Recovery function of somatosensory evoked brain response in patients with carpal tunnel syndrome: A magnetoencephalographic study

Abstract

Objective: The recovery function of somatosensory evoked magnetic fields (SEFs) was recorded to investigate excitatory and inhibitory balance in the somatosensory cortex of patients with carpal tunnel syndrome.

Methods: SEFs were recorded in patients and controls. Recordings were taken following median nerve stimulation with single and double pulses with interstimulus intervals of 10-200ms. The root mean square for the N20m component following the second stimulation was analyzed. SEFs following stimulation of the first and middle digits were also recorded and the location for the equivalent current dipoles was estimated in three-dimensional planes.

Results: Distances on the vertical axis between the equivalent current dipoles for the first and third digits were shorter in patients than in control participants. The root mean square for the N20m recovered earlier in patients compared to controls; this was statistically significant at an interstimulus interval of 10ms. There was no relationship between N20m recovery and the equivalent current dipole location in the primary somatosensory cortex.

Conclusions: Carpal tunnel syndrome was associated with functional disinhibition and destruction of the somatotopic organization in the primary somatosensory cortex.

Significance: Disinhibitory changes might induce a maladaptation of the central nervous system relating to pain.

Keywords: Carpal tunnel syndrome; Magnetoencephalography; N20m; Pain; Somatosensory cortex; Somatosensory evoked magnetic field.