Median nerve evoked potential changes in an acute carpal tunnel syndrome model in Macaca Mulatta

Abstract

We devised an acute, carpal tunnel syndrome (CTS) model in rhesus monkey, Macaca mulatta. This model was used to observe the relationship between increases in compartmental pressure and nerve function as reflected in the electrophysiologically generated, averaged evoked potential recorded from the skin superficial to the median nerve at the elbow. Two waves, an Aβ and Aδ were monitored. Increased carpal tunnel pressure produced a decrease in the Aβ wave amplitude which was occasionally preceded by a slight elevation, but which eventually resulted in Aβ wave abolition with pressures ⩾ 31 mm Hg. The Aδ wave showed an initial increase in amplitude followed by a decline and abolition. Recovery rate from increased pressure for the Aβ wave was directly proportional to the rate of abolition of that wave. The implications of these data are discussed in the context of CTS neuropathology and diagnosis.