A proposed model for the reorganization of sensory tracts in hemispherectomy patients

Abstract

In this thesis we investigate the remaining light touch and proprioceptive function after hemispherectomy surgery. The main focus is on differences in reorganization between the two pathways processing these sensory functions. Sensory performance scores for light touch and proprioception are collected from 18 hemispherectomy patients using Fugl Meyer, before and after therapeutic intervention which focused on gait, balance and mobility in these individuals. Our results show that scores for sensory tasks affecting the spinothalamic (ST) tract differ from sensory tasks utilizing the medial lemniscus (ML), with proprioception being more impaired than light touch in the contralateral arm. Other recent studies report that in the ipsilateral arm sensory function of the ML is more impaired than ST. Our main hypothesis is that the sensory tracts undergo distinct types of reorganizations causing differences in performances on sensory tasks. We suggest that this distinction can either be correlated to evolutionary differences or differences in the reorganization of the tracts, such as the disinhibition/strengthening of pre-existing ipsilateral tracts or reorganization of existing contralateral tracts by making a double cross of ipsilateral sensory information through subcortical areas. Based on differences in the sensory impairments for the different pathways, we hypothesize that the distinction in sensory functions executed by the ST and ML is based on the presence of ipsilateral tracts, in which the ST tract is provided with either more or stronger ipsilateral tracts than the ML.