Important dermatomes and anatomical landmarks

Important dermatomes and anatomical landmarks


Dermatome

  • Area of skin that is mainly supplied by a single spinal nerve.

There are:

  1. 8 cervical nerves (C1 being an exception with no dermatome)
  2. 12 thoracic nerves
  3. 5 lumbar nerves 
  4. 5 sacral nerves
  • Each of these nerves relays sensation (including pain) from a particular region of skin to the brain.
  • A dermatome also refers to the part of an embryonic somite.

Important dermatome & anatomical landmarks

Following is a list of spinal nerves and points that are characteristically belonging to the dermatome of each nerve.

  • C2 – At least one cm lateral to the occipital protuberance at the base of the skull. Alternately, a point at least 3 cm behind the ear.
  • C3 – In the supraclavicular fossa, at the midclavicular line.
  • C4 – Over the acromioclavicular joint.
  • C5 – On the lateral (radial) side of the antecubital fossa, just proximally to the elbow.
  • C6 – On the dorsal surface of the proximal phalanx of the thumb.
  • C7 – On the dorsal surface of the proximal phalanx of the middle finger.
  • C8 – On the dorsal surface of the proximal phalanx of the little finger.
  • T1 – On the medial (ulnar) side of the antecubital fossa, just proximally to the medial epicondyle of the humerus.
  • T2 – At the apex of the axilla.
  • T3 – Intersection of the midclavicular line and the third intercostal space
  • T4 – Intersection of the midclavicular line and the fourth intercostal space, located at the level of the nipples.
  • T5 – Intersection of the midclavicular line and the fifth intercostal space, horizontally located midway between the level of the nipples and the level of the xiphoid process.
  • T6 – Intersection of the midclavicular line and the horizontal level of the xiphoid process.
  • T7 – Intersection of the midclavicular line and the horizontal level at one quarter the distance between the level of the xiphoid process and the level of the umbilicus.
  • T8 – Intersection of the midclavicular line and the horizontal level at one half the distance between the level of the xiphoid process and the level of the umbilicus.
  • T9 – Intersection of the midclavicular line and the horizontal level at three quarters of the distance between the level of the xiphoid process and the level of the umbilicus.
  • T10 – Intersection of the midclavicular line, at the horizontal level of the umbilicus.
  • T11 – Intersection of the midclavicular line, at the horizontal level midway between the level of the umbilicus and the inguinal ligament.
  • T12 – Intersection of the midclavicular line and the midpoint of the inguinal ligament.
  • L1 – Midway between the key sensory points for T12 and L2.
  • L2 – On the anterior medial thigh, at the midpoint of a line connecting the midpoint of the inguinal ligament and the medial epicondyle of the femur.
  • L3 – At the medial epicondyle of the femur.
  • L4 – Over the medial malleolus.
  • L5 – On the dorsum of the foot at the third metatarsophalangeal joint.
  • S1 – On the lateral aspect of the calcaneus.
  • S2 – At the midpoint of the popliteal fossa.
  • S3 – Over the tuberosity of the ischium or infragluteal fold
  • S4 and S5 – In the perianal area, less than one cm lateral to the mucocutaneous zone

 

Exam Important

Important dermatome & anatomical landmarks

  • C2 – At least one cm lateral to the occipital protuberance at the base of the skull. Alternately, a point at least 3 cm behind the ear.
  • C3 – In the supraclavicular fossa, at the midclavicular line.
  • C4 – Over the acromioclavicular joint.
  • C5 – On the lateral (radial) side of the antecubital fossa, just proximally to the elbow.
  • C6 – On the dorsal surface of the proximal phalanx of the thumb.
  • C7 – On the dorsal surface of the proximal phalanx of the middle finger.
  • C8 – On the dorsal surface of the proximal phalanx of the little finger.
  • T1 – On the medial (ulnar) side of the antecubital fossa, just proximally to the medial epicondyle of the humerus.
  • T2 – At the apex of the axilla.
  • T3 – Intersection of the midclavicular line and the third intercostal space
  • T4 – Intersection of the midclavicular line and the fourth intercostal space, located at the level of the nipples.
  • T5 – Intersection of the midclavicular line and the fifth intercostal space, horizontally located midway between the level of the nipples and the level of the xiphoid process.
  • T6 – Intersection of the midclavicular line and the horizontal level of the xiphoid process.
  • T7 – Intersection of the midclavicular line and the horizontal level at one quarter the distance between the level of the xiphoid process and the level of the umbilicus.
  • T8 – Intersection of the midclavicular line and the horizontal level at one half the distance between the level of the xiphoid process and the level of the umbilicus.
  • T9 – Intersection of the midclavicular line and the horizontal level at three quarters of the distance between the level of the xiphoid process and the level of the umbilicus.
  • T10 – Intersection of the midclavicular line, at the horizontal level of the umbilicus.
  • T11 – Intersection of the midclavicular line, at the horizontal level midway between the level of the umbilicus and the inguinal ligament.
  • T12 – Intersection of the midclavicular line and the midpoint of the inguinal ligament.
  • L1 – Midway between the key sensory points for T12 and L2.
  • L2 – On the anterior medial thigh, at the midpoint of a line connecting the midpoint of the inguinal ligament and the medial epicondyle of the femur.
  • L3 – At the medial epicondyle of the femur.
  • L4 – Over the medial malleolus.
  • L5 – On the dorsum of the foot at the third metatarsophalangeal joint.
  • S1 – On the lateral aspect of the calcaneus.
  • S2 – At the midpoint of the popliteal fossa.
  • S3 – Over the tuberosity of the ischium or infragluteal fold
  • S4 and S5 – In the perianal area, less than one cm lateral to the mucocutaneous zone
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