An EMG and nerve conduction study, as well as repetitive stimulation
studies, were performed. Nerve conduction studies were performed on the
right median, ulnar, radial, sural, peroneal, and tibial nerves (Table 1).
Sensory action potentials for the median nerve were within normal
limits, as were those for the ulnar nerve, radial nerve, and for the
sural nerve (recorded antidromically). Compound muscle action
potentials for the median nerve and ulnar nerve were of normal latency,
but had significantly reduced amplitudes. There was no conduction block
or temporal dispersion with proximal stimulation of either nerve.
Peroneal and tibial compound muscle action potentials in the right leg
were of normal distal latency, but showed very reduced amplitudes.
Conduction velocities were normal across the lower leg in the peroneal
nerve, with slowing across the fibular head consistent with focal
entrapment. Conduction velocity was normal across the lower leg in the
tibial nerve, and there was no evidence of conduction block. F waves
were within normal limits for the peroneal and tibial nerves.
Repetitive stimulation of the ulnar and median nerve before and
after exercise, and in the median nerve with 20-Hz stimulation, showed
no decremental or incremental response. EMG performed in a variety of
muscles showed moderate numbers of fibrillation potentials and positive
sharp waves. There were no fasciculations. Recruitment patterns were
decreased for both proximal and distal muscles. Motor units were
increased in amplitude, polyphasic, with occasional satellite
potentials. Motor units were absent in distal muscles of the hand. The
study was consistent with a severe lower motor neuron disorder.