1. INTERMANUAL REFERRAL OF
SENSATION 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.
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2. OBJECTIVE
TO STUDY INTERMANUAL
REFERRAL OF SENSATION IN
PERIPHERAL AND CENTRAL
LESIONS OF SOMATO
SENSORY SYSTEM.
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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)
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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
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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
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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.
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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 MONTHS
OCCURANCE
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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.
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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.
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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.
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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.
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