Signs
 

Light Touch Sensation

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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)
     
     
    3rd Order Nuclei
    Ventral posterolateral (VPL) nucleus of thalamus
     
     
    Decussation
    Medulla (spinothalamic tract), level of entry into spinal cord (dorsal column)
     
    2nd Order Nuclei
    Dorsal horn (spinothalamic tract),
    lower medulla (dorsal column)
     
     
    1st Order Nuclei
    Dorsal root ganglion
     
     
    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.
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