Dermatome (anatomy)

For other uses, see Dermatome (disambiguation).

Dermatomes and major cutaneous nerves.

A dermatome is an area of skin that is mainly supplied by a single spinal nerve. There are eight ( However C 1 is not related to dermatomes) cervical nerves, twelve thoracic nerves, five lumbar nerves and five sacral nerves. Each of these nerves relays sensation (including pain) from a particular region of skin to the brain.

Along the thorax and abdomen the dermatomes are like a stack of discs forming a human, each supplied by a different spinal nerve. Along the arms and the legs, the pattern is different: the dermatomes run longitudinally along the limbs. Although the general pattern is similar in all people, the precise areas of innervation are as unique to an individual as fingerprints.

A similar area innervated by peripheral nerves is called a peripheral nerve field.

Clinical significance

A dermatome is an area of skin supplied by sensory neurons that arise from a spinal nerve ganglion. Symptoms that follow a dermatome (e.g. like pain or a rash) may indicate a pathology that involves the related nerve root. Examples include somatic dysfunction of the spine or viral infection. Referred pain usually involves a specific, "referred" location so is not associated with a dermatome.

Viruses that hibernate in nerve ganglia (e.g. Herpes zoster or Varicella Zoster viridae) often cause either pain, rash or both in a pattern defined by a dermatome. However, the symptoms may not appear across the entire dermatome.

Important dermatomes and anatomical landmarks

• C2 - posterior half of the skull cap
• C3 - area correlating to a high turtle neck shirt
• C4 - area correlating to a low-collar shirt
• C6 - (radial nerve) 1st digit (thumb)
• C7 - (median nerve) 2nd and 3rd digit
• C8 - (ulnar nerve) 4th and 5th digit and medial-posterior aspect of arm
• T4 - nipples.
• T5 - Inframammary fold.
• T6/T7 - xiphoid process.
• T10 - umbilicus (important for early appendicitis pain)
• T12 - pubic bone area.
• L1 - inguinal ligament
• L4 - includes the knee caps
• S2/S3 - genitalia

Additional images

• 

  Cutaneous nerves of right upper extremity.

• 

  Diagram of segmental distribution of the cutaneous nerves of the right upper extremity.

• 

  Lower limb.

• 

  Foot.

See also

• Cutaneous innervation
• Peripheral nerve field
• Dorsal root

External links

• Hand kinesiology at UK nerves/dermatome.htm
• Diagram "Adult Dermatome", The New York Times