Stimulation of the second (S1) or third (S2) digit elicits a median sensory potential at the wrist. Similarly, a shock applied to the median (Sm) or ulnar (Su) nerve at the wrist evokes a sensory potential of the fourth digit and a muscle potential over the thenar eminence. Hence, a concomitant application of S1 and S2 or Sm and Su with varying interstimulus intervals simulates the effect of desynchronized inputs. In 10 hands, a shift in latency on the order of 1 msec between S1 and S2 or Sm and Su caused a major reduction in sensory potential by as much as 30-40% but little change in muscle action potential. A latency difference slightly less than one-half the total duration of unit discharge maximized the phase cancellation between the two components and consequently the loss of area under the waveform.
A 63-year-old man collided with a vehicle while riding a motorcycle. At an emergency hospital, he was diagnosed with cerebral concussion, incomplete cervical cord injury, C6 fracture, facial bone fractures, and lacerations. Radiographical findings indicated that his neck was forced into an extended position. At our rehabilitation hospital, we evaluated the patient’s hoarseness and dysphagia 1 month posttrauma and determined the diagnosis to be due to “traumatic right recurrent laryngeal nerve palsy (RLNP).” We followed the patient’s RLNP during admission and at our outpatient clinic. His right RLNP gradually recovered and finally disappeared 6 months after the accident. We describe this case within the context of a review of the literature.
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