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Show Journal of Clinical Neuro- ophtlullmology 11( 4): 250- 253, 1991. © 1991 Raven Press, Ltd., New York Medulloblastoma Presenting as Blindness of Rapid Evolution A Case Report Fernanda Teixeira, M. D., Ph. D., Pedro Penagos, M. D., David Lozano., M. D., Mercedes Lopez, M. D., Viktor Romero, Ph. D., Alma Ortiz, PH. D., and Perla Salgado, M. D. An I8- year- old man reported rapid decrease of visual acuity that progressed to total blindness in 1 month. Computed tomographic scanning showed two neoplastic masses: a large one, intra- and suprasellar, and a smaller cerebellar nodule. Histologically, the former proved to be a large metastasis of the small cerebellar medulloblastoma, which infiltrated and compressed the chiasm. Direct compression of the optic pathways by metastasis of a medulloblastoma is a rare event. Key Words: Medulloblastoma- Optic atrophy- Visual loss- Optic chiasm. From the Department of Experimental Neuropathology ( F. T., V. R., A. D.), Neurosurgery ( P. P.), Neuro- ophthalmology ( D. L., M. L.), and Neuroradiology ( P. S.), National Institute of Neurology and Neurosurgery, Mexico City, Mexico. Address correspondence and reprint requests to Dr. F. Teixeira at Instituto Naciona! de Neurologia y Neurocirugia, Insur- - - · · --_ · · · : c. ,,:> 1 :~ f, r~ DF.. Mexico. 250 Bitemporal hemianopic field defects that progress to total blindness suggest a primary midline chiasmallesion, usually an aneurysm or a tumor of pituitary or other origin ( 1). Direct compression of the optic nerve as a result of seeding of a medulloblastoma has been reported rarely ( 2,3). We encountered a case in which loss of visual acuity that progressed rapidly to amaurosis was the first manifestation of a cerebellar medulloblastoma. CASE REPORT This young man was first assessed at 18 years of age because of bilateral temporoparietal headaches and rapid decrease of visual acuity that progressed to total blindness in the interval of 1 month. On admission, the findings of neurologic and general examinations were within normal limits, except for the visual changes. On ophthalmologic examination, visual acuity was no light perception in both eyes. The anterior segment was normal, and there were no lens opacities. No alterations in ocular motility were seen, except for some searching eye movements on lateral gaze. Ophthalmoscopy showed bilateral optic pallor, +-. 5 D elevation of the optic nerve head, with a neovascular membrane on its surface, Paton rings on both sides, and some diffuse retinal edema with white soft exudates on the macular areas. There was generalized attenuation of retinal vessels. With the provisional diagnosis of a pituitary adenoma, the patient underwent brain computed tomographic ( CT) scanning, which showed a dense space- occupying lesion with a maximum diameter of 3.6 cm in the sellar region; the lesion totally MEDULLOBLASTOMA 251 FIG. 1. Axial computed tomographic scan with contrast enhancement, showing a sellar/ suprasellar space- occupying lesion, and a smaller mass in the region of the fourth ventricle. obliterated the suprachiasmatic and suprasellar cisterns and invaded the third ventricle. In the region of the fourth ventricle, there was also a smaller mass that was dense, with areas of calcification, that produced dilatation of the aqueduct and rostral 4th ventricle. Both lateral ventricles were enlarged as well. The neoplastic masses in both locations were enhanced by contrast medium ( Fig. 1), appeared hypointense on II- weighted magnetic resonance imaging ( MRI) ( Fig. 2), and became hyperintense on T2- weighted images ( Fig. 3). In the period before surgery, the patient developed generalized hypotonia, bilateral Babinski signs, ataxia and dysmetria. A right subfrontal approach to the sellar region revealed an intra- and suprasellar purplish tumor that infiltrated the optic chiasm and extended towards the interpeduncular fossa. A frozen section revealed a malignant, small- celled tumor. This mass was partially resected and a ventriculoperitoneal shunt device with microfilter was installed. Permanent sections of paraffin- embedded material showed monotonous sheets of small anaplastic cells, with scant cytoplasm and dense, carrotshaped or oval nuclei. Mitotic figures were numerous. There were rare Homer Wright rosettes. The monotony of the tumor was, in some areas, interrupted by discrete foci of rarefaction that gave a " follicular" appearance to this lesion. Immunoperoxidase stains using antisera against cytokeratin, neurofilaments, and leucocyte common antigen were negative. Rare cells showed positivity for glial fibrillary acidic protein. The final diagnosis was medulloblastoma ( Fig. 4). Postoperative MRI did not show other foci of dissemination. The patient was sent to the National Institute of Cancerology, where he was treated with cranial radiation of 50 Gy in 25 sessions from a Cobalt 60 beam generator, for a total period of 46 days. There was marked regression of all signs and symptoms, except vision. Ophthal- FIG. 2. A sagittal. T1- weighted MRI scan shows a discrete intra- and suprasellar lesion, which invades the optic chiasm. The smaller cerebellar lesion is of the same density as the sellar neoplasm. I Gin Neuro- ophthalmol, Vol. 11, No. 4, 1991 252 F. TEIXEIRA ET AL. FIG. 3. A coronal MRI scan ( T2- weighted image) shows the extensive ventricular dilatation provoked by the larger tumor mass. The tumor extended dorsally towards the basal ganglia and hypothalamus. mologic examination after radiation showed no significant changes from previous studies, except for flattening of the disc and reduction of macular exudates bilaterally. Radiotherapy of the spinal canal was then performed. DISCUSSION Medulloblastomas are malignant neoplasms that arise in the cerebellum. They account for approximately 6% of all intracranial tumors, but are much more common in children, in whom this percentage rises to 25% ( 4). Neuroaxial spread via the cerebrospinal fluid pathways is a common event in medulloblasto-mas, occurring early in the disease process, complicating the clinical picture and worsening its prognosis. Metastases can be solitary or multiple. In one series ( 5), 83% of the metastases were found in the subarachnoid space, and the remainder inside the ventricular system. Ten to forty percent of the secondary deposits are clinically silent ( 6), whereas other metastases may be larger than the original tumor and are responsible for the first abnormal manifestations, as in the present case. Visual loss or blurred vision secondary to increased intracranial pressure has been recorded in 39% of cases of medulloblastoma ( 6). In our case, there was a rapid evolution towards total blindness, which suggested that optic atrophy was not secondary solely to papilledema, but possibly also to compression and/ or infiltration by the tumor. This clinical impression was confirmed at surgery. Direct compression of the optic pathways by seeding from a medulloblastoma is a distinctly uncommon event, and as far as we are aware, there are only two previous reports dealing with similar cases ( 2,3). The patient described by Hirst et a1. ( 3) is unusual in that his unilateral diminution of visual acuity was diagnosed at first as a demyelinating or inflammatory optic neuritis because of the rapid improvement with the use of corticosteroids. The signs and symptoms recurred with tapering of the dosage, and CT scanning demonstrated a posterior fossa medulloblastoma with a large suprasellar metastasis. The possibility of a primary suprasellar neuroblastoma with metastasis to the cerebellum was excluded because, unlike medulloblastomas, the former tumor does not show glial differentiation ( 7). The immunoperoxidase stains used also ex- FIG. 4. Paraffin section of a fragment of the sellar mass. This is composed of small anaplastic cells that form follicles or sheets. ( Hematoxylin and eosin, x 600.) J Clin Neuro- ophthnlmol. Vol. 11, N,', - I, J",. MEDULLOBLASTOMA 253 clude the diagnoses of lymphoma and small- cell metastasic carcinoma ( 8,9). It is likely that two mechanisms may take part in the visual dysfunction in patients with compression/ infiltration of the optic pathways by medulloblastomas: interruption of blood supply and direct axonal damage. The relative participation of each may be reflected in the clinical results after decompression. In the present case, there was no improvement, which indicates that axonal degeneration had occurred. REFERENCES 1. Rosenberg M. Neuro- ophthalmology. In: Wilkins RH, Rengachary 55, I'd. Nc" ro," rgay. New York: McGraw- Hili, 1985: 81. 2. Fukusumi A, Maehara F, Hayashi T, 5hojima K, Okudera T, Fukushima T. Two cases of cerebellar medulloblastoma associated with seeding in the suprasellar cistern. Rinsho Ho, ha'CIl 1985; 30: 901- 4, 3. Hirst LW, Miller NR, Kumar Aj, Udvarhelyi GB. Medulloblastoma causing a corticosteroid- responsive optic neuropathy. Am I Ophtlza/ mo/ 1980; 89: 437- 42. 4, Rubinstein LJ. TI/ mors or / heel'lItral nervollS ' lIstl'm. Bethesda: Armed Forces Institute of Pathology, 1985~ 13o- 53. 5. Em: mann DR, Norman D, Levin V, Wilson C. Newton TH. Computed tomography in the follow- up of medulloblastomas and ependymomas, RadioloJlY 1978; 128: 57-<> 3. 6. Al- Mefty 0, Jinkins JR, EI- 5enoussi M, EI- 5haker M, Fox JL. Medulloblastomas: a review of modern management with a report on 75 cases. SlIrs Neural 1985; 24: 606- 24. 7. Okazaki H, 5cheithauer BW. At/ a, of ' Jwropathology. New York: Gower Medical Publishing, 1988: 114. 8, Kurtin Pj, Pinkus G5, Leucocyte common antigen. A diagnostic discriminant between hematopoietic and nonhematopoietic neoplasms in paraffin sections using monoclonal antibodies. Correlation with immunologic studies and ultrastructural localization. Hllm Pathol 1985; 16: 353-<> 5. 9. Bonnin JM, Rubinstein LJ. Immunohistochemistry of central nervous system tumors. Its contributions to neurosurgical diagnosis, I Ne" ro," rg 1984; 60: 1121- 33. JOill Neuro- ophtha/ mol, Vol. 11, No. 4. 1991 |
