353 - Traumatic Cervical & Thoracic Nerve Root Avulsion without Injury to the Brachial Plexus Confirmed by EMG/NCS at 4 Weeks

Case Diagnosis: C5 incomplete and C6-T1 complete nerve root avulsion without brachial plexus injury

Case Description: 20-year-old male admitted to inpatient rehab for monoplegia of the right upper extremity (RUE) following a highspeed motor vehicle accident. MRI neck without contrast showed leftward deviation of the lateral aspect of the thecal sac spanning from C3-T2 suggestive of nerve root avulsion. At admission RUE was flaccid with 0/5 strength. At 4 weeks patient exhibited 2/5 strength in right elbow flexion and supination. Nerve conduction studies (NCS) of the ulnar, median, and radial nerve were no response, sensory NCS of the medial and lateral antecubital cutaneous, ulnar, median, and radial sensory nerves were intact. Electromyography demonstrated active denervation in all muscles tested in the right upper extremity without evidence of reinnervation in the pronator teres, triceps, or first dorsal interossei. Biceps with 1+ polyphasic waveforms. Patient had retained volitional motor function of the medial and posterior deltoid. Cervical paraspinals demonstrated increased insertional pattern with fibrillations and positive sharp waves.

Discussions: Nerve root avulsions may coincide with brachial plexopathies, therefore electrodiagnostic studies may be used to differentiate these injuries in surgical planning. Preservation of sensory NCS and inability to evoke action potentials in EMG suggests injury proximal to the dorsal root ganglion, such as a nerve root avulsion in this patient. Denervation changes on EMG may take up to 6 weeks in distal muscles, however they may present as early as 10-14 days proximally. This case demonstrated denervation within 4 weeks distally.

Conclusions: Electrodiagnostic studies performed 4 weeks after injury may distinguish nerve root avulsions from other peripheral nerve injures to assist with timely diagnosis, prognosis and surgical planning.