You are in: eMedicine Specialties > Physical Medicine and Rehabilitation > SPINAL CORD INJURY Spinal Cord Injury: Definition, Epidemiology, PathophysiologyArticle Last Updated: Feb 21, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 4
  Author: Segun T Dawodu, MD, FAAPMR, FAANEM, CIME, DipMI(RCSed), Former Clinical Instructor, Mount Sinai Medical School, Current Director, Pain and Injuries Rehabilitation Services, PMRehab Pain & Sports Medicine Associates Segun T Dawodu is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, American College of Sports Medicine, American Medical Association, American Medical Informatics Association, Association of Academic Physiatrists, International Society of Physical and Rehabilitation Medicine, and Royal College of Surgeons of England Editors: Milton J Klein, DO, MBA, Consulting Physiatrist, Sewickley Valley Hospital, Allegheny General Hospital, Harmarville Rehabilitation Center, Ohio Valley General Hospital and Aliquippa Community Hospital; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Richard Salcido, MD, Chairman, Erdman Professor of Rehabilitation, Department of Physical Medicine and Rehabilitation, University of Pennsylvania School of Medicine; Kelly L Allen, MD, Consulting Staff, Department of Physical Medicine and Rehabilitation, Lourdes Regional Rehabilitation Center, Our Lady of Lourdes Medical Center; Denise I Campagnolo, MD, MS, Director of Multiple Sclerosis Clinical Research and Staff Physiatrist, Barrow Neurology Clinics, St. Joseph's Hospital and Medical Center; Investigator for Barrow Neurology Clinics; Director, NARCOMS Project for Consortium of MS Centers, Phoenix Author and Editor Disclosure Synonyms and related keywords: Brown-Séquard syndrome, central cord syndrome, anterior cord syndrome, conus medullaris syndrome, cauda equina syndrome DEFINITIONS AND PATHOPHYSIOLOGYSection 2 of 4
  Spinal cord injury (SCI) is an insult to the spinal cord resulting in a change, either temporary or permanent, in its normal motor, sensory, or autonomic function. The International Standards for Neurological and Functional Classification of Spinal Cord Injury is a widely accepted system describing the level and the extent of injury based on a systematic motor and sensory examination of neurologic function. The following terminology has developed around classification of SCI:
SCI can be sustained through different mechanisms with the following 3 common abnormalities leading to tissue damage:
Edema could ensue subsequent to any of these types of damage. The different clinical presentations of the above causes of tissue damage are explained further below. Spinal shock Spinal shock is a state of transient physiological (rather than anatomical) reflex depression of cord function below the level of injury with associated loss of all sensorimotor functions. An initial increase in blood pressure is noted due to the release of catecholamines, followed by hypotension. Flaccid paralysis, including of the bowel and bladder, is observed, and sometimes sustained priapism develops. These symptoms tend to last several hours to days until the reflex arcs below the level of the injury begin to function again (eg, bulbocavernosus reflex, muscle stretch reflex [MSR]). Neurogenic shock Neurogenic shock is manifested by the triad of hypotension, bradycardia, and hypothermia. Shock tends to occur more commonly in injuries above T6, secondary to the disruption of the sympathetic outflow from T1-L2 and to unopposed vagal tone, leading to decrease in vascular resistance with associated vascular dilatation. Neurogenic shock needs to be differentiated from spinal and hypovolemic shock. Hypovolemic shock tends to be associated with tachycardia. Autonomic dysreflexia See the article Autonomic Dysreflexia. In a recent study showing high incidence of autonomic dysfunction, including orthostatic hypotension and impaired cardiovascular control, assessment of autonomic function was recommended as a routine along with American Spinal Injury Association (ASIA) assessment. Motor strengths and sensory testing The extent of injury is defined by the ASIA Impairment Scale (modified from the Frankel classification), using the following categories:
Perform rectal examination to check motor function or sensation at the anal mucocutaneous junction. The presence of either is considered sacral-sparing. Definitions of complete and incomplete SCI are based on the above ASIA definition with sacral-sparing.
Sacral-sparing is evidence of the physiologic continuity of spinal cord long tract fibers with the sacral fibers located more at the periphery of the cord. Indication of the presence of sacral fibers is of significance in defining the completeness of the injury and the potential for some motor recovery. This finding tends to be repeated and better defined after the period of spinal shock. With the ASIA classification system, the terms paraparesis and quadriparesis now have become obsolete. The ASIA classification using the description of the neurologic level of injury is used in defining the type of SCI (eg, C8 ASIA A with zone of partial preservation of pinprick to T2). See the entire ASIA Impairment Scale (requires Acrobat reader). Other classifications of SCI include the following:
Muscle strengths are graded using the following Medical Research Council (MRC) scale of 0-5:
Muscle strength always should be graded according to maximum strength attained, no matter how briefly that strength is maintained during the examination. The muscles are tested with the patient supine. The following key muscles are tested in patients with SCI, and the corresponding level of injury is indicated:
Sensory testing is performed at the following levels:
Sensory scoring is for light touch and pinprick, as follows:
A score of zero is given if the patient cannot differentiate between the point of a sharp pin and the dull edge. Motor level - Determined by the most caudal key muscles that have muscle strength of 3 or above while the segment above is normal (= 5) Motor index scoring - Using the 0-5 scoring of each key muscle with total points being 25/extremity and a total possible score of 100 Sensory level - Most caudal dermatome with a normal score of 2/2 for both pinprick and light touch Sensory index scoring - Total score from adding each dermatomal score with possible total score (= 112 each for pinprick and light touch) Neurologic level of injury - Most caudal level at which both motor and sensory levels are intact, with motor level as defined above and sensory level defined by a sensory score of 2 Zone of partial preservation - This index is used only when the injury is complete. All segments below the neurologic level of injury with preservation of motor or sensory findings Skeletal level of injury - Level of greatest vertebral damage on radiograph Lower extremities motor score (LEMS) - Uses the ASIA key muscles in both lower extremities with a total possible score of 50 (ie, maximum score of 5 for each key muscle L2, L3, L4, L5, and S1 per extremity). A LEMS score of 20 or less indicates patients are likely to be limited ambulators. A LEMS of 30 or more suggests that patients are likely to be community ambulators. EPIDEMIOLOGYSection 3 of 4
SCI due to trauma is not a common condition, but it has a major effect on the injured person's functional, medical, financial, and psychosocial well-being. The most common causes of SCI include the following:
Other causes of SCI include the following:
The incidence of traumatic SCI in the United States is 30-60 new cases per million population, or 10,000 cases per year in the United States. Some sources cite 8 cases per 10,000 population per year. Figures on estimated prevalence vary from approximately 183,000 to 230,000 cases in the United States, the equivalent of 700-900 cases per million population. Race Incidence among whites is higher than among African Americans, which is higher than among Hispanics in the United States. Current studies indicate whites at 66.4%, African Americans at 21.1%, Hispanics at 8.8%, Asians at 1.6%, Native Americans at 1.1%, and others at 1%. Sex The male-to-female ratio of individuals with SCI in the United States is 4:1, ie, males constituting about 80%. Age More than 50% of all cases of SCI occur in persons aged 16-30 years. The median age is 26.4 years, while the mean age is 31.8 years and the mode age at injury is 19 years. Traumatic SCI is more common in persons younger than 40 years, while nontraumatic SCI is more common in persons older than 40 years. Greater mortality is reported in the older patients with SCI. In a recent study on pediatric SCI using information from the Kids' Inpatient Database (KID) and the National Trauma Database (NTDB), significant differences in the annual incidence rate of pediatric SCI were found to exist between patient populations stratified by race and sex. African Americans exhibit a significantly higher rate of pediatric SCI (1.53 cases per 100,000 children) than Native Americans (1.0 case per 100,000 children), Hispanics (0.87 case per 100,000 children), while Asians show a significantly lower incidence than all other races (0.36 per 100,000 children). Also, boys (2.79 cases per 100,000 children) are more than twice as likely to experience SCI as girls (1.15 cases per 100,000 children). The overall incidence of pediatric SCI in the United States is 1.99 cases per 100,000 children. From these data, 1455 children are estimated to be admitted to US hospitals each year for treatment of SCI. The etiology of pediatric SCI was also investigated, and the major causative factors were identified: motor vehicle accident (56%), accidental fall (14%), firearm injury (9%), and sports injury (7%). Of those children injured in a motor vehicle accident, 67.7% (n = 107) were reported as not wearing a seatbelt. The role of alcohol and drugs was also investigated and found to be involved in 30% (n = 82) of all pediatric SCI cases. Associated injuries Other injuries are often associated with traumatic SCI, and these include bone fractures (29.3%), loss of consciousness (17.8%), and traumatic brain injury affecting emotional/cognitive functioning (11.5%). Marital status Single persons sustain SCI more commonly than married persons. Approximately one third of patients with SCI sustained at least 15 years before remain single 20 years after injury. The marriage rate after SCI is about 59% below that of the general population of comparable gender, age, and marital status annually. The divorce rate annually among individuals with SCI within the first 3 years following injury is approximately 2.5 times that of the general population, while that of marriages contracted after the injury is about 1.7 times that of the general population. Marriage is more likely if the patient is a college graduate, previously divorced, paraplegic (not tetraplegic), ambulatory, living in a private residence, and independent in performance of ADL. The divorce rate among those married at the time of injury is higher if the patient is younger, female, African American, without children, nonambulatory, and previously divorced. The divorce rate among those who were married after the SCI is higher if the individual is male, has less than a college education, has a thoracic level injury, and has been divorced previously. Educational status At the time of injury, educational status figures are less than high school graduate at 39.8%, high school graduate at 49.9%, associate degree at 1.6%, bachelors degree at 5.9%, masters or doctorate degree at 2.1%, and other degrees at 0.7%. Level and type of injury The most common levels of injury on admission are C4, C5 (the most common), and C6, while the level for paraplegia is the thoracolumbar junction (T12). The most common type of injury on admission is ASIA level A. Season SCIs occur most frequently in the month of July and least commonly in February. The most common day when SCIs occur is Saturday. SCIs occur more frequently in the daylight hours, which may be due to the increased frequency of vehicular, diving, and other recreational sports accidents. Substance abuse The rate of alcohol intoxication among individuals who sustain SCI is 17-49%. Injuries by ASIA classification
The most common neurologic level of injury is C5. In paraplegia, T12 is the most common level. Employment Patients with SCI classified as ASIA D are more likely to be employed than individuals with ASIA A, B, and C. Persons employed tend to work full-time. Individuals who return to work within a year of injury tend to return to the same job. Those individuals who return to work after a year of injury tend to work for a different employer at a different job requiring retraining. The likelihood of employment after injury is greater in patients who are younger, male, and white and who have more formal education, higher reported intelligence quotient (IQ), greater functional capacity, and less severe injury. Patients with greater functional capacity, less severe injury, history of employment at the time of injury, greater motivation to return to work, nonviolent injury, and ability to drive are more likely to return to work, especially after more elapsed time following injury. Life expectancy Approximately 10-20% of patients who have sustained SCI do not survive to reach acute hospitalization, with approximately 3% of patients dying during acute hospitalization. Patients aged 20 years at the time of sustaining SCI have life expectancies of approximately 33 years as tetraplegics, 39 years as low tetraplegics, and 44 years as paraplegics. Individuals aged 60 years at the time of injury have a life expectancy of approximately 7 years as tetraplegics, 9 years as low tetraplegics, and 13 years as paraplegics. The annual death rate for patients with acute SCI is 750-1000 deaths per year in the United States. Recent studies also found that those with pain have less life satisfaction than those whose pain is well controlled, which may also affect a general outlook on life. In a 2006 study by Strauss et al, over the last 3 decades a 40% decline in mortality occurred during the critical first 2 years after injury. However, the decline in mortality over time in the post 2-year period is small and not statistically significant. Leading cause of death The leading cause of death in patients following SCI is pneumonia and other respiratory conditions, followed by heart disease, subsequent trauma, and septicemia. Among patients with incomplete paraplegia, the leading causes of death among incomplete paraplegics are cancer and suicide (1:1 ratio); among complete paraplegic patients, the leading cause of death is suicide, followed by heart disease. Suicide and alcohol-related deaths are also major causes of death in patients with SCI. The suicide rate is higher among the SCI population who are younger than 25 years. No statistical/epidemiological data have been compiled for nontraumatic SCI, but cancer alone may account for more SCI than trauma. Spondylosis is also a common cause of SCI. Trauma is more common in those younger than 40 years, while nontraumatic injury is more common in persons older than 40 years. REFERENCESSection 4 of 4
Spinal Cord Injury: Definition, Epidemiology, Pathophysiology excerpt Article Last Updated: Feb 21, 2007 |
