Discriminatory Sensation

Discriminatory Sensation:
Impairment of discrimination indicates a lesion or deficit of higher cortical function.
1) Two point discrimination
Two identical stimuli applied simultaneously a distance apart – then progressively closer together – should be able to perceive two objects on sole of foot until 2 – 3mm apart.
Can use on unwound metal paper clip or a set of dividers, or especially developed divider wheels.

Tests peripheral sensation as well as posterior columns of spinal cord and higher cortical sensory ability.

2) Stereognosis:
Test central interpretation and peripheral sensation. A simple object (eg coin) placed in palm of hand – with eyes closed they are asked to say what object is. May indicate a parietal lobe lesion.

3) Graphesthesia:
Letter or number is drawn on palm and patients is asked which one it is – inability to identify may indicate a parietal lobe lesion

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