Scalpellum occulta: A rare case of dorsal spinal arachnoid web without the scalpel sign.

Spinal arachnoid web is a rare condition characterized by extramedullary bands of arachnoid tissue at the level of the dorsal thoracic spinal cord that may lead to progressive, permanent neurological deficits. To date, this condition has been radiographically characterized by a scalpel sign, which has been pathognomonic in all reported cases of spinal arachnoid webs. In this case, we report the first known patient with confirmed spinal arachnoid web without radiographic evidence of the scalpel sign.