21st Century VA Independent Study Course: Medical Care of Persons with Spinal Cord Injury, Autonomic Nervous System, Symptoms, Treatment, Related Diseases, Motor Neuron Injury, Autonomic Dysreflexia
Department of Veterans Affairs
Smashwords Edition
Copyright 2011 Progressive Management
Questions? Suggestions? Comments? Concerns? Please contact the publisher directly at
Remember, the book retailer can't answer your questions, but we can!
* * * * * * * * * * *
Smashwords Edition, License Notes
This ebook is licensed for your personal enjoyment only. This ebook may not be re-sold or given away to other people. If you would like to share this book with another person, please purchase an additional copy for each person you share it with. If you're reading this book and did not purchase it, or it was not purchased for your use only, then you should return to Smashwords.com and purchase your own copy. Thank you for respecting the hard work of this author.
* * * * * * * * * * *
This is a privately authored news service and educational publication of Progressive Management. Our publications synthesize official government information with original material - they are not produced by the federal government. They are designed to provide a convenient user-friendly reference work to uniformly present authoritative knowledge that can be rapidly read, reviewed, or searched. Vast archives of important data that might otherwise remain inaccessible are available for instant review no matter where you are. This e-book format makes a great reference work and educational tool. There is no other reference book that is as convenient, comprehensive, thoroughly researched, and portable - everything you need to know, from renowned experts you trust. For over a quarter of a century, our news, educational, technical, scientific, and medical publications have made unique and valuable references accessible to all people. Our e-books put knowledge at your fingertips, and an expert in your pocket!
Medical Care of Persons with Spinal Cord Injury
Independent Study Course
Department of Veterans Affairs
Independent Study Outline
This program is designed to familiarize you with the unique aspects of SCI medicine. Its purpose is to help you gain knowledge so that any clinical encounter is more comfortable and informational for both you and the veteran served. This is not an attempt to make you a specialist, but to provide information so you can manage the patient until a subspecialist is available.
Upon completion of this self-study program, participants should be able to:
1. delineate the most common conditions affecting persons with SCI;
2. identify the changes in physiology, compensatory mechanisms, common disorders, physical functioning, and general health care needs of individuals with spinal cord injury;
3. specify the unique aspects of SCI medicine so that clinical encounters are more informative and comfortable for clinicians and the veterans served; and
4. describe the various treatments for persons with SCI.
1. PATHOPHYSIOLOGYAND CLASSIFICATION
Stephen P. Burns, MD
Objectives for the Learner
1. Identify the important tracts of the spinal cord and their location and functions.
2. Identify components of the neurologic examination of a person with SCI.
3. Describe findings of upper vs. lower motor neuron injury and their clinical significance in SCI.
4. Conduct motor and sensory evaluations that will provide accurate American Spinal Injury Association (ASIA) neurologic classification, along with identification of neurologic level, completeness of impairment, and clinical syndromes.
5. Know the five clinical syndromes of incomplete SCI.
6. Describe changes in autonomic nervous system function following SCI, including the effects secondary to impaired control.
Overview
The spinal cord is the primary pathway for transmission of information between the brain and the peripheral nervous system. Injury to the spinal cord causes disruption of movement, sensation, and autonomic nervous system function. Knowledge of the relevant neuroanatomy and the types of information carried by spinal cord tracts allows a more complete understanding of the consequences of SCI.
Anatomy and Physiology
Gray matter is centrally located in the cord and is the site of all nerve cell bodies, including those of the lower motor neurons that innervate muscle fibers. White matter contains groupings of axons called tracts. The tracts of primary importance for understanding loss of neurologic function after SCI are shown in Table 1-1.
TABLE 1-1.
MAJOR SPINAL CORD TRACTS AND THEIR FUNCTIONS
Tract / Location Within Cord / Direction of Signals / Function
Corticospinal: Lateral & anterior / Descending / Motor: Precise control of movement
Spinothalamic: Anterolateral / Ascending / Sensory: pain and temperature
Dorsal Columns: Posterior / Ascending / Sensory: proprioception and vibration
Pathophysiology of Spinal Cord Injury
Immediate events in acute injury include damage to tracts and motor neurons due to:
• Fracture of vertebral body with cord impingement from bony fragments
• Dislocation of vertebral bodies with loss of normal spinal canal diameter
• Transient narrowing of spinal canal diameter without bony fracture
• Traction on cord with disruption of neurologic structures
Only rarely is the complete cord transected. Subacute and secondary effects include cord edema, hemorrhage, ischemia, and onset of the inflammatory response.
Nontraumatic spinal cord conditions include multiple sclerosis, spondylotic myelopathy, syringomyelia, epidural abscess or hemorrhage, spinal cord tumor, virus-related transverse myelitis, spinal cord infarction, vitamin B12 deficiency, HIV-related myelopathy, and familial and degenerative spinal cord disease. Examples include epidural tumor metastasis and cervical spondylotic myelopathy (degenerative changes and ligament hypertrophy in the cervical spine with loss of canal diameter). Vascular compromise results when there is occlusion of critical branches of either the anterior or posterior spinal arteries resulting in cord ischemia and necrosis.
Upper vs. Lower Motor Neuron Injury
Upper motor neuron injury results from damage to the descending tracts with preservation of reflex spinal activity below the site of the lesion. Findings on neurologic examination include:
• Increased muscle tone (spasticity)
• Brisk reflexes
• Involuntary muscle spasms
• Relative preservation of muscle bulk
• Weakness or paralysis
• Extensor plantar responses
Lower motor neuron injury results from damage to the cell bodies or axons of the lower motor neurons. Findings include:
• Decreased muscle tone (flaccidity)
• Absent reflexes
• Marked muscle atrophy
• Weakness or paralysis
The spinal cord ends at about the level of the L1 vertebral body. The most caudal portion of the spinal cord is termed the conus medullaris. Most injuries above the conus medullaris will result in upper motor neuron findings in the lower extremities. An injury to the conus will damage both the terminal portion of the cord and multiple nerve roots, resulting in primarily lower motor neuron findings involving the low lumbar and sacral levels. The continuing bundle of nerve roots below the conus medullaris is named the cauda equina. Injury at this level will result in lower motor neuron findings exclusively. An occasional individual will have injury to the blood supply of the spinal cord (infarction) and show unexpected flaccidity and atrophy below the level of infarction, indicating an injury to anterior horn cells.
Some individuals with long-standing injuries will show gradual change from upper to lower motor neuron findings. Although this change is common in those who are 20 or 30 years from time of injury, it could indicate development of new cord pathology. For additional information, see Chapter 10.
Neurologic Examination
Accurate neurologic examination is required in treating both acute and chronic SCI. A standardized system for classification of neurologic function in SCI has been developed by the American Spinal Injury Association (ASIA) (References 1, 2). Use of a standardized system allows:
• Determination that neurologic function is remaining stable over time, even with different examiners
• Effective communication between physicians regarding patients
• Prediction of an expected level of function for a patient based on motor level (3); for example, persons with C5 ASIAA tetraplegia will require assist for transfers (4)
• Assessment of the effectiveness of interventions to treat SCI
The ASIA classification system uses findings from the motor and sensory examination to determine the level of injury and degree of preserved neurologic function. Additional components of the examination, as described below, allow further characterization of impairment.
The motor examination for ASIA classification involves manual muscle testing of ten key muscles bilaterally (Table 1-2). Strength is graded on a 0-5 scale: 0=absent; 1=trace; 2=less than antigravity; 3=antigravity; 4=less than normal; 5=normal. The examination also includes assessment of voluntary anal contraction, graded as either present or absent.
The sensory examination required for ASIA classification requires testing of light touch sensation and sharp/dull discrimination in each dermatome from C2 through S4-S5 (tested as a single dermatome). The presence or absence of sensation on rectal examination is also recorded (see Dermatone Chart from ASIA Standards).
TABLE 1-2.
KEY MUSCLES USED IN NEUROLOGIC TESTING
Root / Movement / Muscle(s)
C5: Elbow Flexion / Biceps, brachialis
C6: Wrist Extension / Extensor carpi radialis longus and brevis
C7: Elbow Extension / Triceps
C8: Finger Flexion / Flexor digitorum profundus to middle finger
T1: Finger Abduction / Abductor digiti minimi
L2: Hip Flexion / Iliopsoas
L3: Knee Extension / Quadriceps
L4: Ankle Dorsiflexion / Tibialis anterior
L5: Long Toe Extension / Extensor hallucis longus
S1: Ankle Plantarflexion / Gastrocnemius and soleus
Additional examination components
Although not required for ASIA classification, the following are essential components of a comprehensive neurologic examination.
• Motor: Depending on the neurologic status of the patient, additional muscles to test may include the diaphragm (assessed with either fluoroscopy or measurement of vital capacity), deltoids, hip extensors, and hip abductors.
• Sensory: Assessment of vibratory sensation and proprioception tests the function of the dorsal columns.
• Deep tendon reflexes (DTR) and spasticity: These give information on degree of upper vs. lower motor neuron involvement. In the first few weeks following SCI, there is a depression or loss of DTRs, which in the case of upper motor neuron injury is followed by development of brisk reflexes and spasticity. In the case of lower motor neuron injury, reflexes remain absent and there is no development of spasticity.
Neurologic Classification
Neurologic level
By convention, the neurologic level refers to the most caudal level with normal function, rather than the first level with abnormal function. For sensation, the neurologic level is defined as the most caudal level with normal light touch and sharp/dull discrimination, provided all rostral levels have normal sensory function. For motor function, the neurologic level is defined as the most caudal key muscle with at least 3/5 strength, provided that all rostral levels have normal motor function.
The level is determined separately for motor and sensory functions, as well as for right and left sides, since frequently there is asymmetry or a lack of correspondence between motor and sensory level. For example, a level of C7 motor, C6 sensory would indicate a patient with at least 3/5 strength in the C7 key muscle (triceps) bilaterally with normal strength in all rostral groups, and with sensory function intact in the C6 dermatome and in all rostral dermatomes.
ASIA Impairment Scale
The ASIA Impairment Scale defines complete and incomplete injuries and categorizes the incomplete injuries as shown in Table 1-3. A complete injury is defined as an absence of motor and sensory function in the S4-S5 dermatome or sensation on rectal examination, and an incomplete injury is defined as a preservation of sensation in the S4-S5 dermatome or sensation on rectal examination (5).
The ASIA Impairment Scale is a modification of a previous scale, the Frankel Scale, and there is a general agreement between the two scales, such that an ASIA C is similar to a Frankel C. Many individuals with chronic SCI remain classified with this older terminology.
TABLE 1-3.
ASIA IMPAIRMENT SCALE (ADAPTED FROM ASIA DEFINITIONS)
A= Motor complete, sensory complete:
No motor or sensory function is preserved in the sacral segments S4-S5.
B= Motor complete, sensory incomplete:
Sensory but not motor function is present below NL* and includes the S4-S5 dermatome.
C=Motor incomplete, sensory incomplete:
Motor function is preserved below NL, and the majority of key muscles below the NL are less than grade 3.
D=Motor incomplete, sensory incomplete:
Motor function is preserved below NL, and at least half of key muscles below NL are grade 3 or more.
E= Normal:
Motor and sensory function are normal.
*Neurologic level
Clinical Syndromes
Distinct patterns of neurologic deficit are recognized with incomplete SCI. It is common for certain pathways to be relatively spared from injury, and this results in recognizable syndromes.
Central cord syndrome
• Occurs with cervical level injuries, often in older individuals with preexisting cervical spinal canal narrowing
• Results from preferential damage to upper limb corticospinal tracts
• Greater weakness in upper limbs than in lower limbs
Brown-Sequard syndrome
• Results from asymmetric cord lesion, classically thought of as a cord hemisection, although a true hemisection is uncommon with trauma
• Relatively greater proprioceptive and motor loss ipsilateral to the lesion, with contralateral loss of sensitivity to pain and temperature
Anterior cord syndrome
• Results from occlusion of anterior spinal artery
• Variable loss of motor function and of sensitivity to pain and temperature with preservation of proprioception
Conus medullaris syndrome
• Injury to the sacral cord and lumbar nerve roots within the spinal canal
• Usually results in lower motor neuron findings, although sacral reflexes may occasionally be preserved
Cauda equina syndrome
• Injury to the lumbosacral nerve roots within the neural canal resulting in areflexic bladder, bowel, and lower limbs
• A purely lower motor neuron injury
Alteration of Autonomic Nervous System Function
Loss of motor and sensory function is obvious in a person with SCI. Alterations of autonomic function are not as visible, although they have significant consequences for the individual. The sympathetic supply to the entire body, including the head, leaves the spinal cord through the roots between T1 and L2. Parasympathetic supply to the body is derived from the vagus nerve (usually spared in SCI) and sacral roots. Varying degrees of dysfunction result based on the level of the injury. Changes in autonomic function are in fact a source of many medical complications in persons with SCI.
• A complete cervical-level lesion, with interruption of all sympathetic input to the body, may result in unopposed vagal input to the heart causing marked bradycardia.
• Impairment of vasoconstriction may result in a baseline low blood pressure as well as orthostatic hypotension for an individual with tetraplegia6.
• Autonomic dysreflexia results from loss of descending sympathetic control of responses to noxious stimuli (see Chapter 3) (7).
• Impaired ability to modulate blood flow to the skin and control of sweat gland secretion alters the control of thermoregulation. The normal temperature of a person with SCI may be 1-2 degrees Fahrenheit cooler than for a neurologically intact person. Thus, a relatively mild temperature elevation may actually indicate a significant infection. Persons with SCI are also predisposed to development of body temperature elevation in a warm environment.
• Neurogenic bladder dysfunction results from impaired storage and emptying.
• Neurogenic bowel dysfunction results from impaired peristalsis and evacuation.
• Sexual dysfunction derives from impaired sensation, erection, ejaculation, or vaginal lubrication.
Self-Study Review
1. What are the important tracts of the spinal cord? Where are they located? What direction do they travel? What are their functions?
2. What are the clinical signs and implications for upper motor neuron injury vs. lower motor neuron injury? Where are these types of injury most likely to occur? Which types of SCI are likely to occur immediately? Which types of injury are more likely to be subacute or secondary? What are some types of nontraumatic injury?
3. List the key muscles to be tested for motor function along with the movement and corresponding neurologic root.
4. How are the sensory and motor neurologic levels defined?
5. What are the characteristics of the five severity levels on the ASIA Impairment Scale?
6. What are the differential diagnostic features of five SCI syndromes?
7. Describe the effects of autonomic dysfunction on several organ systems and the corresponding impairment of control.