FIGURE 1: COMPOUND MUSCLE ACTION POTENTIAL
OF VARIOUS NERVES SHOWING NORMAL OR ABSENT IMPUSES WITH THE PERONEAL NERVE MOST FREQUENTLY INVOLVED.
We do try to identify the nerve during surgery by producing a compound muscle action potential
through stimulation, but in this case the nerves were elusive.
Repeat nerve conduction studies / extensor indices proprius showed normalization of radial compound muscle action potential
In the RA group, electrophysiologically diagnosed neuropathy was detected in 20 (36%) patients: 3 (5%) had sensorimotor polyneuropathy, 7 (13%) had low sural sensory CV or absence of sensory action potentials (SAP), 2 (4%) had carpal tunnel syndrome (CTS), 6 (11%) had low amplitude peroneal compound muscle action potentials, 1 (2%) had low amplitude peroneal compound muscle action potential and low ulnar sensory nerve conduction, and 1 (2%) had low sural and ulnar sensory nerve conduction.
Low amplitude sensory nerve action potential and multifocal compound muscle action potential and normal or minimally decreased velocity were reported in the previous studies with RA patients (14-16).
At various intervals, DPN was measured by well-established tests, namely sensory nerve conduction velocity (SNCV), latency of compound muscle action potential
(CMAP), and the number of intra-epidermal nerve fibers (IENF).
Repetitive nerve stimulation showed a clear decrement of the compound muscle action potentials
at 3 Hz only.
Although the amplitude of compound muscle action potentials
(CMAP) of the left ulnar nerve were within normal limits, they were lower than the asymptomatic side.
In electrodiagnostic study, severe bilateral facial neuropathy with reduction in facial nerve compound muscle action potentials
(CMAP) amplitude and severe denervation in needle electromyography (EMG) was present.
The amplitude of the compound muscle action potentials
recorded from the intrinsic foot muscles and the right hand were normal.