Sensory Localisation: Dermatomes & Peripheral Nerves

///Sensory Localisation: Dermatomes & Peripheral Nerves
Sensory Localisation: Dermatomes & Peripheral Nerves 2018-01-30T16:37:22+08:00

This is a very clear depiction of the dermatomes and peripheral nerves supplying sensation to the body.

  • Testing sensation:
    • Vibration (128Hz tuning fork): dorsal column
    • Touch: dorsal column, diffuse ascending fibres, anterolateral tract
    • Pain and temperature: anterolateral / spinothalamic tract
  • Cortical sensation
    • Sensation to pain, vibration intact
    • Loss of two-point discrimination: 3mm at the pump of each finger
    • Agraphia: inability to recognize numbers / letters drawn on pal with eyes closed
    • Stereognosis: inability to identify common objects (e.g. key) using touch only (i.e., by feeling the objects, one hand at a time, with eyes closed)
  • Spinal cord: ends at L1. Nerve roots hence take an increasingly long course to reach their respective exit foramina. Spinal cord levels relative to vertebral bodies are:
    • Upper cervical: same level
    • Lower cervical: one level higher
    • Upper thoracic: two levels higher
    • Lower thoracic: two to three levels higher
    • Lumbar: T10 – T12
    • Sacral: T12 – L1
  • Dermatomes
    • C4: regimental patch
    • C5: lateral aspect of arm
    • C6: thumb, lateral aspect of forearm
    • C7: middle finger
    • C8: little finger
    • T1: medial aspect of arm
    • L1: anterior aspect of inguinal ligament
    • L2: mid-thigh, especially lateral aspect
    • L3: just proximal to the knee, anterior aspect
    • L4: medial calf
    • L5: lateral calf, dorsal aspect of proximal foot
    • S1: plantar aspect of foot, dorsal aspect of toes
    • S2: posterior aspect of thigh, in the midline
  • Peripheral nerve distribution
    • Axillary nerve: lateral aspect of arm, over deltoid
    • Median cutaneous nerve: median aspect of arm
    • Lateral cutaneous nerve of forearm: lateral aspect of forearm
    • Median cutaneous nerve of forearm: median aspect of forearm
    • Median nerve: lateral three-and-a-half digits, palmar aspect
    • Ulnar nerve: median one-and-a-half digits, palmar aspect
    • Radial nerve: anatomical snuffbox / first dorsal web space
    • Lateral femoral cutaneous nerve: lateral aspect of thigh
    • Anterior femoral cutaneous nerve: anterior aspect of thigh (midline)
    • Obturator nerve: medial aspect of upper thigh
    • Posterior femoral cutaneous nerve: posterior aspect of thigh
    • Lateral sural cutaneous nerve: lateral aspect of leg
    • Saphenous nerve: medial aspect of leg
    • Superficial peroneal nerve: dorsal aspect of medial foot, except first web space
    • Deep peroneal nerve: first dorsal web space of foot
    • Sural nerve: dorsal aspect of 5th toe, posterior aspect of leg (midline)

Sensory Localisation

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