Progressive Radial Nerve Entrapment Resulted in Finger Drop: A Case Report

Introduction: Posterior interosseous nerve (PIN) palsy gives rise to various symptoms. The PIN due to lipoma is rare. Here, we report a case of progressive loss of finger extension due to a giant painless parosteal lipoma. Case Presentation: A 52-year-old patient with progressive weakness of finger extension with diagnosis of posterior interosseous nerve (PIN) palsy was referred to our clinic. Electrophysiological studies showed a right PIN neuropathy at the level of the forearm. The patient had no history of trauma of the hand. The patient underwent surgery for tumor removal and nerve decompression. The loss of finger extension due to PIN palsy gradually recovered after tumor removal and the nerve recovered from the motor deficits. The patient showed no recurrence of motor deficit after the surgery in the follow-up. Conclusions: Since PIN palsy may arise from lipoma early surgical exploration and the excision of deep-seated lipoma in the proximal forearm is recommended in order to avoid permanent damage to PIN or other branches of the radial nerve.