Syringomyelia is a progressive chronic degenerative spinal disorder characterized by segmental dissociation of pain and thermal sensation, atrophy of hand muscles and gait disturbances.MRI defines the anatomy of the spinal cord. Electrophysiological methods can assess functions of the spinal cord in details. We studied electromyography and neurography, somatosensory and motor evoked potentials (SEPs andMEPs), cutaneous and mixed nerve silent periods (CSPs,MNSPs) in ten patients with cervical syringomyelia documented by magnetic resonance imaging. Six patients had thoracic syringomyelia, one subject had syringobulbia. Six patients presented Chiari malformation type I. On clinical examination all subjects but one presented with dissociated loss of pain and temperature sensation. In nine patients, CSP and later part of MNSP were abolished or shortened on their affected side. The cervical SEP response N13 was of abnormally low amplitude in four patients on their affected sides, one patient had absence of N13. The central motor conduction time was abnormally prolonged in three patients. A chronic neurogenic EMG pattern was observed in two patients on their affected upper extremities. Absence (and/or shortening) of CSP and MNSP were the most sensitive parameter of spinal cord dysfunction in cervical syringomyelia. The cervical SEP response N13 was a reliable parameter of gray matter dysfunction. Impairment of the corticospinal tract was less frequently observed in syringomyelia and correlated with progression of the disease.

        Key words: syringomyelia, electrophysiology,somatosensory and motor evoked potentials, silent period