Posttraumatic syringomyelia should be considered in any patient showing a delayed neurological deterioration after spinal cord injury. The purpose of this article is to assess the posttraumatic syringomyelia on magnetic resonance images and to evaluate the results of its surgical treatment. Fourteen patients with posttraumatic syringomyelia were studied. There were 10 men and 4 women ranging in age from 25 to 67 years. Eleven patients with syringomyelia were symptomatic, and the three others were asymptomatic. The periods from spinal cord injury to onset of symptoms due to syringomyelia ranged from 3 to 33 years with a mean of 14 years. On magnetic resonance images, the mean length of the syrinx was 14 vertebral levels and ranged from 3 to 20 levels. At the rostral part of the injured cord, the syrinx was located off center. In contrast, at the caudal part of the injury, the syrinx was markedly large in size and its location was central. In 6 of 13 patients, the syringes extended into the medulla oblongata. Eleven symptomatic patients underwent surgical treatments: a syringosubarachnoid shunt was done in six patients, a syringoperitoneal shunt was done in four, and a ventriculoperitoneal shunt was carried out in one. Shunt malfunction was encountered in three of the four syringoperitoneal shunts and in the one ventriculoperitoneal shunt. Final neurological outcomes were satisfactory in all 11 patients who underwent surgery. Motor function improved in eight of nine patients, sensory disturbance improved in five of five patients, and relief of local pain or numbness was obtained in four of four patients.(ABSTRACT TRUNCATED AT 250 WORDS)