Intramedullary angiographically occult vascular malformations of the spinal cord.

OBJECTIVE This study was performed to elucidate the differences between angiographically occult vascular malformations of the spinal cord and the histological subtypes. METHODS The cases of six patients with spinal intramedullary angiographically occult vascular malformations encountered during the past 10 years were examined regarding clinical course, neuroradiological manifestations, and surgical consideration. RESULTS There were four cavernous malformations and two arteriovenous malformations. The cervical section of the spinal cord was involved in four cases, and the thoracic section of the spinal cord was involved in two. All of the patients had presented with motor weakness and sensory disturbance below the level of the lesion. Two distinct clinical courses were observed; they were neurological decline with repeated episodes of relapse and remission (four patients) and continuing neurological decline (two patients). Although a mixed-intensity core surrounded by a low-intensity rim is thought to be characteristic of cavernous malformations, we were not able to differentiate the histological types on the basis of magnetic resonance imaging findings alone. CONCLUSION In cases of spinal intramedullary angiographically occult vascular malformations, even if clinical course and magnetic resonance imaging findings are consistent with cavernous malformation, other histological subtypes need to be considered. Surgery should be considered for symptomatic patients, because symptoms and signs that are probably caused by bleeding tend to worsen rather than stabilize.