Accessory nerve ancient schwannoma: A case report

Abstract

Background: Lower cranial nerve schwannomas are rare and only 63 cases originating from the accessory nerve have been documented. Case Description: We report a 61-year-old man who presented with a 3-month history of dysmetria, ataxic gait, and frequent falls. Magnetic resonance imaging revealed a giant rim-enhancing cystic lesion at the right cerebellomedullary cistern, which markedly displaced the brainstem and caused a critical compression on surrounding structures and mild hydrocephalus. Even though the nature of this lesion was not clear, it received a radiological diagnosis of meningioma as first option. Surgery was performed through an extended far lateral retrosigmoid approach with C1 hemilaminectomy, with intraoperative neurophysiological monitoring. A near-total resection was achieved due to the adhesion of the lesion to the brainstem and to the cranial nerves VII, VIII, IX, X, XI, and XII. Intraoperatively, the tumor was found to arise from the accessory nerve. The histopathological analysis concluded with a final diagnosis of ancient schwannoma, a rare histological subtype characterized by degenerative changes, typical from long-standing tumors. Conclusion: Very few cases of intracranial ancient schwannomas have been described. To the best of our knowledge, this is the first report of this extremely rare histological variant arising from the intracisternal component of the XI nerve. The rarity of this disease at this location may lead to preoperative misdiagnosis.

Clinical and radiological features of intracranial ancient schwannomas: a single-institution, retrospective analysis

“…In this study, the presence of cysts was significantly associated with AS; 12/13 (92.3%) AS cases were cystic AS. In the seven previous reports of intracranial AS, five mentioned the presence of cysts (71.4%), which confirms our results [ 2 , 3 , 22 , 25 , 32 , 35 ]. Therefore, AS may be a subtype of cystic schwannomas.…”

“…AS is a benign tumor (World Health Organization [WHO] tumors of the central nervous system [CNS] grade 1) with a low Ki-67 index (2–3%) [ 36 ], and malignancy is rare. Immunostaining of this tumor is positive for S-100, similar to that for other schwannoma subtypes [ 15 , 25 , 28 , 34 ]. Since diagnosis is difficult based only on clinical and radiological features [ 36 ], pathological diagnosis is important [ 21 ].…”

“…On the other hand, reports focused on intracranial AS are rare. To our knowledge, only seven cases of intracranial AS have been reported, all in case reports [ 2 , 3 , 22 , 25 , 32 , 34 , 35 ]. Therefore, the clinical and radiological features of intracranial AS remain unknown.…”