Innervation pattern of dorsal roots and their effects on the specificity of dermatomal somatosensory evoked potentials.

Dermatomal somatosensory evoked potentials are used to monitor individual nerve root function during degenerative spinal surgery. However, a less than 100% agreement between level(s) of dermatomal somatosensory evoked potentials abnormality and nerve root involvement has been reported. The purpose of this article was to determine the possible cause of this discrepancy. Results from humans suggest that variations in peripheral innervation patterns of the dorsal nerve roots are the main reason for dermatomal somatosensory evoked potentials discrepancy both for cervical and lumbar nerve roots. Because these variations cannot be controlled, the authors recommend that dermatomal somatosensory evoked potentials and additional neurophysiologic methods be used during degenerative surgeries to provide the surgeon with information about individual nerve root function. A patient profile for these methods was provided.