[Pseudo-paralysis of the brachial biceps in obstetrical brachial plexus lesions (OBPL):concerning the "overly optimistic" EMG in OBPL].

In birth palsy of the brachial plexus, the mixed interference pattern recorded for the brachial biceps on the electromyogram often conflicts with the muscle's inability to flex the elbow. We report our observations of a six-month-old infant who presented paralysis of the upper and medial elements of the brachial plexus, in whom we demonstrated early biceps-triceps co-contractions, which may explain this discrepancy and 'pseudo-paralysis' of the biceps. We analyse and discuss the practical consequences of these findings, and notably the possible therapeutic use of triceps-to-biceps surgical transposition.