Median nerve mononeuropathy in spondylotic cervical myelopathy: double crush syndrome?

Abstract

We studied the association between spondylotic cervical myelopathy (SCM) and median nerve mononeuropathy (MNM) and examined the validity of the double-crush hypothesis. Sixty consecutive patients with clinically overt spondylotic cervical myelopathy were examined by means of nerve conduction studies, electromyography, and median nerve somatosensory evoked potentials; the frequency of the electrophysiological signs of focal MNM at the wrist was compared with that of a control group comprising 100 sex- and age-matched patients. Electrophysiological signs of MNM were found in 20 myelopathic patients (33%) in comparison with an 11% prevalence in the control group (P<0.05). The signs of motor anterior horn cell lesion at the C8-Th1 level and concomitant motor axonal MNM ipsilaterally were found in three hands, while the signs of sensory axonal loss at C6-7 segments due to ganglionic or postganglionic sensory lesion outside the wrist and concomitant sensory axonal MNM were present in one hand. While demonstrating a statistically significant association between SCM and MNM, we found no evidence of an etiological relationship between these two conditions. Electrophysiological signs of MNM fail anatomical (segmental level and side) and pathophysiological (axonal type of lesion) requirements of the double-crush hypothesis in most of patients with concomitant SCM and MNM.