The Role of the Cutaneous Silent Period in the Electrophysiological Diagnosis of Guillain-Barré Syndrome.

Introduction/aims: Electrophysiological assessment of small fiber neuropathy in Guillain-Barré syndrome (GBS) remains underexplored in the current literature. This study evaluated the cutaneous silent period (CSP) to assess small fiber involvement in GBS and its utility for differentiating subtypes.

Methods: We conducted a prospective study of 27 patients with GBS (15 with acute inflammatory demyelinating polyneuropathy [AIDP] and 12 with other subtypes), 20 with diabetic polyneuropathy, and 20 healthy controls. CSP was recorded from the abductor pollicis brevis (APB) and tibialis anterior (TA) muscles using surface electrodes and standardized stimulation protocols.

Results: CSP latencies were significantly prolonged in AIDP patients compared to healthy controls: median APB onset and offset latencies were 117.9 and 161.9 ms versus 69.9 and 123.5 ms, respectively (both p < 0.001), while median TA onset and offset latencies were 144.3 and 176.4 ms versus 106.3 and 137.1 ms (both p < 0.001). AIDP patients also showed longer median APB onset (117.9 vs. 78.2 ms; p < 0.01) and offset (161.9 vs. 130.9 ms; p < 0.05) latencies than other GBS patients. Median CSP duration was shorter in AIDP patients compared to healthy controls (39.2 vs. 57.4 ms; p < 0.05).

Discussion: CSP assessment may complement standard nerve conduction studies by identifying thinly myelinated fiber involvement that helps distinguish demyelinating GBS subtypes. While these findings may not change disease management, they enhance understanding of pathophysiology and may facilitate earlier diagnosis.