Cutaneous silent period in cervical root avulsion

Abstract

Objectives The cutaneous silent period (CSP) is a spinal inhibitory reflex mediated by small-diameter A-delta fibers. Nociceptive impulses enter the spinal dorsal horn and suppress activity in spinal motor nuclei in neighboring myotomes. The aim of the study was to determine if CSP testing may serve as a useful aid in evaluation of brachial plexus injury involving root avulsion. Methods In 19 patients with traumatic brachial plexus injury (15 males, age 18–62 years) we performed clinical examination, imaging studies (CT myelogram) and neurophysiologic testing. Needle EMG was obtained from muscles supplied by C5-T1 myotomes. CSP was recorded after painful stimuli were delivered to thumb (C6 dermatome), middle (C7) and little (C8) fingers while subjects maintained voluntary contraction of intrinsic hand muscles. Results Electrodiagnostic and imaging studies confirmed severe brachial plexopathy in most of patients. In 6 subjects with sensory disturbances, one of the CSP was absent. In the remaining 13 patients, a well defined CSPs were present. Conclusion In brachial plexopathy with presumed avulsion, the CSP can provide quick physiologic confirmation of preserved or impaired conduction through damaged trunks and roots. In the cases of multiple sensory disturbances, the CSP is impaired or absent.