Sensory axons excitability changes in carpal tunnel syndrome after neural mobilization.

Abstract

Increased mechanosensitivity of the median nerve in carpal tunnel syndrome (CTS) has been demonstrated during upper limb tension test 1 (ULTT1) when the nerve is passively elongated. However, the neurophysiological changes of the sensory axons during stressing activities are unknown. The aim of present study was to verify possible changes in the excitability of median nerve afferent axons following nerve stress in elongation, in subjects with and without CTS. Eight CTS hands and eight controls were selected. Recruitment properties of the median nerve were studied by analyzing the relationship between the intensity of electrical stimulation and the size of motor response, before and after intermittent-repetitive neural mobilization. Only in CTS hands, after the intervention, the stimulus-response curve was strikingly abnormal: both plateau and slope values were significantly lower. During anatomical stress across the median nerve in elongation, compressive forces may exert mechanical traction on the median nerve, since it is 'tethered' at the carpal tunnel, resulting inactivation of Na(+) channels at the wrist, or impairment of energy-dependent processes which affect axonal conduction block. We conclude that in entrapment neuropathies, neural mobilization during nerve elongation may generate conduction failure in peripheral nerve. Our study supports specific considerations for patient education and therapeutic approaches.