Intraoperative nerve action and compound motor action potential recordings in patients with obstetric brachial plexus lesions

Object. A typical finding in supraclavicular exploration of infants with severe obstetric brachial plexus lesions (OBPLs) is a neuroma-in-continuity with the superior trunk and/or a root avulsion at C-5, C-6, or C-7. The operative strategy in these cases is determined by the intraoperative assessment of the severity of the lesion. Intraoperative nerve action potential (NAP) and evoked compound motor action potential (CMAP) recordings have been shown to be helpful diagnostic tools in adults, whereas their Value in the intraoperative assessment of infants with OBPLs remains to be determined. Methods. Intraoperative NAPs and CMAPs were systematically recorded from damaged and normal nerves of the tipper brachial plexus in a consecutive series of 95 infants (mean age 175 days) with OBPLs. A total of 599 intraoperative NAP and 836 CMAP recordings were analyzed. The severity of the nerve lesions was graded as normal, axonotmesis, neurotmesis, or root avulsion, based on surgical, clinical, histological, and radiographic criteria. Results. The correlation of NAP and CMAP recordings with the severity of the lesion was assessed. The specificity of an absent NAP or CMAP to predict a severe lesion (neurotmesis or avulsion) was > 0.9. However, the sensitivity of an absent NAP or CMAP for predicting a severe lesion was low (typically < 0.3). The severity of the nerve lesion was related to CMAP and NAP amplitudes. Cutoff points useful for intraoperative decision making could not be found to differentiate between lesion types in individual patients. Conclusions. Intraoperative NAP and CMAP recordings do not assist in decision making in the surgical treatment of infants with OBPLs. The authors' findings in infants cannot be generalized to adults.