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Extraventricular choroid cysts
Extraventricular choroid cysts
J. Vaquero, S. Coca, J. C. Gómez-Angulo, C. Piqueras, M. V. Huertas and S. Ramón y Cajal. Departments of Neurosurgery and Pathology. Puerta de Hierro Clínic, Autonomous University, and Department of Pathology, Air Force Hospital, Madrid, Spain.
Summary
Introduction
Intraparenchymatous cerebral cysts covered by choroid epithelium are extremely uncommon malformative lesions. We present three cases of extraventricular choroid cysts which became symptomatic in patients at 38, 60 and 65 years of age. The identification, at least in two of these cases, of venous structures fIoating inside the cystic cavity suggests a mechanism of secretion and reabsortion of CSF, the alteration of which could lead to the growth of the cyst. At present, immunohistochemical study of epithelium that covers the socalled neuroepithelial cysts of the brain can achieve a better knowledge of these malformative lesions and to help in the selection of the best therapeutic approach for each case.
Benign intracerebral cysts without communication with the cerebral ventricles or the subarachnoid space are uncommon, and only 34 cases have been recorded by Wester and Pedersen in a recent revision of the literature25 • On the other hand, intracranial cystic lesions are generally classified according to the histology of the wal1s that delimit them. This guideline is particularly applied to malformative cysts, the most cornmon example of which is the arachnoid cyst18 , described by Bright as early as 1831 4 • Other intracranial malformative cysts, reported less often in the literature, are the so-called simple or glial cysts, in which there is on1y glial tissue to limit the cystic cavity21. 24.26, the infrequent neuroenteric cysts, which are totally or partially limited by an epithelium analogous to that of the digestive tract 1, and the so-cal1ed neuroepithelial cysts, characterized by their covering consisting of a cuboidal or prismatic epithelium, occasionally having cilia. The most cornmon example of intracranial neuroepithelial cyst would be represented by the so-cal1ed col1oid cysts of the third ventricle, the origin of which is still cause for discussion as to whether they may derive from the embryonal paraphysis 12 , from the ependyma5 , from the choroid plexus 8 , from endodermic structures 9 , or even from a characteristic developmental anomaly of primitive neuroectoderm in the embryo 13. Although from a practical point of view, the correct identification of the epithelium that covers the so-called neuroepithelial cysts is of little importance, it is obvious that under this denomination are at present included those cysts covered by epithelium of ependymal origin as wel1 as those covered by epithelium of choroidal origino The possible modifications that the two 'type's of epithelium might undergo due to the effects of the pressure of the cystic content and/or their own malformative nature (greater or lesser flattening in the choroid cel1s, and loss of cilia in the ependymal cells), as wel1 as the observation that cysts that are supposedly ependymal must be reclassified as choroidal when studied under the electron microscope, are arguments that contribute to the consideration that it is
KEY WORDS: Choroid cysts,. Neuroepithelial cysts. Ependymal cysts. Cerebrospinal fluid. Resumen Los quistes coroideos intracerebrales representan lesiones malformativas extraordinariamente infrecuentes. En el presente trabajo se presentan tres casos de quistes coroideos extraventriculares que se hicieron sintomáticos a las edades de 38, 60 Y 65 años. La identificación, al menos en dos de los casos, de estructuras venosas fIotando en la cavidad quística, sugiere la existencia de un mecanismo de formación y reabsorción de LCR, cuya alteración podría dar lugar al crecimiento del quiste. En el momento actual, el estudio inmunohistoquímico del epitelio que recubre los llamados quistes neuroepiteliales cerebrales, puede llevar a un mejor conocimiento de estas lesiones malformativas y contribuir a la selección del tratamiento más adecuado para cada uno de los casos. PALABRAS CLAVE: Quistes coroideos. Quistes neuroepiteliales. Quistes ependimarios. Líquido cefalorraquídeo.
317
Extraventricular choroid cysts
Neurocirugía
Figure 1.- Case l. CT-scan, after contrast administration, showing the right parieto-occipital cyst. A vein can be seen floating within the cyst (arrow).
of little use to try to define the exact ependymal or choroidal nature of these lesions. Despite all this, and thanks to the modero diagnostic irnaging techniques, the reports of intracranial malformative cysts in the literature have become more frequent. When these lesions are resected and identified as neuroepithelial cysts, we can now use immunohistochemical techniques to resolve the pathological differential diagnosis between ependymal epithelium and choroid epithelium. On the other hand, the question why many of these lesions, being malformative, become symptomatic when the patient reaches adult age, suggests, moreover, the need for a more detailed study of them, in both their etiopathogenic and physiopathological aspects. Rere we present our clinico-pathological experience with three cases of cerebral intraprenchymatous choroid cysts with no apparent communication with the ventricular system. Report of Cases
Case 1 A 38-year-old woman was exarnined because of a threeyear history of increasingly intense headaches, localized in right hemicranium. During this period, she had experienced several poorly defined episodes of loss of consciousness and onset of volitional tremor of the left hand which appeared to have become more pronounced in recent months. The neurological exarnination confirmed the tremor and revealed an incipient papilledema and left homonymous hemianopsia. CT-scan showed a large cystic lesion in the right parieto-occipital region. Mter administration of contrast medium, no reinforcement of the walls of the cyst was detected, although there was lineal reinforcement in its most lateral portion, which was interpreted to be a vascular structure (Fig. 1). She underwent surgery 318
Figure 2.- Case 2. CT-scan, after contrast administration, showing the septated cyst on the left parietallobe.
which revealed on the cerebral surface a cyst with content similar in appearance to cerebrospinal fluid (CSF), limited by a wall with arachnoid aspect and by an atrophic-looking cerebral parenchyma, and which extended toward the depths of the cerebral hemisphere. Floating inside the cyst, and covered by slender tracts of what appeared to be arachnoid tissue, which joined it to the outer wall, a vein was identified. After removing a large part of the walls of the cyst, there appeared a slight protrusion of the ventricular wall toward the cavity created, although the two structures remained separated by a thin layer of nervous tissue. Two years after surgery, the patient is asymptomatic, although in CT-scan there can still be observed a residual cystic cavity, with no mass effect. Case 2. This 60-year-old man complained a s!~.years history of progressive right hemiparesis, and neurological exarnination disclosed a pronunced spastic paresis of right limbs. CT-scan, after contrast administration, showed a septated cystic lesion on the left parietal lobe (Fig. 2). A craniotomy was performed and an intraparenchymatous bilobulated cyst, attached to the ventricular wall was removed (Fig. 3). Remiparesis resolved in the following three months, and at present, seven months after surgeI)', he is
Extraventricular choroid cysts
Neurocirugía
parieto-occipital region, which showed no wall reinforcement after contrast adrninistration. Nevertheless, after adrninistration of the contrast medium, a lineal image, septating the cyst, was observed (Fig. 4). She underwent surgery, which disclosed a lesion, the macroscopic aspect of which coincided completely with that described in Case 1, including the finding of a partially floating vein within the cyst. Three months after the operation, the results of neurological exarnination have not varied substantially and the CT-scan study shows a residual cavity in the surgical field.
Histological studies Figure 3.- Case 2. Surgical aspect of the intraparenchymatous cyst.
symptom-free. CT-scan study shows a residual cavity in the surgical field, without mass effect.
Case 3. A 65-year-old woman had a one-month history, preceded by a chance fati, consisting of an increasing feeling of instability and left herniparesis. The neurological exarnination revealed, as significant findings, a pronounced spastic paresis of left limbs and a left homonymous hernianopsia. CT-scan disclosed a cystic lesion in the right
Paraffin sections of resected cystic walls were stained with hematoxylin and eosin, and periodic acid-Schiff (PAS) techniques. In addition, immunohistochemical study for detection of glial fibrillary acidic protein (GFAP), vimentin, S-lOO, prealbumin, low molecular weight cytokeratin, and epithelial membrane antigen (EMA), were performed. In all the cases, histological study of the cyst walls revealed a flat cuboid epithelium, with occasional intracellular vacuolization, and without cilia. The cells showed the tendency to form papillary structures in some areas, and to form several.layers. Using the PAS technique, a well-distingued basallarnina could be observed. Epithelial cells were negative for GFAP, but they were positive for cytokeratin, S-lOO, vimentin, EMA and prealburnin (Figs. 5 and 6). With these data, in each case, a diagnosis of intraparenchymatous choroid cyst was established. Discussion
Figure 4.- Case 3. CT-scan, after contrast administration, showing the right parieto-occipital cyst. A vein can be seen floating in the lateral wall of the cyst (arrows).
Our three cases are examples of cerebral intraprenchymatous cysts covered with neuroepithelial tissue. In each case, the histological and imrnunohistochernical study of the resected walls led to the conclusion that said epithelium was of choroid origin lO. Although the formation of cysts covered with choroid epithelium is frequently related to the development of choroid plexuses, possibly persisting as intraventricular lesions and becorning symptomatic in the aduW 5. 16. 19.2>, the finding of extraventricular cysts covered with choroid epithelium is considered to be uncomrnon2. 6.11.14. To explain its pathogenesis, different hypotheses have been proposed, such as the possible existence of ectopic nests of choroid tissue 7 or an alteration in the emb'tyological development, with the formation of small diverticuli of the developing choroid plexus, which could move toward the extraventricular brain tissue 19 • In the latter interpretation, it appears logical to accept a fault in the formation of the telencephalus or minor defects in the constitution of the 319
Neurocirugía
Extraventricular choroid cysts
I I
Figure 5.- Histological and histochemical aspects ofthe resected cysts. Upper left: Histology of the resected walls in case 1, showing a cuboid epithelium, with tendency to form papillary structures. Hematoxylineosin technique, original magnification, x 75. Upper right: Detail of the epithelial cells limiting the cavity of the cyst, in the case 1. A clear subepithelial basal lamina can be seen. PAS technique, original magnification, x 400. Lower left: Case 2. PAS technique, showing a thick basal lamina. Original magnification, x 125. Lower right: Case 2. 1mmunohistochemical demonstration ofprealbumin in the cells limiting the cyst. Original magnification, x 125.
mantle and marginal layers, which would favor the extraventricular displacement of ventricular structures, whether ependymal or choroid, which might later remain isolated in the white matter of the brain, or even in the subarachnoid space, if during later embryonal development the communication with the ventriele is lost. This pathogenic hypothesis also explains the finding of extraventricular ependymal cysts3. 17.29, and oflarge malformative diverticuli of the ventricular walP3. In our cases, and in the majority of the extraventricular coroid cysts described to date, the finding of a elear fluid, 320
Figure 6.- Case 3. Immunohistoc/¡emiml demollstration of cytokeratin in the epithelial cells limili/lg ¡ji' "i> i(i 411/< cyst.Original magnification, x 200.
similar to the eSF, in the interior, suggests a circulation of this fluid between the cyst and structures like the subarachnoid space or the ventricular cavity, even when this communication can not be observed during surgery. If this circulation is hindered, the cyst could grow, as a result of a valvular effect, and become symptomatic. An altemative hypothesis might be proposed in sorne cases of extraventricular choroid cysts, supposing that an active secretion of eSF, at the expense of the choroid epithelium, could be countered by its reabsorption by structures analogous to the arachnoid villi, which may be present in the veins that, as at least in two of our cases, exist in the wall of the cyst or floating within it. According to this hypothesis, if there is an imbalance between the formation and reabsorption of the fluid in the cyst, the cyst could grow and become syrnptomatic. It is obvious that for the purpose of confirming this hypothesis, an in-depth pathological study of these venous structures should be carried out in future observations. With respect to the treatrnent of extraventricular choroid cysts, proposals inelude repeated aspirations, shunts, or rernoval of the cystic walls 2• In our cases, the last of these options was chosen, and, at least in two patients, this procedure brought the remission of the symptoms. When resection of cystic walls is incomplete, recurrent symptomatology can occurs, due to persistent secretion of CSF by the rernnants of the choroid epitheliurn. In these cases, it is possible that the establishment of a wide communication between the cystic cavity .and~the ventricular systern, or the placement of a cyst-peritoneal shunt might be considered.
Acknowledgements The authors thank Martha Messman for her expert editorial assistance.
Extraventricular cboroid cysts
References 1. AFSHAR, F.; SCHOLTZ, C. L.: Enterogenous cyst of the fourth ventricle. Casereport. J. Neurosurg.; 1981; 54: 846-838. 2. AZZAM, N. l.; TIMPERLEY, W. R: lntracerebral cyst due to ectopic choroid plexus. Case report. J. Neurosurg.; 1981; 55: 651-653. 3. BOUCH, D. C.; MITCHELL, l.; MALONEY, A F. J.: Ependymal lined paraventricular cerebral cysts; a report of three cases. J. Neurol. Neurosurg. Psychiatry; 1973; 36: 611-617. 4. BRIGHT, R.: Serous cysts in the arachnoid. In: Reports of Medical Cases Selected with a View of Illustrating the Symptoms and Cure of Diseases by a Reference to Morbid Anatomy. Vol. n. Diseases of the Brain and Nervous System, Parto 1. London. Longman, Rees, Orme, Brown and Oreen, Paternoster-Row and Highley S, 1831, pp: 437-439. 5. COKE, W. S.; LUSE, S. A.: Colloid cyst of third ventricle. An electron microscopic study. J. Neuropath. Exp. Neurol.; 1964; 23: 431-445. 6. FANDIÑO, J.; OLIVER, J.; VILADRICH, A.; BOTANA, C.; MARTINEZ-GEIJO, P.; GOMEz-BUENO, J.: Quiste coroideo intraparenquimatoso. Neurocirugía; 1990; 1: 171-173. 7. HANDA. H.; Bucy, P. c.: Bening cysts ofthe brain simulating brain tumor. J. Neurosurg.; 1956; 13: 489-499. 8. HAYMAKER, W.; YERNERMAN, M. H.: Pathological features of colloid cysts of the third véntricle: a consideration of 60 cases. Excerpta Med.; 1955; 8:788. 9. HIRANO, A; GHATAK, N. R: The fine structure of colloid cysts of the third ventricle. J. Neuropath. Exp. Neurol.; 1974; 33: 333-341. 10. INOUE, T.; MATSUSHIMA, T.; FUKill, M.; IWAKI, T.; TAKESHITA, l.; KUROMATSU, C.: lmmunohistochernical study of intracranial cysts. Neurosurgery; 1988; 23: 576-581. 11. JAKUBIAK, P.; DUNSMORE, R H.; BECKETT, R. S.: Supratentoria! brain cysts. J. Neurosurg.; 1968; 28: 129-139. 12. KApPERS, J. A: The development of the paraphysis cerebri in man with comments on its relationship to the intercolumnar tubercle and its significance for the origin of cystic tumors in the third ventricle. J. Comp. Neurol.; 1955; 102: 425-509. 13. KONDZIOLKA, D.; BILBAO, J. M.: An immunohistochemical study of neuroepithelial (colloid) cysts. J. Neurosurg.; 1989; 71: 91-97.
Neurocirugía
14. KOTO, A; HOROUPIAN, D. S.; SHULMAN, K.: Choroidal epithelial cyst. Case reporto J. Neurosurg.; 1977; 47: 955-960. 15. NETSKY, M. G.; SHUANGSHOTI, S.: The Choroid Plexus in Health and Disease. Charlottesville, University of Virginia Press, 1975; pp: 351. 16. ODAKE, G.; TENJIN, H.; MURAKAMI, N.: Cyst of the choroid plexus in the lateral ventricle: Case report and review of the literature. Neurosurgery; 1990; 27: 470-476. 17. PATRICK, B. S.: Ependymal cyst of the Sylvian fissure. Case reporto J. Neurosurg.; 1971; 35: 751-754. 18. RAMIRo, J.; VAQUERO, J.: Quistes aracnoideos congénitos intracraneales. Phronesis; 1990; 11: 57-84. 19. SHUANGSHOTI, S.; NETSKY, M. G.: Neuroepithelial (colloid) cysts of the nervous system. Further observations on pathogenesis, location, incidence, and histochemistry. Neurology; 1966; 16: 887-903. 20. TANDON, P. N.; Roy, S.; ELVIDGE, A.: Subarachnoid ependymal cyst. Report of two cases. J. Neurosurg.; 1972; 37: 741-745. 21. VAQUERO, J.; CABEZUDO, J. M.; AREITIO, E.: Glial cysts of the cerebellum. Surg. Neurol.; 1981; 16: 288-289. 22. VAQUERO, J.; CABEZUDO, J. M.; LEUNDA, G.: Symptomatic cyst of choroid plexus ofthe lateral ventricle. J. Neurol. Neurosurg. Psychiatry; 1980; 43: 555 (letter). 23. VAQUERO, J.; MARTINEZ, R.; COCA, S.; SAUCEDO, G.: Symptomatic diverticulum of the 4th ventricle. Neurosurgery; 1991; 28: 164-165. 24. VAQUERO, J.; MARTINEZ, R.; ESCANDON, J.; BRAVO, G.: Symptomatic glial cysts of the pinea! gland. Surg. Neurol.; 1988; 30: 468-470. 25. WESTER, K.; PEDERSEN, P. H.: Benign intracerebral cysts treated with internal shunts: Review and report of two patients. Neurosurgery; 1992; 30: 432-436. 26. WILKINS, R. H.; BURGER, P. C.: Bening intraparenchymal brain cysts without an epitheliallining. J. Neurosurg.; 1988; 68: 378-382.
Vaquero, J.; Coca, S.; Gómez-Angulo, J. c.; Piqueras, c.; Huertas, M. V.; Ramón y Cajal, S.: Extraventricular choroid cysts. Neurocirugía 1993; 4: 317-321.
321
J. Vaquero, S. Coca, J. C. Gómez-Angulo, C. Piqueras, M. V. Huertas and S. Ramón y Cajal. Departments of Neurosurgery and Pathology. Puerta de Hierro Clínic, Autonomous University, and Department of Pathology, Air Force Hospital, Madrid, Spain.
Summary
Introduction
Intraparenchymatous cerebral cysts covered by choroid epithelium are extremely uncommon malformative lesions. We present three cases of extraventricular choroid cysts which became symptomatic in patients at 38, 60 and 65 years of age. The identification, at least in two of these cases, of venous structures fIoating inside the cystic cavity suggests a mechanism of secretion and reabsortion of CSF, the alteration of which could lead to the growth of the cyst. At present, immunohistochemical study of epithelium that covers the socalled neuroepithelial cysts of the brain can achieve a better knowledge of these malformative lesions and to help in the selection of the best therapeutic approach for each case.
Benign intracerebral cysts without communication with the cerebral ventricles or the subarachnoid space are uncommon, and only 34 cases have been recorded by Wester and Pedersen in a recent revision of the literature25 • On the other hand, intracranial cystic lesions are generally classified according to the histology of the wal1s that delimit them. This guideline is particularly applied to malformative cysts, the most cornmon example of which is the arachnoid cyst18 , described by Bright as early as 1831 4 • Other intracranial malformative cysts, reported less often in the literature, are the so-called simple or glial cysts, in which there is on1y glial tissue to limit the cystic cavity21. 24.26, the infrequent neuroenteric cysts, which are totally or partially limited by an epithelium analogous to that of the digestive tract 1, and the so-cal1ed neuroepithelial cysts, characterized by their covering consisting of a cuboidal or prismatic epithelium, occasionally having cilia. The most cornmon example of intracranial neuroepithelial cyst would be represented by the so-cal1ed col1oid cysts of the third ventricle, the origin of which is still cause for discussion as to whether they may derive from the embryonal paraphysis 12 , from the ependyma5 , from the choroid plexus 8 , from endodermic structures 9 , or even from a characteristic developmental anomaly of primitive neuroectoderm in the embryo 13. Although from a practical point of view, the correct identification of the epithelium that covers the so-called neuroepithelial cysts is of little importance, it is obvious that under this denomination are at present included those cysts covered by epithelium of ependymal origin as wel1 as those covered by epithelium of choroidal origino The possible modifications that the two 'type's of epithelium might undergo due to the effects of the pressure of the cystic content and/or their own malformative nature (greater or lesser flattening in the choroid cel1s, and loss of cilia in the ependymal cells), as wel1 as the observation that cysts that are supposedly ependymal must be reclassified as choroidal when studied under the electron microscope, are arguments that contribute to the consideration that it is
KEY WORDS: Choroid cysts,. Neuroepithelial cysts. Ependymal cysts. Cerebrospinal fluid. Resumen Los quistes coroideos intracerebrales representan lesiones malformativas extraordinariamente infrecuentes. En el presente trabajo se presentan tres casos de quistes coroideos extraventriculares que se hicieron sintomáticos a las edades de 38, 60 Y 65 años. La identificación, al menos en dos de los casos, de estructuras venosas fIotando en la cavidad quística, sugiere la existencia de un mecanismo de formación y reabsorción de LCR, cuya alteración podría dar lugar al crecimiento del quiste. En el momento actual, el estudio inmunohistoquímico del epitelio que recubre los llamados quistes neuroepiteliales cerebrales, puede llevar a un mejor conocimiento de estas lesiones malformativas y contribuir a la selección del tratamiento más adecuado para cada uno de los casos. PALABRAS CLAVE: Quistes coroideos. Quistes neuroepiteliales. Quistes ependimarios. Líquido cefalorraquídeo.
317
Extraventricular choroid cysts
Neurocirugía
Figure 1.- Case l. CT-scan, after contrast administration, showing the right parieto-occipital cyst. A vein can be seen floating within the cyst (arrow).
of little use to try to define the exact ependymal or choroidal nature of these lesions. Despite all this, and thanks to the modero diagnostic irnaging techniques, the reports of intracranial malformative cysts in the literature have become more frequent. When these lesions are resected and identified as neuroepithelial cysts, we can now use immunohistochemical techniques to resolve the pathological differential diagnosis between ependymal epithelium and choroid epithelium. On the other hand, the question why many of these lesions, being malformative, become symptomatic when the patient reaches adult age, suggests, moreover, the need for a more detailed study of them, in both their etiopathogenic and physiopathological aspects. Rere we present our clinico-pathological experience with three cases of cerebral intraprenchymatous choroid cysts with no apparent communication with the ventricular system. Report of Cases
Case 1 A 38-year-old woman was exarnined because of a threeyear history of increasingly intense headaches, localized in right hemicranium. During this period, she had experienced several poorly defined episodes of loss of consciousness and onset of volitional tremor of the left hand which appeared to have become more pronounced in recent months. The neurological exarnination confirmed the tremor and revealed an incipient papilledema and left homonymous hemianopsia. CT-scan showed a large cystic lesion in the right parieto-occipital region. Mter administration of contrast medium, no reinforcement of the walls of the cyst was detected, although there was lineal reinforcement in its most lateral portion, which was interpreted to be a vascular structure (Fig. 1). She underwent surgery 318
Figure 2.- Case 2. CT-scan, after contrast administration, showing the septated cyst on the left parietallobe.
which revealed on the cerebral surface a cyst with content similar in appearance to cerebrospinal fluid (CSF), limited by a wall with arachnoid aspect and by an atrophic-looking cerebral parenchyma, and which extended toward the depths of the cerebral hemisphere. Floating inside the cyst, and covered by slender tracts of what appeared to be arachnoid tissue, which joined it to the outer wall, a vein was identified. After removing a large part of the walls of the cyst, there appeared a slight protrusion of the ventricular wall toward the cavity created, although the two structures remained separated by a thin layer of nervous tissue. Two years after surgery, the patient is asymptomatic, although in CT-scan there can still be observed a residual cystic cavity, with no mass effect. Case 2. This 60-year-old man complained a s!~.years history of progressive right hemiparesis, and neurological exarnination disclosed a pronunced spastic paresis of right limbs. CT-scan, after contrast administration, showed a septated cystic lesion on the left parietal lobe (Fig. 2). A craniotomy was performed and an intraparenchymatous bilobulated cyst, attached to the ventricular wall was removed (Fig. 3). Remiparesis resolved in the following three months, and at present, seven months after surgeI)', he is
Extraventricular choroid cysts
Neurocirugía
parieto-occipital region, which showed no wall reinforcement after contrast adrninistration. Nevertheless, after adrninistration of the contrast medium, a lineal image, septating the cyst, was observed (Fig. 4). She underwent surgery, which disclosed a lesion, the macroscopic aspect of which coincided completely with that described in Case 1, including the finding of a partially floating vein within the cyst. Three months after the operation, the results of neurological exarnination have not varied substantially and the CT-scan study shows a residual cavity in the surgical field.
Histological studies Figure 3.- Case 2. Surgical aspect of the intraparenchymatous cyst.
symptom-free. CT-scan study shows a residual cavity in the surgical field, without mass effect.
Case 3. A 65-year-old woman had a one-month history, preceded by a chance fati, consisting of an increasing feeling of instability and left herniparesis. The neurological exarnination revealed, as significant findings, a pronounced spastic paresis of left limbs and a left homonymous hernianopsia. CT-scan disclosed a cystic lesion in the right
Paraffin sections of resected cystic walls were stained with hematoxylin and eosin, and periodic acid-Schiff (PAS) techniques. In addition, immunohistochemical study for detection of glial fibrillary acidic protein (GFAP), vimentin, S-lOO, prealbumin, low molecular weight cytokeratin, and epithelial membrane antigen (EMA), were performed. In all the cases, histological study of the cyst walls revealed a flat cuboid epithelium, with occasional intracellular vacuolization, and without cilia. The cells showed the tendency to form papillary structures in some areas, and to form several.layers. Using the PAS technique, a well-distingued basallarnina could be observed. Epithelial cells were negative for GFAP, but they were positive for cytokeratin, S-lOO, vimentin, EMA and prealburnin (Figs. 5 and 6). With these data, in each case, a diagnosis of intraparenchymatous choroid cyst was established. Discussion
Figure 4.- Case 3. CT-scan, after contrast administration, showing the right parieto-occipital cyst. A vein can be seen floating in the lateral wall of the cyst (arrows).
Our three cases are examples of cerebral intraprenchymatous cysts covered with neuroepithelial tissue. In each case, the histological and imrnunohistochernical study of the resected walls led to the conclusion that said epithelium was of choroid origin lO. Although the formation of cysts covered with choroid epithelium is frequently related to the development of choroid plexuses, possibly persisting as intraventricular lesions and becorning symptomatic in the aduW 5. 16. 19.2>, the finding of extraventricular cysts covered with choroid epithelium is considered to be uncomrnon2. 6.11.14. To explain its pathogenesis, different hypotheses have been proposed, such as the possible existence of ectopic nests of choroid tissue 7 or an alteration in the emb'tyological development, with the formation of small diverticuli of the developing choroid plexus, which could move toward the extraventricular brain tissue 19 • In the latter interpretation, it appears logical to accept a fault in the formation of the telencephalus or minor defects in the constitution of the 319
Neurocirugía
Extraventricular choroid cysts
I I
Figure 5.- Histological and histochemical aspects ofthe resected cysts. Upper left: Histology of the resected walls in case 1, showing a cuboid epithelium, with tendency to form papillary structures. Hematoxylineosin technique, original magnification, x 75. Upper right: Detail of the epithelial cells limiting the cavity of the cyst, in the case 1. A clear subepithelial basal lamina can be seen. PAS technique, original magnification, x 400. Lower left: Case 2. PAS technique, showing a thick basal lamina. Original magnification, x 125. Lower right: Case 2. 1mmunohistochemical demonstration ofprealbumin in the cells limiting the cyst. Original magnification, x 125.
mantle and marginal layers, which would favor the extraventricular displacement of ventricular structures, whether ependymal or choroid, which might later remain isolated in the white matter of the brain, or even in the subarachnoid space, if during later embryonal development the communication with the ventriele is lost. This pathogenic hypothesis also explains the finding of extraventricular ependymal cysts3. 17.29, and oflarge malformative diverticuli of the ventricular walP3. In our cases, and in the majority of the extraventricular coroid cysts described to date, the finding of a elear fluid, 320
Figure 6.- Case 3. Immunohistoc/¡emiml demollstration of cytokeratin in the epithelial cells limili/lg ¡ji' "i> i(i 411/< cyst.Original magnification, x 200.
similar to the eSF, in the interior, suggests a circulation of this fluid between the cyst and structures like the subarachnoid space or the ventricular cavity, even when this communication can not be observed during surgery. If this circulation is hindered, the cyst could grow, as a result of a valvular effect, and become symptomatic. An altemative hypothesis might be proposed in sorne cases of extraventricular choroid cysts, supposing that an active secretion of eSF, at the expense of the choroid epithelium, could be countered by its reabsorption by structures analogous to the arachnoid villi, which may be present in the veins that, as at least in two of our cases, exist in the wall of the cyst or floating within it. According to this hypothesis, if there is an imbalance between the formation and reabsorption of the fluid in the cyst, the cyst could grow and become syrnptomatic. It is obvious that for the purpose of confirming this hypothesis, an in-depth pathological study of these venous structures should be carried out in future observations. With respect to the treatrnent of extraventricular choroid cysts, proposals inelude repeated aspirations, shunts, or rernoval of the cystic walls 2• In our cases, the last of these options was chosen, and, at least in two patients, this procedure brought the remission of the symptoms. When resection of cystic walls is incomplete, recurrent symptomatology can occurs, due to persistent secretion of CSF by the rernnants of the choroid epitheliurn. In these cases, it is possible that the establishment of a wide communication between the cystic cavity .and~the ventricular systern, or the placement of a cyst-peritoneal shunt might be considered.
Acknowledgements The authors thank Martha Messman for her expert editorial assistance.
Extraventricular cboroid cysts
References 1. AFSHAR, F.; SCHOLTZ, C. L.: Enterogenous cyst of the fourth ventricle. Casereport. J. Neurosurg.; 1981; 54: 846-838. 2. AZZAM, N. l.; TIMPERLEY, W. R: lntracerebral cyst due to ectopic choroid plexus. Case report. J. Neurosurg.; 1981; 55: 651-653. 3. BOUCH, D. C.; MITCHELL, l.; MALONEY, A F. J.: Ependymal lined paraventricular cerebral cysts; a report of three cases. J. Neurol. Neurosurg. Psychiatry; 1973; 36: 611-617. 4. BRIGHT, R.: Serous cysts in the arachnoid. In: Reports of Medical Cases Selected with a View of Illustrating the Symptoms and Cure of Diseases by a Reference to Morbid Anatomy. Vol. n. Diseases of the Brain and Nervous System, Parto 1. London. Longman, Rees, Orme, Brown and Oreen, Paternoster-Row and Highley S, 1831, pp: 437-439. 5. COKE, W. S.; LUSE, S. A.: Colloid cyst of third ventricle. An electron microscopic study. J. Neuropath. Exp. Neurol.; 1964; 23: 431-445. 6. FANDIÑO, J.; OLIVER, J.; VILADRICH, A.; BOTANA, C.; MARTINEZ-GEIJO, P.; GOMEz-BUENO, J.: Quiste coroideo intraparenquimatoso. Neurocirugía; 1990; 1: 171-173. 7. HANDA. H.; Bucy, P. c.: Bening cysts ofthe brain simulating brain tumor. J. Neurosurg.; 1956; 13: 489-499. 8. HAYMAKER, W.; YERNERMAN, M. H.: Pathological features of colloid cysts of the third véntricle: a consideration of 60 cases. Excerpta Med.; 1955; 8:788. 9. HIRANO, A; GHATAK, N. R: The fine structure of colloid cysts of the third ventricle. J. Neuropath. Exp. Neurol.; 1974; 33: 333-341. 10. INOUE, T.; MATSUSHIMA, T.; FUKill, M.; IWAKI, T.; TAKESHITA, l.; KUROMATSU, C.: lmmunohistochernical study of intracranial cysts. Neurosurgery; 1988; 23: 576-581. 11. JAKUBIAK, P.; DUNSMORE, R H.; BECKETT, R. S.: Supratentoria! brain cysts. J. Neurosurg.; 1968; 28: 129-139. 12. KApPERS, J. A: The development of the paraphysis cerebri in man with comments on its relationship to the intercolumnar tubercle and its significance for the origin of cystic tumors in the third ventricle. J. Comp. Neurol.; 1955; 102: 425-509. 13. KONDZIOLKA, D.; BILBAO, J. M.: An immunohistochemical study of neuroepithelial (colloid) cysts. J. Neurosurg.; 1989; 71: 91-97.
Neurocirugía
14. KOTO, A; HOROUPIAN, D. S.; SHULMAN, K.: Choroidal epithelial cyst. Case reporto J. Neurosurg.; 1977; 47: 955-960. 15. NETSKY, M. G.; SHUANGSHOTI, S.: The Choroid Plexus in Health and Disease. Charlottesville, University of Virginia Press, 1975; pp: 351. 16. ODAKE, G.; TENJIN, H.; MURAKAMI, N.: Cyst of the choroid plexus in the lateral ventricle: Case report and review of the literature. Neurosurgery; 1990; 27: 470-476. 17. PATRICK, B. S.: Ependymal cyst of the Sylvian fissure. Case reporto J. Neurosurg.; 1971; 35: 751-754. 18. RAMIRo, J.; VAQUERO, J.: Quistes aracnoideos congénitos intracraneales. Phronesis; 1990; 11: 57-84. 19. SHUANGSHOTI, S.; NETSKY, M. G.: Neuroepithelial (colloid) cysts of the nervous system. Further observations on pathogenesis, location, incidence, and histochemistry. Neurology; 1966; 16: 887-903. 20. TANDON, P. N.; Roy, S.; ELVIDGE, A.: Subarachnoid ependymal cyst. Report of two cases. J. Neurosurg.; 1972; 37: 741-745. 21. VAQUERO, J.; CABEZUDO, J. M.; AREITIO, E.: Glial cysts of the cerebellum. Surg. Neurol.; 1981; 16: 288-289. 22. VAQUERO, J.; CABEZUDO, J. M.; LEUNDA, G.: Symptomatic cyst of choroid plexus ofthe lateral ventricle. J. Neurol. Neurosurg. Psychiatry; 1980; 43: 555 (letter). 23. VAQUERO, J.; MARTINEZ, R.; COCA, S.; SAUCEDO, G.: Symptomatic diverticulum of the 4th ventricle. Neurosurgery; 1991; 28: 164-165. 24. VAQUERO, J.; MARTINEZ, R.; ESCANDON, J.; BRAVO, G.: Symptomatic glial cysts of the pinea! gland. Surg. Neurol.; 1988; 30: 468-470. 25. WESTER, K.; PEDERSEN, P. H.: Benign intracerebral cysts treated with internal shunts: Review and report of two patients. Neurosurgery; 1992; 30: 432-436. 26. WILKINS, R. H.; BURGER, P. C.: Bening intraparenchymal brain cysts without an epitheliallining. J. Neurosurg.; 1988; 68: 378-382.
Vaquero, J.; Coca, S.; Gómez-Angulo, J. c.; Piqueras, c.; Huertas, M. V.; Ramón y Cajal, S.: Extraventricular choroid cysts. Neurocirugía 1993; 4: 317-321.
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