1Khodulev V.I., 1Nechipurenko N.I., 2Arkind G.D.
1State Institution “Republican Research and Clinical Center of Neurology and Neurosurgery” of the Ministry of Health of the Republic of Belarus, 24 F. Skoriny Street, Мinsk,220114, Belarus, khodulev@tut.by
221 Central District Clinic of Zavadski District of Minsk, 13 Filatova Street, Minsk, 220026 Belarus

The radial nerve can be involved in pathological process on the different levels. Most often it is damaged at the spiral groove due to compression during asleep or secondary to fracture of the humerus. We hypothesized that the compound muscle action potentials (CMAP) area recorded over the posterior compartment muscles of the forearm at the brachial plexus stimulation will be summation of the motor unit action potentials not only radial innervated muscles, but also median and ulnar innervated muscles. Moreover, it was assumed that the sum of the CMAP area recording from extensor digitorum communis in stimulation of radial nerve on lateral brachium on the one hand and CMAP area in stimulation of median and ulnar nerves on median brachium on the other hand will not change significantly in relation to the CMAP area in the brachial plexus stimulation in healthy subjects. Objective. The study deals with design of an electrophysiological technique of radial nerve investigation and conduction block (CB) definition at the spiral groove level using surface electrodes. Methods. Twenty-one healthy volunteers, 55 patients with radial nerve neuropathy in the spiral groove and 32 patients with complete injury of the radial nerve were studied. Control group was consisted of healthy subjects and patients with undamaged side aged from 18 to 49 years. In total, 65 radial nerve were investigated. CMAP was recorded from the extensor digitorum communis. Stimulation was performed at: (1) the distal part of lateral brachium (distal point); (2) Erb’s point (proximal point); (3) the mean part of medial brachium (additional point). CB was calculated under the formula: ((distal CMAP area + additional CMAP area) – proximal CMAP area)) x 100/(distal CMAP area + additional CMAP area). Results. In control group and patients with complete injury CB was not registered (4.2 ± 9.8% and -6.6 ± 23.4), whereas in patients with radial nerve neuropathy CB was 61.2 ± 11.2% (P < 0.001). There was shown the correlation between CB and the percentage contribution of additional CMAP to proximal CMAP in patients with radial nerve neuropathy in the spiral groove. In patients with complete injury of the radial nerve proximal CMAP did not differ from the additional one. Conclusion. The presented technique for testing the radial nerve may be used for CB definition in patients with compression radial nerve neuropathy in the spiral groove.