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. 2018 May 22;90(21):e1842–e1848. doi: 10.1212/WNL.0000000000005566

Figure 1. Clinical and electrophysiologic features.

Figure 1

(A) Photographs of the patient show the asymmetric focal neuropathy. (B) Right abductor pollicis brevis (APB) compound muscle action potentials (CMAPs) obtained by stimulating the median nerve at the wrist (top), the antecubital fossa (middle), and above the elbow (bottom) demonstrate significant conduction block (with desynchronization) affecting the right median nerve within the forearm. In the lower traces, proximal responses (black lines) are superimposed on the distal CMAP (plotted in gray), thus facilitating visualization of the conduction block at each location (the percentage drop in CMAP amplitude at each site is also indicated). (C) Right abductor digiti minimi (ADM) CMAPs evoked by stimulating the ulnar nerve at the wrist (top) and below (middle) and above (bottom) the medial epicondyle demonstrate significant conduction block (with dispersion) affecting the right ulnar nerve within the forearm. Maximal distal CMAPs were obtained using stimulus currents of ∼10 mA and to confirm conduction block currents of ∼25 mA were used at proximal locations (pulse duration 0.5 ms). Stimulus artefacts have been removed for clarity. Arrowheads mark CMAP onset. *Significantly higher stimulus currents (up to 100 mA) were used to confirm conduction block during clinical testing. (D) Electropherogram shows the de novo heterozygous c.269T>C, p.(Phe90Ser) PTEN mutation. (E) Evolutionary conservation of the mutation.