Relationship between Cutaneous Silent Period Characteristics and Lesion Site in the Cervical Spinal Cord

Objective: The transient suppression of voluntary muscle contraction after nociceptive stimulation is termed the cutaneous silent period (CSP), and is thought to be a spinal inhibitory reflex mediated by A-delta fibers. In CSP testing using the abductor pollicis brevis (APB) muscle (C8-T1 myotome) and the index finger (C6-C7 dermatome), the intramedullary CSP circuit is thought to be localized to the C6-T1 spinal segments. Notably, CSPs are altered or abolished in cervical cord disorders. However, the association between the site of cord lesion and CSP changes is not clearly defined.

Methods: We prospectively reviewed the onset latency and duration of preoperative CSPs in 40 hands from 22 patients with cervical compression myelopathy (CCM) and single-level cord compression. CCM patients were divided into 2 groups: those with compression involving the C6-T1 spinal segments (CCM at the middle and lower cervical spine, the ML group; 10 hands) or other segments (CCM at the upper cervical spine; the U group, 30 hands).

Results: Onset latency was significantly delayed in the ML group compared to the U group (P = 0.0001), whereas duration was not significantly different between groups (P = 0.9).

Conclusion: Changes in the CSP onset latency were influenced by the CCM lesion site. The results of this study inform the evaluation of patients with cervical cord disorders when using CSP testing.