Anatomical and functional assessment of the intradural segment of the spinal nerves is imperative in brachial plexus surgery, as the repair of postganglionic elements in the setting of a confirmed nerve root avulsion is of no benefit. None of the current techniques to detect these avulsions can provide full information that ensures the functional status of the preganglionic segment of the roots. The objective of this study was to evaluate intraoperative electrical stimulation of the supraclavicular segment of the long thoracic nerve (LTN) as a method to differentiate C-5 nerve root extraforaminal rupture from its intradural avulsion.
The author performed a prospective analysis of data obtained in 14 patients presenting with the loss of C-5 nerve root function secondary to traumatic brachial plexus injury. The patients were divided into 2 groups: 8 patients in whom the intradural segment of C-5 nerve root was preserved (5 cases of closed traction injuries in whom the computed tomography [CT] myelograms confirmed the integrity of C-5 root and 3 cases of open sharp injuries) and a control group of 6 patients in whom CT myelography demonstrated avulsion of the root.
The results of the intraoperative electrical stimulation of the LTN and the surgical outcome of each patient were recorded. The LTN electrical stimulation elicited serratus anterior muscle contraction in cases in which C-5 root was not avulsed, and there were no responses in patients whose radiological evaluation had demonstrated nerve root avulsion. In those patients in whom LTN stimulation proved to be positive, the C-5 root was used as a graftable stump to the suprascapular nerve and/or to the posterior division of the superior trunk. In these cases, favorable results were observed regarding arm abduction in all cases—Medical Research Council Grades M3 (37%) and M4 (62%). In the control group, the C-5 root was not used as a donor stump and a multiple nerve transfer technique was adopted as the preferred surgical option.
Intraoperative electrical stimulation of the supraclavicular segment of the LTN is a useful complementary method to test the functional status of the C-5 ventral rootlets. If the test is positive (that is, a response is present) it is indicative of extraforaminal rupture of the root, and if negative, it is suggestive of its avulsion.