Spinal Cord Injuries Clinical Presentation

As with all trauma patients, initial clinical evaluation of a patient with suspected spinal cord injury (SCI) begins with a primary survey. The primary survey focuses on life-threatening conditions. Assessment of airway, breathing, and circulation (ABCs) takes precedence. A spinal cord injury must be considered concurrently. ^{[31, 32, 4]}

Perform careful history taking, focusing on symptoms related to the vertebral column (most commonly pain) and any motor or sensory deficits. Ascertaining the mechanism of injury is also important in identifying the potential for spinal injury.

The axial skeleton should be examined to identify and provide initial treatment of potentially unstable spinal fractures from both a mechanical and a neurologic basis. The posterior cervical spine and paraspinal tissues should be evaluated for pain, swelling, bruising, or possible malalignment. Logrolling the patient to systematically examine each spinous process of the entire axial skeleton from the occiput to the sacrum can help identify and localize injury. The skeletal level of injury is the level of the greatest vertebral damage on radiograph.

Complete bilateral loss of sensation or motor function below a certain level indicates a complete spinal cord injury.

Pulmonary evaluation

The clinical assessment of pulmonary function in acute spinal cord injury begins with careful history taking regarding respiratory symptoms and a review of underlying cardiopulmonary comorbidity such as chronic obstructive pulmonary disease (COPD) or heart failure.

Carefully evaluate respiratory rate, chest wall expansion, abdominal wall movement, cough, and chest wall and/or pulmonary injuries. Arterial blood gas (ABG) analysis and pulse oximetry are especially useful, because the bedside diagnosis of hypoxia or carbon dioxide retention may be difficult.

The degree of respiratory dysfunction is ultimately dependent on preexisting pulmonary comorbidity, the level of the spinal cord injury, and any associated chest wall or lung injury. Any or all of the following determinants of pulmonary function may be impaired in the setting of spinal cord injury:

• Loss of ventilatory muscle function from denervation and/or associated chest wall injury

• Lung injury, such as pneumothorax, hemothorax, or pulmonary contusion

• Decreased central ventilatory drive that is associated with head injury or exogenous effects of alcohol and drugs

A direct relationship exists between the level of cord injury and the degree of respiratory dysfunction, as follows:

• With high lesions (ie, C1 or C2), vital capacity is only 5-10% of normal, and cough is absent

• With lesions at C3 through C6, vital capacity is 20% of normal, and cough is weak and ineffective

• With high thoracic cord injuries (ie, T2 through T4), vital capacity is 30-50% of normal, and cough is weak

• With lower cord injuries, respiratory function improves

• With injuries at T11, respiratory dysfunction is minimal; vital capacity is essentially normal, and cough is strong.

Other findings of respiratory disfunction include the following:

• Agitation, anxiety, or restlessness

• Poor chest wall expansion

• Decreased air entry

• Rales, rhonchi

• Pallor, cyanosis

• Increased heart rate

• Paradoxic movement of the chest wall

• Increased accessory muscle use

• Moist cough

Hemorrhage, hypotension, and hemorrhagic and neurogenic shock

Hemorrhagic shock may be difficult to diagnose, because the clinical findings may be affected by autonomic dysfunction. Disruption of autonomic pathways prevents tachycardia and peripheral vasoconstriction that normally characterizes hemorrhagic shock. This vital sign confusion may falsely reassure. In addition, occult internal injuries with associated hemorrhage may be missed.

In a study showing a high incidence of autonomic dysfunction, including orthostatic hypotension and impaired cardiovascular control, following spinal cord injury, it was recommended that an assessment of autonomic function be routinely used, along with American Spinal Injury Association (ASIA) assessment, in the neurologic evaluation of patients with spinal cord injury. ^[33]

In all patients with spinal cord injury and hypotension, a diligent search for sources of hemorrhage must be made before hypotension is attributed to neurogenic shock. In acute spinal cord injury, shock may be neurogenic, hemorrhagic, or both.

The following are clinical "pearls" useful in distinguishing hemorrhagic shock from neurogenic shock:

• Neurogenic shock occurs only in the presence of acute spinal cord injury above T6; hypotension and/or shock with acute spinal cord injury at or below T6 is caused by hemorrhage

• Hypotension with a spinal fracture alone, without any neurologic deficit or apparent spinal cord injury, is invariably due to hemorrhage

• Patients with a spinal cord injury above T6 may not have the classic physical findings associated with hemorrhage (eg, tachycardia, peripheral vasoconstriction); this vital sign confusion attributed to autonomic dysfunction is common in spinal cord injury

• The presence of vital sign confusion in acute spinal cord injury and a high incidence of associated injuries requires a diligent search for occult sources of hemorrhage

Cord syndromes and nerve root injury

A careful neurologic assessment, including motor function, sensory evaluation, deep tendon reflexes, and perineal evaluation, is critical and required to establish the presence or absence of spinal cord injury and to classify the lesion according to a specific cord syndrome.

The presence or absence of sacral sparing is a key prognostic indicator. 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.

Determine the level of injury and try to differentiate nerve root injury from spinal cord injury, but recognize that both may be present. Differentiating a nerve root injury from spinal cord injury can be difficult. The presence of neurologic deficits that indicate multilevel involvement suggests spinal cord injury rather than a nerve root injury. In the absence of spinal shock, motor weakness with intact reflexes indicates spinal cord injury, whereas motor weakness with absent reflexes indicates a nerve root lesion.

ASIA has established pertinent definitions (see the following image). The neurologic level of injury is the lowest (most caudal) level with normal sensory and motor function. For example, a patient with C5 quadriplegia has, by definition, abnormal motor and sensory function from C6 down.

Sensory function testing

Assessment of sensory function helps to identify the different pathways for light touch, proprioception, vibration, and pain. Use a pinprick to evaluate pain sensation.

Sensory level is the most caudal dermatome with a normal score of 2/2 for pinprick and light touch.

Sensory index scoring is the total score from adding each dermatomal score with a possible total score of 112 each for pinprick and light touch.

Sensory testing is performed at the following levels:

• C2: Occipital protuberance

• C3: Supraclavicular fossa

• C4: Top of the acromioclavicular joint

• C5: Lateral side of antecubital fossa

• C6: Thumb

• C7: Middle finger

• C8: Little finger

• T1: Medial side of antecubital fossa

• T2: Apex of axilla

• T3: Third intercostal space

• T4: Fourth intercostal space at nipple line

• T5: Fifth intercostal space (midway between T4 and T6)

• T6: Sixth intercostal space at the level of the xiphisternum

• T7: Seventh intercostal space (midway between T6 and T8)

• T8: Eighth intercostal space (midway between T6 and T10)

• T9: Ninth intercostal space (midway between T8 and T10)

• T10: 10th intercostal space or umbilicus

• T11: 11th intercostal space (midway between T10 and T12)

• T12: Midpoint of inguinal ligament

• L1: Half the distance between T12 and L2

• L2: Midanterior thigh

• L3: Medial femoral condyle

• L4: Medial malleolus

• L5: Dorsum of the foot at third metatarsophalangeal joint

• S1: Lateral heel

• S2: Popliteal fossa in the midline

• S3: Ischial tuberosity

• S4-5: Perianal area (taken as 1 level)

Sensory scoring is for light touch and pinprick, as follows:

• 0: Absent; a score of zero is given if the patient cannot differentiate between the point of a sharp pin and the dull edge

• 1: Impaired or hyperesthesia

• 2: Intact

Motor strength testing

Muscle strength always should be graded according to the maximum strength attained, no matter how briefly that strength is maintained during the examination. The muscles are tested with the patient supine.

Motor level is 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 uses the 0-5 scoring of each key muscle, with total points being 25 per extremity and with the total possible score being 100.

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 of 20 or less indicates that the patient is likely to be a limited ambulator. A LEMS of 30 or more suggests that the individual is likely to be a community ambulator.

ASIA recommends use of the following scale of findings for the assessment of motor strength in spinal cord injury:

• 0: No contraction or movement

• 1: Minimal movement

• 2: Active movement, but not against gravity

• 3: Active movement against gravity

• 4: Active movement against resistance

• 5: Active movement against full resistance

Neurologic level and extent of injury

Neurologic level of injury is the most caudal level at which 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 is all segments below the neurologic level of injury with preservation of motor or sensory findings. This index is used only when the injury is complete.

The key muscles that need to be tested to establish neurologic level are as follows:

• C5: Elbow flexors (biceps, brachialis)

• C6: Wrist extensors (extensor carpi radialis longus and brevis)

• C7: Elbow extensors (triceps)

• C8: Long finger flexors (flexor digitorum profundus)

• T1: Small finger abductors (abductor digiti minimi)

• L2: Hip flexors (iliopsoas)

• L3: Knee extensors (quadriceps)

• L4: Ankle dorsiflexors (tibialis anterior)

• L5: Long toe extensors (extensor hallucis longus)

• S1: Ankle plantar flexors (gastrocnemius, soleus)

Perform a rectal examination to check motor function or sensation at the anal mucocutaneous junction. The presence of either is considered sacral-sparing.

The sacral roots may be evaluated by documenting the following:

• Perineal sensation to light touch and pinprick

• Bulbocavernous reflex, S3 or S4

• Anal wink, S5

• Rectal tone

• Urine retention or incontinence

• Priapism

The extent of injury is defined by the ASIA Impairment Scale (modified from the Frankel classification), using the following categories ^{[1, 2]} :

• A = Complete: No sensory or motor function is preserved in sacral segments S4-S5 ^[3]

• B = Incomplete: Sensory, but not motor, function is preserved below the neurologic level and extends through sacral segments S4-S5

• C = Incomplete: Motor function is preserved below the neurologic level, and most key muscles below the neurologic level have muscle grade less than 3

• D = Incomplete: Motor function is preserved below the neurologic level, and most key muscles below the neurologic level have muscle grade greater than or equal to 3

• E = Normal: Sensory and motor functions are normal

Thus, definitions of complete and incomplete spinal cord injury, as based on the above ASIA definition, with sacral-sparing, are as follows ^{[1, 2, 3]} :

• Complete: Absence of sensory and motor functions in the lowest sacral segments

• Incomplete: Preservation of sensory or motor function below the level of injury, including the lowest sacral segments

With the ASIA classification system, the terms paraparesis and quadriparesis have become obsolete. Instead, the ASIA classification uses the description of the neurologic level of injury in defining the type of spinal cord injury (eg, "C8 ASIA A with zone of partial preservation of pinprick to T2").