Lumbar Spinal Nerves (2024)

Two spinal nerves branch off from the right and left sides of the spinal cord or the cauda equina at each spinal segment. These spinal nerves are formed by 2 types of fibers—sensory fibers that send messages to the brain (feeling pain when the leg is hurt) and motor fibers that receive messages from the brain (lifting the leg to get out of a car).

There are 5 pairs of lumbar spinal nerves that progressively increase in size from L1 to L5. These nerves exit the intervertebral foramina below the corresponding vertebra. For example, the L4 nerve exits beneath the L4 vertebra through the L4-L5 foramen. These nerves course down from the lower back and merge with other nerves to form the lumbar and lumbosacral plexuses (a network of nerves), which innervate the lower limbs.

In This Article:

  • Lumbar Spine Anatomy and Pain
  • Lumbar Vertebrae
  • Lumbar Discs
  • Lumbar Spinal Nerves
  • Soft Tissues of the Lumbar Spine
  • Spinal Cord and Cauda Equina of the Lumbar Spine
  • Causes of Pain in the Lumbar Spine
  • Lumbar Spine Anatomy Video

Nerve Root and Spinal Nerve

The structure of a spinal nerve as it leaves the spinal cord or cauda equina includes:

  • Nerve root: Part of the nerve that branches off the spinal cord or cauda equina. At each level, a pair of nerve roots emerge from the right and left sides of the spinal cord. Each pair consists of a dorsal root at the back and a ventral root in the front.
  • Spinal nerve: A single nerve formed when the dorsal and ventral nerve roots merge, typically inside the intervertebral foramen (bony opening in between adjacent vertebrae). The spinal nerve travels a short distance inside the intervertebral foramen, after which it branches off into several nerves that innervate different parts of the body.

Doctors may sometimes refer to the part of the spinal nerve exiting the intervertebral foramen as the nerve root or use the terms nerve root and spinal nerve interchangeably.

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Dermatomes and Myotomes

The spinal nerves innervate the skin and the muscles of a specific region.

  • A dermatome is a specific area of skin that is supplied by the dorsal root fibers of a spinal nerve. The dorsal root fibers carry sensory information from the dermatome to the brain.
  • A myotome is a group of muscles controlled by the ventral root fibers of a spinal nerve. The ventral root fibers carry motor signals from the brain to the myotome.

When a spinal nerve gets irritated or compressed, sensory and/or motor deficits may occur in the corresponding dermatome and myotome.

Functions of the Lumbar Spinal Nerves

The 5 pairs of lumbar spinal nerves innervate the lower limbs.

While innervation can vary among individuals, some common patterns include 2 Dulebohn SC, Ngnitewe Massa R, Mesfin FB. Disc Herniation. [Updated 2019 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441822/:

  • L1 spinal nerve provides sensation to the groin and genital regions and may contribute to the movement of the hip muscles.
  • L2, L3, and L4 spinal nerves provide sensation to the front part of the thigh and inner side of the lower leg. These nerves also control movements of the hip and knee muscles.
  • L5 spinal nerve provides sensation to the outer side of the lower leg, the upper part of the foot, and the web-space between the first and second toe. The L5 spinal nerve controls hip, knee, foot, and toe movements.

Read more about Spinal Cord and Spinal Nerve Roots

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The L4 and L5 nerves (along with other sacral nerves) contribute to the formation of the large sciatic nerve that runs down from the rear pelvis into the back of the leg and terminates in the foot. Symptoms and signs arising from these nerves, typically referred to as sciatica, can cause a sharp, burning pain radiating down the leg with associated weakness and numbness.

See Sciatic Nerve and Sciatica

While the lumbar spinal nerves progressively increase in size, the openings for these nerves (intervertebral foramina) decrease in size from L1 to L5. 1 Waxenbaum JA, Futterman B. Anatomy, Back, Lumbar Vertebrae. [Updated 2018 Dec 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459278/ This anatomy, in addition to lower back disorders, such as disc herniation or degeneration may cause the nerve to get compressed, resulting in leg pain and weakness.

See Causes of Lower Back Pain

  • 1 Waxenbaum JA, Futterman B. Anatomy, Back, Lumbar Vertebrae. [Updated 2018 Dec 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459278/
  • 2 Dulebohn SC, Ngnitewe Massa R, Mesfin FB. Disc Herniation. [Updated 2019 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441822/

Dr. Kara Beasley is a neurosurgeon practicing at Boulder Neurosurgical & Spine Associates, where she has several years of experience specializing in spine and brain surgery.

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Editor’s Top Picks

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Lumbar Spinal Nerves (2024)

FAQs

What is the best painkiller for spinal stenosis? ›

While the effectiveness of these medications can vary from patient to patient, baclofen, cyclobenzaprine, and methocarbamol are often considered among the top options for alleviating spinal stenosis discomfort.

How serious is lumbar spinal stenosis? ›

Lumbar spinal stenosis can cause cauda equina syndrome, which needs medical attention right away. Call your healthcare provider if you have: Loss of bowel or bladder control.

What is lumbar 5 nerve damage? ›

L5 radiculopathy is usually associated with numbness down the side of the leg and into the top of the foot. S1 radiculopathy typically results in numbness down the back of the leg into the outside or bottom of the foot. Weakness is another symptom of nerve root compression.

What are the symptoms of L4-L5 nerve damage? ›

What Are the Symptoms of L4-L5 Nerve Damage? The symptoms of L4-L5 nerve damage are typically chronic lower back pain, numbness, tingling, and weakness that radiate to the legs and feet. Spinal nerve damage can be severe.

What is the single best exercise for spinal stenosis? ›

#1 Walking For Spinal Stenosis

Walking is good, for spinal stenosis. Once your posture is changed enough the distance that you can walk will increase. If you can walk without pain with your new posture you are ready for the next step.

How can I get immediate relief from spinal stenosis? ›

Anti–inflammatory medications to help relieve inflammation and pain. Over-the-counter pain relievers taken by mouth or applied to the skin. Prescription pain relievers for severe or acute pain. Anti-inflammatory or numbing injections for pain that radiates or travels due to nerve compression or irritation.

What is the most successful treatment for spinal stenosis? ›

Laminectomy. This surgery removes the back part (lamina) of the affected spinal bone. This eases pressure on the nerves by making more space around them. In some cases, that bone may need to be linked to nearby spinal bones with metal hardware and a bone graft.

What worsens spinal stenosis? ›

Walking, standing, or extending the lumbar area of the spine can cause symptoms to worsen. Sitting or flexing the lower back or neck may relieve symptoms. The flexed position “opens up” the spinal column, enlarging the spaces between vertebrae at the back of the spine.

Will I end up in a wheelchair with spinal stenosis? ›

Severe spinal stenosis can lead to partial or complete leg paralysis. This may lead to some individuals using mobility devices such as a wheelchair. However, most people with stenosis regain the use of their legs following surgery, and the outlook is positive depending on their overall health.

Can lumbar nerves heal? ›

Adult nerve cells in the spinal cord don't regrow after damage. Why they don't, and how they might be encouraged to do so, have been areas of extensive research. Axons require a great deal of energy to regrow.

What does lumbar nerve damage feel like? ›

Numbness or less feeling in the area supplied by the nerve. Sharp, aching or burning pain, which may radiate outward. Tingling, or a pins and needles feeling. Muscle weakness in the affected area.

Does L4 and L5 affect bowels? ›

A pinched nerve can be caused by a slipped disc. A L4–L5 disc bulge (or slip-disc) in the L4-L5 region can cause severe health issues such as impotence and reproduction issues. It can also lead to infertility, loss or control of the bowel or bladder, paralysis in one or both of your legs, and even death.

Is walking good for L4-L5 disc bulge? ›

Low-impact movements, such as walking, swimming, using a stationary bike, and cycling, are ideal because they minimize the stress on the injured disc. Pay attention to your body's pain signals, and call your doctor if your symptoms do not improve or worsen with rest and/or modified activity.

What organs are affected by L4 and L5? ›

The L5 nerve root exits the spine at the level of the L4-L5 vertebrae and innervates (supplies sensation to) the muscles of the thigh and knee, as well as the skin over the front and side of the thigh. A herniated disc at this level can cause pain, numbness, or weakness in the thigh, knee, and leg.

Can you have unbearable pain from spinal stenosis? ›

Spinal stenosis is a condition that results in the narrowing of the spinal column, often accompanied by painful, debilitating compression of the spinal cord as well as nerve roots. For some people, the pain can be so severe it is incapacitating, making even everyday activities nearly impossible.

What is the strongest drug for nerve pain? ›

Anticonvulsants are one of the most effective medications for treating nerve pain. Examples include pregabalin (Lyrica) and gabapentin (Neurontin). These medications are typically very effective in treating nerve pain, but they may also cause undesired side effects, such as: lethargy.

What causes spinal stenosis pain to flare up? ›

Flare ups may be caused by muscle spasms, which can be caused by bending or twisting suddenly. They may be caused by an additional problem such as a slipped disc. Some patients may just reach a tipping point where their stenosis becomes symptomatic without any identifiable cause or event.

Do muscle relaxers help with spinal stenosis pain? ›

Muscle relaxants can improve muscle spasms, numbness, tingling, and radiating pain caused by spinal stenosis.

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