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

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