INTRODUCTION: The Somatosensory system is a complex network of neurons, synapses, and receptors, through which we perceive and navigate our environment. The afferent sensory system interacts via direct and indirect projections with the brain stem, cerebellum, subcortical and cortical structures. This communication brings out the motor sensory modulation in neurological rehabilitation in intermanual referral of sensation and extinction of pain in the peripheral and central lesions of somatosensory system. (stroke, hemineglect, brachialplexes, phantom limb, cancer breast and cancer penis).

METHODOLOGY:  All these patients were examined and investigated in our Institution’s movement disorder clinic with basic investigations, MRI and ENMG in all cases. All the patients were studied with vestibular simulation and posterior column sensations. (pressure, vibration, movement, position, and touch.

CASE STUDIES (VIDEO SEGMENTS ACCOMPANY THIS PRESENTATION): Case Vignette 1 – Stroke: Three patients, one with thalamic stroke and two patients with temparo parietal were analysed. There was no intermanual referral to the ipsilateral normal leg. When intense pressure was applied on the normal hand it resulted in extinction of pain in the stroke side after one minute.  This intermanual referral of sensation only occurred after 3-4 months in the paralysed hand and leg. The spatial organisation was poor, but the localisation was present in the normal limb. The temparo parietal stroke patient had hemineglect with left hemiplegia. The patient had left visual neglect with left hemianopia with no auditory neglect. Absent sensory perception in the left upper and lower limb with neglect. This patient had Anosognosia, body neglect and somatoparaphrenia. Vestibular simulation test was done for this patient. It clearly showed that the patient was able to touch the left arm in whatever position the examiner kept the arm. Thus, proving the first case of blind touch in world literature. Blind sight has already been well described.

Case Vignette 2 - Brachialplexes: 21-year-old girl who had total brachialplexes lesion was studied at 6months, 1 year and 2 years. She had referred in a topographically organised manner in the phantom limb on the ipsilateral side.

Case Vignette 3 - Amputation: Two patients (one with below elbow amputation and another with knee amputation) showed intermanual referral of sensation within 10days. The referred sensation of touch and vibration lacked spatial organisation and poor localisation with a relatively high threshold.

DISCUSSION: Contralateral referral of sensation was not found in normal subjects or in hemiparetic patients without hemisensory loss. Neural mechanisms for perceptual alteration not clear. The possible mechanism is due reactivation of pre-existing connections linking the hands and legs. Pain and temperature sensations are not referred because there are no commissural fibres. The sensory modulation in spatial neglect was done with magnetic stimulation, neck vibration training and repetitive auto kinetic simulation. Drug treatment is currently unsuccessful, and this is the first case in the world literature where vestibular sensory stimulation was useful in treating the Neglect in the stroke patients. It appears that a decrease in somatosensory input to one cerebral hemisphere from the contralateral hand allows responsiveness of neurons in this hemisphere to moderately intense tactile stimuli on the ipsilateral hand to exceed perceptual threshold (which does not normally occur). Intermanual referral and extinction of pain sensation was excellent in special organisation and localisation in brachialplexes, whereas it was poor in amputation and stroke. The pain relief occurred immediately in brachialplexes and amputation within 7 days, whereas it was 3-4 months in stoke.

He is Emeritus Professor in the Tamil Nadu Dr. M.G.R. Medical University; Former Adjunct Prof.–IIT (Madras) – (Bio – Technology) and Visiting Professor in Cleveland –Ohio – USA; Hershey Medical College, USA and Former Adjunct Prof. –IIT (Madras) –(Bio– Technology)