Evaluation of magnetic stimulation in obstetrical brachial plexus palsy

Introduction: Obstetrical brachial plexus palsies result in a poor functional outcome with significant neurological deficit in one arm or hand in about 5 - 10% of cases. Microsurgical techniques lead to an increasing number of brachial plexus repairs in infancy and early childhood. At the same time, an early differentiation concerning type of lesion and prognosis is required. Especially for lower brachial plexus palsies clinical assessment is uncertain. This pilot project was started to evaluate the possible role of magnetic stimulation in this matter. Materials and Methods: 31 children in the age group 1 month to 5 1/4 years with neonatal brachial plexus injury were treated by stimulation at the nerve roots. Target muscles were mostly M. biceps brachii and hypothenar. Results: For evaluation of the lower plexus, magnetic stimulation displayed a good discrimination between severe and mild damage, although this is not statistically significant because of the small case numbers. For diagnosis in the upper parts of the plexus this method did not seem to be reliable. Discussion: Magnetic stimulation of nerve roots in children with neonatal plexus palsy can provide via the sum of muscular potentials an overview of the functional state of preserved and reinnervated nerve fibres. The decisive information, in addition to that derived from clinical evaluation, is the possibility to demonstrate synchronicity or dispersion of the impulse wave over the lesion. Important sources of error may be inherent due to the complex anatomical situation and the poorly-defined sites of stimulation. Conclusion: For the evaluation of the severity of lesions in the lower part of the brachial plexus we have found magnetic stimulation of the nerve roots to be a valuable diagnostic tool for children older than 3 months.