Electrodiagnostic findings in syringomyelia

Electrodiagnostic abnormalities are well known to occur in syringomyelia al though the findings are nonspecific. The objective of this work was to desc ribe different types of spontaneous electromyographic (EMG) activity and re flex responses, which may be useful and more specific than conventional fin dings for the electrodiagnosis of syringomyelia. We studied 43 patients wit h syringomyelia by four-channel surface EMG and by recording the long-laten cy responses to distal stimulation of the median and tibial nerves. Continu ous motor unit activity (CMUA) was found in 18 patients, synchronous motor unit potentials (SMUP) in 10, respiratory synkinesis (RS) in 5, and myokymi c discharges in 4, Long-latency responses (LLR) with latencies ranging from 55 to 150 ms were found in 14 patients. Patients with syringomyelia thus s how a wide variation of spontaneous EMG activity. An increase in excitabili ty of spinal motor neurons is probably the basic underlying mechanism. (C) 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 1653-1659, 1999.