A dermatome is an area of skin that is mainly supplied by a single spinal nerve. There are eight cervical nerves (C1 being an exception with no dermatome), 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.
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[clarification needed] in nerve ganglia (e.g. Varicella zoster virus, which causes both chickenpox and herpes zoster) often cause either pain, rash or both in a pattern defined by a dermatome. However, the symptoms may not appear across the entire dermatome.
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...
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