An electrophysiological exploration of the double crush hypothesis

The double crush hypothesis has not been rigorously evaluated in humans. We therefore analyzed cases of C6, C7, and C8 radiculopathy and exploited the fact that the median sensory response is of C6/C7 origin and the median motor response is primarily of C8 origin. We hypothesized that C6 and/or C7 cases would demonstrate an increased frequency of median mononeuropathy by sensory criteria, and C8 cases would demonstrate an increased frequency of median mononeuropathy by motor criteria. We also hypothesized that median sensory and motor response parameters among these same groups would be altered in ways consistent with a proximal influence on distal nerve conduction studies. Although median mononeuropathy was unexpectedly common (22.1%) among cases of cervical radiculopathy (which may explain the clinical acceptance of the double crush hypothesis), none of the hypotheses was supported. This study identified no evidence to support a neurophysiological explanation for the double crush hypothesis.