[Intramedullary schwannoma with extradural extension: case report].

Intramedullary schwannoma without evidence of von Recklinghausen's disease is extremely rare. Only 23 cases have been reported in the literature. A 42-years-old woman with transverse type myelopathy at the level of Th 6, was referred to our department. Myelography showed diffuse swelling of the thoracic cord. Delayed myelo CT scan revealed the existence of syrinx at C 6 and Th 10 spinal cord level. On NMR spin echo image, high intensity signal with an ovoid shape was visualized in Th 7-8 spinal cord parenchyma and the syrinx was verified below the level of C 5. Based on these findings, she was diagnosed as having Th 7-8 intramedullary spinal cord tumor. Th 6 to Th 9 laminectomy followed by the complete removal of well encapsulated tumor was performed. The rostral and caudal pole of the tumor was found to be located intramedullary. The tumor at the level of Th 7-8, extended not only to the extramedullary space but also to the extradural space. Histopathological examination revealed that the specimen was Antoni A type neurinoma. She showed good recovery. Following hypotheses have been postulated on the cytogenesis of intramedullary schwannoma in the literature: Central displacement of Schwann cells during embryonic development. Schwann cells ensheathing aberrant intramedullary nerve fibers. Schwann cells along the intramedullary perivascular nerve plexus. A critical area where posterior root loose their sheath on entering the pia mater. Transformation of pial cells of neuroectodermal origin into Schwann cells. The cytogenesis of these reported cases may not be identical.(ABSTRACT TRUNCATED AT 250 WORDS)