Periodic limb movements in syringomyelia and syringobulbia

Twenty-six patients with syringomyelia were studied with polysomnography to determine the frequency of periodic limb movements (PLM) and its relationship to the presence of a Chiari anomaly, the severity of corticospinal tract involvement, and localization of the syrinx. Sixteen patients showed PLM in stages I and II of non-REM sleep and three PLM also while awake. There were no statistically significant differences in overall disability, corticospinal signs, presence of an associated Chiari anomaly, and disease duration between patients with and without PLM, although there was a trend for patients with PLM to have more severe disease. There was preservation of the lumbosacral enlargement of the spinal cord by the syrinx in all patients with PLM. The latency delay between lower and upper limb muscles was suggestive of conduction along propriospinal pathways. Syringomyelia may lead to an abnormal state of spinal hyperexcitability favoring the appearance of PLM. Detailed magnetic resonance image studies of patients with different localizations of the syrinx cavities may help to determine which tracts are involved in the production of PLM.