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Epidermoid tumors of the IV ventricle: Report of 3 cases
Epidermoid tumors of the IV ventric1e: Report of 3 cases
W. Bini;A. Sepehrnia*; M. Dündar* y M. Samii*. HSK Neurochirurgische Klinik (Priv. Doz. Dr. R. Schonmayr), Wiesbaden-Germany. haus Hannover-Germany
Summary Epidermoid tumors of the fourth ventricle constitute a rarity and pose diagnostic difficulties. We present 3 cases of IV ventric1e epidermoid tumor extracted from our serie of 35 posterior fossa epidermoids (cerebellopontine angle) operated between 1977 and 1992. Clinical and radiological data are presented and the best diagnostic screening method and considerations concerning total removal are discussed. KEY WORDS: intracranial epidermoids, IVth ventricle, surgical management.
Resumen Los epidermoides del IV ventrículo constituyen una rara entidad clínico-quirúrgi~a debido a su baja frecuencia y pueden determinar dificultades en su diagnóstico. De nuestra serie de 35 epidermoides de fosa posterior (ángulo pontocerebeloso) operados entre 1977 y 1992, se presentan 3 casos de lesiones a nivel del IV ventrículo. Se analizan los datos clínicos y neuroradiológicos y se discute el mejor método para llevar a cabo un «screening» diagnóstico y una exéresis total. PALABRAS CLAVE: epidermoides intracraneales, IV ventrículo, tratamiento quirúrgico.
Introduction Since Cruveilhier's first description in 1829 3, epidermoid tumors have in the recent decade regained the attention of both neuroradiologists and neurosurgeons. Nevertheless, their preoperative diagnosis and the possibility of total removal are still a matter of discussion 15,28,29,35,36,38,39. The usually long interval between the onset of symptoms and diagnosis is a direct consequence of their intracisternal location but also relates to the fact that these lesions have CT attenuation values (-2 to +12 Hu) similar to those of CSF and characteristically show no enhancement contributing to the delayed diagnosis 7,11-14,18-20. We report on 3
* Neurochirurgische Klinik, Nordstadt Kranken-
cases of epidermoid of the fourth ventricle which were totally removed.
Material and Method Case 1
A 46 year old female with a long history of vertigo reported three weeks before admission two acute episodes of vertigo. The patient had a normal neurological exarnination with the exception of a mild truncal ataxia and a positive Romberg sign to the right. A CT scan evidenciated an hypodense area located in the midline of the posterior fossa. It appeared cystic and did not enhance. The cyst seemed to be located in the fourth ventricle extending to the foramen magnum. There was no evidence of hydrocephalus. A vertebral angiography showed signs of mass effect without pathological vascularization (Fig. la). A midline posterior fossa craniectomy was performed in a semi-sitting position. A white «pearly» tumor could be seen protruding out of the foramen of Magendie just after dural opening. Microsurgical piecemeal complete removal could be achieved. Care was taken to avoid the spilling of cholesterol crystals in the subarachnoidal space via constant irrigation (HydroflowlPortex). The tumor was 4 x 5 cm in diameter, avascular and «originated» on the floor of the IVth ventricle having a lateral expansion in both foramen of Luschka and posteriorly to the cisterna magna. Postoperatively the patient presented a slight abducens dysfunction on the right which resolved by discharge two weeks after surgery (Fig. lb). Case 2
A 57 year old female with a three yeár history of vertigo and gait disturbances. These symptoms were progressive and worsening. On admission she presented with a truncal ataxia, a left horizontal and moderate vertical nystagmus. A CT scan showed evidence of a cystic posterior fossa lesion with low attenuation values and no enhancement. It was located in the IVth ventricle and had a left lateral extension that could not be well delimitated. The brain stem 205
Epidermoid tumors of the IV ventricle: Report of 3 cases
Neurocirugía
Fig. la- Enhanced CT scan with sagittal reconstruction demonstrating the hypodense midline posterior lossa lesion compatible with an epidermoid tumor.
was compressed anteriorly and to the right. There was no hydrocephalus. The actual border of the tumor was identified after performing an MR study. A 1-2 mm thick tissue layer contrasting with the tumor tissue on the floor of the IVth ventricle was also evidenciated (Fig. 2a, b).
Fig. 2a- Non-enhanced CT scan demonstrating an hypodense lesion located within the IVth ventricle.
A rnidline exposure in a serni-sitting position was performed and rnicrosurgical complete removal of the «pearly» avascular tumor achieved. Gn the floor of the fourth ventricle a yellow glistening tissue, extremely adherent to the floor was found. It was difficult to differenciate whether it was tumor capsule or gliosis. The histological exarnination confirmed the gliotic nature (Fig. 2c). A few hours after recovery on the Intensive Care ward, the patient presented deterioration of the level of consciousness with a facial palsy and abscence of corneal reflex on the left with hemiparesis on the right. The control CT showed no evidence of brain stem compression, hemorrhage nor infarction. The patient was placed on antioedema therapy. The clinical course improved and the patient was discharged four weeks after surgery with a residual facial palsy and a rnild abducens dysrunction on the left. Case 3 Fig. lb- Immediate post-operative non-enhanced CT control study. B6th lateral recessus 01 the IVth ventricle can be observed.
206
A 34 year old male patient was referred to us after having been screened via MRi and diagnosed of a rnidline posterior fossa «cystic» expansive process involving the
Epidermoid tumors of the IV ventricle: Report of 3 cases
Neurocirugía
Fig. 2b- MR study (sagittal projection). Note the intense signal region deliminating the pons and floor of the IVth ventricle. This area corresponded to the gliotic adherent layer found intraoperatively.
IVth ventricle and cisterna magna. Sagittal slices clearly demonstrated a dorsal brain stem pinching in the area of the foramen magnum. The enhanced CT study demonstrated a lateral extension in the right foramen of Luschka with primary involvement of the cisterna magna. Hydrocephalus was absent as well as tumor enhancement. The process was 3 x 5 cm in its major diameter. The patient presented an unspecific clinical picture of vertigo and ocular motor nerve dysfunction (Fig. 3a, b, c). In a semi-sitting position and through a midline suboccipital craniectomy, the lesion, which appeared to be an epidermoid tumor, could be completely removed. Moderate adherencies were detected on the floor of the IVth ventricle. The patient was discharged 2 wee].cs after surgery presenting sorne ataxia and a slight abducens palsy on the right.
** At three months follow-up all patients had improved as far as residual signs/symptoms. Abducens function was normal, gait disturbances or ataxia were not present. Nevertheless, patient 2 still presented facial nerve dysfunction. Discussion
Epidermoids are benign neoplasms growing by retention of desquamated epidermall cell debris containing queratin and colesterol, originating from the stratum basa-
Fig. 2c- Intraoperative view. The tumor extended caudally to the cerebello-medular cistem.
lis of the lining of the cyst. The cyst wall is formed by fibrous connective tissue. Dermoid tumors contain in addition, pilosebaceous components and sweat glands enlarging also by a true glandular secretion. Epidermoids and dermoids are thought to arise from ectodermal tissue that fails to properly separate from it' s neuroectodermal counterpart between the 3rd and 5th weeks of gestation at the time of closure of the neural tube. The lateral location of many epidermoids may be related to epithelial enclosement at the time of formation of secondary vesicles. It has been suggested that dermoids are formed at a later time of gestational development 1.8. Trauma and repeated subdural taps have been related to the development of intracranial epidermoids and this is not surprisíng ~onsidering that spinal epidermoids have long been taken to be associated to repeated spinal taps and that experimentally the implantation of skin fragments into the brain of newborn rats may give rise to intracranial dermoids or epidermoids 6.16. Intrapetrous epidermoids (cholesteatomas) are the result of chronic otitis media or may be secondary to laterally implanted epithelial cells. 207
Epidermoid tumors of the IV ventricle: Report of 3 cases
Neurocirugía
Fig. 3a- Enhanced CT sean demonstrating a 3,5 x 5 cm midline lesion involving the lVth ventricle and the cisterna magna.
Fig. 3c- Coronal MRi slice. There is a clear caudal and right foramen Luschka extension.
Epidermoids and dermoids occur along the whole lenght of the neuroaxis. Intracranial epidermoids are more common than dermoids. They are usually located in a lateral position and are commonly less associated with other anomalies. Epidermoids represent 0,5-1,8% of aH intracranial tumors. These tumors accounted for 3,6% of all CPA lesions operated upon during the time period considered in our material. The most common locations of CNS involvement in order of decreasing frequency are; CPA, parapituitary region, diploe of the skull (fronto-parietal bones), spinal canal and the paratrigerninal region 2.4, S, lO, 16, 17,22, 24.25. 32. 33. The growth rate has been estimated to be the tumover of normal human skin, but the true neoplastic nature of these lesions is underscored by the documented, eventhough rare, possibility of malignant transformation leading to the development of squamous carcinomas 21,27,34. The tumors must obliterate a significant part of the subarachnoid space before permanent functional compromise of the intracistemal structures.leads to diagnosis. There
is a frequent disproportion between the tumor' s volume and the symptoms and abscence of hydrocephalus. Fluctuating symptoms have been often reported in these tumors and can lead to a false diagnosis of degenerative CNSdisease 15,23,30,36.38. As for fourth ventricle epidermoids predorninant and typical symptoms may be ataxia, diplopia, nystagmus and headaches 30. The CT appearance resembles a poorly delimitated cyst involving the IVth ventricle with attenuation values similar to that of CSF ranging from -8 to +32 Hu. There is no enhancement after endovenous contrast administration but ring enhancement as sign of malignant epithelial component has been reported. The abscence of hydrocephalus can reinfOl:ce the diagnosis. Other lesions which should be considered are: cystic astrocytoma, hemangioblastoma, dermoid tumor, arachnoidal cyst and cysticercosis. Saponification of the cholesterol elements or hemosiderin deposits can determine higher Hounsfield values 7,14.18,19.26.31. For the pre-operative delimitation of the tumor borders and . better evaluation of the surgical anatomy with exclusion of possible bony artifacts and with sagital plane views, MRi is the screening method of choice 37. It is non-invasive and belongs to the neurosurgical-neuroradiological protocol for the evaluation of skull base lesions. The role of post-operative MR controls is questionable for the inmediate postoperative evaluation and the images must be carefully interpreted as there are often discrepancies between eventual rests of tumor and signal from iatrogenic tissue changes caused by the surgical exposure and mani,pulation. We consider that CT-metrizamide cistemography is superior to control and document the extent of surgical removal 20 • The treatment of these lesions is definitely a surgical one. The difficulties encountered in their removal must be considered 35,36,38.39. The main technical difficulty relates not so much to the extension of the tumor which can be easily followed in the enlarged subarachnoid spaces, but
Fig. 3b- Sagittal MRi slice. Note the compressive effect on the brain stem with dorsal pinching at the level of the craniocervical juncture.
208
Epidermoid tumors of the IV ventricle: Report of 3 cases
rather on the adhesions of the tumor and the nearby neurovascular structures. It is speculated that bouts of even mild chemical meningitis may result in a strong inflamatory reaction with intimate binding of the tumor capsule and the surrounding structures 9. Our 3 cases illustrate this problem. In the first and the third cases removal could be achieved without post-operative complications. In the second case, the removal of the fine tissue layer adherent to the IVth ventricle (fibrillary gliosis with foreign body giant ceUs, perhaps triggered by spillage of tumor irritating substances ie. cholesterol) caused a transient brain stem dysfunction. We conclude that a total microsurgical removal should be attempted, the usual technique being intracapsular debulking and extracapsular dissection. Nevertheless, when total capsular removal is difficult then it is better to leave minute tumor remnants than to force the procedure. This is especiaUy so when dealing with fourth ventricle epidermoids which can lead to brain stem damage. There seems to be a subgroup of patients, probably those with history of chemical meningitis, in whom the goal of total removal is not safely achievable. These patients should be foUowed-up periodically with MR scails. Re-operation should be offered with caution, based on a combination of clinical and neuroradiological data considering that despite tumor growth, it may take a period of time equal to the patient' s age plus 9 months before a congenital tumor, as epidermoids undoubtedly are, become again symptomatic (CoUin's Law). This consideration must be balanced by the fact that it is easier to remove a small tumor than a large one. Bibliography 1. ALVORD, E.G. JR.: Growth rates of epidermoid tumors. Ann Neurol 1977; 2: 367-370. 2. ALBANESE, V., TOMASELLO, F., PICOZZI, P.: Paramedian hourglass epidennoid extending aboye and below the tentorium. Surg Neuro11982; 18: 356-363. 3. BAILEY, P.: Cruveilhier's «Tumeurs Perlees». Surg Gynecol Obstet 1920; 31: 390-401. 4. BAUMANN, CRR, Bucy, P.e.: Paratrigeminal epidermoid tumors. J. Neurosurg 1956; 13: 455-468. 5. BERGER, M.S., WILSON, e.B.: Epidermoid cysts of the posterior fossa. Neurosurgery 1985; 62: 214-219. 6. BLOCKLEY, N.J., SCHORSTEIN, J.: Intraspinal epidermoid tumors in the lumbar spine of children. J. Bone Joint Surg 1961; 43: 556-562. 7. BRAUN, LP., NADICH, T.P., LEEDS, N.E.: Dense intracrania1 epidermoid tumors. Computed tomographic observations. Radio10gy 1977; 122: 717-719. 8. BURGER, P.C., VOGEL, F.S.: Epidermoid and dermoid cysts. En: Surgica1 Pathology of the Nervous System and its coverings. John Wiley and Sonso New York 1982; pp. 117-122. 9. CANTU, R.e., OJEMANN, R.G.: Glucosteroid treatment of keratin meningitis following removal of a fourth ventricle epidennoid tumor. J Neurol Neu~osurg Psychiatry 1968; 31: 73-75.
Neurocirugía
10. CHANDLER, W.P., FARHAT, S.M., PAULI, F.J.: Intrathalarnic epidennoid tumor. Case Report. J Neurosurg 1975; 43: 614617. 11. DAVIS, K.R., ROBERTSON, G.H., TAVERAS, J.M., NEW, P.P.J., TREVOR, R: Diagnosis of epidennoid tumor by computed tomography. Radiology 1976; 119: 347-353. 12. DUNN, RC., ARCHER, C.A., RAPPORT, RL.: Unusual CTdense posterior fossa epidennoid cyst. Case Report. J Neurosurg 1981; 55: 654-656. 13. FAWCI'IT, RA., lARERWOOD, 1.: Radiodiagnosis of intracranial pearly tumors with particular reference to the value of computed tomography. Neuroradiology 1976; 11: 235-242. 14. GAGLIARDI, F.M., VAGNOZZI, R., CARUSA, R.: Epidermoids of the cerebello-pontine angle (cpa): Usefullness of CT scan. Acta Neurochir 1980; 54: 271-281. 15. GUIDETTI, B., GAGLIARDI, P.M.: Epidermoid and dermoid cysts. Clínical evaluation and late surgical results. J Neurosurg 1977; 47: 12-18. 16. GUTIN, P.R. ET AL.: Cerebral convexity epidermoid tumor subsequent to multiple percutaneous subdural aspirations. Case reporto J Neurosurg 1980; 52: 574-577. 17. HIGASHl, K., WAKUTA, Y.: Epidermoid tumor of the lateral ventricle. Surg Neuro11976; 5: 363-365. 18. HIRAJ:SUKA, H., OKADA, K., MATSUNAGA, M., TANAKA, K., FuKAI, N., INABA, Y.: Diagnosis of epidermoid cysts by metrizamide CT cisternography. Neuroradiology 1984; 26: 153155. 19. HWANG, W.-Z., HASEGAWA, T., ITO, H., SHlMon, T., IKEDA, K., YAMAMOTO, SH.: Intracranial Epidermoids-Concerning the 10w absorption value on computerized tomography. Acta Neurochir 1985; 78: 33-37. 20. INOUE, H., TOYA, SH., OHTANI, M.: Characteristic findings of metrizarnide CT cisternography in epidermoids. Acta Neurochir 1984; 73: 207-211. 21. LANDERS, J.W., DANIELSKI, J.J.: Malígnant intracranial epidennoid cyst. Arch Pathology 1960; 70: 419-423. 22. LEAL, O., MILES, J.: Epidennoid cyst in the brain stem. Case reporto J Neurosurg 1978; 48: 811-813. 23. MCCURDY, J.A., PITKETHLY, D.T., FLECKENSTEIN, L.D.: Central nervous system epidennoids presenting as trigeminal neuralgia. Surg Neuro11974; 2: 147-150. 24. McDoNNEL, D.E.: Pineal epidermoid cyst: Its surgical therapy. Surg NeurolI977; 7: 387-391. 25. MOHANTY, S., BHATTACHARYA, R.N., TANDON, S.e., SHUKLA, P.K.: Intracerebral cystic epidermoid. Report of two cases. Acta Neurochir 1981; 57: 107-113. 26. NAGASHIMA, C., TAKAHAMA, M., SAKAGUCHI, A.: Dense cerebellopontine epidermoid cyst. Surg Neurol 1982; 17: 172-177. 27. NOSAKA, Y., NAGOR, S., TABUCHI, K.: Primary intracranial epidermoid carcinoma. Case report. J Neurosurg 1979; 50: 830-833. 28. OBRADOR, S., LOPEZ-ZAFRA, IJ.: Clínical features of the epidermoids of the basal cisterns of the brain. J Neurol Neurosurg Psychiatry 1969; 32: 450-454. 29. SALAZAR, l, VAQUERO, l, SAUCEDO, G., BRAVO, G.: Posterior fossa epidermoid cysts. Acta Neurochir 1987; 85: 34-39. 30. SCHRAEDER, P.L., COREN, M.M., GOLDMAN, W.: Bilateral internuclear ophthalmoplegia associated with fourth ventricular epidermoid tumor. Case reporto J Neurosurg 1981; 54: 403-405. 209
Epidermoid tumors of the IV ventricle: Report of 3 cases
31. SCHUBIGER, O., VALAVANIS, A., GESSAGA, E.: Dense suprasellar epidermoid cyst. A case reporto Neuroradiology 1983; 24: 269-272. 32. TAN, T.I.: Epidermoids and dermoids of the central nervous system (with two exceptional cases not presented in the literature). Acta Neurochir 1972; 26: 13-24. 33. WEAVER, E.N., COULON, RA.: Excision of a brain stem epidermoid cyst. Case reporto J Neurosurg 1979; 51: 254-257. 34. WONG, S.W., DUCKER, T.B., POWERS, J.M.: Fulminating parapontine epidermoid carcinoma in a four-year old boy Cancer 1978;37: 1525-1531. 35. RUBIN, G., SCIENZA, R, PASQUALIN, A., ROSTA, L., DA PIAN, R: Craniocerebral epidermoids and dermoids. A review of 44 cases. Acta Neurochir 1989; 97: 1-16. 36. SABIN, H.I., BORDI, L.T., SYMON, L.: Epidermoid cysts and cholesterol granulomas centered on the posterior fossa: twenty years of diagnosis and management. Neurosurgery 1987; 21: 798-805.
210
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37. STEFFEY, D.J., DE FILIPP, G.J., SPERA, T., GABRIELSEN, T.O.: MR imaging of primary epidermoid tumors. J Comput Assist Tomogr 1988; 12: 438-440. 38. YAMAKAWA, K., SHITARA, N., GENKA, S., MANAKA, S., TAKAKURA, K.: Clinical course and surgical prognosis of 33 cases of intracranial epidermoid tumors. Neurosurgery 1989; 24: 568-574. 39. YASARGIL, M.G., ABERNATHEY, C.D., SARIOGLU, A.C.: Microneurosurgical treatment of intracranial dermoid and epidermoid tumors. Neurosurgery 1989; 24: 561-567.
Bici, W.; Sepehmia, A.; Dündar, M.; Sarnii, M: Epidermoid tumors of the IV ventricle: Report of 3 cases. Neurocirugía 1993; 4: 205-210.
W. Bini;A. Sepehrnia*; M. Dündar* y M. Samii*. HSK Neurochirurgische Klinik (Priv. Doz. Dr. R. Schonmayr), Wiesbaden-Germany. haus Hannover-Germany
Summary Epidermoid tumors of the fourth ventricle constitute a rarity and pose diagnostic difficulties. We present 3 cases of IV ventric1e epidermoid tumor extracted from our serie of 35 posterior fossa epidermoids (cerebellopontine angle) operated between 1977 and 1992. Clinical and radiological data are presented and the best diagnostic screening method and considerations concerning total removal are discussed. KEY WORDS: intracranial epidermoids, IVth ventricle, surgical management.
Resumen Los epidermoides del IV ventrículo constituyen una rara entidad clínico-quirúrgi~a debido a su baja frecuencia y pueden determinar dificultades en su diagnóstico. De nuestra serie de 35 epidermoides de fosa posterior (ángulo pontocerebeloso) operados entre 1977 y 1992, se presentan 3 casos de lesiones a nivel del IV ventrículo. Se analizan los datos clínicos y neuroradiológicos y se discute el mejor método para llevar a cabo un «screening» diagnóstico y una exéresis total. PALABRAS CLAVE: epidermoides intracraneales, IV ventrículo, tratamiento quirúrgico.
Introduction Since Cruveilhier's first description in 1829 3, epidermoid tumors have in the recent decade regained the attention of both neuroradiologists and neurosurgeons. Nevertheless, their preoperative diagnosis and the possibility of total removal are still a matter of discussion 15,28,29,35,36,38,39. The usually long interval between the onset of symptoms and diagnosis is a direct consequence of their intracisternal location but also relates to the fact that these lesions have CT attenuation values (-2 to +12 Hu) similar to those of CSF and characteristically show no enhancement contributing to the delayed diagnosis 7,11-14,18-20. We report on 3
* Neurochirurgische Klinik, Nordstadt Kranken-
cases of epidermoid of the fourth ventricle which were totally removed.
Material and Method Case 1
A 46 year old female with a long history of vertigo reported three weeks before admission two acute episodes of vertigo. The patient had a normal neurological exarnination with the exception of a mild truncal ataxia and a positive Romberg sign to the right. A CT scan evidenciated an hypodense area located in the midline of the posterior fossa. It appeared cystic and did not enhance. The cyst seemed to be located in the fourth ventricle extending to the foramen magnum. There was no evidence of hydrocephalus. A vertebral angiography showed signs of mass effect without pathological vascularization (Fig. la). A midline posterior fossa craniectomy was performed in a semi-sitting position. A white «pearly» tumor could be seen protruding out of the foramen of Magendie just after dural opening. Microsurgical piecemeal complete removal could be achieved. Care was taken to avoid the spilling of cholesterol crystals in the subarachnoidal space via constant irrigation (HydroflowlPortex). The tumor was 4 x 5 cm in diameter, avascular and «originated» on the floor of the IVth ventricle having a lateral expansion in both foramen of Luschka and posteriorly to the cisterna magna. Postoperatively the patient presented a slight abducens dysfunction on the right which resolved by discharge two weeks after surgery (Fig. lb). Case 2
A 57 year old female with a three yeár history of vertigo and gait disturbances. These symptoms were progressive and worsening. On admission she presented with a truncal ataxia, a left horizontal and moderate vertical nystagmus. A CT scan showed evidence of a cystic posterior fossa lesion with low attenuation values and no enhancement. It was located in the IVth ventricle and had a left lateral extension that could not be well delimitated. The brain stem 205
Epidermoid tumors of the IV ventricle: Report of 3 cases
Neurocirugía
Fig. la- Enhanced CT scan with sagittal reconstruction demonstrating the hypodense midline posterior lossa lesion compatible with an epidermoid tumor.
was compressed anteriorly and to the right. There was no hydrocephalus. The actual border of the tumor was identified after performing an MR study. A 1-2 mm thick tissue layer contrasting with the tumor tissue on the floor of the IVth ventricle was also evidenciated (Fig. 2a, b).
Fig. 2a- Non-enhanced CT scan demonstrating an hypodense lesion located within the IVth ventricle.
A rnidline exposure in a serni-sitting position was performed and rnicrosurgical complete removal of the «pearly» avascular tumor achieved. Gn the floor of the fourth ventricle a yellow glistening tissue, extremely adherent to the floor was found. It was difficult to differenciate whether it was tumor capsule or gliosis. The histological exarnination confirmed the gliotic nature (Fig. 2c). A few hours after recovery on the Intensive Care ward, the patient presented deterioration of the level of consciousness with a facial palsy and abscence of corneal reflex on the left with hemiparesis on the right. The control CT showed no evidence of brain stem compression, hemorrhage nor infarction. The patient was placed on antioedema therapy. The clinical course improved and the patient was discharged four weeks after surgery with a residual facial palsy and a rnild abducens dysrunction on the left. Case 3 Fig. lb- Immediate post-operative non-enhanced CT control study. B6th lateral recessus 01 the IVth ventricle can be observed.
206
A 34 year old male patient was referred to us after having been screened via MRi and diagnosed of a rnidline posterior fossa «cystic» expansive process involving the
Epidermoid tumors of the IV ventricle: Report of 3 cases
Neurocirugía
Fig. 2b- MR study (sagittal projection). Note the intense signal region deliminating the pons and floor of the IVth ventricle. This area corresponded to the gliotic adherent layer found intraoperatively.
IVth ventricle and cisterna magna. Sagittal slices clearly demonstrated a dorsal brain stem pinching in the area of the foramen magnum. The enhanced CT study demonstrated a lateral extension in the right foramen of Luschka with primary involvement of the cisterna magna. Hydrocephalus was absent as well as tumor enhancement. The process was 3 x 5 cm in its major diameter. The patient presented an unspecific clinical picture of vertigo and ocular motor nerve dysfunction (Fig. 3a, b, c). In a semi-sitting position and through a midline suboccipital craniectomy, the lesion, which appeared to be an epidermoid tumor, could be completely removed. Moderate adherencies were detected on the floor of the IVth ventricle. The patient was discharged 2 wee].cs after surgery presenting sorne ataxia and a slight abducens palsy on the right.
** At three months follow-up all patients had improved as far as residual signs/symptoms. Abducens function was normal, gait disturbances or ataxia were not present. Nevertheless, patient 2 still presented facial nerve dysfunction. Discussion
Epidermoids are benign neoplasms growing by retention of desquamated epidermall cell debris containing queratin and colesterol, originating from the stratum basa-
Fig. 2c- Intraoperative view. The tumor extended caudally to the cerebello-medular cistem.
lis of the lining of the cyst. The cyst wall is formed by fibrous connective tissue. Dermoid tumors contain in addition, pilosebaceous components and sweat glands enlarging also by a true glandular secretion. Epidermoids and dermoids are thought to arise from ectodermal tissue that fails to properly separate from it' s neuroectodermal counterpart between the 3rd and 5th weeks of gestation at the time of closure of the neural tube. The lateral location of many epidermoids may be related to epithelial enclosement at the time of formation of secondary vesicles. It has been suggested that dermoids are formed at a later time of gestational development 1.8. Trauma and repeated subdural taps have been related to the development of intracranial epidermoids and this is not surprisíng ~onsidering that spinal epidermoids have long been taken to be associated to repeated spinal taps and that experimentally the implantation of skin fragments into the brain of newborn rats may give rise to intracranial dermoids or epidermoids 6.16. Intrapetrous epidermoids (cholesteatomas) are the result of chronic otitis media or may be secondary to laterally implanted epithelial cells. 207
Epidermoid tumors of the IV ventricle: Report of 3 cases
Neurocirugía
Fig. 3a- Enhanced CT sean demonstrating a 3,5 x 5 cm midline lesion involving the lVth ventricle and the cisterna magna.
Fig. 3c- Coronal MRi slice. There is a clear caudal and right foramen Luschka extension.
Epidermoids and dermoids occur along the whole lenght of the neuroaxis. Intracranial epidermoids are more common than dermoids. They are usually located in a lateral position and are commonly less associated with other anomalies. Epidermoids represent 0,5-1,8% of aH intracranial tumors. These tumors accounted for 3,6% of all CPA lesions operated upon during the time period considered in our material. The most common locations of CNS involvement in order of decreasing frequency are; CPA, parapituitary region, diploe of the skull (fronto-parietal bones), spinal canal and the paratrigerninal region 2.4, S, lO, 16, 17,22, 24.25. 32. 33. The growth rate has been estimated to be the tumover of normal human skin, but the true neoplastic nature of these lesions is underscored by the documented, eventhough rare, possibility of malignant transformation leading to the development of squamous carcinomas 21,27,34. The tumors must obliterate a significant part of the subarachnoid space before permanent functional compromise of the intracistemal structures.leads to diagnosis. There
is a frequent disproportion between the tumor' s volume and the symptoms and abscence of hydrocephalus. Fluctuating symptoms have been often reported in these tumors and can lead to a false diagnosis of degenerative CNSdisease 15,23,30,36.38. As for fourth ventricle epidermoids predorninant and typical symptoms may be ataxia, diplopia, nystagmus and headaches 30. The CT appearance resembles a poorly delimitated cyst involving the IVth ventricle with attenuation values similar to that of CSF ranging from -8 to +32 Hu. There is no enhancement after endovenous contrast administration but ring enhancement as sign of malignant epithelial component has been reported. The abscence of hydrocephalus can reinfOl:ce the diagnosis. Other lesions which should be considered are: cystic astrocytoma, hemangioblastoma, dermoid tumor, arachnoidal cyst and cysticercosis. Saponification of the cholesterol elements or hemosiderin deposits can determine higher Hounsfield values 7,14.18,19.26.31. For the pre-operative delimitation of the tumor borders and . better evaluation of the surgical anatomy with exclusion of possible bony artifacts and with sagital plane views, MRi is the screening method of choice 37. It is non-invasive and belongs to the neurosurgical-neuroradiological protocol for the evaluation of skull base lesions. The role of post-operative MR controls is questionable for the inmediate postoperative evaluation and the images must be carefully interpreted as there are often discrepancies between eventual rests of tumor and signal from iatrogenic tissue changes caused by the surgical exposure and mani,pulation. We consider that CT-metrizamide cistemography is superior to control and document the extent of surgical removal 20 • The treatment of these lesions is definitely a surgical one. The difficulties encountered in their removal must be considered 35,36,38.39. The main technical difficulty relates not so much to the extension of the tumor which can be easily followed in the enlarged subarachnoid spaces, but
Fig. 3b- Sagittal MRi slice. Note the compressive effect on the brain stem with dorsal pinching at the level of the craniocervical juncture.
208
Epidermoid tumors of the IV ventricle: Report of 3 cases
rather on the adhesions of the tumor and the nearby neurovascular structures. It is speculated that bouts of even mild chemical meningitis may result in a strong inflamatory reaction with intimate binding of the tumor capsule and the surrounding structures 9. Our 3 cases illustrate this problem. In the first and the third cases removal could be achieved without post-operative complications. In the second case, the removal of the fine tissue layer adherent to the IVth ventricle (fibrillary gliosis with foreign body giant ceUs, perhaps triggered by spillage of tumor irritating substances ie. cholesterol) caused a transient brain stem dysfunction. We conclude that a total microsurgical removal should be attempted, the usual technique being intracapsular debulking and extracapsular dissection. Nevertheless, when total capsular removal is difficult then it is better to leave minute tumor remnants than to force the procedure. This is especiaUy so when dealing with fourth ventricle epidermoids which can lead to brain stem damage. There seems to be a subgroup of patients, probably those with history of chemical meningitis, in whom the goal of total removal is not safely achievable. These patients should be foUowed-up periodically with MR scails. Re-operation should be offered with caution, based on a combination of clinical and neuroradiological data considering that despite tumor growth, it may take a period of time equal to the patient' s age plus 9 months before a congenital tumor, as epidermoids undoubtedly are, become again symptomatic (CoUin's Law). This consideration must be balanced by the fact that it is easier to remove a small tumor than a large one. Bibliography 1. ALVORD, E.G. JR.: Growth rates of epidermoid tumors. Ann Neurol 1977; 2: 367-370. 2. ALBANESE, V., TOMASELLO, F., PICOZZI, P.: Paramedian hourglass epidennoid extending aboye and below the tentorium. Surg Neuro11982; 18: 356-363. 3. BAILEY, P.: Cruveilhier's «Tumeurs Perlees». Surg Gynecol Obstet 1920; 31: 390-401. 4. BAUMANN, CRR, Bucy, P.e.: Paratrigeminal epidermoid tumors. J. Neurosurg 1956; 13: 455-468. 5. BERGER, M.S., WILSON, e.B.: Epidermoid cysts of the posterior fossa. Neurosurgery 1985; 62: 214-219. 6. BLOCKLEY, N.J., SCHORSTEIN, J.: Intraspinal epidermoid tumors in the lumbar spine of children. J. Bone Joint Surg 1961; 43: 556-562. 7. BRAUN, LP., NADICH, T.P., LEEDS, N.E.: Dense intracrania1 epidermoid tumors. Computed tomographic observations. Radio10gy 1977; 122: 717-719. 8. BURGER, P.C., VOGEL, F.S.: Epidermoid and dermoid cysts. En: Surgica1 Pathology of the Nervous System and its coverings. John Wiley and Sonso New York 1982; pp. 117-122. 9. CANTU, R.e., OJEMANN, R.G.: Glucosteroid treatment of keratin meningitis following removal of a fourth ventricle epidennoid tumor. J Neurol Neu~osurg Psychiatry 1968; 31: 73-75.
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Epidermoid tumors of the IV ventricle: Report of 3 cases
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Bici, W.; Sepehmia, A.; Dündar, M.; Sarnii, M: Epidermoid tumors of the IV ventricle: Report of 3 cases. Neurocirugía 1993; 4: 205-210.