P346 Median nerve conduction across the wrist in GBS and CTS

Abstract

Objectives Wrist is the only segment where both sensory and motor conduction studies of the same nerve can be applied together for two diseases with different pathophysiology: “carpal tunnel syndrome (CTS)”, a chronic compression neuropathy and “Guillain Barre syndrome (GBS)”, an acquired monophasic inflammatory neuropathy. This study aims to point out how GBS differs from CTS by means of median nerve conduction at wrist level. Methods Nerve conduction studies of GBS and CTS patients admitted to EMG lab between the years of 2013 and 2017 were reanalyzed in retrospective manner. Patients with prolonged median motor distal latency either unilateral or bilateral were included. For each group, 24 median nerve conduction studies were reevaluated. Orthodromic sensory response of median nerve which was recorded just proximal to carpal tunnel in response to 2nd digit stimulation and thenar eminence recorded median motor response were considered. Results Among the hands of CTS patients, only 1 sensory response could not be evoked however for GBS group, 7 out of 24 were absent ( p 0.05 ). In patients where both sensory and motor responses were elicited, GBS hands revealed significantly prolonged motor latencies (mean: 6.2 ± 1.85; range 4.2–11.6 versus mean: 4.86 ± 0.5, range 4.22–6.46) although their sensory conduction velocity was much faster (mean: 43.72 ± 9.25; range 32.4–60 versus mean: 35.8 ± 4.54; range 27.4–45.2). Conclusion In GBS, acquired conduction deficit leads to prolonged motor latency combined with absent sensory response. If sensory response was present, it tends to be conducted faster compared to CTS although the motor latency is profoundly prolonged.