Temperature dependent conduction block in peripheral neuropathy

In animals with a demyelinating neuropathy, conduction block (CB) can be induced by small increments of temperature within the physiologic range. The purpose of this study was to investigate whether CB in patients with neuropathy also increases with temperature. We investigated 6 patients with peripheral neuropathy, who had evidence of CB on routine examination. Motor nerve conduction was measured in 19 nerve segments. It was found that the reduction of amplitude and area of the compound muscle action potential (CMAP) on proximal versus distal stimulation of the nerve segment was more pronounced at 40°C than at 25°C while the increase of CMAP duration on proximal versus distal stimulation was unaffected. The most likely explanation for these findings is that at 40°C more motor fibres were blocked than at 25°C. In order to enhance the detection of CB in patients with peripheral neuropathy we recommend that the investigated extremity is warmed at 37°C before nerve conduction studies are done.