The 30 Dermatomes Explained: A Complete Nerve Map of The Body

A dermatome is a patch of skin innervated by a single spinal nerve. Although the human body has 31 pairs of spinal nerves branching from the spinal cord, there are only 30 dermatomes.

Your spinal nerves serve to transmit sensory, motor, and autonomic signals between the rest of your body and your central nervous system (CNS).

So why do dermatomes matter? How many exist and where are they located? Read on as we explore these questions and more about dermatomes.

Dermatomes in perspective

Each spinal nerve carries sensation from specific regions of skin, which correspond to individual dermatomes.

Your spinal nerves

Spinal nerves belong to the peripheral nervous system (PNS). The PNS functions to link the body to the CNS, which consists of the brain and spinal cord.

There are 31 pairs of spinal nerves. These form nerve roots that emerge from the spinal cord and are named according to the spinal region they arise from.

The five clusters of spinal nerves include:

• Cervical nerves: Eight pairs, labeled C1–C8, arising from the neck region.
• Thoracic nerves: Twelve pairs, T1–T12, originating in the thoracic (torso) portion of the spine.
• Lumbar nerves: Five pairs, L1–L5, coming from the lower back segment of the spine.
• Sacral nerves: Five pairs tied to the sacrum, one of the pelvic bones.
• Coccygeal nerves: A single pair emerging near the coccyx, or tailbone.

Your dermatomes

Each of your dermatomes corresponds to a single spinal nerve. These nerves convey sensations, such as pain, from a defined patch of skin to the CNS.

There are 30 dermatomes in the body, one fewer than the total spinal nerve pairs. This discrepancy occurs because the C1 nerve typically lacks a sensory root, so dermatome mapping usually begins with C2.

Dermatomes are arranged in a segmental pattern across the body. The precise distribution can differ between individuals, and neighboring dermatomes may overlap.

Because spinal nerves exit the vertebral column laterally, dermatomes of the trunk are laid out horizontally. On a body chart they resemble stacked bands.

In the limbs the layout is somewhat altered due to limb shape. Generally, limb dermatomes descend along the long axis of the limbs, running lengthwise down an arm or leg.

Locations of individual dermatomes

Dermatomes are numbered according to the spinal nerve they reflect. Below is a general guide to each dermatome and the region of skin it typically covers.

Keep in mind the exact boundaries can vary, and overlaps do occur, so treat the following as an approximate map.

Cervical spinal nerves

• C2: lower jaw and posterior aspect of the head
• C3: upper neck and back of the head
• C4: lower neck and upper shoulder region
• C5: area around the collarbones, top of shoulders, lateral forearm
• C6: shoulder region, outer arm, thumb
• C7: upper back, posterior arm, index and middle fingers
• C8: upper back, inner arm, ring and little fingers

Thoracic spinal nerves

• T1: upper chest and back, armpit area, anterior arm
• T2: upper chest and back
• T3: upper chest and back
• T4: upper chest (around the nipple line) and back
• T5: mid-chest and corresponding back region
• T6: mid-chest and mid-back
• T7: mid-chest and back
• T8: upper abdomen and mid-back
• T9: upper abdomen and mid-back
• T10: abdominal area (around the navel) and mid-back
• T11: lower abdomen and mid-back
• T12: lower abdominal region and mid-back

Lumbar spinal nerves

• L1: lower back, hips, and groin
• L2: lower back, front and inner thigh
• L3: lower back, front and inner thigh
• L4: lower back, front of thigh and calf, knee area, inner ankle
• L5: lower back, front and outer calf, top and bottom of foot, first four toes

Sacral spinal nerves

• S1: lower back, back of thigh, posterior and inner calf, little toe
• S2: buttocks, genital area, back of thigh and calf
• S3: buttocks and genital region
• S4: buttocks
• S5: buttocks

Coccygeal spinal nerves

Buttocks and area around the coccyx (tailbone)

Dermatomes illustration

Why dermatomes matter

Dermatomes are clinically valuable because they help evaluate and diagnose various neurological issues. Symptoms that follow a distinct dermatome can point to a problem with a particular spinal nerve root.

Examples of conditions involving dermatome-distributed symptoms include:

• Radiculopathies: These occur when a spinal nerve root is compressed or irritated. Pain from radiculopathies may track along one or multiple dermatomes. One common type is sciatica, presenting with pain, weakness, or tingling sensations.
• Shingles: Reactivation of the varicella zoster virus (chickenpox) that persists in nerve roots can lead to shingles. The resulting pain and rash appear along the dermatome supplied by the affected nerve root. For more on paths the virus follows see nerve paths that shingles follow.

Frequently asked questions

What does dermatome pain feel like?

The sensation linked to a dermatome can vary depending on the underlying cause.

Common complaints associated with dermatome involvement include:

• tingling
• itching
• burning
• weakness

How do dermatomes differ from myotomes?

Dermatomes describe skin regions innervated for sensory input by a spinal nerve, whereas myotomes refer to the groups of skeletal muscles a spinal nerve supplies for motor function.

Myotomes typically receive input from multiple spinal nerves, producing more overlap than dermatomes, which are linked to individual spinal nerves.

Summary

Dermatomes are skin zones connected to single spinal nerves. While there are 31 pairs of spinal nerves, the body usually exhibits 30 dermatomes. The precise reach of each dermatome can differ among people.

Spinal nerves carry sensory data from the body to the central nervous system, so each dermatome relays information from a specific skin area to the brain.

Mapping dermatomes is useful for assessing and diagnosing spinal or nerve root disorders. Noting symptoms that trace a particular dermatome helps clinicians pinpoint the likely spinal segment involved.