Newborn brachial plexus palsy: evaluation of severity using quantitative ultrasound of muscle.

INTRODUCTION We studied ultrasound features of muscle after nerve injury. METHODS We evaluated ultrasound measurements of muscle thickness and backscatter in injured and contralateral uninjured elbow flexors of 51 children with newborn brachial plexus palsy (NBPP) and compared the results to elbow flexor function (Active Movement Scale), defined as normal, moderate, or severe. RESULTS Compared with uninjured limbs, muscle in injured arms was 15% thinner with severe impairment, 17% thicker with moderate impairment, and no different with normal function. Relative to uninjured limbs, moderately impaired muscle was thicker than both severely impaired and normal strength muscle. Backscatter was higher in injured than in uninjured limbs regardless of function. In 17 patients with sequential measures, muscle thickness, but not backscatter, increased with function over time. CONCLUSIONS Muscle thickness differentiates moderate from severe impairment after NBPP and increases with recovery over time. Muscle backscatter identifies prior injury regardless of function.