In patients with multiple sclerosis (MS) non-communicating syringomyelia (NCS) has been described as an incidental finding in case studies and small case series. NCS in MS patients commonly leads to uncertainty particularly as the clinical picture of NCS is variable and surgical therapy may be considered. Up to date little is known about the prevalence and clinical importance of NCS in MS. We report the imaging and clinical characteristics of NCS formations in nine MS patients from a 1 year follow-up study in a representative group of 202 MS (4.5%) patients. Brain and spinal cord MRI was performed as part of a genetic study. NCS did commonly extend the central canal and the cord was slightly distended at the level of the syrinx. The cord and syrinx showed no tendency to change in size or shape over 1 year. Despite thorough search into the clinical history and current clinical status no definite but only minimal indications of symptoms potentially related to the NCS were found. We confirm that NCS may occur in MS patients with spinal cord pathology. It can be a subtle finding without clinical correlates. Syrinx formations are more likely to be a consequence of MS cord pathology than a coincidental finding.