Fig. 3
From: Spinal accessory neuropathy in patients with chronic trapezius myofascial pain syndrome
The spinal accessory nerve (SAN) compound muscle action potentials (CMAP) obtained from the symptomatic (upper two traces) and asymptomatic (lower two traces) sides of a patient with electrophysiological evidence of symptomatic side spinal accessory neuropathy. The CMAP of the upper two traces had delayed latency and reduced amplitude. The sweep speed was 5 ms/division and sensitivity was 2 mV/division. The upper two traces: SAN CMAP latency was 2.9 ms and amplitude was 4.8 mV. The lower two traces: SAN CMAP latency was 2.6 ms and amplitude was 8.6 mV