What and where are dermatomes?
Dermatomes are areas of skin that send signals to the brain through the spinal nerves. These signals give rise to sensations involving temperature, pressure, and pain.
The part of a nerve that exits the spinal cord is called the nerve root. Damage to a nerve root can trigger symptoms in the nerve’s corresponding dermatome.
Below, we show the locations of the dermatomes throughout the body. We also describe health conditions that can damage the spinal nerves and affect their dermatomes.
What are they?
A dermatome is an area of skin that sends information to the brain via a single spinal nerve.
Spinal nerves exit the spine in pairs. There are 31 pairs in total, and 30 of these have corresponding dermatomes.
The exception is the C1 spinal nerve, which does not have a corresponding dermatome.
The spinal nerves are classified into five groups, according to the region of the spine from which they exit.
The five groups and their points of exit from the spine are:
Cervical nerves: These exit the neck region and are labeled C1–C8.
Thoracic nerves: These exit the torso region and are labeled T1–T12.
Lumbar nerves: These exit the lower back region and are labeled L1–L5.
Sacral nerves: These exit the base of the spine and are labeled S1–S5.
A coccygeal nerve pair: These exit the tailbone, or coccyx.
Locations of the dermatomes
Each dermatome shares the label of its corresponding spinal nerve.
Some dermatomes overlap to a certain extent, and the precise layout of the dermatomes can vary slightly from one person to the next.
Below, we list the locations of the dermatomes that correspond to the spinal nerves in each group.
Cervical nerves and their dermatomes
C2: the base of the skull, behind the ear
C3: the back of the head and the upper neck
C4: the lower neck and upper shoulders
C5: the upper shoulders and the two collarbones
C6: the upper forearms and the thumbs and index fingers
C7: the upper back, backs of the arms, and middle fingers
C8: the upper back, inner arms, and ring and pinky fingers
Thoracic nerves and their dermatomes
T1: the upper chest and back and upper forearm
T2, T3, and T4: the upper chest and back
T5, T6, and T7: the mid-chest and back
T8 and T9: the upper abdomen and mid-back
T10: the midline of the abdomen and the mid-back
T11 and T12: the lower abdomen and mid-back
Lumbar nerves and their dermatomes
L1: the groin, upper hips, and lower back
L2: the lower back, hips, and tops of the inner thighs
L3: the lower back, inner thighs, and inner legs just below the knees
L4: the backs of the knees, inner sections of the lower legs, and the heels
L5: the tops of the feet and the fronts of the lower legs
Sacral nerves and their dermatomes
S1: the lower back, buttocks, backs of the legs, and outer toes
S2: the buttocks, genitals, backs of the legs, and heels
S3: the buttocks and genitals
S4 and S5: the buttocks
The coccygeal nerves and their dermatome
The dermatome corresponding with the coccygeal nerves is located on the buttocks, in the area directly around the tailbone, or coccyx.
Associated health conditions
Symptoms that occur within a dermatome sometimes indicate damage or disruption to the dermatome’s corresponding nerve. The location of these symptoms can, therefore, help doctors diagnose certain underlying medical conditions.
Some conditions that can affect the nerves and their corresponding dermatomes are:
Shingles, or herpes zoster, is a viral infection caused by the reactivation of the varicella-zoster virus. This is the same virus that causes chickenpox.
After the body recovers from chickenpox, the virus can lie dormant and eventually reactivate as shingles.
In adults, shingles typically causes a rash to form on the trunk, along one of the thoracic dermatomes. The rash may be preceded by pain, itching, or tingling in the area.
Some other symptoms of shingles can include:
sensitivity to bright light
a general feeling of being unwell
A person with a weakened immune system may develop a more widespread shingles rash that covers three or more dermatomes. Doctors refer to this as disseminated zoster.
A pinched nerve occurs when a nerve root has become compressed by a bone, disc, tendon, or ligament. This compression can occur anywhere along the spine, but it usually occurs in the lower, or lumbar, region.
A pinched nerve can cause pain, tingling, or numbness in its corresponding dermatome. As such, the location of the symptoms can help a doctor identify the affected nerve.
The doctor then diagnoses and treats the underlying cause of the pinched nerve and recommends ways to relieve the symptoms.
A traumatic injury to the nerves may result from an accident or surgery.
The severity of symptoms can help doctors determine the extent of the nerve injury.
Dermatomes are areas of skin, each of which is connected to a single spinal nerve. Together, these areas create a surface map of the body.
Dysfunction or damage to a spinal nerve can trigger symptoms in the corresponding dermatome. Nerves damage or dysfunction may result from infection, compression, or traumatic injury.
Doctors can sometimes use the severity of symptoms in a dermatome to determine the extent and location of nerve damage. They then work to diagnose and treat the underlying cause of the damage.
Article Provided By: medicalnewstoday
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