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SOMATOSENSATION: Location of Lesion (PRIMARY SOMATOSENSORY CORTEX…
SOMATOSENSATION: Location of Lesion
TRACTS
Lesions along the somatosensory pathways up to and including the thalamus may result in loss of sensation
Lesions between the thalamus and primary sensory cortex may result in loss of sensation and inability to localise sensations
Lateral spinothalamic tract lesions above brainstem – Contralateral pain and temperature
Anterior spinothalamic tract lesions above brainstem – Contralateral light touch and crude touch
Dorsal column lesions above the brainstem – Contralateral discriminatory touch, pressure, proprioception, kinesthesia
Spinocerebellar tract lesion – Ipsilateral upper-extremity proprioception
PRIMARY SOMATOSENSORY CORTEX
Decrease / loss of discriminative sensations, proprioception, kinesthesia, two-point discrimination, stereognosis, localisation of touch & pinprick (nociceptive) stimuli as it requires cortical processing
Sensory inattention & somatic (body) neglect
Contralateral
SUBCORTICAL LESIONS: BRAINSTEM
Mix of ipsilateral & contralateral signs because axons carrying sensory information cross the midline at various levels
Posterior medulla / lower pons:
Ipsilateral loss of pain & temperature information from face
Discriminative touch & proprioceptive information not affected as these travel in medial medulla & pons
Contralateral loss of pain & temperature information from body
Upper midbrain:
Sensory tracts all crossed the sensory loss will be contralateral
ASSOCIATION AREAS
Result in difficulties recognising and interpreting sensations including:
Body image impairments: lack of mental image of one’s body
Body scheme impairment
Unilateral neglect (of affected side of the body or environment)
Right/left discrimination
Somatognosia (lack of awareness of body & relationship of body parts)
Stereognosis (identify objects without visual input) impairment