P297 Atypical carpal tunnel syndrome caused (mimicked) by bifid median nerve

Objectives We report a case about a patient with atypical carpal tunnel syndrome due to bifid median nerve, verified by nerve ultrasound. Methods 38-year old female patient had low scores both on Symptom severity scale and Functional status of Boston Carpal Tunnel Syndrome Questionnaire but neurophysiological examination showed significantly decreased motor amplitude with mildly prolonged distal latency and mildly decreased sensory amplitude and nerve conduction velocity of the median nerve. Electromyography (EMG) of abductor pollicis brevis muscle revealed normal findings. High resolution peripheral nerve ultra sound (US) showed normal echogenicity of the nerve, but revealed a bifid nerve: median nerve with proximal bifurcation without any obvious sign of compression or anastomosis. Result and discussion Routine nerve conduction studies referred to severe carpal tunnel syndrome which could have been reported to hand surgery. Ultrasound revealed an anatomic variant instead of severe compression neuropathy, explaining atypical nerve conduction findings. Conclusion Beside the routine nerve conduction studies, high resolution peripheral nerve ultrasound examination seems to be highly recommended in order to ensure compression or anatomic variants, especially if the results are not typical to carpal tunnel syndrome. Significance Use of peripheral nerve ultrasound should be a part of everyday routine in neurophysiology labs in order to improve diagnostic accuracy and therapeutic outcome.