1548 - Electrodiagnostic (EMG) Monitoring for Posterior Interosseous Nerve Palsy Recovery

Posterior Interosseous Nerve Palsy

Case Description: A 67-year-old right-handed female fell on ice, sustaining a left distal humerus fracture, splinted, and treated surgically 9 days later. A few days after surgery, she noted a left wrist drop. An EMG 2 months later detected denervation in all left radially innervated muscles distal to the brachioradialis, with a normal superficial sensory response. Another study, 5 months after the injury, revealed a tenfold improvement in amplitude of the left radial motor nerve, but an amplitude still less than 20% of the right radial motor amplitude. Needle study of the left upper extremity revealed complex polyphasic motor units in all radially innervated muscles except the extensor pollicis longus which had no motor units. She was advised to continue self-directed exercises to maintain the wrist range of motion.

Discussions: A traumatic nerve palsy is highly variable in clinical presentation with progression and recovery dependent upon factors such as the degree of nerve damage, time to motor endplate reinnervation, and patient demographics. This patient had signs of motor axon regeneration, polyphasic motor units, with improved radial motor amplitude, which correlated with her improving clinical picture. She will continue to be serially monitored for progress, with education regarding what to expect with a nerve injury and education regarding exercises to maintain and improve her elbow and wrist range of motion and strength.

Conclusions: In conclusion, the electromyographer has the unique ability to delineate the degree of nerve injury and give the referring provider and patient a prognosis for recovery. The latter has implications for whether the patient needs further therapy or intervention such as a nerve transfer. It helps to educate and reassure the patient that they will continue to improve over time. Hence, physiatrists are uniquely positioned to guide decision making and manage traumatic nerve injuries.