P3-4-3. C5/C6/C7 myotome of upper limb muscles documented by MRI-confirmed cervical spondylotic radiculopathy

Many myotomal charts have been published, although there is considerable discordance among them. We aimed to determine C5, C6, and C7 myotomes of upper limb muscles. We retrospectively reviewed the patients with MRI-confirmed isolated C5, C6, or C7 cervical spondylotic radiculopathy (CSR). Twenty-four CSR patients (7 C5, 7 C6, and 10 C7 CSR) were enrolled. Muscle weaknesses were found in 7/7 deltoid, 7/7 infraspinatus, 6/7 biceps brachii (BB), and 5/6 brachioradialis among C5 CSR cases, in 4/4 pronator teres (PT) and 5/7 wrist extensor among C6 cases, and in 5/10 triceps brachii among C7 cases. Denervation potentials on needle EMG were found in 0/5 C5, 6/7 C6, and 1/4 C7 cases at PT, in 0/2 C5 and 4/7 C6 cases at extensor carpi radialis brevis (ECRB), in 2/4 C5 and 2/5 C6 cases at extensor carpi radialis longus (ECRL), and in 1/4 C6 and 5/8 C7 cases at flexor carpi radialis (FCR). Main innervation of deltoid, infraspinatus, and BB by C5, and that of triceps by C7 coincide with most previous literature. Among muscles in which controversy remains regarding myotome, brachioradialis is mainly innervated by C5 root, ECRL by C5/C6, ECRB and PT by C6, and FCR by C7.