Light Touch Sensation
August 19th, 2017
Overview
Soft touch is transmitted via multiple sensory pathways, and can be used as a screening tool to assess for sensory loss.
How to Elicit
- Ask the patient to close their eyes. Using a cotton ball or microfilament, gently touch each dermatome / nerve distribution and ask the patient if they can feel the stimulus. Compare sides and proximally / distally.
Ask About
- Anaesthesia - loss of tactile sensation
- Hypoaesthesia - decreased tactile sensation
- Hyperaesthesia - increased tactile sensation
Light Touch Pathway
Spinothalamic and dorsal column pathways
Cortical Centre
Primary sensory cortex (postcentral gyrus)
Primary sensory cortex (postcentral gyrus)
3rd Order Nuclei
Ventral posterolateral (VPL) nucleus of thalamus
Ventral posterolateral (VPL) nucleus of thalamus
Decussation
Medulla (spinothalamic tract), level of entry into spinal cord (dorsal column)
Medulla (spinothalamic tract), level of entry into spinal cord (dorsal column)
2nd Order Nuclei
Dorsal horn (spinothalamic tract),
lower medulla (dorsal column)
Dorsal horn (spinothalamic tract),
lower medulla (dorsal column)
1st Order Nuclei
Dorsal root ganglion
Dorsal root ganglion
Receptors
Meissner's corpuscles, Merkel discs, Ruffini endings, pacinian corpuscles and hair follicle receptors
Meissner's corpuscles, Merkel discs, Ruffini endings, pacinian corpuscles and hair follicle receptors
Overview
Tacticle sensitivity is greatest on the glabrous hair of the hands, the soles of the feet and the lips.
CNS disorders tend to spare tactile stimulation as both the dolumn column-medial lemniscus and spinothalamic pathways send tactile information to the brain.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------