noted to have an enlarged head (97th percentile), which increased progressively thereafter despite otherwise normal development. His head circumference was 41.5 cm at the age of 2 months and 43 cm at 3 months. No history of head injury or high fever was obtained. He was admitted to Osaka City University Hospital in May, 1976. Examination. The anterior fontanel measured 4.5 • 5.0 cm and the head circumference was 45 cm. Infantile reflexes such as the Moro and grasp reflexes 224
9 hydrocephalus
9
were normal. Plain skull films showed suture separation, and pneumoencephalography revealed air filling of the left lateral ventricle. A structure similar to a cavum veli interpositi was demonstrated. A tap of the left lateral ventricle through the left corner of the anterior fontanel was attempted but the needle entered a cyst instead. The cystic fluid was replaced with air. On pathological examination, the fluid was xanthochromic, with a cell count of 89 a protein content of 390 mg/dl, a sugar content of 92 mg/dl, and a chlorine level of 691 mg/dl. Carotid angiograms revealed lateral displacement of the left anterior cerebral artery. Operation. A left frontoparietal craniotomy was performed in May, 1976. Immediately after dural reflection, a large cyst measuring approximately 7 • 5 cm was encountered, filled with xanthochromic fluid. The falx was normally developed and the cyst was located between both cerebral hemispheres. Below the falx, the cingulate gyrus of the fight cerebral hemisphere could be seen, but the corpus callosum was obscured. Due to its size, the cyst's anatomical relationship to the surrounding structures could not be verified. It was resected as extensively as possible. Pathological examination of its wall resulted in a diagnosis of arachnoid cyst.
Postoperative Course. The postoperative course was complicated by meningitis, which resolved in about 1 month. Postoperative cisternography revealed marked reflux of the contrast medium into the right lateral ventricle and stasis for more than 24 hours. Postoperative pneumoventricuiography showed an enlargement of the right lateral ventricle. A ventriculoperitoneal (VP) J. Neurosurg. / Volume 76/February, 1992
Giant cysts with corpus callosum agenesis
FIG. 1. Case 2. Left: Preoperative enhanced computerized tomography (CT) scan showing a huge frontoparietal midline cyst and enlargement of the lateral ventricles. The cyst wall is not enhanced by contrast medium. Right: Postoperative CT scan showing shrinkage of the cyst and a decrease in the size of the lateral ventricles.
shunt was inserted in October, 1976. Postoperative CT scans showed separation of the lateral ventricles with a collapsed interhemispheric cyst between them. The patient has developed relatively well with normal head size but with slight psychomotor retardation.
Case 2 This 21-month-old infant was found to have an enlarged ventricle at the 37th week of gestation. He was delivered by suction at 38 weeks of gestation. At birth, he weighed 3060 gin, his head circumference was 33.7 era, and his Apgar score was 8. He developed normally until 1 year of age, when he was noted to have an enlarged head (97th percentile). Frontal bossing was noted at his 1-year examination and he was referred to the Tottori University Hospital. He was diagnosed as having an interhemispheric cyst associated with hydrocephalus and was referred to the Department of Neurosurgery. Examination. The patient had no neurological abnormality and his developmental milestones were normal. Computerized tomography scans showed a huge midline cystic lesion and enlargement of the lateral ventricles (Fig. 1 left). Magnetic resonance imaging revealed a huge interhemispheric cyst associated with agenesis of the corpus callosum and separating the lateral ventricles. Metrizamide CT cisternography revealed no filling of the cyst or the left lateral ventricle. These findings suggested that the cyst had no communication with the subarachnoid space, and that the left foramen of Monro might be obstructed. Operation. Because of progressive enlargement of the head and increase in cyst size, a craniotomy was performed. The cyst was opened and communications were made between it and the subarachnoid space and the lateral ventricles. The cyst and its wall were resected as extensively as possible. The pathological diagnosis was that of an arachnoid cyst. J. Neurosurg. / Volume 76 /February, 1992
Fl~. 2. Case 3: Preoperative computerized tomography scans, without (left) and with (right) contrast enhancement, showing a huge left frontoparietal parasagittal cyst associated with agenesis of the corpus callosum. The cyst wall is not enhanced by contrast medium.
Postoperative Course. The postoperative course was uneventful and the patient was discharged in good condition. However, ventricular enlargement was noted 2 months later and a VP shunt was placed. Thereafter, his course was uneventful. Follow-up CT scans showed shrinkage of the cyst and a decrease in the size of the lateral ventricles (Fig. 1 right). Case 3 This 44-month-old girl was born at the 40th week of gestation by suction delivery. She was brought for evaluation of a generalized convulsive seizure that occurred during sleep. An electroencephalogram (EEG) showed frequent spikes and waves, predominantly in the right parietal region. She was placed on a course of anticonvulsant medication and was referred to the Takayama Red Cross Hospital because of abnormal CT scans. Examination. On admission, the patient weighed 15 kg and her head circumference measured 52.4 cm (approximately 2 standard deviations above the mean for her age group). On physical examination all other characteristics were found to be within normal limits. Neurologically, no abnormality was found. Her developmental quotient was greater than 85. No evidence of increased intracranial pressure was present. Optic fundi were normal. A huge interhemispheric cystic lesion, slightly off midline to the left and associated with agenesis of the corpus callosum, was revealed by CT (Fig. 2); the cyst wall was not enhanced by an 225
K. M o i l
FIG. 3. Case 3: Preoperative magnetic resonance images, Tt-weighted (left) and T2-weighted (right), showing no enlargement of the left parasagittal cyst.
injection of contrast medium. The cerebral hemispheres were separated laterally and the left lateral ventricle, especially the body and occilzital horn, was markedly enlarged, probably due to obstruction of the left foramen of Monro. The cyst seemed to have no communication with the lateral ventricle or subarachnoid space, and a thin septum was seen within its cavity at the level of the foramen of Monro. Clinical Course. The patient has been followed without surgical intervention. The results of follow-up MR imaging were similar to those of the CT scans obtained 2 months previously (Fig. 3).
Case 4 This 54-year-old man with an unremarkable history and normal psychomotor development consulted a neighborhood doctor, complaining of dull pain in the occipital and neck regions. He was noted to have an abnormal CT scan and was referred to the National Cardiovascular Center. Examination. Neurological findings on admission were unremarkable. Computerized tomography revealed a large cystic lesion with the same density as cerebrospinal fluid in the fight frontal region close to the midline. This was associated with dilatation of the body and occipital horn of the right lateral ventricle, and agenesis of the corpus callosum. The falx was present. The cyst was separated from the frontal horn of the right lateral ventricle by a thin septum. There was slight bulging and thinning of the frontal bone adjacent to the cyst. Asymmetry of the lateral ventricle, the right side being larger than the left, was thought to be due to obstruction of the fight foramen of Monro by the cyst. Metrizamide CT cisternography demonstrated minimal filling ef the ventricle and the cyst. Magnetic resonance images revealed findings similar 1o those of the CT scans. The sagittal images clearly demonstrated agenesis of the corpus callosum (Fig. 4 left). Gray matter could be seen between the lateral border of the cyst and the medial aspect of the right frontal lobe in the coronal images (Fig. 4 right). This finding suggested that the cyst was extra- rather than intra-axial. Right carotid angiograms revealed opacification of the right anterior cerebral artery in the anteroposterior view. The pericallosal artery ran an abnormal course and appeared to be under slight tension. In the lateral view, this artery was seen to course posterosuperiorly over the corpus callosum. Clinical Course. These findings confirmed the presence of an extra-axial mass lesion between the medial aspect of the right frontal lobe and the falx, and agenesis of the corpus callosum. Continuous pressure moni-
FIG. 4. Case 4. Left: Magnetic resonance T~-weightedimages,sagittal view, showing agenesisof the corpus callosum and a huge cyst in the frontal region, Right: Tl-weighted images,coronal view, showinga parasagittal right frontal cyst associated with agenesis of the corpus callosum. The third ventricle is displaced downward. Gray matter is present in the medial aspect of the fight frontal lobe close to the lateral border of the cyst, suggesting that the cyst is extra-axial. 226
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Giant cysts with corpus callosum agenesis (Table I). Because of the broad spectrum of cerebral malformations accompanying a cystic cavity in the dorsal midline, they may be referred to as dorsal cyst malformations. 39,42'43The differential diagnosis of midline cysts is important from both the prognostic and therapeutic points of view. Interhemispheric araehnoid cysts have been reported to be clinically benign? J,44
toting in the lumbar subarachnoid space showed no pressure waves. Chromosomal examination was noncontributory. The patient has been followed without operation, and has remained neurologically intact.
Discussion
Cyst Classification
Intra-Axia[ Cysts
Interhemispheric cysts are congenital and usually present symptoms during childhood, but they may sometimes be diagnosed in adults, 18'34'44 as in Case 4. Various types of cystic lesions occur in the interhemispheric or parasagittal area and they are often associated with agenesis of the corpus callosum. 3"1~ Previously reported cases of agenesis of the corpus callosum with a midline cyst in the supratentorial compartment have variously been referred to as midline porencepha]y, 36"4i agenesis of the corpus callosum with porencephalic cyst, 23diencephalic cyst, 4 primary or secondary interhemispheric cyst, 26 and dorsal cyst of lobar holoprosencephaly. 24 Some cysts communicate freely with the ventricular system. The common radiographic features are agenesis of the corpus callosum, a midline location, and ventricular dilatation. Gross psychomotor retardation has been reported in many patients with such an anomaly. 42 Two morphologically distinct types of cysts occur in the interhemispheric area: extra-axial cysts associated with agenesis of the corpus callosum, and intra-axial cysts. Diagnosis of the cysts with agenesis of the corpus callosum has been made easier with CT and MR imaging. 3~Extra-axial cysts associated with agenesis of the corpus callosum should be differentiated from such intra-axial midline cysts as porencephalic cyst, dorsal cysts of holoprosencephaly, and upward extension of the third ventricle in agenesis of the corpus callosum
"Congenital midline porencephaly," a different clinical entity, 36'4~ is dysgenetic hydrocephalus associated with scalp anomalies and characterized by a symmetrical defect of the bilateral posterior mantle along the midline and alopecia or cephalocele in the parietal midline. The midline cyst is considered to be a variant of the dorsal cyst of lobar holoprosencephaly 24"4aand arises from primary dysgenesis of cerebral midline structures. It is not the result of hydrocephalus. Holoprosencephaly consists of a monoventricle communicating with the dorsal cyst in the midparietal region. The falx and corpus callosum are absent. The patient may have a facial anomaly such as cleft lip and palate. Hydrocephalus seen in holoprosencephaly is considered to be intractable? ~ Simple agenesis of the corpus callosum is easily recognized on sagittal MR images. 7's Dorsal extension of the third ventricle in agenesis of the corpus callosum or "diencephalic cyst ''4 has been demonstrated in coronal CT scans. Agenesis of the corpus callosum by itself does not present clinical symptoms; ~53a however, its association with various congenital anomalies is well k n o w n . 2&13"14'1~25'27"32 Consequently, the presence of agenesis of the corpus callosum may suggest such related anomalies as Dandy-Walker syndrome, Aicardi syndrome, and Chiari II malformationJ 3 The clinical symptoms depend on the nature of the associated malformations. 34
TABLE
1
Differential diagnosis of interhemispheric or parasagittal cysts* Factor nature of cyst location of cyst
Interhemispheric Cyst extra-axial midline or parasagittal
size of cyst large mass effect communicationwith ventricle corpus callosum
+ _+
falx
+
Poreneephalic HoloprosenAgenesisof Cyst cephaly Corpus Callosum intra-axial dorsal cystic dilatation of 3rd ventricle mJdline or par- midline midline asagittal variable small small + + + + +
-
+
hydrocephalus + • _+ asymmetryof lateral ventricle + __ monoventricle anterior cerebral a r t e r y separation, abnormal course abnormalcourse azygous abnormal course deep cerebral vein abnormal course abnormal course dysgenesis abnormalcourse frequently associated anoma- gyralabnormality, neuronal nonspecific facial anomaly Aicardisyndrome,Dandy-Walkersynlies heterolopia drome, Chiari II malformation onset of symptoms early or late early early early, if present neurologicaldeficits minimal severe severe subclinical or severe * Abbreviations: + = feature present; - = feature absent; _+= presence or absence of feature equivocal.
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227
K. Mori
FIG. 5. Magnetic resonance Trweighted image, coronal view, showing a large right parasagittal intra-axial cyst in a 39year-old. Mass effect is minimal and the corpus callosum is present.
Extra-Axial Cysts Interhemispheric extra-axial cysts are subdivided by location into bilateral midline cysts 19 (Case 2 in the present series) and unilateral parasagittal cysts 17'3~ (Cases 1, 3, and 4). Coronal MR imaging is especially useful in differentiating inlerhemispheric extra-axial cysts from intra-axial cysts (Fig. 5). These cysts have no communication with the subarachnoid space or lateral
or third ventricle, as can be confirmed by CT cisternography ~'3~'34'37or cystography. 22 The third ventricle is displaced downward by the cyst and thus one or both foramina of Monro may be obstructed with resultant mono- or biventricular dilatation (Fig. 4 right). Because of the location of the cyst, ventricular dilatation is asymmetrical and marked in the body and occipital horn; a paper-thin mantle is sandwiched between the cyst and the dilated body of the lateral ventricle (Fig. 2). The frontal horn is compressed and displaced laterally (Fig. 4 right). Interhemispheric cysts are unusually large and noncommunicating, and are often associated with agenesis of the corpus callosum (Fig. 6). Associated neurological deficits are minimal. Neuroradiological images mimic those of porencephalic cyst, holoprosencephaly, and agenesis of the corpus callosum. These anomalies should be differentiated clinically (Table 1).
Histopathological Considerations In two of the four cases presented here, surgical fenestration of the cysts was performed and pathological examination led to a diagnosis of arachnoid cyst. As the interhemispheric or parasagittal area is a rather uncommon site for the occurrence of arachnoid cyst, the pathological findings may be variable. Agenesis of
FIG. 6. Schematic illustration showing coronal sections of interhemispheric or parasagittal cysts. 228
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Giant cysts with corpus callosum agenesis the corpus callosum and interhemispheric cysts containing ependyma, choroid plexus, and glial cells have been reported. 3'9'22-29,34.3s,4~These have been histopathologically diagnosed as neuroepithelial or glioependymal cysts. With or without agenesis of the corpus callosum, interhemispheric or parasagittal arachnoid cysts tend to carry a favorable prognosis ~93c44compared with neuroepithelial or glioependymal cysts. Neuroepithelial cysts are often associated with polymicrogyria ~6and nodular neuronal heterotopia. 3 These associated anomalies might be helpful in preoperative differentiation of neuroepithelial or glioependymal cysts from arachnoid cysts. 33 Ependymal cysts may be intraaxial (intracerebral) or extra-axial (subarachnoid) in location.3'9'22
Therapeutic Considerations When the cyst is large but the mass effect is minimal and the patient is neurologically intact, surgical intervention is not indicated, although the patient should be re-examined periodically. There are two principal surgical treatments for arachnoid cysts: membranectomy and cystoperitoneal shunt insertion.~2'2~ Neither method is clearly preferable. In most cases, direct surgery on the cyst has been performed in order to: 1) leave the patient shunt-independent; 28 2) obtain sufficient decompression and communication between the cyst and the subarachnoid space and/or the ventricle; or 3) facilitate inspection of the underlying brain. ~ In patients without hydrocephalus, cyst fenestration is the treatment of choice. At present, we believe that performing a craniotomy solely for diagnostic purposes is not justifiable. Cystoperitoneal shunt insertion, however, has the following advantages: 1) in the case of a huge cyst or one associated with marked hydrocephalus, a shunt avoids extreme brain shift due to sudden decompression; and 2) the shunting operation is less invasive and thus is preferable in aged patients. Insertion of a VP shunt followed by resection of the cyst wall may also give good results, especially in the presence of hydrocephalus. Jo In the group of patients reported here, craniotomy with fenestration of the cyst was found to be inadequate and a shunt was required to treat the hydrocephalus. It is also now well documented in the literature that attempts at fenestration of arachnoid cysts are unsuccessful in the vast majority of cases and that shunting is required subsequently. 6'35 Considering the complications of craniotomy, and the large number of patients who need shunts even after fenestration, shunting may be the preferred initial surgical treatment for interhemispheric arachnoid cysts. Acknowledgments The author thanks Drs. Shuro Nishimura, Tomokatsu Hori, Mitsuaki Takada, and Yasuhiro Yonekawa for reviewing the cases. Gratitude is also expressed to Dr. Patrick O. Eghwrudjakpor, a clinical fellow at the Department of Neu-
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rosurgery, Kochi Medical School, for review of the English text, and Miss Chisato Hiroi for preparing the manuscript.
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Manuscript received January 15, 1991. Accepted in final form July 15, 1991. Address reprint requests to: Koreaki Moil, M.D., Department of Neurosurgery, Kochi Medical School, Kobasu, Okohcho, Nankoku City, Kochi 783, Japan.
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