How Spinal Nerve Roots and Dermatomes Can Contribute to Your Pain

Nerve cells.

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Spinal conditions such as herniated disc and stenosis can lead to pain that radiates or travels down one leg (known as sciatica) or one arm. One key feature of these back conditions is an irritated or compressed spinal nerve root. So how does a problem located in your spine (i.e., your spinal nerve root) make for pain, weakness, numbness, and/or electrical sensations down an arm or leg? The answer is dermatomes.

Your Spinal Cord, Nerve Roots, and Dermatomes

Your spinal cord has 31 segments, and each has a pair of anterior and posterior nerve roots that supply motor and sensory function. On each side, the anterior and posterior nerve roots combine to form the spinal nerves as they leave the vertebral canal.

These 31 spine segments on each side result in 31 spinal nerves. Each spinal nerve receives sensory nerve input from a specific region of skin on that side of the body These regions are called dermatomes. Except for the first cervical spinal nerve, dermatomes exist for each of these spinal nerves.

These nerves and dermatomes collectively form a network all over the human body.

Dermatome map
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What Are Dermatomes?

Dermatomes are zones of skin whose sensory input is "assigned," so to speak, to individual spinal nerves. Each nerve root has an associated dermatome, and each dermatome is supplied by many branches of that nerve root. Dermatomes are a bit like highways through which information about sensations in your skin related to your central nervous system.

Sensations you physically feel such as pressure and temperature are transmitted to the central nervous system via nerves that converge on single nerve roots. When a spinal nerve root becomes compressed or irritated—often because it comes into contact with another spinal structure—radiculopathy often results.

What Radiculopathy Feels Like

Radiculopathy describes a range of symptoms caused by a pinched nerve root along the spine. Symptoms and sensations will depend on where along the spine the nerve is pinched.

Cervical radiculopathy, a syndrome of pain and/or sensorimotor deficits that occurs when one or more nerve roots in the neck is compressed, often presents with pain that goes down one arm. There also may be electrical sensations like pins and needles, shock, and a burning sensation, as well as motor symptoms such as weakness and numbness.

With lumbar radiculopathy, which is characterized by compression, inflammation, or injury to a spinal nerve root in the lower back, on the other hand, sensations of pain, numbness, or tingling that travel down one leg is common.

When you have nerve pain symptoms that radiate down your extremities, it's time to see the doctor about your neck or back.

Diagnosing Radiculopathy

When you doctor looks for radiculopathy during a physical examination, they will test (among other things) the dermatomes for sensation. Using specific manual tests, your physician will determine the spinal level from which the symptoms arise. Manual exams are quite often accompanied by diagnostic imaging tests such as MRI.

While imaging such as MRI can show abnormalities of the spinal nerve root, a complete physical examination by a doctor is often needed to determine if that spinal nerve root is the source of your symptoms.

Treating Radiculopathy and Underlying Causes

Many back disorders can be treated without surgery, and the treatment often focuses on pain relief. For a herniated disk, for instance, you may be advised to rest and take a nonsteroidal anti-inflammatory medication (NSAID). Physical therapy may also be prescribed. For severe pain, you may be offered an epidural steroid injection that may provide short-term pain relief by reducing inflammation.

For spinal stenosis, on the other hand, your provider may focus on physical therapy to improve your overall fitness, strengthen abdominal and back muscles, and preserve motion in your spine. Pain-relieving medications including NSAIDs and corticosteroids injections can reduce inflammation and relieve pain related to spinal stenosis.

A Word From Verywell

Learning to distinguish between nerve pain and other types of pain (such as muscular) can help you recognize more serious problems requiring medical attention, such as radiculopathy.

Receiving a diagnosis of spinal stenosis, a herniated disk, or another spinal disorder can be scary. But finding out what is behind your pain and learning about the treatment options can help you feel empowered to determine the best treatment plan with your doctor.

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