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Lesión de la Médula Espinal
Accounts of spinal cord injuries and their treatment date back to ancient times, even though there was little chance of recovery from such a devastating injury. The earliest is found in an Egyptian papyrus roll manuscript written in approximately 1700 B.C. that describes two spinal cord injuries involving fracture or dislocation of the neck vertebrae accompanied by paralysis.* The description of each was "an ailment not to be treated."
Centuries later in Greece, treatment for spinal cord injuries had changed little. According to the Greek physician Hippocrates (460-377 B.C.) there were no treatment options for spinal cord injuries that resulted in paralysis; unfortunately, those patients were destined to die. But Hippocrates did use rudimentary forms of traction to treat spinal fractures without paralysis. The Hippocratic Ladder was a device that required the patient to be bound, tied to the rungs upside-down, and shaken vigorously to reduce spinal curvature. Another invention, the Hippocratic Board, allowed the doctor to apply traction to the immobilized patient's back using either his hands and feet or a wheel and axle arrangement.
Hindu, Arab, and Chinese physicians also developed basic forms of traction to correct spinal deformities. These same principles of traction are still applied today.
In about 200 A.D., the Roman physician Galen introduced the concept of the central nervous system when he proposed that the spinal cord was an extension of the brain that carried sensation to the limbs and back. By the seventh century A.D., Paulus of Aegina was recommending surgery for spinal column fracture to remove the bone fragments that he was convinced caused paralysis.
In his influential anatomy textbook published in 1543, the Renaissance physician and teacher Vesalius described and illustrated the spinal cord in all its parts. The illustrations in his books, based on direct observation and dissection of the spine, gave physicians a way to understand the basic structure of the spine and spinal cord and what could happen when it was injured. The words we use today to identify segments of the spine - cervical, thoracic, lumbar, sacral, and coccygeal - come directly from Vesalius.
With the widespread use of antiseptics and sterilization in surgical procedures in the late nineteenth century, spinal surgery could finally be done with a much lower risk of infection. The use of X-rays, beginning in the 1920s, gave surgeons a way to precisely locate the injury and also made diagnosis and prediction of outcome more accurate. By the middle of the twentieth century, a standard method of treating spinal cord injuries was established - reposition the spine, fix it in place, and rehabilitate disabilities with exercise. In the 1990s, the discovery that the steroid drug methylprednisolone could reduce damage to nerve cells if given early enough after injury gave doctors an additional treatment option.
Although the hard bones of the spinal column protect the soft tissues of the spinal cord, vertebrae can still be broken or dislocated in a variety of ways and cause traumatic injury to the spinal cord. Injuries can occur at any level of the spinal cord. The segment of the cord that is injured, and the severity of the injury, will determine which body functions are compromised or lost. Because the spinal cord acts as the main information pathway between the brain and the rest of the body, a spinal cord injury can have significant physiological consequences.
Catastrophic falls, being thrown from a horse or through a windshield, or any kind of physical trauma that crushes and compresses the vertebrae in the neck can cause irreversible damage at the cervical level of the spinal cord and below. Paralysis of most of the body including the arms and legs, called quadriplegia, is the likely result. Automobile accidents are often responsible for spinal cord damage in the middle back (the thoracic or lumbar area), which can cause paralysis of the lower trunk and lower extremities, called paraplegia.
Other kinds of injuries that directly penetrate the spinal cord, such as gunshot or knife wounds, can either completely or partially sever the spinal cord and create life-long disabilities.
Most injuries to the spinal cord don't completely sever it. Instead, an injury is more likely to cause fractures and compression of the vertebrae, which then crush and destroy the axons, extensions of nerve cells that carry signals up and down the spinal cord between the brain and the rest of the body. An injury to the spinal cord can damage a few, many, or almost all of these axons. Some injuries will allow almost complete recovery. Others will result in complete paralysis.
Until World War II, a serious spinal cord injury usually meant certain death, or at best a lifetime confined to a wheelchair and an ongoing struggle to survive secondary complications such as breathing problems or blood clots. But today, improved emergency care for people with spinal cord injuries and aggressive treatment and rehabilitation can minimize damage to the nervous system and even restore limited abilities.
Advances in research are giving doctors and patients hope that all spinal cord injuries will eventually be repairable. With new surgical techniques and exciting developments in spinal nerve regeneration, the future for spinal cord injury survivors looks brighter every day.
This brochure has been written to explain what happens to the spinal cord when it is injured, the current treatments for spinal cord injury patients, and the most promising avenues of research currently under investigation.
Facts and Figures About Spinal Cord Injury
To understand what can happen as the result of a spinal cord injury, it helps to know the anatomy of the spinal cord and its normal functions.
Spine Anatomy
The soft, jelly-like spinal cord is protected by the spinal column. The spinal column is made up of 33 bones called vertebrae, each with a circular opening similar to the hole in a donut. The bones are stacked one on top of the other and the spinal cord runs through the hollow channel created by the holes in the stacked bones.
The vertebrae can be organized into sections, and are named and numbered from top to bottom according to their location along the backbone:
Although the hard vertebrae protect the soft spinal cord from injury most of the time, the spinal column is not all hard bone. Between the vertebrae are discs of semi-rigid cartilage, and in the narrow spaces between them are passages through which the spinal nerves exit to the rest of the body. These are places where the spinal cord is vulnerable to direct injury.
The spinal cord is also organized into segments and named and numbered from top to bottom. Each segment marks where spinal nerves emerge from the cord to connect to specific regions of the body. Locations of spinal cord segments do not correspond exactly to vertebral locations, but they are roughly equivalent.
The single coccygeal nerve carries sensory information from the skin of the lower back.
Spinal Cord Anatomy
The spinal cord has a core of tissue containing nerve cells, surrounded by long tracts of nerve fibers consisting of axons. The tracts extend up and down the spinal cord, carrying signals to and from the brain. The average size of the spinal cord varies in circumference along its length from the width of a thumb to the width of one of the smaller fingers. The spinal cord extends down through the upper two thirds of the vertebral canal, from the base of the brain to the lower back, and is generally 15 to 17 inches long depending on an individual's height.
The interior of the spinal cord is made up of neurons, their support cells called glia, and blood vessels. The neurons and their dendrites (branching projections that help neurons communicate with each other) reside in an H-shaped region called "grey matter."
The H-shaped grey matter of the spinal cord contains motor neurons that control movement, smaller interneurons that handle communication within and between the segments of the spinal cord, and cells that receive sensory signals and then send information up to centers in the brain.
Surrounding the grey matter of neurons is white matter. Most axons are covered with an insulating substance called myelin, which allows electrical signals to flow freely and quickly. Myelin has a whitish appearance, which is why this outer section of the spinal cord is called "white matter."
Axons carry signals downward from the brain (along descending pathways) and upward toward the brain (along ascending pathways) within specific tracts. Axons branch at their ends and can make connections with many other nerve cells simultaneously. Some axons extend along the entire length of the spinal cord.
The descending motor tracts control the smooth muscles of internal organs and the striated (capable of voluntary contractions) muscles of the arms and legs. They also help adjust the autonomic nervous system's regulation of blood pressure, body temperature, and the response to stress. These pathways begin with neurons in the brain that send electrical signals downward to specific levels of the spinal cord. Neurons in these segments then send the impulses out to the rest of the body or coordinate neural activity within the cord itself.
The ascending sensory tracts transmit sensory signals from the skin, extremities, and internal organs that enter at specific segments of the spinal cord. Most of these signals are then relayed to the brain. The spinal cord also contains neuronal circuits that control reflexes and repetitive movements, such as walking, which can be activated by incoming sensory signals without input from the brain.
The circumference of the spinal cord varies depending on its location. It is larger in the cervical and lumbar areas because these areas supply the nerves to the arms and upper body and the legs and lower body, which require the most intense muscular control and receive the most sensory signals.
The ratio of white matter to grey matter also varies at each level of the spinal cord. In the cervical segment, which is located in the neck, there is a large amount of white matter because at this level there are many axons going to and from the brain and the rest of the spinal cord below. In lower segments, such as the sacral, there is less white matter because most ascending axons have not yet entered the cord, and most descending axons have contacted their targets along the way.
To pass between the vertebrae, the axons that link the spinal cord to the muscles and the rest of the body are bundled into 31 pairs of spinal nerves, each pair with a sensory root and a motor root that make connections within the grey matter. Two pairs of nerves - a sensory and motor pair on either side of the cord - emerge from each segment of the spinal cord.
The functions of these nerves are determined by their location in the spinal cord. They control everything from body functions such as breathing, sweating, digestion, and elimination, to gross and fine motor skills, as well as sensations in the arms and legs.
The Nervous Systems
Together, the spinal cord and the brain make up the central nervous system (CNS).
The CNS controls most functions of the body, but it is not the only nervous system in the body. The peripheral nervous system (PNS) includes the nerves that project to the limbs, heart, skin, and other organs outside the brain. The PNS controls the somatic nervous system, which regulates muscle movements and the response to sensations of touch and pain, and the autonomic nervous system, which provides nerve input to the internal organs and generates automatic reflex responses. The autonomic nervous system is divided into the sympathetic nervous system, which mobilizes organs and their functions during times of stress and arousal, and the parasympathetic nervous system, which conserves energy and resources during times of rest and relaxation.
The spinal cord acts as the primary information pathway between the brain and all the other nervous systems of the body. It receives sensory information from the skin, joints, and muscles of the trunk, arms, and legs, which it then relays upward to the brain. It carries messages downward from the brain to the PNS, and contains motor neurons, which direct voluntary movements and adjust reflex movements. Because of the central role it plays in coordinating muscle movements and interpreting sensory input, any kind of injury to the spinal cord can cause significant problems throughout the body.
A spinal cord injury usually begins with a sudden, traumatic blow to the spine that fractures or dislocates vertebrae. The damage begins at the moment of injury when displaced bone fragments, disc material, or ligaments bruise or tear into spinal cord tissue. Axons are cut off or damaged beyond repair, and neural cell membranes are broken. Blood vessels may rupture and cause heavy bleeding in the central grey matter, which can spread to other areas of the spinal cord over the next few hours.
Within minutes, the spinal cord swells to fill the entire cavity of the spinal canal at the injury level. This swelling cuts off blood flow, which also cuts off oxygen to spinal cord tissue. Blood pressure drops, sometimes dramatically, as the body loses its ability to self-regulate. As blood pressure lowers even further, it interferes with the electrical activity of neurons and axons. All these changes can cause a condition known as spinal shock that can last from several hours to several days.
Although there is some controversy among neurologists about the extent and impact of spinal shock, and even its definition in terms of physiological characteristics, it appears to occur in approximately half the cases of spinal cord injury, and it is usually directly related to the size and severity of the injury. During spinal shock, even undamaged portions of the spinal cord become temporarily disabled and can't communicate normally with the brain. Complete paralysis may develop, with loss of reflexes and sensation in the limbs.
The crushing and tearing of axons is just the beginning of the devastation that occurs in the injured spinal cord and continues for days. The initial physical trauma sets off a cascade of biochemical and cellular events that kills neurons, strips axons of their myelin insulation, and triggers an inflammatory immune system response. Days or sometimes even weeks later, after this second wave of damage has passed, the area of destruction has increased - sometimes to several segments above and below the original injury - and so has the extent of disability.
The outcome of any injury to the spinal cord depends upon the number of axons that survive: the higher the number of normally functioning axons, the less the amount of disability. Consequently, the most important consideration when moving people to a hospital or trauma center is preventing further injury to the spine and spinal cord.
Spinal cord injury isn't always obvious. Any injury that involves the head (especially with trauma to the front of the face), pelvic fractures, penetrating injuries in the area of the spine, or injuries that result from falling from heights should be suspect for spinal cord damage.
Until imaging of the spine is done at an emergency or trauma center, people who might have spinal cord injury should be cared for as if any significant movement of the spine could cause further damage. They are usually transported in a recumbent (lying down) position, with a rigid collar and backboard immobilizing the spine.
Respiratory complications are often an indication of the severity of spinal cord injury. About one third of those with injury to the neck area will need help with breathing and require respiratory support via intubation, which involves inserting a tube connected to an oxygen tank through the nose or throat and into the airway.
Methylprednisolone, a steroid drug, became standard treatment for acute spinal cord injury in 1990 when a large-scale clinical trial supported by the National Institute of Neurological Disorders and Stroke showed significantly better recovery in patients who were given the drug within the first 8 hours after their injury. Methylprednisolone appears to reduce the damage to nerve cells and decreases inflammation near the injury site by suppressing activities of immune cells.
Realignment of the spine using a rigid brace or axial traction is usually done as soon as possible to stabilize the spine and prevent additional damage.
On about the third day after the injury, doctors give patients a complete neurological examination to diagnose the severity of the injury and predict the likely extent of recovery. The ASIA Impairment Scale is the standard diagnostic tool used by doctors. X-rays, MRIs, or more advanced imaging techniques are also used to visualize the entire length of the spine.
ASIA (American Spinal Injury Association) Impairment Scale*
Classification | Description | |
A | Complete: no motor or sensory function is preserved below the level of injury, including the sacral segments S4-S5 | |
B | Incomplete: sensory, but not motor, function is preserved below the neurologic level and some sensation in the sacral segments S4-S5 | |
C | Incomplete: motor function is preserved below the neurologic level, however, more than half of key muscles below the neurologic level have a muscle grade less than 3 (i.e., not strong enough to move against gravity) | |
D | Incomplete: motor function is preserved below the neurologic level, and at least half of key muscles below the neurologic level have a muscle grade of 3 or more (i.e., joints can be moved against gravity) | |
E | Normal: motor and sensory functions are normal |
* Used with permission of the American Spinal Injury Association.
Spinal cord injuries are classified as either complete or incomplete, depending on how much cord width is injured. An incomplete injury means that the ability of the spinal cord to convey messages to or from the brain is not completely lost. People with incomplete injuries retain some motor or sensory function below the injury.
A complete injury is indicated by a total lack of sensory and motor function below the level of injury.
People who survive a spinal cord injury will most likely have medical complications such as chronic pain and bladder and bowel dysfunction, along with an increased susceptibility to respiratory and heart problems. Successful recovery depends upon how well these chronic conditions are handled day to day.
No two people will experience the same emotions after surviving a spinal cord injury, but almost everyone will feel frightened, anxious, or confused about what has happened. It's common for people to have very mixed feelings: relief that they are still alive, but disbelief at the nature of their disabilities.
Rehabilitation programs combine physical therapies with skill-building activities and counseling to provide social and emotional support. The education and active involvement of the newly injured person and his or her family and friends is crucial.
A rehabilitation team is usually led by a doctor specializing in physical medicine and rehabilitation (called a physiatrist), and often includes social workers, physical and occupational therapists, recreational therapists, rehabilitation nurses, rehabilitation psychologists, vocational counselors, nutritionists, and other specialists. A case-worker or program manager coordinates care.
In the initial phase of rehabilitation, therapists emphasize regaining leg and arm strength since mobility and communication are the two most important areas of function. For some, mobility will only be possible with the assistance of devices such as a walker, leg braces, or a wheelchair. Communication skills, such as writing, typing, and using the telephone, may also require adaptive devices.
Physical therapy includes exercise programs geared toward muscle strengthening. Occupational therapy helps redevelop fine motor skills. Bladder and bowel management programs teach basic toileting routines, and patients also learn techniques for self-grooming. People acquire coping strategies for recurring episodes of spasticity, autonomic dysreflexia, and neurogenic pain.
Vocational rehabilitation begins with an assessment of basic work skills, current dexterity, and physical and cognitive capabilities to determine the likelihood for employment. A vocational rehabilitation specialist then identifies potential work places, determines the type of assistive equipment that will be needed, and helps arrange for a user-friendly workplace. For those whose disabilities prevent them from returning to the workplace, therapists focus on encouraging productivity through participation in activities that provide a sense of satisfaction and self-esteem. This could include educational classes, hobbies, memberships in special interest groups, and participation in family and community events.
Recreation therapy encourages patients to build on their abilities so that they can participate in recreational or athletic activities at their level of mobility. Engaging in recreational outlets and athletics helps those with spinal cord injuries achieve a more balanced and normal lifestyle and also provides opportunities for socialization and self-expression.
Can an injured spinal cord be rebuilt? This is the question that drives basic research in the field of spinal cord injury. As investigators try to understand the underlying biological mechanisms that either inhibit or promote new growth in the spinal cord, they are making surprising discoveries, not just about how neurons and their axons grow in the CNS, but also about why they fail to regenerate after injury in the adult CNS. Understanding the cellular and molecular mechanisms involved in both the working and the damaged spinal cord could point the way to therapies that might prevent secondary damage, encourage axons to grow past injured areas, and reconnect vital neural circuits within the spinal cord and CNS.
There has been successful research in a number of fields that may someday help people with spinal cord injuries. Genetic studies have revealed a number of molecules that encourage axon growth in the developing CNS but prevent it in the adult. Research into embryonic and adult stem cell biology has furthered knowledge about how cells communicate with each other.
Basic research has helped describe the mechanisms involved in the mysterious process of apoptosis, in which large groups of seemingly healthy cells self-destruct. New rehabilitation therapies that retrain neural circuits through forced motion and electrical stimulation of muscle groups are helping injured patients regain lost function.
Researchers, many of whom are supported by the National Institute of Neurological Disorders and Stroke (NINDS), are focused on advancing our understanding of the four key principles of spinal cord repair:
A spinal cord injury is complex. Repairing it has to take into account all of the different kinds of damage that occur during and after the injury. Because the molecular and cellular environment of the spinal cord is constantly changing from the moment of injury until several weeks or even months later, combination therapies will have to be designed to address specific types of damage at different points in time.
Discoveries in Basic Research
A decade ago, researchers demonstrated a small but significant neuroprotective and anti-inflammatory effect from an adrenal corticosteroid drug called methylprednisolone if it was given within 8 hours of injury. It is the only treatment currently available to limit the extent of spinal cord injury and its risks are relatively low. Researchers continue to search for additional anti-inflammatory treatments that might prove even more effective.
Preliminary clinical trials of another compound, GM-1 ganglioside, indicate that it could be useful in preventing secondary damage in acute spinal cord injury. A large, randomized clinical trial suggested that it might also improve neurological recovery from spinal cord injury during rehabilitation.
These observations and others have led to optimism that recovery can be improved by altering cellular responses immediately after injury. Using what they know about the mechanisms that cause secondary damage - excitotoxicity, inflammation, and cell suicide (apoptosis) - researchers are creating and testing additional neuroprotective therapies to prevent the spread of post-injury damage and preserve surrounding tissue.
Some of the findings in these three different areas follow:
When nerve cells die, they release excessive amounts of a neurotransmitter called glutamate. Since surviving nerve cells also release glutamate as part of their normal communication process, excess glutamate floods the cellular environment, which pushes cells into overdrive and self-destruction. Researchers are investigating compounds that could keep nerve cells from responding to glutamate, potentially minimizing the extent of secondary damage.
Recently, investigators tested agents called receptor antagonists that selectively block a specific type of glutamate receptor that is abundant on oligodendrocytes and neurons. These agents appear to be effective at limiting damage. Some of these receptor antagonists have already been tested in human trials as a therapy for stroke. Similar agents could enter clinical trials within several years for patients with spinal cord injury.
Discoveries in Clinical Research
Advances in basic research are also being matched by progress in clinical research, especially in understanding the kinds of physical rehabilitation that work best to restore function. Some of the more promising rehabilitation techniques are helping spinal cord injury patients become more mobile.
Fueled by significant federal and private funding, the past decade of spinal cord injury research has produced a wealth of discoveries that are making the repair of injured spinal cords a reachable goal. This is good news for the 10,000 to 12,000 Americans every year who sustain these traumatic injuries.
Because spinal cord injuries happen predominantly to people under the age of 30, the human cost is high. Major improvements in emergency and acute care have improved survival rates but have also increased the numbers of individuals who have to cope with severe disabilities for the rest of their lives. The cost to society, in terms of health care costs, disability payments, and lost income, is disproportionately high compared to other medical conditions.
Considering the biological complexity of spinal cord injury, discovering successful ways to repair injuries and create rehabilitative strategies that significantly reduce disabilities is not an easy task. Researchers, many of them supported by the NINDS, are actively developing innovative research strategies aimed at making the kinds of exciting new discoveries that will translate into better clinical care and better lives for all.
For more information on neurological disorders or research programs funded by the National Institute of Neurological Disorders and Stroke, contact the Institute's Brain Resources and Information Network (BRAIN) at:
BRAIN
P.O. Box 5801
Bethesda, MD 20824
(800) 352-9424
http://www.ninds.nih.gov
Information also is available from the following organizations:
Christopher and Dana Reeve Foundation 636 Morris Turnpike Suite 3A Short Hills, NJ 07078 informations@christopherreeve.org http://www.christopherreeve.org Tel: 973-379-2690 800-225-0292 Fax: 973-912-9433 |
National Rehabilitation Information Center (NARIC) 8201 Corporate Drive Suite 600 Landover, MD 20785 naricinfo@heitechservices.com http://www.naric.com Tel: 301-459-5900/301-459-5984 (TTY) 800-346-2742 Fax: 301-562-2401 |
Miami Project to Cure Paralysis/
Buoniconti Fund P.O. Box 016960 R-48 Miami, FL 33101-6960 miamiproject@med.miami.edu http://www.themiamiproject.org Tel: 305-243-6001 800-STANDUP (782-6387) Fax: 305-243-6017 |
National Spinal Cord Injury Association 75-20 Astoria Blvd Suite 120 East Elmhurst, NY 11370-1177 info@spinalcord.org http://www.spinalcord.org Tel: 800-962-9629 Fax: 866-387-2196 |
Paralyzed Veterans of America (PVA) 801 18th Street, NW Washington, DC 20006-3517 info@pva.org http://www.pva.org Tel: 202-USA-1300 (872-1300) 800-555-9140 Fax: 202-785-4452 |
Spinal Cord Society 19051 County Highway 1 Fergus Falls, MN 56537 scs-nc@nc.rr.com http://scsus.org/ Tel: 218-739-5252 or 218-739-5261 Fax: 218-739-5262 |
Clearinghouse on Disability Information Special Education & Rehabilitative Services Communications & Customer Service Team 550 12th Street, SW, Rm. 5133 Washington, DC 20202-2550 http://www.ed.gov/about/offices/list/osers Tel: 202-245-7307 202-205-5637 (TTD) Fax: 292024507636 |
National Institute on Disability and
Rehabilitation Research (NIDRR) U.S. Department of Education Office of Special Education and Rehabilitative Services 400 Maryland Ave., S.W. Washington, DC 20202-7100 http://www.ed.gov/about/offices/list/osers/nidrr Tel: 202-245-7460 202-245-7316 (TTY) |
Glossary agonist - a drug capable of combining with a receptor and initiating action.
antagonist - a drug that opposes the effects of another by physiological or chemical action or by a competitive mechanism.
apoptosis - also called programmed cell death. A form of cell death in which a programmed sequence of events leads to the elimination
of old, unnecessary, and unhealthy cells.
arrhythmia - an abnormal heart rhythm. The heartbeats may be too slow, too rapid, too irregular, or too early.
astrocyte - a type of glial cell responsible for neurotransmission and neuronal metabolism.
autonomic dysreflexia - a potentially dangerous complication of spinal cord injury in which blood pressure rises to dangerous levels. If not treated,
autonomic dysreflexia can lead to stroke and possibly death.
axial traction - the application of a mechanical force to stretch the spine; used to relieve pressure by separating vertebral surfaces and
stretching soft tissues.
axon - the long, thin extension of a nerve cell that conducts impulses away from the cell body.
axonal growth cone - dynamic structures present at the tip of developing and regenerating axons that respond to chemical cues for growth and
direction.
central pattern generators (CPG) - neural circuits that produce self-sustaining patterns of behavior independent of their sensory input. Researchers have
found evidence of a locomotor CPG in the spinal cord that synchronizes muscle activity during alternating stepping of the
legs and feet.
cervical - the part of the spine in the neck region.
coccygeal - the part of the spine at the bottom of the spinal column, above the buttocks.
cytokine - a small protein released by immune cells that has a specific effect on the interactions between cells, or communications
between cells, or on the behavior of cells. dendrite - a short arm-like protuberance from a neuron. Dendrite is from the Greek
for "branched like a tree." disc - shortened terminology for an intervertebral disc, a disc-shaped piece of specialized tissue
that separates the bones of the spinal column.
electroejaculation - a technique that uses an electric probe to stimulate ejaculation.
embryonic stem cells - undifferentiated cells from the embryo that have the potential to become a wide variety of specialized
cell types. excitotoxicity - a neurological process that is the result of the release of excessive amounts of the neurotransmitter glutamate.
extracellular matrix - the material found around cells composed of structural proteins, specialized proteins, and proteoglycans.
fetal spinal cord cells - cells used by scientists to derive undifferentiated embryonic stem cells for transplant into the damaged spinal cord.
free radicals - highly reactive chemicals that attack molecules and modify their chemical structure.
functional electrical stimulation (FES) - the therapeutic use of low-level electrical current to stimulate muscle movement and restore useful movements such as standing
or stepping; also called functional neuromuscular stimulation.
glia -supportive cells in the brain and spinal cord. Glial cells are the most abundant cell types in the central nervous system.
There are three types: astrocytes, oligodendrocytes, and microglia. glutamate - an excitatory neurotransmitter.
growth-inhibiting proteins: protein molecules that inhibit axon regeneration.
guidance molecules - molecules that guide axons to their target. Some guidance molecules attract certain axons while repelling others.
hypothermia - abnormally low body temperature.
interneurons - neurons with axons that remain within the spinal cord.
intubation - the process of putting a tube into a hollow organ or passageway, often into the airway.
ligament - a tough band of connective tissue that connects various structures such as two bones.
lumbar - the part of the spine in the middle back, below the thoracic vertebrae and above the sacral vertebrae.
macrophage - a type of white blood cell that engulfs foreign material. Macrophages are key players in the immune response to foreign
invaders such as infectious microorganisms Macrophages also release substances that stimulate other cells of the immune system.
methylprednisolone - a steroid drug used to improve recovery from spinal cord injury.
microglia - glial cells that function as part of the immune system in the brain and spinal cord.
monocyte - a white blood cell that has a single nucleus and can engulf foreign material. Monocytes emigrate from blood into the tissues
of the body and evolve into macrophages.
myelin - a structure of cell membranes that forms a sheath around axons, insulating them and speeding conduction of nerve impulses.
myelotomy - a surgical procedure that cuts into the spinal cord.
neural prostheses - prosthetic devices that can respond to signals from the brain.
neurogenic pain - generalized pain that results from nervous system malfunction.
neuromodulation - a series of techniques employing electrical stimulation or the administration of medication by means of devices implanted
in the body. These techniques allow the treatment of a range of disorders including certain forms of pain, spasticity, tremor,
and urinary problems.
neuron - also known as a nerve cell; the structural and functional unit of the nervous system. A neuron consists of a cell body
and its processes: an axon and one or more dendrites.
neurostimulation - the act of stimulating neurons with electrical impulses delivered via electrodes attached to the brain.
neurotransmitter - a chemical released from neurons that transmits an impulse to another neuron, muscle, organ, or other tissue.
neurotrophic factors - proteins responsible for the growth and survival of neurons.
neutrophil - a type of white blood cell that engulfs, kills, and digests microorganisms.
oligodendrocyte - a type of nerve cell in the brain and spinal cord that surrounds and insulates axons.
olfactory ensheathing glia - non-myelinating glial cells that ensheath olfactory axons within both the PNS and CNS portions of the primary olfactory
pathway. They are being used in experiments to build bridges between damaged areas of the spinal cord.
paralysis - the inability to control movement of a part of the body.
paraplegia - a condition involving complete paralysis of the legs.
pressure sore (also known as a pressure ulcer or bed sore) - a reddened area or open sore caused by unrelieved pressure on the skin over bony areas such as the hip-bone or tailbone.
quadriplegia - a condition involving complete paralysis of the legs and partial or complete paralysis of the arms.
receptor - a structure on the surface or interior of a cell that selectively receives and binds to a specific substance.
regeneration - repair, regrowth, or restoration of tissues; opposite of degeneration.
rhizotomy - an operation to disconnect specific nerve roots in order to stop severe spasticity.
sacral - refers to the part of the spine in the hip area.
Schwann cell - the cell of the peripheral nervous system that forms the myelin sheath.
spasticity - increased tone in muscles of the arms and legs (due to lesions of the upper motor neurons).
spinal shock - a temporary physiological state that can occur after a spinal cord injury in which all sensory, motor, and sympathetic
functions of the nervous system are lost below the level of injury. Spinal shock can lower blood pressure to dangerous levels
and cause temporary paralysis.
stem cell - special cells that have the ability to grow into any one of the body's more than 200 cell types. Unlike mature cells, which
are permanently committed to their fate, stem cells can both renew themselves and create cells of other tissues.
synapse - a specialized junction between two nerve cells. At the synapse, a neuron releases neurotransmitters that diffuse across
the gap and activate receptors situated on the target cell.
T-cell - an immune system cell that produces substances called cytokines, which stimulate the immune response. thoracic - the part
of the spine at the upper-back to mid-back level.
vertebrae - the 33 hollow bones that make up the spine.
NIH Publication No. 03-160
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Prepared by:
Office of Communications and Public Liaison
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892
NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.
All NINDS-prepared information is in the public domain and may be freely copied. Credit to the NINDS or the NIH is appreciated.
Last updated September 18, 2012