This section offers a little insight into the world of spinal cord injury. This information is meant to serve as reference for those in and around the SCI community, and has been gathered from numerous sources across the web to better serve those interested in learning more.
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The spinal cord is a bundle of nerve cells and fibers wrapped together extending down from the brain stem to the lower back. The cord is protected by a kind of bone tunnel made up of vertebrae which are separated by membranes called discs. The brain sends electrical signals through the spinal cord, giving instructions to the legs, arms, and other areas of the body.
The spinal column is separated into 5 specific functional areas:
There are 33 vertebrae that make up the bone structure of the spinal column, with the last four being fused together to make the tailbone.
Each vertebrae is separated by a soft bone substance, called a disc, which acts as a cushion and a seal at the same time.
There are seven cervical bones or vertebrae.The cervical bones are designed to allow flexion, extension, bending, and turning of the head. They are smaller than the other vertebrae, which allows a greater amount of movement.
Each cervical vertebra consists of two parts, a body and a protective arch for the spinal cord called the neural arch. Fractures or injuries can occur to the body, lim pedicles, or processes. Each vertebra articulates with the one above it and the one below it.
In the chest region the thoracic spine attaches to the ribs. There are 12 vertebrae in the thoracic region.
The spinal canal in the thoracic region is relatively smaller than the cervical or lumbar areas. This makes the thoracic spinal cord at greater risk if there is a fracture.
The motion that occurs in the thoracic spine is mostly rotation. The ribs prevent bending to the side. A small amount of movement occurs in bending forward and backward.
The lumbar vertebrae are large, wide, and thick. There are five vertebrae in the lumbar spine. The lowest lumbar vertebra, L5, articulates with the sacrum. The sacrum attaches to the pelvis.
The main motions of the lumbar area are bending forward and extending backwards. Bending to the side also occurs.
Just like the spinal column is divided into cervical, thoracic, and lumbar regions, so is the spinal cord. Each portion of the spinal cord is divided into specific neurological segments.
The cervical spinal cord is divided into eight levels. Each level contributes to different functions in the neck and the arms. Sensations from the body are similarly transported from the skin and other areas of the body from the neck, shoulders, and arms up to the brain.
In the thoracic region the nerves of the spinal cord supply muscles of the chest that help in breathing and coughing. This region also contains nerves in the sympathetic nervous system.
The lumbosacral spinal cord and nerve supply legs, pelvis, and bowel and bladder. Sensations from the feet, legs, pelvis, and lower abdomen are transmitted through the lumbosacral nerves and spinal cord to higher segments and eventually the brain.
There are many nerve pathways that transmit signals up and down the spinal cord. Some supply sensation from the skin and outer portions of the body. Others supply sensation from deeper structures such as the organs in the belly, the pelvis, or other areas. Other nerves transmit signals from the brain to the body. Still, others work at the level of the spinal cord and act as “go-betweens” in the signal transmission process.
The upper motor neuron refers to injuries that are above the level of the anterior horn cell. This results in a spastic type of paralysis. Conversely, the lower motor neuron injury refers to an injury at or below the anterior horn cell that results in the flaccid type paralysis. The terms neurogenic bowel and neurogenic bladder are used to describe abnormal bowel and bladder function and can be classified as either an upper motor neuron or lower motor neuron type of problem. In general, those patients with an upper motor neuron paralysis will have an upper motor neuron bowel and bladder, and those with lower motor neuron injuries will have a lower motor neuron picture of the bowel and bladder. Adequate bowel and bladder management is critical for adequate reintegration of the patient/client into the community and hopefully into the workplace.
Feelings from the body such as hot, cold, pain, and touch, are transmitted to the skin and other parts of the body to the brain where sensations are “felt”. These pathways are called the sensory pathways.
Once signals enter the spinal cord, they are sent up to the brain. Different types of sensation are sent in different pathways, called “tracts”. The tracts that carry sensations of pain and temperature to the brain are in the middle part of the spinal cord. These tracts are called the “spinothalamic”. Other tracts carry sensation of position and light touch. These nerve impulses are carried along the back part of the spinal cord in what are called “dorsal columns” of the spinal cord.
Another type of special nerves are the autonomic nerves. In spinal cord injuries, they are very important. The autonomic nerves are divided into two types: the sympathetic and parasympathetic nerves.
The autonomic nervous system influences the activities of involuntary (also known as smooth) muscles, the heart muscle, and glands that release certain hormones. It controls cardiovascular, digestive, and respiratory systems. These systems work in a generally “involuntary” fashion. The primary role of the autonomic nervous system is to maintain a stable internal environment within the body. The heart and blood vessels are controlled by the autonomic nervous system. The sympathetic nerves help to control blood pressure based on the physical demands placed on the body. It also helps to control heart rate. The sympathetic nerves, when stimulated, cause the heart to beat faster.
The sympathetic nerves also cause constriction of the blood vessels throughout the body. When this happens, the amount of blood that is returned to the heart increases. These effects will increase blood pressure. Other effects include an increase in sweating and increased irritability or a sensation of anxiety.
When spinal cord injury is at or above the T6 level the sympathetic nerves below the injury become disconnected from the nerves above. They continue to operate automatically once the period of spinal shock is over. Anything that stimulates the sympathetic nerves can cause them to become overactive. This over-activity of the sympathetic nerves is what is called autonomic dysreflexia.
The parasympathetic nerves act in an opposite manner to the sympathetic nerves. These nerves tend to dilate blood vessels and slow down the heart. The most important nerve that carries parasympathetic fibers is the vagus nerve. This nerve carries parasympathetic signals to the heart to decrease heart rate. Other nerves supply the blood vessels to the organs of the abdomen and skin.
The parasympathetic nerves arise from two areas. The fibers that supply the organs of the abdomen, heart, lungs and skin above the waist begin at the level of the brain and very high spinal cord. The nerves that supply the reproductive organs, pelvis, and leg begin at the sacral level, or lowest part of the spinal cord. After a spinal cord injury, the parasympathetic nerves that begin at the brain continue to work, even during the phase of spinal shock. When dysreflexia occurs, the parasympathetic nerves attempt to control rapidly increasing blood pressure by slowing down the heart.
A spinal cord injury (SCI) is categorized as either “complete” or “incomplete”. A “complete” SCI means a total loss of function and sensation below the affected vertebrae, and an “incomplete” SCI means only partial loss of function or sensation.
The spine is the central support of the body. It provides a framework to support the trunk and rigid protection for the spinal cord. Portions of the spine surround the spinal cord providing bony protection for the spinal cord just as the skull protects the brain with a bony shell.
The spine is made up of 24 segments called vertebrae. These bones are stacked on top of one another.
There are seven vertebrae in the neck called cervical vertebrae. These are often referred to as C1 through C7 (top to bottom). The skull sits atop C1.
The 12 vertebrae in the region of the chest are called thoracic vertebrae. From top to bottom, these are referred to as T1 through T12. Two ribs are connected to each thoracic vertebra, one on either side. All the ribs and thoracic vertebrae together form the thoracic cage which surrounds and protects the heart and lungs.
The abdominal portion of the spine is formed by five lumbar vertebrae, referred to as L1 through L5. These vertebrae are much larger than those of the thoracic spine, which in turn are larger and stronger than the cervical vertebrae. The vertebrae increase in size from top to bottom to accommodate the increasing body weight.
Except for C1 and C2, all the vertebrae are similar in structure. A typical vertebrae is shown here. Each vertebrae has a drum shaped front section called the body. The purpose of the body is to support weight. Toward the back of the vertebrae, a bony arch (the lamina) surrounds a space called the spinal canal. The spinal cord and nerve roots are located in the spinal canal. Bony projections from the arch, called processes, serve as points of attachment for ligaments and muscles. The rear-most projection of each vertebrae is called the spinous process and is the only part of the vertebrae that can be felt through the skin (the ridge down the middle of your back).
The manner in which the vertebrae are stacked is shown here. Between vertebral bodies are small fibrocartilage cushions called discs. These act, in part, as shock absorbers. Strong ligaments bind the vertebrae together. Although the ligaments will stretch to permit limited movement, they are rigid enough to maintain alignment of the spinal canal as it passes through each vertebrae. The vertebrae, discs, and ligaments are able to maintain the correct alignment and consequently protect the spinal cord against all but the most violent injury.
Between each adjoining vertebrae on each side of the spinal canal are openings called foramina. The foramina are openings for the nerve roots to pass out of the spinal canal and for blood vessels to pass into the canal.
The L5 vertebrae rests on the sacrum, a large bone made up of several smaller vertebrae-like bones which have fused together. The sacrum forms a base for the spine and the back part of the pelvis.
According to the National Spinal Cord Injury Statistical Center at UAB, the distribution of the causes of SCI has changed drastically from 2015-2018/19.
Researchers have estimated that, as of 2019, 17,730 new SCI cases occur each year, and between 249,000 and 363,000 people are currently living with SCI in the United States.
The average age at injury has moved from 29 years in the 1970s to 43 years in 2018.
The length of hospital stays is declining with the average stay in hospital acute care at 11 days – down from 24 in the 1970’s – and rehabilitation stays at 31 days – down from 98 days in the 1970s.
54 injuries per million population or 17,730 injuries in the US each year
Most researchers feel that these numbers represent significant under- reporting. Injuries not recorded include cases where the patient died instantaneously or soon after the injury, cases with little or no remaining neurological deficit, and people who have neurologic problems secondary to trauma, but are not classified as SCI.
People who return to work in the first year post-injury usually return to the same job for the same employer. People who return to work after the first year post-injury either worked for different employers or were students who found work.
Lengths of stay in the hospital acute care unit have declined from 24 days in the 1970s to 11 days recently. Rehabilitation lengths of stay have also declined from 98 days in the 1970s to 31 days recently.
Average charges (2018 dollars) Note: Specific cases are considerably higher.
Primary Payer of Medical Costs at Time of Injury:
Primary Payer of Medical Costs 10 years Post Injury: (Many people have more than one source of payment.)
Residence at discharge
There is no apparent relationship between severity of injury and nursing home admission, indicating that admission is caused by other factors (i.e. family can’t take care of person, medical complications, etc.) Nursing home admission is more common among elderly persons.
Since 2015, about 30% of persons with SCI are re-hospitalized one or more times during any given year following injury. Among those re-hospitalized, the length of hospital stay averages about 19 days. Diseases of the genitourinary system are the leading cause of re-hospitalization, followed by disease of the skin. Respiratory, digestive, circulatory, and musculoskeletal diseases are also common causes.
Overall, 81% of SCI patients who survive the first 24 hours are still alive 10 years later, compared with 98% of the non-SCI population given similar age and sex.
The most common cause of death is respiratory ailment, whereas, in the past it was renal failure. An increasing number of people with SCI are dying of unrelated causes such as cancer or cardiovascular disease, similar to that of the general population. Mortality rates are significantly higher during the first year after injury than during subsequent years.
Majority of above content: National Spinal Cord Injury Statistical Center at UAB