Longitudinally Extensive Transverse Myelitis in Highly Active Relapsing-remitting Multiple Sclerosis.

Transverse myelitis in multiple sclerosis is typically a short cord lesion with patchy distribution. Rarely, longitudinally extensive transverse myelitis can be seen in those with highly active disease or frequent relapses. The recognition of this uncommon phenotype in multiple sclerosis is important as the treatment is largely different from other demyelinating diseases. We describe a patient with highly active relapsing-remitting multiple sclerosis on interferon beta-1a who developed LETM after multiple relapses.