Functional MRI finding by proprioceptive input in patients with thalamic hemorrhage

Little is known about the recovery mechanism of somatosensory function in thalamic hemorrhage. We investigated the recovery mechanism of somatosensory function, using functional MRI (fMRI) findings by proprioceptive input in chronic patients with thalamic hemorrhage. Eleven consecutive chronic patients with thalamic hemorrhage who showed severe proprioceptive dysfunction were recruited. The subscale for kinesthetic sensation of the Nottingham Sensory Assessment (NSA) was used for determination of proprioceptive function. fMRI was performed during passive movements of the metacarpophalangeal joint. From fMRI, the laterality index (LI) was calculated for assessment of the relative activity in the ipsilateral versus the contralateral primary sensori-motor cortex (SM1). The average LI for affected and unaffected hand stimulation was 0.89 and 0.90, respectively, and there was no significant difference between LIs (p> 0.05). In addition, LI of the affected hand stimulation was positively related to NSA scores (r=0.790, p< 0.05). Our results for LI suggest that the cortical activation pattern of SM1 was similar in the affected and unaffected hemispheres. Therefore, it appears that the proprioceptive function of the affected hand likely recovered by the normally existing medial lemniscus and its thalamocortical pathway in our patients.