The post-syrinx syndrome: stable central myelopathy and collapsed or absent syrinx.

Among 168 cases with neurologic findings of cervicothoracic syringomyelia and MRI findings of Chiari 1 malformation and/or underdevelopment of the posterior cranial fossa, 15 patients (9.1 %) had collapsed, flat syrinxes and 14 patients (8.3 %) did not have syrinxes. Both groups of patients had clinical findings of central myelopathy that had been stable for at least 3 years. Magnetic resonance imaging detected atrophy of the cervical spinal cord in both groups and spontaneous communications between the syrinx and the subarachnoid space in 3 patients of the group with collapsed syrinxes. Analysis of these results and review of the literature suggest that patients with clinical signs of syringomyelia and Chiari 1 malformation or underdeveloped posterior fossa, but with small or absent syringomyelitic cavities, have the "postsyrinx" state as a result of spontaneous collapse of distended syrinxes.