Spinal nerves: anatomy, function and treatment

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The spinal nerves are the main nerves in the body. 31 pairs of spinal nerves control motor, sensory, and other functions. These nerves are found at the cervical, thoracic, lumbar, sacral, and coccygeal levels.

A variety of medical problems can affect the spinal nerves and cause pain, weakness, or decreased sensation. A pinched nerve occurs when a spinal nerve is squeezed or compressed, and it is the most common spinal nerve disorder.

Anatomy

Spinal nerves are peripheral nerves that carry messages between the spinal cord and the rest of the body, including muscles, skin, and internal organs. Each spinal nerve targets specific areas of the body.

Composition

Spinal nerves are relatively large nerves that are formed by the fusion of the sensory nerve root and the motor nerve root. These nerve roots exit directly from the spinal cord: the sensory nerve roots at the back of the spinal cord and the motor nerve roots at the front of the spinal cord. When they connect, they form the spinal nerves on the sides of the spinal cord.

The spinal cord is made up of nerve cells that carry messages between the brain and peripheral nerves.

The spinal nerves receive sensory messages from tiny nerves located in areas such as the skin, internal organs, and bones. The spinal nerves send sensory messages to the sensory roots and then to the sensory fibers in the posterior (posterior or dorsal) part of the spinal cord.

The motor roots receive nerve messages from the anterior (anterior or abdominal) part of the spinal cord and send nerve messages to the spinal nerves and ultimately small nerve branches that activate muscles in the arms, legs, and other parts. of the body. …

There are 31 pairs of spinal nerves, including:

  • Eight cervical spinal nerves on each side of the spine, called C1 through C8.
  • Twelve thoracic spinal nerves on each side of the body, called T1 through T12.
  • Five lumbar spinal nerves on each side, called L1 through L5.
  • Five sacral spinal nerves on each side, labeled S1 through S5.
  • One coccygeal nerve on each side, Co1

Location

The spinal nerves are distributed evenly throughout the spinal cord and spinal column. The spinal column is the spinal column of bones that protects and surrounds the spinal cord. Each spinal nerve exits the spine through openings, which are openings on the right and left sides of the vertebral bones in the spine.

The spinal nerves form a few inches from the spine on each side. Several groups of spinal nerves fuse to form a large plexus. Some spinal nerves divide into smaller branches without forming a plexus.

A plexus is a group of nerves that connect to each other. The spinal nerves form five main plexuses:

  • Cervical plexus : consists of the fusion of spinal nerves C1 to 5, these are divided into smaller nerves that carry sensory messages and provide motor control to the muscles of the neck and shoulders.
  • Brachial plexus : Formed by the fusion of the C5 and T1 spinal nerves, this plexus branches into nerves that carry sensory messages and provide motor control to the muscles of the arm and upper back.
  • Lumbar Plexus : Spinal nerves L1 to L4 converge to form the lumbar plexus. This plexus is divided into nerves that carry sensory messages and provide motor control to the abdominal and leg muscles.
  • Sacral Plexus : Spinal nerves L4 to S4 connect and then branch into nerves that carry sensory messages and provide motor control to the leg muscles.
  • Coccygeal plexus : consists of the fusion of nerves from S4 to Co1, this plexus provides motor and sensory control of the genitals and muscles that control bowel movements.

Anatomical variation

There are many described variations of the spinal nerve anatomy, but they are usually found during preoperative testing or during surgery for an injury to the spine, spinal cord, or spinal nerve. A 2017 study that evaluated the anatomy of the spinal nerve in 33 cadavers (deceased) identified spinal plexus variants in 27.3% of them. This suggests that variations are not uncommon, but they usually do not cause noticeable problems.

Function

The spinal nerves have small sensory and motor branches. Each of the spinal nerves performs functions that correspond to a specific area of the body. These are muscle movements, sensations, and autonomous functions (control of internal organs).

Because its function is so well understood when a particular spinal nerve is affected, the resulting deficit often indicates which spinal nerve or nerves are affected.

Motor

Motor messages to the spinal nerves originate in the brain. A motor strip (homunculus) in the brain initiates a muscle control command. This command is sent to the spine through nerve impulses and then travels through the motor root to the spinal nerve. Motor stimulation is very specific and can activate the entire spinal nerve or just one of its branches to stimulate a very small group of muscles, depending on an order from the brain.

The distribution of spinal nerve control throughout the body is described as a myotome. Each physical movement requires one or more muscles that are activated by a branch of the spinal nerve. For example, the biceps muscle is controlled by C6, while the triceps muscle is controlled by C7.

Autonomous

The autonomous function of the spinal nerves intervenes in the internal organs of the body, such as the bladder and intestines. The vegetative branches of the spinal nerves are smaller than the motor and sensory branches.

Sensory

The spinal nerves receive messages, including touch, temperature, position, vibration, and pain, from the small nerves in the skin, muscles, joints, and internal organs of the body. Each spinal nerve corresponds to a region of the skin of the body, described as a dermatome. For example, navel sensation goes to T10, while hand sensation goes to C6, C7, and 8. Sensory dermatomes do not fully match motor myotomes.

Related conditions

The spinal nerves can be affected by a number of conditions. These situations can cause pain, sensory changes and / or weakness.

Diagnosing a spinal nerve problem involves several steps. The first is a physical examination, which may reveal a lesion compatible with the dermatome and / or myotome. Reflexes also correspond to the spinal nerves, and in these situations they tend to decrease, helping to determine which nerves are involved.

Electromyography (EMG) and nerve conduction studies (NCV) can measure nerve function. These tests help determine which spinal nerves are affected and how extensive the injury is.

Conditions that affect the spinal nerves include the following.

Get Medication Information / Brianna Gilmartin

Disc herniation

A herniated disc, also called a displaced disc, occurs when the structure of the vertebral bones and their cartilage, ligaments, tendons, and muscles rupture, allowing the vertebral structures to slip out of place, compressing the spinal cord and / or the spinal nerve. . Usually the first symptoms include neck pain or tingling in an arm or leg. A herniated disc can be a medical emergency because it can permanently damage the spinal cord.

Treatment includes oral anti-inflammatory medications, therapy, injections of pain relievers or anti-inflammatory drugs, and possibly surgical repair and stabilization of the spine.

Narrowing the hole
The foraminal orifices through which the spinal nerves pass are not much larger than the nerves themselves. Inflammation and bone degeneration can compress the spinal nerve as it passes through the opening, causing pain and tingling. This is often known as a pinched nerve.

Weight gain and swelling can cause or worsen a pinched nerve. For example, many women experience symptoms of a pinched nerve during pregnancy. This can go away after weight loss or even with weight redistribution: some women notice an improvement in symptoms even before the baby is born, and for most, it goes away completely after the baby is born.

There are several treatments for narrowed foramina, including anti-inflammatory drugs and physical therapy. Interventional procedures such as surgery or injections are generally not required.

Herpes

A very common disease, herpes zoster is the reactivation of the virus that causes chickenpox, herpes zoster. Shingles are painful and sometimes accompanied by a rash. If you've ever had chickenpox, the virus remains in your body, at the nerve root, after you recover. When reactivated, usually due to a weak immune system, it causes pain and skin lesions in the nerve root area or the entire spinal nerve.

Shingles usually go away on their own, and medications usually don't speed recovery.

However, there are vaccines that can prevent shingles and may be recommended if you are susceptible to reactivation of the virus.

Guilland-Barré syndrome (GBS)

GBS, also called acute demyelinating polyneuropathy, causes peripheral nerve weakness and can affect multiple spinal nerves. Usually GBS initially causes tingling in the feet, followed by weakness in the feet and legs, which results in weakness in the arms and chest muscles. Ultimately, this can damage the muscles that control breathing. Respiratory support with a ventilator is usually required until the condition resolves.

This disease is caused by demyelination, which is the loss of the protective myelin (fatty layer) that surrounds each nerve. When myelin is lost, the nerves stop working properly, leading to muscle weakness. Ultimately, the myelin is replaced and the nerves can function again, but at the same time, medical attention is needed.

Another similar disorder, chronic demyelinating polyneuropathy (CIDP), is a recurrent form of GBS in which symptoms can occur every few months or years with partial or complete recovery each time.

GBS and CIDP can be treated with steroids and immunotherapy. Medical attention is needed to monitor breathing and oxygen levels and, if necessary, intensive care.

Injury

Spinal nerves can be damaged as a result of a serious injury. Whiplash , falls, or blunt force injuries to the neck (such as from contact sports or intentional injuries) can cause swelling, stretching, or rupture of the cervical spinal nerves or cervical plexus. Weight lifting, falls, and accidents can damage the lumbar spinal nerves or the lumbar plexus.

In rare cases, the spinal nerves are damaged during an interventional procedure, especially during a major surgery involving extensive cancer around the spine. Traumatic spinal nerve injury requires therapy and / or surgery.

Polyneuropathy

Neuropathy is a disease of the peripheral nerves. CIDP and GBS are two types of neuropathy. Most neuropathies involve small nerve branches, but they can also affect the spinal nerves. Common causes of neuropathy include chronic alcohol use, diabetes, chemotherapy, vitamin B12 deficiency, and neurotoxic chemicals.

Sometimes the nerves can restore their function, but often the nerve damage is irreversible and treatment is aimed at identifying the cause to prevent further damage.

Spinal diseases

Some diseases that affect the spine do not directly damage the spinal nerves, but can cause symptoms that correspond to specific spinal nerves. Multiple sclerosis (MS ), vitamin B12 deficiency, subacute combined degeneration of the spinal cord, and inflammatory myelopathy are examples of diseases of the spine that can cause dysfunction of one or more spinal nerves. In these cases, the function of the spinal nerve is affected because the nerve fibers in the adjacent parts of the spine stop sending or receiving messages to and from the spinal nerves.

Treatment of spinal disease depends on the cause. For some of these conditions, such as multiple sclerosis, spinal nerve function can be fully or partially restored with medication.

Meningitis

Infection or inflammation of the meninges that cover and protect the spinal cord (under the spinal column) can affect the function of one or more spinal nerves. Meningitis causes fever, fatigue, and headaches, and it can also cause neurological symptoms such as weakness and sensory loss. Usually, with prompt treatment, meningitis resolves without irreversible damage to the spinal nerves.

Cancer

Cancer in or near the spine can invade (infect) or compress the spinal nerves and cause dysfunction. This can cause pain, weakness, or sensory changes that affect one or more spinal nerves. Treatment includes surgical removal of the cancer, radiation therapy, or chemotherapy. Recovery depends on the extent of spinal nerve damage.

Rehabilitation

In most cases, the spinal nerve injury is treatable. Mild inflammation can usually be treated with anti-inflammatory medications, and pain can be controlled with over-the-counter pain relievers. Physical therapy and exercise can help lower blood pressure, posture, and muscle tone, while reducing pain.

However, the pain can be severe and require more aggressive interventions, such as injections or surgery.

Nerve damage that causes loss of sensation or muscle weakness can be the result of an extensive or prolonged injury to the spinal nerve. Nerves are less likely to heal if they were severed (severed). Physical therapy is generally recommended as a way to optimize function by strengthening muscles that receive healthy nerves.

Spinal nerve surgery is a complex procedure with variable results depending on the extent and duration of the injury. Spinal surgery and spinal nerve surgery may require intraoperative monitoring of nerve function.

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