Spinal Accessory Nerve Neurinoma : Report of Two Cases

Two cases of spinal accessory nerve neurinoma in the spinal canal are reported. The first case was a 32-year-old man who showed progressive numbness in both hands. Magnetic resonance imaging (MRI) revealed an extramedullary mass, located anterolaterally in the spinal canal at the C1-2 level. A suboccipital craniectomy and laminectomies of C1-3 were performed. The tumor originated from the right spinal root of the accessory nerve and was totally removed. Histological examination revealed a neurinoma containing both Antoni type A and B. The postoperative course was uneventful. The second case was a 61-year-old man who showed progressive tetraparesis and hypesthesia of the right lower extremity. MRI revealed the mass extending from C1 to C5, compressing the spinal cord anteriorly. A suboccipital craniectomy and laminectomies of C1-6 with laminoplasties of C3-6 were performed. The tumor, which was attached solely to the right spinal root of the accessory nerve, was well-demarcated and totally removed. Histological examination revealed an Antoni type A neurinoma. The symptoms disappeared completely postoperatively. Spinal accessory nerve neurinoma is rare. Twenty-three cases of accessory nerve neurinoma have been reported in the literature. Usually, these tumors develop at the spinocranial junction or in the posterior fossa. Only one out of 23 cases was confined entirely to the spinal canal. Including our 2 cases of spinal accessory nerve neurinoma, in the spinal canal, surgery was performed successfully via the posterior approach. Even if the tumor is located anteriorly to the spinal cord, it can be removed by very gentle maneuvering and via the posterolateral approach. Monitoring by spinal evoked potential during surgery was greatly helpful. These 3 tumor cases originated from the spinal root of the accessory nerve. Symptoms of the patients were myelopathy due to compression of the spinal cord, but symptoms due to the accessory nerve itself were not observed pre-or postoperatively.