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Intermanual referral of sensation in peripheral and central lesions of somato sensory system
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Intermanual referral of sensation in peripheral and central lesions of somato sensory system

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  • 1. INTERMANUAL REFERRAL OFSENSATION IN PERIPHERAL AND CENTRAL LESIONS OF SOMATO SENSORY SYSTEM A.V. SRINIVASAN, K. BHANU, R. SOWNTHARIYA, S.G. KRISHNA MOORTHY Institute of Neurology Madras Medical College & Research Institute, CHENNAI. 1
  • 2. OBJECTIVE TO STUDY INTERMANUALREFERRAL OF SENSATION INPERIPHERAL AND CENTRAL LESIONS OF SOMATO SENSORY SYSTEM. 2
  • 3. BACKGROUND• ALLESTHESIA AND EXTINCTION OF REFERRAL SENSATION IN BRANCHIAL PLEXUS LESIONS V.S. Ramachandran and A.V. Srinivasan et al (1998)• INTERMANUAL REFERRAL OF SENSATIONS AFTER CENTRAL LESIONS OF THE SOMATOSENSORY SYSTEM K. Sathian et al (2000) 3
  • 4. METHODS• 5 PATIENTS (19-51 YEARS)• BRACHIAL PLEXUS LESION – ONE• AMPUTATION – TWO• STROKE – TWO• PATIENTS WERE VIDEO FILMED IN THE MOVEMENT DISORDER CLINIC.• TOUCH, PAIN, JOINT MOVEMENT & VIBRATION SENSE WERE STUDIED IN ALL PATIENTS 4
  • 5. CASE VIGNETTE (BRACHIAL PLEXUS LESION)• 21 YEAR OLD GIRL, AFTER TOTAL BRACHIAL PLEXUS LESION WAS EXAMINED 6 MONTHS, 1 ½ & 2 ½ YEARS AFTER THE LESION• SHE HAD SENSATIONS INTERMANUALLY REFERRED IN A TOPOGRAPHICALLY ORGANIZED MANNER IN THE PHANTOM LIMB AND SHOWED TELESCOPING OF THE PHANTOM LIMB 5
  • 6. AMPUTATION PATIENTS• BOTH THE PATIENTS (BELOW ELBOW & KNEE AMPUTATION) SHOWED INTERMANUAL REFERRAL OF SENSATION WITHIN 10 DAYS. THE REFERRED SENSATIONS OF TOUCH AND VIBRATION LACKED SPATIAL ORGANIZATION AND POOR LOCALIZATION WITH A RELATIVELY HIGH THRESHOLD HEMIPARESIS PATIENTS• BOTH THE PATIENTS SHOWED INTERMANUAL SENSATION AFTER 4 MONTHS OF DEVELOPING HEMISENSORY DEFICIT. ONE HAD THALAMIC STROKE ANOTHER HAD TEMPARO PARIETAL INFARCT. TACTILE STIMULI TO THE AFFECTED HAND IN THESE PATIENTS WERE NOT REFERRED TO THE AFFECTED LEG. INTERMANUAL REFERRED SENSATIONS WERE POORLY LOCALIZED AND THE FACIAL SENSATIONS WERE REFERRED WITH INCREASED INTENSITY IN THE THALAMIC PATIENT. 6
  • 7. INTERMANUAL REFERAL OF SENSATIONS HEMIPARESIS BRACHIAL WITH AMPUTATION PLEXUS HEMISENSORY DEFICIT SPATIAL ORGANI- EXCELLENT POOR POOR SATION LOCALI- EXCELLENT POOR GOOD SATION TIME OF IMMEDIATE IMMEDIATE AFTER 4 MONTHSOCCURANCE 7
  • 8. OBSERVATIONS• SENSATIONS WERE REFERRED INTERMANUALLY IN A TOPOGRAPHICALLY ORGANIZED MANNER IN BRACHIAL PLEXUS LESIONS WHEREAS, IN AMPUTATIONS AND HEMIPARESIS WITH HEMISENSORY DEFICIT LACKED SPATIAL ORGANIZATION AND POOR LOCALIZATION.• WHILE INTERMANUAL REFERRAL OF SENSATION OCCURRED IMMEDIATELY IN BRACHIAL PLEXUS AND AMPUTATION, IT OCCURRED AFTER A DELAY OF 4 MONTHS IN HEMIPARESIS WITH HEMISENSORY DEFICIT. 8
  • 9. DISCUSSION• INTERMANUAL REFERRAL OF SENSATIONS CAN OCCUR, NOT ONLY AFTER PERIPHERAL DEAFFERENTATION DUE TO AMPUTATION, BUT ALSO AFTER CENTRAL LESIONS OF THE SOMATOSENSORY SYSTEM. THE RELEVANT LESION MAY BE EITHER CORTICAL OR SUBCORTICAL AND ARE NOT LATERALIZED.• CONTRALATERAL REFERRAL OF SENSATIONS WAS NOT FOUND IN NORMAL SUBJECTS OR IN HEMIPARETIC PATIENTS WITHOUT SENSORY LOSS AFFECTING THE HAND• ALLESTHESIA IS WHEN PATIENTS WITH CERTAIN CENTRAL LESIONS DETECT STIMULI ON THE CONTRALATERAL SIDE. 9
  • 10. DISCUSSION Contd…• Although contralateral referral almost certainly depends on callosal connections, the connections involved are unlikely to originate in are 3b of the primary somatosensory cortex. This area, which is located in the posterior bank of the central sulcus and is the primary recipient of low-threshold cutaneous inputs from the thalamus, had a precise topographic organization and neurons with discrete spatially organized receptive fields which support fine spatial resolution. Furthermore, within area 3b, callosal connections are quite sparse in the hand representation. The characteristics of the referred sensations suggest instead that referral may depend on higher order somatosensory areas in parietal cortex such as area 1 and 2 (located posterior to area 3b in the postcentral gyrus) or second somatosensory cortex and neighboring areas in the parietal operculum. In these cortex areas, receptive fields are larger than in are 3b and are often bilateral and callosal connections are more abundant. 10
  • 11. DISCUSSION Contd… The influence of visual input in at least some patients point alternatively, to a role for multimodal areas concerned with the body image, such as those in the posterior partial cortex. Thus 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). Although the neural mechanisms underlying such perceptual alterations remain unclear, the current observations suggest involvement of callosal connections and long- term reorganization in parietal cortical areas, other than are 3b. 11