28. UMN lesion dependent asymmetry?

Abstract

Introduction A microsurgical partial deafferentation (Rhizotomy) of specific sensory nerve roots (L-1S2) is performed in UMN (upper motor neuron) lesions in order to reduce spasticity and improve walking. The purpose of IOM is to determine which rootlets are to be transected. This study evaluates the anatomical distribution of the obtained IOM grading and will hopefully be of use to others in selecting the right rootlets. Material and methods Selective dorsal rhizotomy (SDR), accompanied by IOM, was performed in 123 children. For each rootlet, the 50 Hz response was graded according to the criteria of Phillips&Park, ranging from grade 0 (normal) to 4+ (highly abnormal). The results obtained for 100 children were incorporated into a retrospective evaluation, which was approved by the local ethics committee. As a statistical test procedure in investigating the frequency distribution of grades with regard to segment, side of the body and order of surgical transsection,a non-parametric analysis of variance with repeated measurements (−2/3-factorial) was conducted. Results Within the selected patient group, a total of 4604 rootlets were tested by means of IOM. Responses deviating from grade 0 were found in 2991 rootlets. The hypothesis was hereby refuted that side plays no role in the distribution of hyperactive responses, as we found a highly significant difference with regard to grades 3 + 4 (p = 0.0066). These differences were observed primarily at L5/S1. The hypothesis that grades are distributed homogeneously over the segments L-2S1 was likewise refuted (p 0.00005). No interdependencies were observed. Conclusion The distribution of rootlets showing hyperactive responses does not follow a specific set pattern, that is, it is not uniform. Since the choice of rootlets to be transected must not be left to chance, IOM will remain an indispensable part of this microsurgical intervention.