Neonatal brachial plexus palsy. Outcome of absent biceps function at three months of age.

BACKGROUND: An important prognostic factor in neonatal brachial plexus palsy is the time interval to biceps muscle recovery. Although the natural history is not clear, biceps muscle recovery after more than three months of age has been used to predict poor long-term shoulder function. The absence of biceps muscle function at three months of age has been adopted as an indication for early brachial plexus microsurgery, in an attempt to improve recovery. To provide a benchmark for outcome comparison, the long-term outcome of patients with absent biceps muscle function at three months of age was studied.
METHODS: Between 1980 and 1992, 170 patients with neonatal brachial plexus palsy were entered into a prospective study in which details of the birth and serial clinical examinations were recorded. Patients were grouped according to the level of injury and the time interval to biceps muscle recovery. Twenty-nine patients were observed to have absent biceps muscle function at three months of age. Twenty-eight of those patients were available for long-term followup at a mean age of eleven years and one month. At the time of follow-up, patients answered a questionnaire and underwent manual muscle strength testing, sensory evaluation, and grading of their shoulder function according to Gilbert's modification of the Mallet score, in which the function was graded as II, III, or IV with class I (no function) and V (normal) eliminated. The level of injury and the time that biceps muscle function returned were compared with the final outcomes.
RESULTS: The level of injury was C5-C6 in thirteen (46%) of our twenty-eight patients with absent biceps muscle function at three months of age, C5-C7 in five (18%), and pan-plexus (C5-T1) in ten (36%). Biceps contraction was observed by six months of age in twenty patients (71%), including all thirteen patients with a C5-C6 level of injury. Twenty-two patients did not have surgery on the brachial plexus, but nine of those patients had subsequent orthopaedic procedures. At the time of follow-up, twenty-seven of the twenty-eight patients had at least antigravity biceps muscle function. Patients who regained biceps muscle function between three and six months of age had better scores for abduction (p = 0.04) and for hand-to-neck (p = 0.05) and hand-to-back (p < 0.001) function than did patients who regained biceps muscle function after six months of age. Patients with a C5-C6 lesion had better scores for external rotation (p = 0.04) and for hand-to-neck (p = 0.05), hand-to-mouth (p < 0.01), and hand-to-back (p < 0.001) function than did patients with a pan-plexus lesion. Twelve (55%) of the twenty-two patients who did not have brachial plexus surgery had a class-IV shoulder (good function) according to the modified Mallet score. Of the twelve patients with a C5-C6 level of injury who did not have brachial plexus surgery, eight had a class-IV shoulder.
CONCLUSIONS: This study indicated associations between prolonged neurological recovery and a more extensive level of injury and worse long-term shoulder function. Patients with a C5-C6 injury and absent biceps muscle function at three months of age often have good long-term shoulder function without brachial plexus surgery.