Definition

Spinal cord injury is damage to the spinal cord that causes loss of sensation and motor control.

Description

Approximately 10,000 new spinal cord injuries (SCIs) occur each year in the United States. About 250,000 people are currently affected. Spinal cord injuries can happen to anyone at any time of life. The typical patient, however, is a man between the ages of 19 and 26, injured in a motor vehicle accident (about 50% of all SCIs), a fall (20%), an act of violence (15%), or a sporting accident (14%). Alcohol or other drug abuse plays an important role in a large percentage of all spinal cord injuries. Six percent of people who receive injuries to the lower spine die within a year, and 40% of people who receive the more frequent higher injuries die within a year.

Short-term costs for hospitalization, equipment, and home modifications are approximately $140,000 for an SCI patient capable of independent living. Lifetime costs may exceed one million dollars. Costs may be three to four times higher for the SCI patient who needs long-term institutional care. Overall costs to the American economy in direct payments and lost productivity are more than $10 billion per year.

— Richard Robinson

Definition

Spinal cord injury is damage to the spinal cord that causes loss of sensation and motor control.

Description

Approximately 10,000 new spinal cord injuries (SCIs) occur each year in the United States. About 250,000 people are currently affected. Spinal cord injuries can happen to anyone at any time of life. The typical patient, however, is a man between the ages of 19 and 26, injured in a motor vehicle accident (about 50% of all SCIs), a fall (20%), an act of violence (15%), or a sporting accident (14%). Most SCI patients are white, but the nonwhite fraction of SCI patients is larger than the nonwhite fraction of the general population. Alcohol or other drug abuse plays an important role in a large percentage of all spinal cord injuries. Six percent of people who receive injuries to the lower spine die within a year, and 40% of people who receive the more frequent higher injuries die within a year.

Short-term costs for hospitalization, equipment, and home modifications are approximately $140,000 for an SCI patient capable of independent living. Lifetime costs may exceed one million dollars. Costs may be three to four times higher for the SCI patient who needs long-term institutional care. Overall costs to the American economy in direct payments and lost productivity are more than $10 billion per year.

Causes and symptoms

The spinal cord is about as big around as the index finger. It descends from the brain down the back through hollow channels of the backbone. The spinal cord is made of nerve cells (neurons). The nerve cells carry sensory data from the areas outside the spinal cord (periphery) to the brain, and they carry motor commands from brain to periphery. Peripheral neurons are bundled together to make up the 31 pairs of peripheral nerve roots. The peripheral nerve roots enter and exit the spinal cord by passing through the spaces between the stacked vertebrae. Each pair of nerves is named for the vertebra from which it exits. These are known as:

• C1-8. These nerves enter from the eight cervical or neck vertebrae.
• T1-12. These nerves enter from the thoracic or chest vertebrae.
• L1-5. These nerves enter from the lumbar vertebrae of the lower back.
• S1-5. These nerves enter through the sacral or pelvic vertebrae.
• Coccygeal. These nerves enter through the coccyx or tailbone.

Peripheral nerves carry motor commands to the muscles and internal organs, and they carry sensations from these areas and from the body's surface. (Sensory data from the head, including sight, sound, smell, and taste, do not pass through the spinal cord and are not affected by most SCIs.) Damage to the spinal cord interrupts these signals. The interruption damages motor functions that allow the muscles to move, sensory functions such as feeling heat and cold, and autonomic functions such as urination, sexual function, sweating, and blood pressure.

Spinal cord injuries most often occur where the spine is most flexible, in the regions of C5-C7 of the neck, and T10-L2 at the base of the rib cage. Several physically distinct types of damage are recognized. Sudden and violent jolts to nearby tissues can jar the cord. This jarring causes a temporary spinal concussion. Concussion symptoms usually disappear completely within several hours. A spinal contusion or bruise is bleeding within the spinal column. The pressure from the excess fluid may kill spinal cord neurons. Spinal compression is caused by some object, such as a tumor, pressing on the cord. Lacerations or tears cause direct damage to cord neurons. Lacerations can be caused by bone fragments or missiles such as bullets. Spinal transection describes the complete severing of the cord. Most spinal cord injuries involve two or more of these types of damage.

PARALYSIS AND LOSS OF SENSATION The extent to which movement and sensation are damaged depends on the level of the spinal cord injury. Nerves leaving the spinal cord at different levels control sensation and movement in different parts of the body. The distribution is roughly as follows:

• C1-C4: head and neck
• C3-C5: diaphragm (chest and breathing)
• C5-T1: shoulders, arms and hands

• T2-T12: chest and abdomen (excluding internal organs)
• L1-L4: abdomen (excluding internal organs), buttocks, genitals, and upper legs
• L4-S1: legs
• S2-S4: genitals and muscles of the perineum

Damage below T1, which lies at the base of the rib cage, causes paralysis and loss of sensation in the legs and trunk below the injury. Injury at this level usually does no damage to the arms and hands. Paralysis of the legs is called paraplegia. Damage above T1 involves the arms as well as the legs. Paralysis of all four limbs is called quadriplegia or tetraplegia. Cervical or neck injuries not only cause quadriplegia but also may cause difficulty in breathing. Damage in the lower part of the neck may leave enough diaphragm control to allow unassisted breathing. Patients with damage at C3 or above, just below the base of the skull, require mechanical assistance to breathe.

Symptoms also depend on the extent of spinal cord injury. A completely severed cord causes paralysis and loss of sensation below the wound. If the cord is only partially severed, some function will remain below the injury. Damage limited to the front portion of the cord causes paralysis and loss of sensations of pain and temperature. Other sensation may be preserved. Damage to the center of the cord may spare the legs but paralyze the arms. Damage to the right or left half causes loss of position sense, paralysis on the side of the injury, and loss of pain and temperature sensation on the opposite side.

DEEP VENOUS THROMBOSIS Blood does not flow normally to a paralyzed limb that is inactive for long periods. The blood pools in the deep veins and forms clots, a condition known as deep vein thrombosis. A clot or thrombus can break free and lodge in smaller arteries in the brain, causing a stroke, or in the lungs, causing pulmonary embolism.

PRESSURE ULCERS Inability to move also leads to pressure ulcers or bed sores. Pressure ulcers form where skin remains in contact with a bed or chair for a long time. The most common sites of pressure ulcers are the buttocks, hips, and heels.

SPASTICITY AND CONTRACTURE A paralyzed limb is incapable of active movement, but the muscle still has tone, a constant low level of contraction. Normal muscle tone requires communication between the muscle and the brain. Spinal cord injury prevents the brain from telling the muscle to relax. The result is prolonged muscle contraction or spasticity. Because the muscles that extend and those that bend a joint are not usually equal in strength, the involved joint is bent, often severely. This constant pressure causes deformity. As the muscle remains in the shortened position over several weeks or months, the tendons remodel and cause permanent muscle shortening or contracture. When muscles have permanently shortened, the inner surfaces of joints, such as armpits or palms, cannot be cleaned and the skin breaks down in that area.

HETEROTOPIC OSSIFICATION Heterotopic ossification is an abnormal deposit of bone in muscles and tendons that may occur after injury. It is most common in the hips and knees. Initially heterotopic ossification causes localized swelling, warmth, redness, and stiffness of the muscle. It usually begins one to four months after the injury and is rare after one year.

AUTONOMIC DYSREFLEXIA Body organs that regulate themselves, such as the heart, gastrointestinal tract, and glands, are controlled by groups of nerves called autonomic nerves. Autonomic nerves emerge from three different places: above the spinal column, in the lower back from vertebrae T1-L4, and from the lowest regions of the sacrum at the base of the spine. In general, these three groups of autonomic nerves operate in balance. Spinal cord injury can disrupt this balance, a condition called autonomic dysreflexia or autonomic hyperreflexia. Patients with injuries at T6 or above are at greatest risk.

In autonomic dysreflexia, irritation of the skin, bowel, or bladder causes a highly exaggerated response from autonomic nerves. This response is caused by the uncontrolled release of norepinephrine, a hormone similar to adrenaline. Uncontrolled release of norepinephrine causes a rapid rise in blood pressure and a slowing of the heart rate. These symptoms are accompanied by throbbing headache, nausea, anxiety, sweating, and goose bumps below the level of the injury. The elevated blood pressure can rapidly cause loss of consciousness, seizures, cerebral hemorrhage, and death. Autonomic dysreflexia is most often caused by an over-full bladder or bladder infection, impaction or hard impassable fecal mass in the bowel, or skin irritation from tight clothing, sunburn, or other irritant. Inability to sense these irritants before the autonomic reaction begins is a major cause of dysreflexia.

LOSS OF BLADDER AND BOWEL CONTROL Bladder and bowel control require both motor nerves and the autonomic nervous system. Both of these systems may be damaged by SCI. When the autonomic nervous system triggers an urge to urinate or defecate, continence is maintained by contracting the anal or urethral sphincters. A sphincter is a ring of muscle that contracts to close off a passage or opening in the body. When the neural connections to these muscles are severed, conscious control is lost. In addition, loss of feeling may prevent sensations of fullness from reaching the brain. To compensate, the patient may help empty the bowel or bladder by using physical maneuvers that stimulate autonomic contractions before they would otherwise begin. However, the patient may not be able to relax the sphincters. If the sphincters cannot be relaxed, the patient will retain urine or feces.

Retention of urine may cause muscular changes in the bladder and urethral sphincter that make the problem worse. Urinary tract infection is common. Retention of feces can cause impaction. Symptoms of impaction include loss of appetite and nausea. Untreated impaction may cause perforation of the large intestine and rapid overwhelming infection.

SEXUAL DYSFUNCTION Men who have sustained SCI may be unable to achieve an erection or ejaculate. Sperm formation may be abnormal too, reducing fertility. Fertility and the ability to achieve orgasm are less impaired for women. Women may still be able to become pregnant and deliver vaginally with proper medical care.

Diagnosis

The location and extent of spinal cord injury is determined with computed tomography scans (CT scans), magnetic resonance imaging (MRI) scans, and x rays. X rays may be enhanced with an injected contrast dye.

Treatment

A person who may have a spinal cord injury should not be moved. Treatment of SCI begins with immobilization. This strategy prevents partial injuries of the cord from severing it completely. Use of splints to completely immobilize suspected SCI at the scene of the injury has helped reduce the severity of spinal cord injuries in the last two decades. Intravenous methylprednisone, a steroidal anti-inflammatory drug, is given during the first 24 hours to reduce inflammation and tissue destruction.

Rehabilitation after spinal cord injury seeks to prevent complications, promote recovery, and make the most of remaining function. Rehabilitation is a complex and long-term process. It requires a team of professionals, including a neurologist, physiatrist or rehabilitation specialist, physical therapist, and occupational therapist. Other specialists who may be needed include a respiratory therapist, vocational rehabilitation counselor, social worker, speech-language pathologist, nutritionist, special education teacher, recreation therapist, and clinical psychologist. Support groups provide a critical source of information, advice, and support for SCI patients.

Paralysis and loss of sensation

Some limited mobility and sensation may be recovered, but the extent and speed of this recovery cannot be predicted. Experimental electrical stimulation has been shown to allow some control of muscle contraction in paraplegia. This experimental technique offers the possibility of unaided walking. Further development of current control systems will be needed before useful movement is possible outside the laboratory.

The physical therapist focuses on mobility, to maintain range of motion of affected limbs and reduce contracture and deformity. Physical therapy helps compensate for lost skills by using those muscles that are still functional. It also helps to increase any residual strength and control in affected muscles. A physical therapist suggests adaptive equipment such as braces, canes, or wheelchairs.

An occupational therapist works to restore ability to perform the activities of daily living, such as eating and grooming, with tools and new techniques. The occupational therapist also designs modifications of the home and workplace to match the individual impairment.

A pulmonologist or respiratory therapist promotes airway hygiene through instruction in assisted coughing techniques and postural drainage. The respiratory professional also prescribes and provides instruction in the use of ventilators, facial or nasal masks, and tracheostomy equipment where necessary.

Pressure ulcers

Pressure ulcers are prevented by turning in bed at least every two hours. The patient should be turned more frequently when redness begins to develop in sensitive areas. Special mattresses and chair cushions can distribute weight more evenly to reduce pressure. Electrical stimulation is sometimes used to promote muscle movement to prevent pressure ulcers.

Spasticity and contracture

Range of motion (ROM) exercises help to prevent contracture. Chemicals can be used to prevent contractures from becoming fixed when ROM exercise is inadequate. Phenol or alcohol can be injected onto the nerve or botulinum toxin directly into the muscle. Botulinum toxin is associated with fewer complications, but it is more expensive than phenol and alcohol. Contractures can be released by cutting the shortened tendon or transferring it surgically to a different site on the bone where its pull will not cause as much deformity. Such tendon transfers may also be used to increase strength in partially functional extremities.

Heterotopic ossification

Etidronate disodium (Didronel), a drug that regulates the body's use of calcium, is used to prevent heterotopic ossification. Treatment begins three weeks after the injury and continues for 12 weeks. Surgical removal of ossified tissue is possible.

Autonomic dysreflexia

Autonomic dysreflexia is prevented by bowel and bladder care and attention to potential irritants. It is treated by prompt removal of the irritant. Drugs to lower blood pressure are used when necessary. People with SCI should educate friends and family members about the symptoms and treatment of dysreflexia, because immediate attention is necessary.

Loss of bladder and bowel control

Normal bowel function is promoted through adequate fluid intake and a diet rich in fiber. Evacuation is stimulated by deliberately increasing the abdominal pressure, either voluntarily or by using an abdominal binder.

Bladder care involves continual or intermittent catheterization. The full bladder may be detected by feeling its bulge against the abdominal wall. Urinary tract infection is a significant complication of catheterization and requires frequent monitoring.

Sexual dysfunction

Counseling can help in adjusting to changes in sexual function after spinal cord injury. Erection may be enhanced through the same means used to treat erectile dysfunction in the general population.

Prognosis

The prognosis of SCI depends on the location and extent of injury. Injuries of the neck above C4 with significant involvement of the diaphragm hold the gravest prognosis. Respiratory infection is one of the leading causes of death in long-term SCI. Overall, 85% of SCI patients who survive the first 24 hours are alive 10 years after their injuries. Recovery of function is impossible to predict. Partial recovery is more likely after an incomplete wound than after the spinal cord has been completely severed.

Prevention

Risk of spinal cord injury can be reduced through prevention of the accidents that lead to it. Chances of injury from automobile accidents, the major cause of SCIs, can be significantly reduced by driving at safe speeds, avoiding alcohol while driving, and using seat belts.

Resources

BOOKS

Bradley, Walter G., et al., eds. Neurology in Clinical Practice. 2nd ed. Boston: Butterworth-Heinemann, 1996.

Martini, F. Fundamentals of Anatomy and Physiology. Englewood Cliffs, NJ: Prentice Hall, 1989.

Yarkony, Gary M., ed. Spinal Cord Injury: Medical Management and Rehabilitation. Gaithersburg, MD: Aspen Publishers, Inc., 1994.

ORGANIZATIONS

The National Spinal Cord Injury Association. 8300 Colesville Road, Silver Spring, Maryland 20910. (301) 588-6959. http://www.erols.com/nscia.

Richard Robinson

Traumatic disruption of the spinal cord as a result of vertebral fractures and dislocations, usually associated with car accidents, sports injuries, and other violent impacts. The degree of paralysis is directly related to the level and severity of the injury. Injury below the first thoracic vertebra may produce paraplegia. Injuries above the first thoracic vertebra may cause quadriplegia.

Definition

Spinal cord injury (SCI) is damage to the spinal cord that results in a loss of function such as mobility or feeling. The spinal cord does not have to be severed in order for a loss of function to occur. In most SCI cases, the spinal cord is intact, but the damage to it results in loss of function.

Description

The spinal cord and the brain are the two components of the central nervous system (CNS). The spinal cord extends from the base of the brain, down the middle of the back, to the lower back, and it coordinates movement and sensation in the body. It contains nerve cells, supporting cells, and long nerve fibers (axons) that connect to the brain and carry signals downward from the brain along descending pathways and upward to the brain along ascending pathways. Axons are covered by sheaths of an insulating whitish substance called myelin, and the region in which they lie is accordingly called white matter. The nerve cells themselves, with long branches (dendrites) that receive signals from other nerve cells, make up the gray matter that lies in a butterfly-shaped region in the center of the spinal cord. Like the brain, the spinal cord is enclosed in three membranes (meninges). The innermost layer is called the pia mater, the middle layer is the arachnoid, and the dura mater is the tougher outer layer. The spinal cord consists of several segments along its length, with higher segments controlling movement and sensation in upper parts of the body and lower segments controlling the lower parts of the body. The segments in the neck (cervical region), referred to as C1 to C8, control signals to the neck, arms, and hands. Those in the thoracic or upper back region (T1 to T12) control signals to the torso and some parts of the arms. Those in the mid-back (upper lumbar region) just below the ribs (L1 to L5) control signals to the hips and legs. Finally, the sacral segments (S1 to S5) lie just below the lumbar segments in the mid-back and control signals to the groin, toes, and some parts of the legs.

The types of disability associated with SCI thus depend directly on the type and severity of the injury, the level of the cord at which the injury occurs, and the nerve fiber pathways that are damaged. Severe injury to the spinal cord causes paralysis and complete loss of sensation to the parts of the body controlled by the spinal cord segments below the point of injury. Spinal cord injuries also can lead to many complications, including pressure sores and increased susceptibility to respiratory diseases.

Demographics

According to the National Institute of Neurological Disorders and Stroke (NINDS), accidents and violence cause an estimated 10,000 spinal cord injuries each year, and more than 200,000 Americans live day-to-day with the disabling effects of SCI. The incidence of spinal cord injuries peaks among people in their early 20s, with a small increase in the elderly population due to falls and degenerative diseases of the spine. SCI is an uncommon source of morbidity and mortality in children.

Causes and Symptoms

According to the National Spinal Cord Injury Association (NSCIA), spinal cord injuries are caused in the United States by motor vehicle accidents (44%), acts of violence (24%), falls (22%), sports (8%), and other causes (2%) such as abscesses, tumors, polio, spina bifida and Friedrich's Ataxia, a rare inherited disorder. For infants, motor vehicle crash is the leading cause of SCI. Falls rank highest for ages two to nine years and sports for the 10 to 14 age group. The most common injury level for the five to 13 age group is the high cervical spine (C1-C4).

SCI symptoms usually appear immediately after the injury. However, symptoms can develop slowly, if an infection or tumor is gradually increasing pressure on the spinal cord. General symptoms are as follows:

• weakness, poor coordination or paralysis, particularly below the level of the injury
• numbness, tingling, or loss of sensation
• loss of bowel or bladder control
• pain

When to Call the Doctor

Immediate medical attention is required if a parent suspects a child may have injured his or her neck or back, or if a child has poor coordination or paralysis in any part of the body. Spinal cord injury is not always obvious: numbness or paralysis may result immediately after SCI or later on as swelling gradually occurs in or around the spinal cord. In either case, the time between injury and treatment is critical and can significantly influence the extent of complications and the level of recovery. Any child who has experienced significant trauma to the head, back, or neck should be medically evaluated for the possibility of SCI.

Diagnosis

The possibility of SCI is usually suspected in anyone with significant trauma to the head and/or neck. Physicians accordingly assume that such patients have a spine fracture until proven otherwise.

Diagnosis is established with the help of x-rays of the spine that allow doctors to determine the extent of the damage. The following imaging tests are also used: CT scan (computed tomography), MRI (magnetic resonance imaging), and myelogram (x ray after injection of dye into the spinal canal).

Treatment

A person suspected of having a spinal cord injury should not be moved and treatment of SCI begins with immobilization, commonly achieved by enclosing the cervical spine in a rigid collar and use of rigid backboards. Paramedics and other rescue workers receive extensive training in immobilizing the spine. Immobilization prevents further injuries to the cord at the scene of the injury and has helped reduce worsening of any neurological SCI injury. At the time of injury, treatment is focused on stabilizing the spine and relieving cord compression. Prompt steroid drug injections (within eight hours of the injury) are also used to minimize cell damage and improve the chance of recovery.

Surgery cannot reverse damage to the spinal cord but is often needed to stabilize the spine to prevent future pain or deformity. It may involve fusing together vertebrae or inserting metal pins; or removing bone chips, bullets, or other foreign objects; or draining fluid to relieve pressure. Long-term treatment of spinal cord injuries usually involves drug therapy, the use of neural prostheses, and rehabilitation. Complementary treatment includes nutrition management, psychological counseling, and careful monitoring by physicians.

Drug Therapy

Effective drug therapy for spinal cord injury was demonstrated in 1990, when methylprednisolone, the first drug shown to improve recovery from spinal cord injury, was approved for standard use. Completely paralyzed patients given methylprednisolone recover an average of about 20 percent of their lost motor function, compared to only 8 percent recovery of function in untreated patients. Partially paralyzed patients recover an average of 75 percent of their function, compared to 59 percent in patients who do not receive the drug.

Neural Prostheses

Neural prostheses are used to compensate for lost function resulting from SCI. These sophisticated electrical and mechanical devices connect with the nervous system to supplement or replace lost motor and sensory functions. Neural prostheses contain many intricate components, such as implanted stimulators, electrodes, leads and connectors, sensors, and programming systems. There are many technical considerations in selecting each component. The electronic components must be as small as possible. Biocompatibility between electrodes and body tissue is also required to prevent the patient from being harmed by contact with the device. One device, a neural prosthesis that allows rudimentary hand control, was approved by the United States Food and Drug Administration (FDA). Patients control the device using shoulder muscles. With training, most patients can open and close their hand in two different grasping movements and lock the grasp in place by moving their shoulder in different ways.

Rehabilitation

Rehabilitation techniques can greatly improve patients' health and quality of life by helping them learn to use their remaining abilities. They start by setting functional goals. Functional goals are a realistic expectation of activities that a person with SCI eventually should be able to do with a particular level of injury. These goals are set during rehabilitation with the medical team. They help the patient with SCI learn new ways to manage his/her daily activities and stay healthy. Developing independence is especially important to kids, particularly teenagers. Many hospitals have SCI units geared to help patients develop their independence, and SCI treatment centers are operational in several states with special programs for children. The SCI units include kitchens and laundry facilities and other equipment so that patients can learn independent living skills, such as cooking meals or ironing clothes. A spinal cord injury can also affect the nerves and muscles and can cause bowel and bladder problems and skin problems. Children are prepared for these changes during rehabilitation and are taught the self-care skills needed to deal with these problems. Parents of spinal cord injured children also need to learn how to take care of their spinal-cord injured child. Having a spinal cord injury does not mean that children have to stop participating in games and enjoyable activities. Most SCI units have recreational therapists on staff to show kids how to play wheelchair basketball, volleyball, and tennis, as well as specially adapted games.

Alternative Treatment

People with spinal cord injuries caused by traumatic events have in the past been considered hopeless cases destined to a life of paralysis. But in the last decades of the twentieth century there were dramatic advances in spinal cord regeneration research. For example, Swiss scientist Martin Schwab actually managed to heal spinal cords in rats and restored their ability to walk. At the Swedish Karolinska Institute, scientists succeeded in constructing a bridge of slender nerve filaments to connect a once-severed spinal cord in rats that subsequently were able to flex their legs. These developments and others offer paralyzed people some hope. In the early 2000s envisioned treatments include an immune therapy procedure that has been tested in Israel with human subjects and possibilities for mechanical neural prostheses.

Acupuncture is a more conservative form of alternative treatment with documented evidence for the reduction of SCI-related muscle spasms, increased level of sensation, improved bladder and bowel function, improvement in lower limb paralysis, with younger patients reported to have better outcomes.

Nutritional Concerns

Because of the changes that occur in the body after SCI, parents need to understand the role that nutrition can play in the overall health of a child following a spinal cord injury.

Special health concerns resulting from SCI are as follows:

• Bowel management. Individuals with SCI may have neurogenic bowel, with the result that the messages from the brain that control the downward muscular movements of the bowel are either absent or not working properly, making it difficult for stool to move through the intestines. SCI diets accordingly include high fiber and plenty of fluids to regulate bowel movements.
• Heart problems. SCI presents a greater risk for cardiovascular and heart problems, hence the necessity to limit salt and cholesterol intake.
• Pressure ulcers. Pressure ulcers are always a concern to individuals with SCI and a diet high in protein, vitamins, and minerals is recommended to promote skin healing.
• Kidney or bladder stones. Individuals with SCI may be prone to developing calcium stones. Certain beverages can cause crystals to form in the urine and excessive consumption of dairy products is accordingly avoided with water highly recommended as the best drink.
• Urinary tract infection. The loss of normal bladder function after SCI places an individual at risk for urinary tract infection. A high fluid intake every day has been shown to reduce the problem of infections.
• Weight control. After SCI, the metabolic rate is usually lower. Metabolic rate is how fast a body burns ingested calories. A lower muscle mass and a decrease in activities cause a lower metabolic rate, meaning that fewer calories are needed each day to maintain a desirable weight. After rehabilitation, the ideal body weight of a person with SCI is lower than for a nondisabled individual. Dieticians normally decrease the amount of calories by 5 percent for those with paraplegia and 10 to 15 percent for those with tetraplegia (quadriplegia).

Prognosis

The prognosis of SCI depends on the location and extent of injury. Once the initial injury heals, functional improvements may continue for at least six months. Any disability that remains after that point is likely to be permanent. Injuries of the neck above C4 with significant involvement of the diaphragm have worse outcomes. Although SCI often results in permanent disability, rehabilitation can maximize the level of function and help patients adapt and lead independent, productive lives.

According to the American Association of Neurological Surgeons, mortality from SCI is influenced by several factors, the most important being the severity of associated injuries. Because of the force that is required to fracture the spine, it is not uncommon for the patient to suffer significant damage to the chest and/or abdomen. Many of these associated injuries are fatal. For isolated SCIs, the mortality after one year is roughly 5 to 7 percent. If a patient survives the first 24 hours after injury, the probability of survival for ten years is approximately 75 to 80 percent. Likewise, the ten-year survival rate for patients who survived the first year after injury is 87 percent.

Prevention

The following guidelines have been shown to help prevent SCI:

• use of safe driving practices
• avoidance of situations that may become violent
• keeping firearms locked away
• taking precautions to prevent falls around the home (walkways free from obstacles, non-slip materials in bathtubs, etc)
• use of proper safety equipment for sports

The American Academy of Orthopedic Surgeons (AAOS) also recommends that playgrounds be made safe to prevent spinal cord injuries. It offers the following checklist to help parents assess the safety of their child's playground:

• Are any pieces of playground equipment missing supports, anchors, or footings?
• Are any supports, anchors, or footings damaged or loose?
• Has the wood started to splinter or rot?
• Are surface materials missing or damaged?
• Are there any missing, loose, or damaged nuts and bolts on the equipment?
• Are any seats broken?
• Are swing hangers and chains broken or worn?
• Are hooks, rings, or links misshapen or deformed?
• Are there any broken, missing, or loose steps?
• Are any ladder rungs missing, broken, or loose?
• Are tree roots visible or rocks sticking up that could cause a child to trip and fall?

If the answer to any of these questions is "Yes," this playground is not safe for a child. The AAOS recommends that the playground be reported to local park or school officials or to contact a local orthopedic surgeon to enquire as how to build a safe, accessible playground for the area.

Parental Concerns

In most cases, SCI requires that the home be modified to be fully accessible to the injured child. Bathrooms need to be fitted with a shower chair, grab bars, a shower wand, a tub lift, or a shower bench. Grab bars should be installed on three sides of the shower, and non-skid strips should be applied to the bottom of the shower or tub. Bedrooms should be located for convenient access to the bathroom and adequate space should be provided around the bed for wheelchair access with convenient storage near the bed for braces, prostheses, and clothing. Light switches should be lowered for easy access and ramps should be built to facilitate displacements.

See also Computed tomography; Magnetic resonance imaging.

Resources

Books

Nesathurai, Shanker. The Rehabilitation of People with Spinal Cord Injury. Oxford, UK: Blackwell Science, 2000.

Palmer, Sara, et al. Spinal Cord Injury: A Guide for Living. Baltimore, MD: Johns Hopkins University Press, 2000.

Somers, Martha Freeman. Spinal Cord Injury: FunctionalRehabilitation. New York: Pearson Education, 2001.

Vikhanski, Luba. In Search of the Lost Cord: Solving theMystery of Spinal Cord Regeneration. Washington, DC: Joseph Henry Press, 2001.

Periodicals

Bakun, M. and K. Haddix. "Spinal cord injury prevention with children and adolescents." SCI Nursing 20, no. 2 (Summer, 2003): 116–118.

Beck, T. "Current spasticity management in children with spinal cord injury." SCI Nursing 19, no. 1 (Spring, 2002): 28–31.

Cirak, B., et al. "Spinal injuries in children." Journal ofPediatric Surgery 39, no. 4 (April, 2004): 607–12.

Dias, M. S. "Traumatic brain and spinal cord injury." Pediatric Clinics of North America 51, no. 2 (April, 2004): 271–303.

Merenda, L. A., et al. "Progressive treatment options for children with spinal cord injury." SCI Nursing 17, no. 3 (Fall, 2000): 102–09.

Vogel, L. C., and C. J. Anderson. "Spinal cord injuries in children and adolescents: a review." Journal of Spinal Cord Medicine 26, no. 3 (Fall, 2003): 193–203.

——. "Self-injurious behavior in children and adolescents with spinal cord injuries." Spinal Cord 40, no. 12 (December, 2002): 666–68.

Wang, M. Y., et al. "High rates of neurological improvement following severe traumatic pediatric spinal cord injury." Spine 29, no. 13 (July, 2004): 1493–97.

Organizations

American Spinal Injury Association (ASIA). 2020 Peachtree Road NW, Atlanta, GA 30309–1402. Web site: www.asia-spinalinjury.org.

International Spinal Cord Regeneration Center. PO Box 451, Bonita, California 91902. Web site: www.electriciti.com/~spinal.

National Association for Home Care (NAHC). 228 7th Street SE, Washington, DC 20003. Web site: www.nahc.org.

National Institute of Neurological Disorders and Stroke(NINDS). PO Box 5801, Bethesda, MD 20824. Web site: www.ninds.nih.gov.

National Spinal Cord Injury Association (NSCIA). 6701 Democracy Blvd, Suite 300–9, Bethesda, MD 20817. Web site: www.spinalcord.org.

Spinal Cord Society. 19051 County Highway 1, Fergus Falls, MN 56537–7609. Web site: .

Web Sites

"Spinal Cord Injury Rehabilitation." Shriner's Hospitals forChildren. Available online at (accessed October 13, 2004).

[Article by: Monique Laberge, Ph.D.]

Damage to cells in the spinal cord or nerve tracts that relay signals up and down the spinal cord. Such injuries include bruising, compression, lacerations, and severance of the spinal cord. Sport situations in which there is a high risk of spinal cord injury include a rugby scrum, particularly when the scrum collapses. Anyone suspected of a spinal cord injury should not be moved unless it is absolutely essential to keep the airway open so the person can breathe, or to maintain circulation.

Spinal cord injuries
Classification and external resources
ICD-10	G95.9, T09.3
DiseasesDB	12327 29466
eMedicine	emerg/553 neuro/711 pmr/182 pmr/183 orthoped/425
MeSH	D013119

Spinal cord injuries cause myelopathy or damage to white matter or myelinated fiber tracts that carry signals to and from the brain. ^[1][2] Depending on its classification and severity, this type of traumatic injury could also damage the gray matter in the central part of the cord, causing segmental losses of interneurons and motorneurons. Spinal cord injury can occur from many causes, including:

• Trauma such as automobile crashes, falls, gunshots, diving accidents, war injuries, etc.
• Tumor such as meningiomas, ependymomas, astrocytomas, and metastatic cancer.
• Ischemia resulting from occlusion of spinal blood vessels, including dissecting aortic aneurysms, emboli, arteriosclerosis.
• Developmental disorders, such as spina bifida, meningomyolcoele, and other.
• Neurodegenerative diseases, such as Friedreich's ataxia, spinocerebellar ataxia, etc.
• Demyelinative diseases, such as Multiple Sclerosis.
• Transverse myelitis, resulting from stroke, inflammation, or other causes.
• Vascular malformations, such as arteriovenous malformation (AVM), dural arteriovenous fistula (AVF), spinal hemangioma, cavernous angioma and aneurysm.

Contents 1 Classification 1.1 Facts and Figures 2 Consequences 2.1 The Location of the Injury 2.1.1 Cervical injuries 2.1.2 Thoracic injuries 2.1.3 Lumbar and Sacral injuries 2.1.4 Central Cord and Other Syndromes 3 Potential Treatments 4 See also 5 External links 6 References

Classification

The American Spinal Injury Association (ASIA) defined an international classification based on neurological responses, touch and pinprick sensations tested in each dermatome, and strength of ten key muscles on each side of the body, i.e. shoulder shrug (C4), elbow flexion (C5), wrist extension (C6), elbow extension (C7), hip flexion (L2). Traumatic spinal cord injury is classified into five categories by the American Spinal Injury Association and the International Spinal Cord Injury Classification System:

• A indicates a "complete" spinal cord injury where no motor or sensory function is preserved in the sacral segments S4-S5.
• B indicates an "incomplete" spinal cord injury where sensory but not motor function is preserved below the neurological level and includes the sacral segments S4-S5. This is typically a transient phase and if the person recovers any motor function below the neurological level, that person essentially becomes a motor incomplete, i.e. ASIA C or D.
• C indicates an "incomplete" spinal cord injury where motor function is preserved below the neurological level and more than half of key muscles below the neurological level have a muscle grade of less than 3, which indicates active movement with full range of motion against gravity.
• D indicates an "incomplete" spinal cord injury where motor function is preserved below the neurological level and at least half of the key muscles below the neurological level have a muscle grade of 3 or more.
• E indicates "normal" where motor and sensory scores are normal. Note that it is possible to have spinal cord injury and neurological deficits with completely normal motor and sensory scores.

In addition, there are several clinical syndromes associated with incomplete spinal cord injuries.

• The Central cord syndrome is associated with greater loss of upper limb function compared to lower limbs.
• The Brown-Séquard syndrome results from injury to one side with the spinal cord, causing weakness and loss of proprioception on the side of the injury and loss of pain and thermal sensation of the other side.
• The Anterior cord syndrome results from injury to the anterior part of the spinal cord, causing weakness and loss of pain and thermal sensations below the injury site but preservation of proprioception that is usually carried in the posterior part of the spinal cord.
• Tabes Dorsalis results from injury to the posterior part of the spinal cord, usually from infection diseases such as syphilis, causing loss of touch and proprioceptive sensation.
• Conus medullaris syndrome results from injury to the tip of the spinal cord, located at L1 vertebra.
• Cauda equina syndrome is, strictly speaking, not really spinal cord injury but injury to the spinal roots below the L1 vertebra.

Facts and Figures

One can have spine injury without spinal cord injury. Many people suffer transient loss of function ("stingers") in sports accidents or pain in "whiplash" of the neck without neurological loss and relatively few of these suffer spinal cord injury sufficient to warrant hospitalization. In the United States, the incidence of spinal cord injury has been estimated to be about 35 cases per million per year, or approximately 10,500 per year (35 * 300). In China, the incidence of spinal cord injury was recently estimated to be as high as 65 cases per million per year in urban areas. If so, assuming a population of 1.3 billion, this would suggest an incidence of 84,500 per year (65 * 1300).

The prevalence of spinal cord injury is not well known in many large countries. In some countries, such as Sweden and Iceland, registries are available. According to new data collected by the Christopher and Dana Reeve Foundation, in the US, there are currently 1.3 million individuals living with spinal cord injuries- a number five times that previously estimated in 2007. 61% of spinal cord injuries occur in males, and 39% in females. The average age for spinal cord injuries is 48 years old. There are many causes leading to spinal cord injuries. These include motor vehicle accidents (24%), work-related accidents (28%), sporting/recreation accidents (16%), and falls (9%).

Consequences

Divisions of Spinal Segments

Segmental Spinal Cord Level and Function
Level	Function
Cl-C6	Neck flexors
Cl-Tl	Neck extensors
C3, C4, C5	Supply diaphragm (mostly C4)
C5, C6	Shoulder movement, raise arm (deltoid); flexion of elbow (biceps); C6 externally rotates the arm (supinates)
C6, C7	Extends elbow and wrist (triceps and wrist extensors); pronates wrist
C7, T1	Flexes wrist
C7, T1	Supply small muscles of the hand
T1 -T6	Intercostals and trunk above the waist
T7-L1	Abdominal muscles
L1, L2, L3, L4	Thigh flexion
L2, L3, L4	Thigh adduction
L4, L5, S1	Thigh abduction
L5, S1, S2	Extension of leg at the hip (gluteus maximus)
L2, L3, L4	Extension of leg at the knee (quadriceps femoris)
L4, L5, S1, S2	Flexion of leg at the knee (hamstrings)
L4, L5, S1	Dorsiflexion of foot (tibialis anterior)
L4, L5, S1	Extension of toes
L5, S1, S2	Plantar flexion of foot
L5, S1, S2	Flexion of toes

The consequences of a spinal cord injury may vary depending on the type, level, and severity of injury, but can be classified into two general categories:

• In a complete injury, function below the "neurological" level is lost. Absence of motor and sensory function below a specific spinal level is considered a "complete injury". Recent evidence suggests that less than 5% of people with "complete" spinal cord injuries recover locomotion.
• In an incomplete injury, some sensation and/or movement below the level of the injury is retained. The lowest spinal segment in humans is located at vertebral levels S4-5, corresponding to the anal sphincter and peri-anal sensation. The ability to contract the anal sphincter voluntarily or to feel peri-anal pinprick or touch, the injury is considered to be "incomplete". Recent evidence suggests that over 95% of people with "incomplete" spinal cord injuries recover some locomotor function.

In addition to loss of sensation and motor function below the level of injury, individuals with spinal cord injuries will also often experience other complications:

• Bowel and bladder function is regulated by the sacral region of the spine. In that regard, it is very common to experience dysfunction of the bowel and bladder, including infections of the bladder and anal incontinence, after traumatic injury.
• Sexual function is also associated with the sacral spinal segments, and is often affected after injury. During a psychogenic sexual experience, signals from the brain are sent to spinal levels T10-L2 and in case of men, are then relayed to the penis where they trigger an erection. A reflex erection, on the other hand, occurs as a result of direct physical contact to the penis or other erotic areas such as the ears, nipples or neck. A reflex erection is involuntary and can occur without sexually stimulating thoughts. The nerves that control a man’s ability to have a reflex erection are located in the sacral nerves (S2-S4) of the spinal cord and could be affected after a spinal cord injury. ^[3]
• Injuries at the C-1/C-2 levels will often result in loss of breathing, necessitating mechanical ventilators or phrenic nerve pacing.
• Inability or reduced ability to regulate heart rate, blood pressure, sweating and hence body temperature.
• Spasticity (increased reflexes and stiffness of the limbs).
• Neuropathic pain.
• Autonomic dysreflexia or abnormal increases in blood pressure, sweating, and other autonomic responses to pain or sensory disturbances.
• Atrophy of muscle.
• Superior Mesenteric Artery Syndrome.
• Osteoporosis (loss of calcium) and bone degeneration.
• Gallbladder and renal stones.

The Location of the Injury

Determining the exact level of injury is critical in making accurate predictions about the specific parts of the body that may be affected by paralysis and loss of function.

The symptoms observed after a spinal cord injury differ by location (refer to the spinal cord map on the right to determine location). Notably, while the prognosis of complete injuries are generally predictable, the symptoms of incomplete injuries span a variable range. Accordingly, it is difficult to make an accurate prognosis for these types of injuries.

Cervical injuries

Cervical (neck) injuries usually result in full or partial tetraplegia (Quadriplegia). However, depending on the specific location and severity of trauma, limited function may be retained.

• C3 vertebrae and above : Typically results in loss of diaphragm function, necessitating the use of a ventilator for breathing.
• C4 : Results in significant loss of function at the biceps and shoulders.
• C5 : Results in potential loss of function at the shoulders and biceps, and complete loss of function at the wrists and hands.
• C6 : Results in limited wrist control, and complete loss of hand function.
• C7 and T1 : Results in lack of dexterity in the hands and fingers, but allows for limited use of arms. C7 is generally the threshold level for retaining functional independence.

Thoracic injuries

Injuries at or below the thoracic spinal levels result in paraplegia. Function of the hands, arms, neck, and breathing is usually not affected.

• T1 to T8 : Results in the inability to control the abdominal muscles. Accordingly, trunk stability is affected. The lower the level of injury, the less severe the effects.
• T9 to T12 : Results in partial loss of trunk and abdominal muscle control.

Lumbar and Sacral injuries

The effects of injuries to the lumbar or sacral regions of the spinal cord are decreased control of the legs and hips, urinary system, and anus.

Central Cord and Other Syndromes

Central cord syndrome (picture 1) is a form of incomplete spinal cord injury characterized by impairment in the arms and hands and, to a lesser extent, in the legs. This is also referred to as inverse paraplegia, because the hands and arms are paralyzed while the legs and lower extremities work correctly.

Most often the damage is to the cervical or upper thoracic regions of the spinal cord, and characterized by weakness in the arms with relative sparing of the legs with variable sensory loss.

This condition is associated with ischemia, hemorrhage, or necrosis involving the central portions of the spinal cord (the large nerve fibers that carry information directly from the cerebral cortex). Corticospinal fibers destined for the legs are spared due to their more external location in the spinal cord.

This clinical pattern may emerge during recovery from spinal shock due to prolonged swelling around or near the vertebrae, causing pressures on the cord. The symptoms may be transient or permanent.

Anterior cord syndrome (picture 2) is also an incomplete spinal cord injury. Below the injury, motor function, pain sensation, and temperature sensation is lost; touch, proprioception (sense of position in space), and vibration sense remain intact. Posterior cord syndrome (not pictured) can also occur, but is very rare.

Brown-Séquard syndrome (picture 3) usually occurs when the spinal cord is hemisectioned or injured on the lateral side. On the ipsilateral side of the injury (same side), there is a loss of motor function, proprioception, vibration, and light touch. Contralaterally (opposite side of injury), there is a loss of pain, temperature, and deep touch sensations

Potential Treatments

Treatment options for acute, traumatic non-penetrating spinal cord injuries include the administration of a high dose of an anti-inflammatory agent, methylprednisolone, within 8 hours of injury. This recommendation is primarily based on the National Acute Spinal Cord Injury Studies (NASCIS) I and II. However, in a third study, methylprednisolone failed to demonstrate an effect in comparison to placebo. Additionally, due to increased risk of infections, the use of this anti-inflammatory drug after spinal cord injuries is no longer recommended ^[4][5]. Presently, administration of cold saline acutely after injury is gaining popularity, but there is a paucity of empirical evidence for the beneficial effects of therapeutic hypothermia.

Scientists are investigating many promising avenues for treatment of spinal cord injury. Numerous articles in the medical literature describe research, mostly in animal models, aimed at reducing the paralyzing effects of injury and promoting regrowth of functional nerve fibers. Despite the devastating effects of the condition, commercial funding for research investigating a cure after spinal cord injury is limited, partially due to the small size of the population of potential beneficiaries. Despite this limitation, a number of experimental treatments have reached controlled human trials^{[citation needed]}. In addition, therapeutic strategies involving neuronal protection and regeneration are also being investigated in other neurodegenerative diseases such as Alzheimer's Disease, Parkinson's Disease, Amyotrophic Lateral Sclerosis and Multiple sclerosis. There are many similarities between these conditions of the CNS and spinal cord injuries, thus increasing the potential for discovery of a treatment after spinal cord injuries.

Advances in identification of an effective therapeutic target after spinal cord injury have been newsworthy, and considerable media attention is often drawn towards new developments in this area. However, aside from methylprednisolone, none of these developments have reached even limited use in the clinical care of human spinal cord injury in the U.S.^{[citation needed]}. Around the world, proprietary centers offering stem cell transplants and treatment with neuroregenerative substances are fueled by glowing testimonial reports of neurological improvement. Independent validation of the results of these treatments is lacking.^[6] However, in January 2009, the Geron Corporation received FDA clearance to begin human safety testing of its stem cell treatment candidate, GRNOPC1, on newly injured patients with complete thoracic injury.^[7] A diverse array of other treatments are being researched, including biomaterial solutions,^[8] cell replacement therapies, and electronic stimulative devices.

See also

• Brown-Sequard Syndrome
• Paraplegia
• Quadriplegia/Tetraplegia

External links

• Miami Project to Cure Paralysis Noted for experimental cooling protocol used on Kevin Everett
• United Spinal Association A membership organization dedicated to improving the quality of life of individuals with spinal cord injuries and related disorders.
• Rehabilitation Research and Training Center (RRTC) on Spinal Cord Injury: Promoting Health and Preventing Complications through Exercise
• SCI Images - Images of Spinal Cord Injury
• [1]- Spinal Cord Injury Levels and Classification
• [2] The Spinal Cord Injury Project, W.M. Keck Center for Collaborative Neuroscience at Rutgers University
• EMSCI Network European Multicenter Study about Spinal Cord Injury
• Brigham and Women's Hospital Translational Pain Research Clinical trials for pain following SCI
• Pediatric and Adolescent Spinal Cord Injury
• Rehabilitation Engineering Research Center on Wheeled Mobility
• International Institute for Research in Paraplegia Research funding foundation, based in Zurich
• Spinal Cord Injuries Emergency Medicine for Spinal Cord Injuries
• Trefethen, Tre. User's Manual for the Paralyzed Penis: Love after spinal cord injury American Sexuality Magazine. Accessed 3-22-07.
• About Spinal Cord Injury Spinal Cord Injury FAQ for those with SCI, and their families, by Canadian Paraplegic Association - Ontario.
• ICF based Case studies in Spinal Cord Injury Rehabilitation

v • d • e Nervous system (TA A14, GA 9) Central nervous system Meninges Spinal cord Brain: Rhombencephalon (Medulla oblongata, Pons, Cerebellum) • Mesencephalon • Prosencephalon (Diencephalon, Telencephalon) Peripheral nervous system Somatic Sensory nerve • Motor nerve • Cranial nerves • Spinal nerves Autonomic Sympathetic • Parasympathetic • Enteric nervous system central nervous system navs: anat/physio/dev, noncongen/congen/neoplasia, symptoms+signs/eponymous, proc peripheral nervous system navs: anat/histo/physio/dev, noncongen PNS somatic/autonomic/congen/neoplasia, symptoms+signs/eponymous, proc

v • d • e Nerves: spinal nerves (TA A14.2, GA 9.916) Cervical (8) C1, C2, C3, C4, C5, C6, C7, C8 anterior (Cervical plexus, Brachial plexus) - posterior (Posterior branches of cervical nerves, Suboccipital - C1, Greater occipital - C2, Third occipital - C3) Thoracic (12) T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 anterior (Intercostal, Intercostobrachial - T2, Thoraco-abdominal nerves - T7-T11, Subcostal - T12) - posterior (Posterior branches of thoracic nerves) Lumbar (5) L1, L2, L3, L4, L5 anterior (Lumbar plexus, Lumbosacral trunk) · posterior (Posterior branches of the lumbar nerves, Superior cluneal L1-L3) Sacral (5) S1, S2, S3, S4, S5 anterior (Sacral plexus) · posterior (Posterior branches of sacral nerves, Medial cluneal nerves) Coccygeal (1) anterior (Coccygeal plexus) · posterior (Posterior branch of coccygeal nerve)

v • d • e Injuries, other than fractures, dislocations, sprains and strains (S00-T14, 850-929) Head (head injury) and neck Traumatic brain injury (Concussion, Diffuse axonal injury, Cerebral contusion, Epidural hematoma, Subdural hematoma, Subarachnoid hemorrhage) Facial trauma (Black eye  · Eye injury) Thorax (chest trauma) lung: pleural disease (Pneumothorax, Hemothorax, Hemopneumothorax)  · Pulmonary contusion  · Pulmonary laceration heart and circulatory: Cardiac tamponade  · Commotio cordis  · Hemopericardium  · Traumatic aortic rupture Abdomen, lower back, lumbar spine and pelvis Ruptured spleen  · Traumatic diaphragmatic hernia Shoulder and upper arm Rotator cuff tear Knee and leg Achilles tendon rupture General Spinal cord injury  · Brachial plexus lesion Abrasion  · Amputation  · Avulsion  · Bite  · Blister  · Bruise  · Burn  · Hematoma Wound

References

1. ^ Spinal Cord Medicine: Principles and Practice (2002) Lin VWH, Cardenas DD, Cutter NC, Frost FS, Hammond MC. Demos Medical Publishing
2. ^ Spinal Cord Medicine (2001) Kirshblum S, Campagnolo D, Delisa J. Lippincott Williams & Wilkins
3. ^ Klebin, Phil Sexual Function of Men with Spinal Cord Injury May 2007
4. ^ "UpToDate Inc.". http://www.uptodate.com/online/content/topic.do?topicKey=medneuro/10703&selectedTitle=3~150&source=search_result. 
5. ^ "BestBets: Steroids in acute spinal cord injury". http://www.bestbets.org/bets/bet.php?id=105. 
6. ^ Dobkin, BH.; Curt, A.; Guest, J. “Cellular transplants in China: observational study from the largest human experiment in chronic spinal cord injury.” Neurorehabilitation and Neural Repair, v. 20 issue 1, 2006, p. 5-13.
7. ^ Geron press release January 23 2009: Geron Receives FDA Clearance to Begin World's First Human Clinical Trial of Embryonic Stem Cell-Based Therapy
8. ^ See for example Benton Martin, Eric Minner, Sherri Wiseman, Rebecca Klank, Ryan Gilbert, 2008, “Injectable agarose and methylcellulose hydrogel blends for nerve regeneration applications,” Journal of Neural Engineering, Vol. 5, No. 2, pp. 221-231.

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