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ANATOMY AND PHYSIOLOGY 133
ASIA Impairment Scale (AIS) Steps in Classification
The following order is recommended for determining the classification of individuals with SCI.
1. Determine sensory levels for right and left sides.
The sensory level is the most caudal, intact dermatome for both pin prick and light touch sensation.
2. Determine motor levels for right and left sides.
Defined by the lowest key muscle function that has a grade of at least 3 (on supine testing), providing the key muscle functions represented by segments above that level are judged to be intact (graded as a 5).
Note: in regions where there is no myotome to test, the motor level is presumed to be the same as the sensory level, if testable motor function above that level is also normal.
3. Determine the neurological level of injury (NLI) This refers to the most caudal segment of the cord with intact sensation and antigravity (3 or more) muscle function strength, provided that there is normal (intact) sensory and motor function rostrally respectively.
The NLI is the most cephalad of the sensory and motor levels determined in steps 1 and 2.
4. Determine whether the injury is Complete or Incomplete.
(i.e. absence or presence of sacral sparing)
If voluntary anal contraction = No AND all S4-5 sensory scores = 0 AND deep anal pressure = No, then injury is Complete.
Otherwise, injury is Incomplete.
5. Determine ASIA Impairment Scale (AIS) Grade:
Is injury Complete? If YES, AIS=A and can record
Is injury Motor Complete? If YES, AIS=B
(No=voluntary anal contraction OR motor function more than three levels below the motor level on a given side, if the patient has sensory incomplete classification)
Are at least half (half or more) of the key muscles below the neurological level of injury graded 3 or better?
If sensation and motor function is normal in all segments, AIS=E Note: AIS E is used in follow-up testing when an individual with a documented SCI has recovered normal function. If at initial testing no deficits are found, the individual is neurologically intact; the ASIA Impairment Scale does not apply.
AIS=C NO
NO
NO YES
AIS=D Movement Root level
Shoulder: Flexion, extension, abduction, adduction, internal C5 and external rotation
Elbow: Supination
Elbow: Pronation C6
Wrist: Flexion
Finger: Flexion at proximal joint, extension. C7 Thumb: Flexion, extension and abduction in plane of thumb Finger: Flexion at MCP joint C8 Thumb: Opposition, adduction and abduction perpendicular to palm
Finger: Abduction of the index finger T1
Hip: Adduction L2
Hip: External rotation L3
Hip: Extension, abduction, internal rotation L4 Knee: Flexion
Ankle: Inversion and eversion Toe: MP and IP extension
Hallux and Toe: DIP and PIP flexion and abduction L5
Hallux: Adduction S1
A = Complete. No sensory or motor function is preserved in the sacral segments S4-5.
B = Sensory Incomplete. Sensory but not motor function is preserved below the neurological level and includes the sacral segments S4-5 (light touch or pin prick at S4-5 or deep anal pressure) AND no motor function is preserved more than three levels below the motor level on either side of the body.
C = Motor Incomplete. Motor function is preserved at the most caudal sacral segments for voluntary anal contraction (VAC) OR the patient meets the criteria for sensory incomplete status (sensory function preserved at the most caudal sacral segments (S4-S5) by LT, PP or DAP), and has some sparing of motor function more than three levels below the ipsilateral motor level on either side of the body.
(This includes key or non-key muscle functions to determine motor incomplete status.) For AIS C – less than half of key muscle functions below the single NLI have a muscle grade ≥ 3.
D = Motor Incomplete. Motor incomplete status as defined above, with at least half (half or more) of key muscle functions below the single NLI having a muscle grade ≥ 3.
E = Normal. If sensation and motor function as tested with the ISNCSCI are graded as normal in all segments, and the patient had prior deficits, then the AIS grade is E. Someone without an initial SCI does not receive an AIS grade.
Using ND: To document the sensory, motor and NLI levels, the ASIA Impairment Scale grade, and/or the zone of partial preservation (ZPP) when they are unable to be determined based on the examination results.
INTERNATIONAL STANDARDS FOR NEUROLOGICAL CLASSIFICATION OF SPINAL CORD INJURY
ZPP (lowest dermatome or myotome on each side with some preservation)
Muscle Function Grading 0 = total paralysis
1 = palpable or visible contraction
2 = active movement, full range of motion (ROM) with gravity eliminated 3 = active movement, full ROM against gravity
4 = active movement, full ROM against gravity and moderate resistance in a muscle specific position
5 = (normal) active movement, full ROM against gravity and full resistance in a functional muscle position expected from an otherwise unimpaired person 5* = (normal) active movement, full ROM against gravity and sufficient resistance to be considered normal if identified inhibiting factors (i.e. pain, disuse) were not present NT = not testable (i.e. due to immobilization, severe pain such that the patient cannot be graded, amputation of limb, or contracture of > 50% of the normal ROM)
Sensory Grading 0 = Absent
1 = Altered, either decreased/impaired sensation or hypersensitivity 2 = Normal
NT = Not testable
When to Test Non-Key Muscles:
In a patient with an apparent AIS B classification, non-key muscle functions more than 3 levels below the motor level on each side should be tested to most accurately classify the injury (differentiate between AIS B and C).
0 = absent 1 = altered 2 = normal NT = not testable
0 = absent 1 = altered 2 = normal NT = not testable
C2
C3 C4
S3
S2
L5S1 L5 L4
L3 L2 L1 T12 T11 T10 T9 T8 T7 T6 T5 T4 T3 C4 C3 C2
T2 C5
T1 C6
Palm
Dorsum C6C8
C7 0 = absent
1 = altered 2 = normal NT = not testable
Dorsum C6 C8
C7 S4-5
•Key Sensory Points
0 = absent 1 = altered 2 = normal NT = not testable
0 = absent 1 = altered 2 = normal NT = not testable
C2
C3 C4
S3
S2
L5S1 L5 L4
L3 L2 L1 T12 T11 T10 T9 T8 T7 T6 T5 T4 T3 C4 C3 C2
T2 C5
T1 C6
Palm
Dorsum C6C8
C7 0 = absent
1 = altered 2 = normal NT = not testable
Dorsum C6 C8
C7 S4-5 •Key Sensory
Points
C5 C6 C7 C8 T1
L2 L3 L4 L5 S1 MOTOR
KEY MUSCLES
SENSORY KEY SENSORY POINTS
Pin Prick (PPR) Light Touch (LTR)
(VAC) Voluntary anal contraction (Yes/No) Comments (Non-key Muscle? Reason for NT? Pain?):
NEUROLOGICAL LEVELS Steps 1-5 for classification
as on reverse
1. SENSORY 2. MOTOR
R L 3. NEUROLOGICAL LEVEL OF INJURY
(NLI)
4. COMPLETE OR INCOMPLETE?
Incomplete = Any sensory or motor function in S4-5 5. ASIA IMPAIRMENT SCALE (AIS)
(In complete injuries only)
ZONE OF PARTIAL PRESERVATION
Most caudal level with any innervation
SENSORY MOTOR
R L
REV 02/13 This form may be copied freely but should not be altered without permission from the American Spinal Injury Association.
134 CHAPTER 7 n Spine and Spinal Cord Trauma
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neurological improvement or deterioration on subsequent examinations.
neUrogeniC sHoCk VersUs spinaL sHoCk
Neurogenic shock results in the loss of vasomotor tone and sympathetic innervation to the heart. Injury to the cervical or upper thoracic spinal cord (T6 and above) can cause impairment of the descending sympathetic pathways. The resultant loss of vasomotor tone causes vasodilation of visceral and peripheral blood vessels, pooling of blood, and, consequently, hypotension.
Loss of sympathetic innervation to the heart can cause bradycardia or at least the inability to mount a tachycardic response to hypovolemia. However, when shock is present, it is still necessary to rule out other sources because hypovolemic (hemorrhagic) shock is the most common type of shock in trauma patients and can be present in addition to neurogenic shock. The physiologic effects of neurogenic shock are not reversed with fluid resuscitation alone, and n FIGURE 7-3 Key Myotomes. Myotomes are used to evaluate the level of motor function.
pitfAll pReveNtioN
The sensory and motor examination is confounded by pain.
• When necessary, repeat the exam multiple times.
A patient is able to observe the examination itself, which may alter the findings.
• Attempt to prevent or distract the patient from watching your clinical exam.
A patient’s altered level of consciousness limits your ability to perform a defini-tive neurological examination.
• Always presume the presence of an injury, restrict movement of the spine while managing life-threatening injuries, reassess, and perform radiographic evaluation as necessary.
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massive resuscitation can result in fluid overload and/
or pulmonary edema. Judicious use of vasopressors may be required after moderate volume replacement, and atropine may be used to counteract hemodynamically significant bradycardia.
Spinal shock refers to the flaccidity (loss of muscle tone) and loss of reflexes that occur immediately after spinal cord injury. After a period of time, spasticity ensues.
eFFeCts oF spine injUry on otHer organ systeMs
When a patient’s spine is injured, the primary concern should be potential respiratory failure. Hypoventilation can occur from paralysis of the intercostal muscles (i.e., injury to the lower cervical or upper thoracic spinal cord) or the diaphragm (i.e., injury to C3 to C5).
The inability to perceive pain can mask a potentially serious injury elsewhere in the body, such as the usual signs of acute abdominal or pelvic pain associated with pelvic fracture.
documeNtAtioN of spiNAl coRd iNjuRies
Spinal cord injuries can be classified according to level, severity of neurological deficit, spinal cord syndromes, and morphology.
LeVeL
The bony level of injury refers to the specific vertebral level at which bony damage has occurred. The neurological level of injury describes the most caudal segment of the spinal cord that has normal sensory and motor function on both sides of the body. The neurological level of injury is determined primarily by clinical examination. The term sensory level is used when referring to the most caudal segment of the spinal cord with normal sensory function. The motor level is defined similarly with respect to motor function as the lowest key muscle that has a muscle-strength grade of at least 3 on a 6-point scale. The zone of partial preservation is the area just below the injury level where some impaired sensory and/or motor function is found.
Frequently, there is a discrepancy between the bony and neurological levels of injury because the spinal nerves enter the spinal canal through the foramina and ascend or descend inside the spinal canal before actually entering the spinal cord. Determining the level of injury on both sides is important.
Apart from the initial management to stabilize the bony injury, all subsequent descriptions of injury level are based on the neurological level.
seVerity oF neUroLogiCaL deFiCit
Spinal cord injury can be categorized as:
• Incomplete or complete paraplegia (thoracic injury)
• Incomplete or complete quadriplegia/
tetraplegia (cervical injury)
Any motor or sensory function below the injury level constitutes an incomplete injury and should be documented appropriately. Signs of an incomplete injury include any sensation (including position sense) or voluntary movement in the lower extremities, sacral sparing, voluntary anal sphincter contraction, and voluntary toe flexion. Sacral reflexes, such as the bulbocavernosus reflex or anal wink, do not qualify as sacral sparing.
spinaL Cord syndroMes
Characteristic patterns of neurological injury are encountered in patients with spinal cord injuries, such as central cord syndrome, anterior cord syndrome, and Brown-Séquard syndrome. It is helpful to recognize these patterns, as their prognoses differ from complete and incomplete spinal cord injuries.
Central cord syndrome is characterized by a dispro-portionately greater loss of motor strength in the upper extremities than in the lower extremities, with varying degrees of sensory loss. This syndrome typically occurs after a hyperextension injury in a patient with preexisting cervical canal stenosis.
The mechanism is commonly that of a forward fall resulting in a facial impact. Central cord syndrome can occur with or without cervical spine fracture or dislocation. The prognosis for recovery in central cord injuries is somewhat better than with other incom-plete injuries. These injuries are frequently found in patients, especially the elderly, who have underlying spinal stenosis and suffer a ground-level fall.
Anterior cord syndrome results from injury to the motor and sensory pathways in the anterior part of the cord. It is characterized by paraplegia and a bilateral loss of pain and temperature sensation. However, sensation from the intact dorsal column (i.e., position, vibration, and deep pressure sense) is preserved. This syndrome has the poorest prognosis of the incomplete DOCUMENTATION OF SPINAL CORD INJURIES 135
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injuries and occurs most commonly following cord ischemia.
Brown-Séquard syndrome results from hemisection of the cord, usually due to a penetrating trauma. In its pure form, the syndrome consists of ipsilateral motor loss (corticospinal tract) and loss of position sense (dorsal column), associated with contralateral loss of pain and temperature sensation beginning one to two levels below the level of injury (spino-thalamic tract). Even when the syndrome is caused by a direct penetrating injury to the cord, some recovery is usually achieved.
MorpHoLogy
Spinal injuries can be described as fractures, fracture-dislocations, spinal cord injury without radiographic abnormalities (SCIWORA), and penetrating injuries.
Each of these categories can be further described as stable or unstable. However, determining the stability of a particular type of injury is not always simple and, indeed, even experts may disagree. Particularly during the initial treatment, all patients with radiographic evidence of injury and all those with neurological deficits should be considered to have an unstable spinal injury. Spinal motion of these patients should be restricted, and turning and/or repositioning requires adequate personnel using logrolling technique until consultation with a specialist, typically a neurosurgeon or orthopedic surgeon.
specific types of spiNAl iNjuRies
Spinal injuries of particular concern to clinicians in the trauma setting include cervical spine fractures, thoracic spine fractures, thoracolumbar junction fractures, lumbar fractures, penetrating injuries, and the potential for associated blunt carotid and vertebral vascular injuries.
CerViCaL spine FraCtUres
Cervical spine injuries can result from one or a combination of the following mechanisms of injury:
axial loading, flexion, extension, rotation, lateral bending, and distraction.
Cervical spine injury in children is a relatively rare event, occurring in less than 1% of cases. Of note, upper cervical spine injuries in children (C1–C4) are almost twice as common as lower cervical spine injuries.
Additionally, anatomical differences, emotional
distress, and inability to communicate make evaluation of the spine even more challenging in this population.
(See Chapter 10: Pediatric Trauma.)
Specific types of cervical spine injuries of note to clinicians in the trauma setting are atlanto-occipital dislocation, atlas (C1) fracture, C1 rotary subluxation, and axis (C2) fractures.
Atlanto-Occipital Dislocation
Craniocervical disruption injuries are uncommon and result from severe traumatic flexion and distraction. Most patients with this injury die of brainstem destruction and apnea or have profound neurological impairments (e.g., ventilator dependence and quadriplegia/tetraplegia). Patients may survive if they are promptly resuscitated at the injury scene.
Atlanto-occipital dislocation is a common cause of death in cases of shaken baby syndrome.
Atlas (C1) Fracture
The atlas is a thin, bony ring with broad articular surfaces. Fractures of the atlas represent approximately 5% of acute cervical spine fractures, and up to 40%
of atlas fractures are associated with fractures of the axis (C2). The most common C1 fracture is a burst fracture (Jefferson fracture). The typical mechanism of injury is axial loading, which occurs when a large load falls vertically on the head or a patient lands on the top of his or her head in a relatively neutral position. Jefferson fractures involve disruption of the anterior and posterior rings of C1 with lateral displacement of the lateral masses. The fracture is best seen on an open-mouth view of the C1 to C2 region and axial computed tomography (CT) scans (nFIGURE 7-4).
These fractures usually are not associated with spinal cord injuries; however, they are unstable and should be initially treated with a properly sized rigid cervical collar. Unilateral ring or lateral mass fractures are not uncommon and tend to be stable injuries. However, treat all such fractures as unstable until the patient is examined by a specialist, typically a neurosurgeon or orthopedic surgeon.
C1 Rotary Subluxation
The C1 rotary subluxation injury is most often seen in children. It can occur spontaneously, after major or minor trauma, with an upper respiratory infection, or with rheumatoid arthritis. The patient presents with
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a persistent rotation of the head (torticollis). With this injury, the odontoid is not equidistant from the two lateral masses of C1. Do not force the patient to overcome the rotation, but restrict motion with him or her in the rotated position and refer for further specialized treatment.
Axis (C2) Fractures
The axis is the largest cervical vertebra and the most unusual in shape. Thus it is susceptible to various fractures, depending on the force and direction of the impact. Acute fractures of C2 represent approximately 18% of all cervical spine injuries. Axis fractures of note to trauma care providers include odontoid fractures and posterior element fractures.
Odontoid Fractures
Approximately 60% of C2 fractures involve the odontoid process, a peg-shaped bony protuberance that projects upward and is normally positioned in contact with the anterior arch of C1. The odontoid process is held in place primarily by the transverse ligament. Type I odontoid fractures typically involve the tip of the odontoid and are relatively uncommon.
Type II odontoid fractures occur through the base of the dens and are the most common odontoid fracture (n FIGURE 7-5). In children younger than 6 years of age, the epiphysis may be prominent and resemble a fracture at this level. Type III odontoid fractures occur at the base of the dens and extend obliquely into the body of the axis.
Posterior Element Fractures
A posterior element fracture, or hangman’s fracture, involves the posterior elements of C2—the pars inter- articularis (nFIGURE 7-6). This type of fracture is usually caused by an extension-type injury. Ensure that patients with this fracture are maintained in properly sized rigid cervical collar until specialized care is available.
Fractures and Dislocations (C3 through C7) The area of greatest flexion and extension of the cervical spine occurs at C5–C6 and is thus most vulnerable to injury. In adults, the most common level of cervical vertebral fracture is C5, and the most common level of subluxation is C5 on C6. Other injuries include subluxation of the articular processes (including unilateral or bilateral locked facets) and fractures of the laminae, spinous processes, pedicles, or lateral masses. Rarely, ligamentous disruption occurs without fractures or facet dislocations.
The incidence of neurological injury increases significantly with facet dislocations and is much more severe with bilateral locked facets.
tHoraCiC spine FraCtUres
Thoracic spine fractures may be classified into four broad categories: anterior wedge compression injuries, burst injuries, Chance fractures, and fracture-dislocations.
Axial loading with flexion produces an anterior wedge compression injury. The amount of wedging usually is quite minor, and the anterior portion of the vertebral SPECIFIC TYPES OF SPINAL INJURIES 137
n FIGURE 7-4 Jefferson Fracture. Open-mouth view radiograph showing a Jefferson fracture. This fracture involves disruption of both the anterior and posterior rings of C1, with lateral displacement of the lateral masses.
n FIGURE 7-5 Odontoid Fracture. CT view of a Type II odontoid fracture, which occurs through the base of the dens.
138 CHAPTER 7 n Spine and Spinal Cord Trauma
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body rarely is more than 25% shorter than the posterior body. Due to the rigidity of the rib cage, most of these fractures are stable.
Burst injury is caused by vertical-axial compression.
Chance fractures are transverse fractures through the vertebral body (nFIGURE 7-7). They are caused by flexion about an axis anterior to the vertebral column and are most frequently seen following motor vehicle crashes in which the patient was restrained by only an improperly placed lap belt. Chance fractures can be associated with retroperitoneal and abdominal visceral injuries.
Due to the orientation of the facet joints, fracture-dislocations are relatively uncommon in the thoracic and lumbar spine. These injuries nearly always result from extreme flexion or severe blunt trauma to the spine, which causes disruption of the posterior elements (pedicles, facets, and lamina) of the vertebra. The thoracic spinal canal is narrow in relation to the spinal cord, so fracture subluxations in
the thoracic spine commonly result in complete neurological deficits.
Simple compression fractures are usually stable and often treated with a rigid brace. Burst fractures, Chance fractures, and fracture-dislocations are extremely unstable and nearly always require internal fixation.
tHoraCoLUMbar jUnCtion FraCtUres (t11 tHroUgH L1)
Fractures at the level of the thoracolumbar junction are due to the immobility of the thoracic spine compared with the lumbar spine. Because these fractures most often result from a combination of acute hyperflexion and rotation, they are usually unstable. People who fall from a height and restrained drivers who sustain severe flexion with high kinetic energy transfer are at particular risk for this type of injury.
The spinal cord terminates as the conus medullaris at approximately the level of L1, and injury to this part of the cord commonly results in bladder and bowel dysfunction, as well as decreased sensation and strength in the lower extremities. Patients with thoracolumbar fractures are particularly vulnerable to rotational movement, so be extremely careful when logrolling them. (See Logroll video on MyATLS mobile app.)
LUMbar FraCtUres
The radiographic signs associated with a lumbar frac- ture are similar to those of thoracic and thoracolumbar fractures. However, because only the cauda equina is involved, the probability of a complete neurological deficit is much lower with these injuries.
n FIGURE 7-7 Chance Fracture. Radiograph showing a Chance fracture, which is a transverse fracture through the vertebral body.
n FIGURE 7-6 Hangman’s Fracture (arrows). Demonstrated in CT reconstructions: A. axial; B. sagittal paramedian; and C. sagittal midline.
Note the anterior angulation and excessive distance between the spinous processes of C1 and C2 (double arrows).
A B C
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penetrating injUries
Penetrating injuries often result in a complete neuro- logical deficit due to the path of the missile involved (most often a bullet or knife). These deficits also can result from the energy transfer associated with a high-velocity missile (e.g., bullet) passing close to the spinal cord rather than through it. Penetrating injuries of the spine usually are stable unless the missile destroys a significant portion of the vertebra.
bLUnt Carotid and VertebraL artery injUries
Blunt trauma to the neck can result in carotid and vertebral arterial injuries; early recognition and treatment of these injuries may reduce the patient’s risk of stroke. Specific spinal indications in screening for these injuries include C1–C3 fractures, cervical spine fracture with subluxation, and fractures involving the foramen transversarium.
Both careful clinical examination and thorough radiographic assessment are critical in identifying significant spine injury.
CerViCaL spine
Many trauma patients have a c-collar placed by emer-gency medical services (EMS) in the field. Current guidelines for spinal motion restriction in the prehospital setting allow for more flexibility in the use of long spine boards and cervical collars. With the use of clinical screening decision tools such as the Canadian C-Spine Rule (CCR; nFIGURE 7-8) and the National Emergency X-Radiography Utili- zation Study (NEXUS; nFIGURE 7-9), c-spine collars and blocks may be discontinued in many of these patients without the need for radiologic imaging.
RADIOGRAPHIC EVALUATION 139
n FIGURE 7-8 Canadian C-Spine Rule. A clinical decision tool for cervical spine evaluation. MVC = motor vehicle collison;
ED = emergency department. Adapted from Stiell IG, Wells GA, Vandemheen KL, et al.
The Canadian C-Spine rule of radiography in alert and stable trauma patients. JAMA 2001;286:1841–1848.