Digital nerve somatosensory evoked potentials and flexor carpi radialis H reflexes in cervical disc protrusion and involvement of the sixth or seventh cervical root: relations to clinical and myelographic findings.

Peak latencies of somatosensory evoked potentials (SEPs) from nerves of the first digit (digit 1-SEP), 39 controls, and third digit (digit 3-SEP), 47 controls, and indicated for Erb's point, second cervical vertebra (Cv2) and contralateral cortical hand area correlated significantly with arm length. Single regression analysis for arm length for Erb's potentials and the Cv2 potential in digit 1-SEP, and multiple regression analysis for arm length and age for the Cv2 potential in digit 3-SEP, the cortical potentials and flexor carpi radialis H reflex were used for demonstration of root C6 or C7 pathology. Upper crossing of +3 S.D. was defined as abnormal. The combined examination yielded abnormalities in 81% of our 22 patients operated for compression of root C6 or C7 due to cervical disc protrusion. A minority of the patients showed multiple positive correlations between symptoms and electrophysiologic and myelographic findings. In others only one or the other investigative procedure provided confirmatory information, while, in a notable number (6 patients), these approaches revealed abnormalities when there were no or non-specific symptoms. The presented electrophysiological investigations are useful to determine the presence and severity of root C6 or C7 compression as well as the functional relevance of a myelographic abnormality.