Intradural cervical root adjacent interconnections in the normal, prefixed, and postfixed brachial plexus

Abstract

Intradural intercommunications between adjacent nerve roots have received scant attention in the literature. Moreover, the pattern of these connections among individuals harboring normal, pre-, and postfixed brachial plexuses, to the authors' knowledge, has not been explored. Sixty adult cadavers were evaluated for the presence of a normal, prefixed, or postfixed brachial plexus. Next, with the cadaver placed prone, laminectomies of all cervical and the upper thoracic vertebrae were performed. The dura mater was opened and observations were made for the presence of neural intercommunications between the roots of adjacent spinal levels. Any correlations between such root communications and pre- and postfixed brachial plexuses were explored. Among the cadavers, 28% harbored prefixed and 5% harbored postfixed brachial plexuses. Intercommunications between adjacent dorsal roots were more or less equally distributed between left and right sides. A total of 134 interconnections were identified between C-1 and T-2 levels. No interconnection spanned more than one spinal segment. When all sides were included, in ascending order based on the number of interconnections present, interconnections between roots were found between T-1 and T-2, C-1 and C-2, C-8 and T-1, C-2 and C-3, C-3 and C-4, C-4 and C-5, C-7 and C-8, C-6 and C-7, and C-5 and C-6. In this same order, the percent of total connections for each of these levels was 0, 0.8, 2, 7, 13, 15, 16, 20, and 25%. For left and right sides, a total of 73 and 61 interconnections were identified, respectively. This order of concentration was found to have no statistical difference between cadavers that had a normal arrangement of the brachial plexus, a prefixed brachial plexus, or a postfixed brachial plexus. No specimen was found to have interconnections between adjacent ventral roots. Such variations as intradural interconnections may lead to misinterpretation of spinal levels harboring pathological entities of the spinal axis and should be considered during surgical procedures of this region such as rhizotomy. However, the present study did not find a correlation between the level of these interconnections and whether the brachial plexus was pre- or postfixed (that is, there were no observable shifts intradurally that corresponded to the extradural segmental contributions to the brachial plexus).