Ultrasound-Detected Ulnar Nerve Entrapment With Normal Electrodiagnostic Studies Following Thoracic Outlet Decompression: A Case Report

We report the case of a 38-year-old female who developed persistent right upper extremity paresthesia, neuropathic pain, and ulnar-sided sensory disturbance following surgical decompression for thoracic outlet syndrome (TOS). Despite clinically significant cubital tunnel tenderness and ultrasound evidence of focal ulnar nerve impingement, electrodiagnostic studies, including nerve conduction studies (NCS) and electromyography (EMG), were normal. The patient underwent ultrasound-guided ulnar nerve hydrodissection with corticosteroid and dextrose solution as part of conservative management. This case underscores that cubital tunnel syndrome should not be excluded solely on the basis of normal electrodiagnostic studies, particularly when clinical and imaging findings are suggestive.