A Case of Anterior Interosseous Nerve Palsy following Breast Cancer Surgery

Abstract

Spontaneous anterior interosseous nerve palsy (sAINP) is a peripheral nerve disorder of unknown cause. It often appears suddenly and can be associated with viral infections, stress, overuse injuries, surgery, or trauma. We report a rare case of sAINP following breast cancer surgery. A 55-year-old Japanese woman underwent breast-conserving surgery and axillary lymph node dissection for right breast cancer. Postoperative diagnosis revealed stage IIA (pT1c N1 M0) disease. Her recovery was uneventful, and she was discharged seven days post-surgery. However, on postoperative day 20, she developed pain in her right elbow joint. Two weeks later, a characteristic “teardrop sign” appeared, characterized by hyperextension of the thumb's interphalangeal joint and inability to flex the index finger's distal interphalangeal joint. Upper limb nerve ultrasonography confirmed swelling of the anterior interosseous nerve on the affected side. Needle electromyography indicated a nerve disorder pattern, suggestive of inflammation. Based on these findings, including typical pattern of muscle involvement and evidence of inflammatory neuropathy, the diagnosis of sAINP was established. We will include a literature-based discussion in this report.