Dermatomes

What are dermatomes?

A dermatome is an area on your body that relies on a specific spinal nerve. That spinal nerve is critical for its dermatome because it carries all the nerve signals traveling between the dermatome and your brain.

Usually, this is a two-way connection. Your brain sends signals out to dermatomes, which is how you control your muscles. The nerves in the dermatomes also send signals back, which is how you have your sense of touch, the sensations of hot and cold, and your ability to feel pain. However, some conditions can make this a one-way connection, or that can completely cut off the connection.

Why do dermatomes matter to me or my healthcare provider?

Dermatomes can offer helpful clues when healthcare providers are trying to diagnose or treat certain types of medical problems. To understand this, think of your spinal cord as a freeway. It handles tremendous amounts of traffic — nerve signals — traveling between your body and brain.

Your spinal nerves are like the on- and off-ramps of your spinal cord. Your spinal nerves allow access for nerve signals coming and going. If there’s an area of your body where you don’t have muscle control, or you can’t feel temperature, touch or pain, that can mean a problem with the connected spinal nerve. In effect, the on- and off-ramps are closed, so there’s no traffic traveling to and from that area.

Dermatomes are an important clue that can tell healthcare providers if there’s a problem with the bones of your spine, your spinal cord, spinal nerves or any of their related nerve branches. Depending on the affected dermatome(s), healthcare providers can rule out some conditions and narrow down the possibilities while trying to help care for you.

Where are the dermatomes?

Dermatomes are areas of your skin that rely on nerves that connect to your spinal cord. That means that dermatomes cover your entire body except for your face. The nerves in your face are an exception because they don’t have connections that travel through your spinal cord.

The structure of the nerve connections at your spine also means there’s a lot of overlap between a dermatome and its neighbors. So, sensations you feel from a specific dermatome travel through multiple spinal nerves simultaneously.

To understand the layout of the dermatomes, it helps to know about the anatomy of the spine. Your spine (also known as your backbone) is a series of interlocking bones called vertebrae (just one is a vertebra). Your spinal nerves branch outward to the left and right from your spinal cord, passing between gaps in your vertebrae.

Your spine has five sections:

• Cervical spine: The cervical spine is in your neck. It has seven vertebrae and eight spinal nerves.
• Thoracic spine: The thoracic spine makes up your upper and middle back. There are 12 vertebrae and 12 pairs of spinal nerves in this section.
• Lumbar spine: This is in your lower back. It has five and five pairs of spinal nerves.
• Sacral spine: This part of your spine joins your backbone to your pelvis. It has five vertebrae (which usually fuse together by the time you become an adult) and five pairs of spinal nerves. Your sacral spine and pelvic bones together look very much like a butterfly. Your sacral spine makes up what would be the butterfly’s main body, while the pelvic bones make up the wings.
• Coccygeal spine (pronounced “cah-kij-ee-ul”): These make up your tailbone (coccyx). It has four vertebrae — which also usually fuse by the time you become an adult — and one pair of spinal nerves.

Healthcare providers refer to the spinal nerves using a letter-number combination. For example, the abbreviation for the eighth spinal nerve is C8. Those letter-number combinations can also indicate the affected dermatomes.

Dermatomes related to the cervical spine

Nerves in the cervical section of your spine connect to dermatomes in your head, neck, shoulders, arms and hands. The dermatomes of nerves in your cervical spine are as follows:

• C1: It’s common for people not to have a C1 spinal nerve, which means they also don’t have a C1 dermatome. For people who do, this dermatome is at the center of the back of their head.
• C2 to C3: Upper neck, a small area of your jaw underneath each ear and back of your head
• C3 to C4: Lower neck, upper chest and upper back.
• C4 to C5: Shoulders and upper arms.
• C5 to C6: Thumb side of your upper arm and forearm, and your thumb itself.
• C6 to C7: Thumb side of your forearm and your index and middle fingers.
• C6 to C8: Pinky side of your lower forearm and wrist, as well as your ring and pinky fingers.

Dermatomes related to the thoracic spine

The dermatomes of your thoracic spine are mostly on the trunk of your body, which includes your chest, belly and back. The only thoracic-connected dermatomes not on your trunk are the dermatomes of T1 (which is entirely on your arms) and T2 (which is on your arms and trunk). The dermatomes from T3 to T12 form rings around your body’s trunk.

The location of the dermatomes are:

• T1 to T2: Pinky side of your upper forearm and upper arm, and the chest and back area just above your armpits.
• T2 to T3: Pinky side of your upper arm, as well as your upper chest and upper back (just above the level of your armpits and shoulder blades).
• T3 to T4: Chest and back just at the same level as your armpit and center of your shoulder blades.
• T4 to T5: Lower edge of your pectoral muscles and lower part of your shoulder blades.
• T6 to T7: At the same level as the bottom edge of your sternum (also known as your breastbone).
• T7 to T8: At the same level as the lower edges of the lowermost part of your ribcage.
• T8 to T9: Upper belly, including the top parts of your abdominal muscles.
• T9 to T10: The area just above and level with your bellybutton (navel) and the upper-middle section of your back.
• T10 to T11: The area level with and just below your bellybutton and the center section of your middle back.
• T11 to T12: The lowest part of your abdomen just above the level of your hipbones (pelvis) and the lower section of your middle back.

Dermatomes of the lumbar spine

Dermatomes of your lumbar spine connect to areas on your hips, legs and feet. The locations of the dermatomes are:

• L1 to L2: The upper part of your hips, pubic area, the upper part of the small of your back and the sex organs (penis and testicles in men and people assigned male at birth and vagina in women and people assigned female at birth).
• L2 to L3: Includes the muscles of your upper thigh and groin and the middle of the small of your back.
• L3 to L4: Includes the front and outer sides of your thigh muscles (quadriceps), your kneecaps, the outer edge of your leg just above your knee and the middle-lower section of the small of your back.
• L4 to L5: The kneecap and front of your lower leg, the inner sides of your calf muscles and the inner front surface of your feet, including your big toe and second and third toes.

Dermatomes of the sacral and coccygeal spine

The dermatomes of your sacral spine include areas around your buttocks and the back of your legs. There’s only one spinal nerve in the coccygeal section of your spine and only one connected dermatome as a result.

• S1 to S2: The uppermost section of your buttocks (including the gluteal cleft, which is the uppermost area where your buttocks separate), the middle and outer sections of the back of your thighs and calf muscles, the outer side of your ankles, and your fourth and fifth toes.
• S2 to S3: A vertical area at the middle of your buttocks, extending downward through the inner-middle section of the back of your thigh and the upper-middle section of your calf muscles.
• S3 and below: Every spinal nerve from S3 down (including your coccygeal spinal nerve) connects to an area that includes your genitals, anus and the area of skin between the two (known as the perineum).

What are the common conditions and disorders that affect the dermatomes?

While dermatomes are areas of skin, the conditions that affect them typically happen because of issues deeper within your body. The issues that affect the dermatomes do so because they affect specific spinal nerves or the spinal cord in that region. Because of this, any condition affecting your spinal cord or spinal nerves can cause symptoms that affect dermatomes. In these cases, the damage is very localized, but the effects are widespread depending on the dermatomes affected.

Conditions that can cause this kind of damage or effect include:

• Injuries. An injury to one or more spinal nerve roots or your spinal cord can affect one or more dermatomes. The most common causes for these kinds of injuries include car crashes, penetrating trauma (like knife or gunshot wounds) and spinal fractures due to falls. Injuries that happen during birth or within the first few weeks of life can also cause this (cerebral palsy is an example).
• Spine tumors, including cancers. This can involve cancer that develops on or around your spinal cord, or that starts elsewhere in your body and spreads to your spine.
• Cysts or fluid-filled cavities. When these form around your spinal cord, they’re known as syringomyelia.
• Infections. These can directly attack your spinal cord and nerve roots or cause inflammation and swelling. Because there isn’t much room for that swelling around your spinal cord, it can put too much pressure on your spinal nerves or your spinal cord itself.
• Lack of blood flow (ischemia). Your spinal cord and spinal nerves need blood flow like all other body tissues. Loss of blood flow can happen because of a blocked blood vessel or blood vessel rupture.
• Congenital conditions. These are conditions you have when you’re born. Some congenital conditions affect the structure of your spine, spinal cord or spinal nerves. Examples of this include myelomeningocele or spina bifida.

What are the common signs or symptoms of conditions that affect the dermatomes?

Conditions that affect the dermatomes happen because of disruptions in your nerves or spinal cord. Disruptions like this can cause many symptoms. Those symptoms fall into three categories:

• Motor (movement-related).
• Sensory (touch-related).
• Autonomic (automatic body process-related).

Motor symptoms

• Muscle weakness or paralysis.
• Uncontrolled muscle movements (either muscles that are inactive or uncontrollably active).
• Muscle atrophy (muscle wasting and shrinking from lack of use).

Sensory symptoms

• Tingling.
• Numbness.
• Pain.

Autonomic symptoms

Autonomic processes are body functions that are constantly working regardless of whether or not you think about them. These functions are important because they help your body maintain and regulate itself. If you have damage that disrupts autonomic functions to a dermatome, you might notice symptoms that indicate your body can’t automatically control processes in that area. Examples include:

• Sweating too much (hyperhidrosis) or not sweating enough (anhidrosis).
• Problems controlling muscles in your bladder or bowels, affecting your control over when you pee (urinary incontinence) or poop (fecal incontinence).
• Sexual dysfunction.

What are some common tests that can check for problems with dermatomes?

Several tests can detect or diagnose problems related to your spinal nerves and their dermatomes. The most common are imaging tests and tests that detect nerve signals, including:

• Computed tomography (CT) scans.
• Magnetic resonance imaging (MRI) scans.
• Cisternogram scan.
• Electromyogram (EMG) tests.

What treatments are available for dermatome-related conditions?

The treatments for conditions that affect your spinal nerves and their dermatomes depend on the underlying condition and circumstances. Because the treatment options can vary so widely, a healthcare provider is the best person to tell you the available treatments and what they recommend.

What can I do to prevent conditions and problems that affect the dermatomes?

Dermatomes are indicators of how your spinal cord and spinal nerves are working, so taking care of them starts with taking care of your spine. Remember the following about your spine and spinal nerve health:

• Wear safety equipment, including safety restraints like seat belts, as recommended. Motor vehicle crashes are among the top causes of spinal injuries. Seat belts and other restraints can help you avoid severe injuries.
• Lift safely. Lifting with the strain on your legs instead of your back can help you avoid injuries to your spinal cord and spinal nerves (such as a herniated disk). If you have a history of back problems, you may need to wear a back support brace, especially if you work in a job that requires a lot of lifting or regularly lift weights as a form of physical activity.
• Be careful when using firearms. Gunshot wounds are one of the most common causes of spinal cord injuries. You should ALWAYS treat firearms with extreme caution, no matter the circumstance. Act as if they’re loaded, even if you’re absolutely certain they aren’t. You should also store firearms unloaded, secured with a trigger lock and out of reach of children. It’s also wise to store ammunition separately under lock and key.
• Take precautions to avoid falls. Safety equipment, especially safety harnesses, is essential when working in elevated places. You should also take steps to avoid falls at home, especially with stairs or in bathrooms. This can include installing handrails, using nonslip footwear and floor surfaces, and keeping stairs clear of tripping hazards.
• Make bone health a priority. Conditions related to bone loss, such as osteoporosis and osteopenia, can lead to vertebrae fractures. These fractures can lead to severe spinal cord and spinal nerve damage.
• Posture is important. Poor posture while sitting or standing can strain your back in ways it isn’t meant to handle. That can put pressure on your spinal cord and spinal nerves. An example of this is a pinched nerve.

A note from Cleveland Clinic

Dermatomes are like a map when it comes to the health and function of your spine and the dozens of nerves that connect to it. For most people, dermatomes are just another detail about how your body works. You don’t think about them otherwise. However, dermatomes are a key way healthcare providers can detect and diagnose health problems, especially ones related to your spine, spinal cord and spinal nerves. By taking precautions to guard and maintain the health of your spine, you can help avoid conditions that can impact the dermatomes of your body.