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Overview of Spinal Cord Disorders

by Michael Rubin, MDCM

  • Causes of spinal cord disorders include injuries (see Injuries of the Spinal Cord and Vertebrae), infections, a blocked blood supply, and compression by a fractured bone or a tumor.

  • Typically, muscles are weak or paralyzed, sensation is abnormal or lost, and controlling bladder and bowel function may be difficult.

  • Doctors base the diagnosis on symptoms and results of a physical examination and imaging tests, such as magnetic resonance imaging.

  • The condition causing the spinal cord disorder is corrected if possible.

  • Often, rehabilitation is needed to recover as much function as possible.

The spinal cord is the main pathway of communication between the brain and the rest of the body. It is a long, fragile, tubelike structure that extends downward from the base of the brain. The cord is protected by the back bones (vertebrae) of the spine (spinal column). The vertebrae are separated and cushioned by disks made of cartilage.

Where Is the Spinal Cord Damaged?

The spine (spinal column) contains the spinal cord, which is divided into four sections: cervical (neck), thoracic (chest), lumbar (lower back), and sacral (pelvis). Each section is referred to by a letter (C, T, L, or S).

The vertebrae in each section of the spine are numbered beginning at the top. For example, the first vertebra in the cervical spine is labeled C1, the second in the cervical spine is C2, the second in the thoracic spine is T2, the fourth in the lumbar spine is L4, and so forth. These labels are also used to identify specific locations (called levels) in the spinal cord.

Nerves run from a specific level of the spinal cord to a specific area of the body. By noting where a person has weakness, paralysis, sensory loss, or other loss of function, a neurologist can determine where the spinal cord is damaged.

The spine is divided into four sections, and each section is referred to by a letter.

  • Cervical (C): Neck

  • Thoracic (T): Chest

  • Lumbar (L): Lower back

  • Sacral (S): Pelvis

Within each section of the spine, the vertebrae are numbered beginning at the top. These labels (letter plus a number) are used to indicate locations (levels) in the spinal cord.

Along the length of the spinal cord, 31 pairs of spinal nerves emerge through spaces between the vertebrae. Each spinal nerve runs from a specific vertebra in the spinal cord to a specific area of the body. Based on this fact, the skin’s surface has been divided into areas called dermatomes. A dermatome is an area of skin whose sensory nerves all come from a single spinal nerve root. Loss of sensation in a particular dermatome enables doctors to locate where the spinal cord is damaged.

Dermatomes

The surface of the skin is divided into specific areas, called dermatomes. A dermatome is an area of skin whose sensory nerves all come from a single spinal nerve root. (Sensory nerves carry information about such things as touch, pain, temperature, and vibration from the skin to the spinal cord.)

Spinal roots come in pairs—one of each pair on each side of the body. There are 31 pairs:

  • There are 8 pairs of sensory nerve roots for the 7 cervical vertebrae.

  • Each of the 12 thoracic, 5 lumbar, and 5 sacral vertebrae has one pair of spinal nerve roots.

  • In addition, at the end of the spinal cord, there is a pair of coccygeal nerve roots, which supply a small area of the skin around the tailbone (coccyx).

There are dermatomes for each of these nerve roots.

Sensory information from a specific dermatome is carried by sensory nerve fibers to the spinal nerve root of a specific vertebra. For example, sensory information from a strip of skin along the back of the thigh, is carried by sensory nerve fibers to the 2nd sacral vertebra (S2) nerve root.

A spinal nerve has two nerve roots. The only exception is the first spinal nerve, which has no sensory root. The root in the front (the motor or anterior root) contains nerve fibers that carry impulses (signals) from the spinal cord to muscles to stimulate muscle movement (contraction). The root in the back (the sensory or posterior root) contains nerve fibers that carry sensory information about touch, position, pain, and temperature from the body to the spinal cord.

Did You Know...

  • Doctors can often tell where the spinal cord is damaged based on symptoms and results of a physical examination.

Did You Know...

  • Nerves from the lowest parts of the spinal cord go to the anus, not to the feet.

The spinal cord ends in the lower back (around L1 or L2), but the lower spinal nerve roots continue, forming a bundle that resembles a horse’s tail (called the cauda equina—see What Is the Cauda Equina Syndrome?).

The spinal cord is highly organized (see Figure: How the Spine Is Organized). The center of the cord consists of gray matter shaped like a butterfly. The front "wings" (anterior or motor horns) contain nerve cells that carry signals from the brain or spinal cord through the motor root to muscles. The back (posterior or sensory) horns contain nerve cells that receive signals about pain, temperature, and other sensory information through the sensory root from nerve cells outside the spinal cord.

The outer part of the spinal cord consists of white matter that contains pathways of nerve fibers (called tracts or columns). Each tract carries a specific type of nerve signal either going to the brain (ascending tracts) or from the brain (descending tracts).

To and From and Up and Down the Spinal Cord

Spinal nerves carry nerve impulses to and from the spinal cord through two nerve roots:

  • Motor (anterior) root: Located toward the front, this root carries impulses from the spinal cord to muscles to stimulate muscle movement.

  • Sensory (posterior) root: Located toward the back, this root carries sensory information about touch, position, pain, and temperature from the body to the spinal cord.

In the center of the spinal cord, a butterfly-shaped area of gray matter helps relay impulses to and from spinal nerves. Its "wings" are called horns.

  • Motor (anterior) horns: These horns contain nerve cells that carry signals from the brain or spinal cord through the motor root to muscles.

  • Posterior (sensory) horns: These horns contain nerve cells that receive signals about pain, temperature, and other sensory information through the sensory root from nerve cells outside the spinal cord.

Impulses travel up (to the brain) or down (from the brain) the spinal cord through distinct pathways (tracts). Each tract carries a different type of nerve signal either going to or from the brain. The following are examples:

  • Lateral spinothalamic tract: Signals about pain and temperature, received by the sensory horn, travel through this tract to the brain.

  • Dorsal columns: Signals about the position of the arms and legs travel through the dorsal columns to the brain.

  • Corticospinal tracts: Signals to move a muscle travel from the brain through these tracts to the motor horn, which routes them to the muscle.

Causes

Some spinal cord disorders may originate outside the cord or, less commonly, inside the cord.

Outside the spinal cord

These disorders include

The spinal cord may be compressed by bone (which may result from cervical spondylosis or a fracture), an accumulation of blood (hematoma), a tumor, a pocket of pus (abscess), or a ruptured or herniated disk.


Inside the spinal cord

These disorders include fluid-filled cavities (syrinxes), blockage of the blood supply, inflammation (as occurs in acute transverse myelitis), tumors, abscesses, bleeding (hemorrhage), vitamin B 12 or copper deficiency, infection with the human immunodeficiency virus (HIV), multiple sclerosis, and syphilis.


Symptoms

Because of the way the spinal cord functions and is organized, damage to the cord often produces specific patterns of symptoms based on where the damage occurred. The following may occur in various patterns:

  • Weakness

  • Loss of sensation (such as the ability to feel a light touch, pain, temperature, or vibration or to sense where the arms and legs are)

  • Changes in reflexes

  • Loss of bladder control (urinary incontinence)

  • Loss of bowel control (fecal incontinence)

  • Erectile dysfunction

  • Paralysis

  • Back pain

By identifying which functions are lost, doctors can tell which part of the spinal cord (such as the front, back, side, center, or entire cord) is damaged. By identifying the specific location of symptoms (for example, which muscles are paralyzed and which parts of the body lack sensation), doctors can determine exactly where the spinal cord is damaged (that is, the specific level in the spinal cord).

Functions may be completely or partially lost. Functions controlled by areas of the spinal cord above the damage are not affected.

When weakness or paralysis occurs suddenly, muscles go limp (flaccid), losing their tone. After muscles become flaccid, muscle tone eventually increases and muscles tend to contract involuntarily (called spasms, or spasticity).

When disorders (such as cervical spondylosis and hereditary spastic paraparesis) slowly damage the spinal cord, they can cause paralysis with increased muscle tone and muscle spasms (called spastic paralysis).

Spasms can occur because signals from the brain cannot pass through the damaged area to help control some reflexes. As a result, the reflexes become more pronounced over days to weeks. Then, the muscles controlled by the reflex may tighten, feel hard, and twitch uncontrollably from time to time.

Diagnosis

  • Physical examination

  • Magnetic resonance imaging or myelography with computed tomography

Often, doctors can recognize a spinal cord disorder based on its characteristic pattern of symptoms. Doctors always do a physical examination, which provides clues to the diagnosis and, if the spinal cord is damaged, helps doctors determine where the damage is. An imaging test is done to confirm the diagnosis and determine the cause.

Magnetic resonance imaging (MRI) is the most accurate imaging test for spinal cord disorders. MRI shows the spinal cord, as well as abnormalities in the soft tissues around the cord (such as abscesses, hematomas, tumors, and ruptured disks) and in bone (such as tumors, fractures, and cervical spondylosis). If MRI is not available, myelography with computed tomography (CT) is used (see Tests for Brain, Spinal Cord, and Nerve Disorders : Myelography). For myelography with CT, CT is done after a radiopaque dye is injected into the space around the spinal cord.

Did You Know...

  • People who suddenly lose sensation, experience weakness in one or more limbs, or develop incontinence should go to the emergency department immediately.

Treatment

  • Treatment of the cause when possible

  • Prevention of complications

  • Physical and occupational therapy

If symptoms of spinal cord dysfunction (such as paralysis or loss of sensation) suddenly occur, people should immediately go to the emergency department. Sometimes doing so can prevent permanent nerve damage or paralysis. If possible, the cause is treated or corrected. However, such treatment is often impossible or unsuccessful.

People who are paralyzed or confined to bed because of a spinal cord disorder require skilled nursing care to prevent complications, which include the following:

  • Pressure sores: Nurses inspect the person's skin daily, keep the skin dry and clean, and turn the person frequently (see Pressure Sores). When necessary, a special bed called a Stryker frame is used. It can be turned to shift pressure on the body from front to back and from side to side.

  • Urinary problems: If a person is immobile and cannot use a toilet, a urinary catheter may be needed. To help reduce the risk of a urinary tract infection, nurses use sterile techniques when the catheter is inserted and apply antimicrobial ointments or solutions daily.

  • Pneumonia: To reduce the risk of pneumonia, therapists and nurses may teach the person deep breathing exercises. They may also place the person at an angle to help drain secretions that accumulate in the lungs (postural drainage), or they may suction secretions out.

  • Blood clots: Anticoagulant drugs, such as heparin or low molecular weight heparin, may be given by injection. If a person cannot take anticoagulants (for example, because of a bleeding disorder or stomach ulcers), a filter, sometimes called an umbrella (see Figure: ), is inserted into the inferior vena cava (the large vein that carries blood from the abdomen to the heart). The filter traps blood clots that have broken loose from leg veins before they reach the heart.

Extensive loss of body functions can be devastating, causing depression and loss of self-esteem. Formal counseling can be very helpful. Learning exactly what has happened and what to expect in the near and distant future helps people cope with the loss and prepare them for rehabilitation.

Rehabilitation: Rehabilitation helps people recover as much function as possible. The best care is provided by a team that includes nurses, physical and occupational therapists (see Physical Therapy (PT)), a social worker, a nutritionist, a psychologist, and a counselor, as well as the person and family members. A nurse may teach the person ways to manage bladder and bowel dysfunction, such as how to insert a catheter, when to use laxatives, or how to stimulate bowel movements using a finger.

Physical therapy involves exercises for muscle strengthening and stretching. People may learn how to use assistive devices such as braces, a walker, or a wheelchair and how to manage muscle spasms.

Occupational therapy helps people relearn how to do their daily tasks and helps them improve dexterity and coordination. They learn special techniques to help compensate for lost functions. Therapists or counselors help some people make the adjustments needed to return to work and to hobbies and activities. People are taught ways to deal with sexual dysfunction. Sex is still possible for many people, even though sensation is usually lost.

Emotional support from family members and close friends is important.

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  • PANHEPRIN