Electrophysiologic findings in post-traumatic syringomyelia: implications for clinical management

Traumatic spinal cord injured (SCI) patients may develop pain, new weakness and/or sensory loss due to an enlarging fluid-filled cyst in the spinal cord. The clinical history and physical exam are nonspecific and insensitive, particularly for diagnosing and monitoring recurrent or progressive post-traumatic syringomyelia (PTS). We compare the sensitivity and specificity of three electrodiagnostic tests, median and ulnar F waves, electromagnetic motor evoked potentials (MEP), and needle electromyography, with respect to syrinx by imaging (MRI or CT scan) and neurologic progression on serial clinical exams. Central motor conduction time (CMCT) calculated from scalp and spine MEP was the most sensitive diagnostic test. F waves were less sensitive and less specific than the CMCT, and did not provide evidence of syrinxes in the mid or upper cervical cord. Positive sharp wave and fibrillation potentials were the least sensitive and least specific. The CMCT is a useful adjunct to imaging studies for diagnosing and monitoring PTS.