Evaluation of Patients Referred for Isolated Distal Upper Limb Extensor Weakness: A Retrospective Electrophysiological Study

This study investigated the clinical and electrophysiological features of patients with isolated distal upper extremity extensor weakness, focusing on etiologies and anatomical levels of peripheral nerve involvement. A retrospective review included 57 patients evaluated between 2007 and 2025 with wrist or finger drop. All underwent motor and sensory conduction studies of the median, ulnar, and radial nerves, as well as needle EMG of radial nerve–innervated muscles and C7–C8 roots. Radial nerve lesions were classified into three levels: Level 1 (proximal to the triceps branch), Level 2 (distal to triceps and proximal to supinator branches), and Level 3 (posterior interosseous nerve). Nerve injuries were categorized as axonal or demyelinating. Of the 57 patients (40 men, 17 women), 56 had confirmed radial nerve injury. Trauma was the leading cause, followed by surgical and compression-related injuries. Electrophysiologically, Level 2 was the most frequent site, typically corresponding to distal humeral injuries. Level 1 injuries were associated with proximal humeral lesions, while Level 3 was linked to radial shaft involvement. All patients showed axonal damage: 49% partial, 28% total, and 23% prominent partial. Our results show that trauma-related radial nerve injury is the predominant cause of isolated distal extensor weakness. Electrophysiological evaluation is essential for accurate localization, diagnosis, and management.