Spinal cord injury

Spinal cord injury (SCI) is a partial or complete disruption of the spinal cord resulting in paralysis, sensory loss, altered spinal reflexes, and altered autonomic function.

The causes of spinal cord injury can be falls, motor vehicle accidents, penetrating wounds, disc prolapse, or vascular compromise.

Pathophysiology

• Primary injury: direct injury to the spinal cord or disruption of vascular supply
• Secondary injury: edema, demyelination, or necrosis of axons

Definitions

Sacral sparing

Preserved sensory and/or motor function in the lowest sacral segments (S4-S5), tested around the anus. Its presence makes an injury incomplete, and it indicates a better prognosis for recovery.

American Spinal Injury Association (ASIA) levels of injury

• A: complete
  • No motor or sensory function preserved below the level of injury
  • No motor or sensory function in sacral segments S4-S5 (no sacral sparing)
• B: incomplete
  • Sensory but no motor below the level of injury
  • Sensory to sacral segments S4-S5, but no motor to these segments
• C: incomplete
  • Motor function is preserved below the level of injury, and more than half of the key muscles below that level have a manual muscle test grade less than 3
• D: incomplete
  • Motor function is preserved below the level of injury, and at least half of the key muscles below that level have a manual muscle test grade of 3 or greater
• E: normal
  • Motor and sensory are normal

PTA scope of practice: The PTA collects objective data, such as ASIA classification findings and Modified Ashworth Scale scores, and reports changes to the supervising PT. The PTA does not reclassify the injury or alter the plan of care independently.

Classifications of incomplete spinal cord injuries

The four incomplete cord syndromes below are easiest to tell apart by tracking which of three tracts is affected: the corticospinal tract (motor), the spinothalamic tract (pain and temperature), and the dorsal columns (proprioception and vibration).

Example: identifying an incomplete spinal cord syndrome

After a hyperflexion injury to the cervical spine, a patient has bilateral loss of motor function and bilateral loss of pain and temperature sensation below the level of injury. Proprioception, vibration sense, and kinesthesia are intact. Which incomplete spinal cord syndrome does this presentation match?

Answer: Anterior cord syndrome - the corticospinal (motor) and spinothalamic (pain/temperature) tracts are affected, but the dorsal columns (proprioception, vibration, and kinesthesia) are spared.

Cauda equina injury is not a cord syndrome; it damages the lumbosacral nerve roots below the end of the cord:

• Cauda equina injury (classified as lower motor neuron lesion)
  • Etiology: Trauma, herniated disk, spinal stenosis, or infection affecting the nerve roots below the L1-L2 vertebral level
  • Deficits:
    • Flaccid paralysis of bladder, bowel function (incontinence)
    • Impaired motor function - specifically lower extremities
    • Absent spinal reflexes
  • Intact: Variable dependent upon the severity of injury
  • Contrast with a spinal cord injury above the conus, which is an upper motor neuron lesion:
    • Tone: spastic (UMN) vs. flaccid (LMN)
    • Reflexes: hyperreflexive (UMN) vs. absent (LMN)
    • Bladder: reflexive, spastic bladder (UMN) vs. flaccid, areflexic bladder (LMN)

Associated disorders with spinal cord injury

• Spinal shock
  • A temporary period of absent reflexes and flaccidity below the level of injury caused by sudden loss of descending input to the cord
  • Timeframe can vary from 24 hours to 12 weeks
    • Difficult to get an accurate ASIA assessment due to spinal shock and changes in the level of injury
    • The return of reflexes, such as the bulbocavernosus reflex, signals that spinal shock is ending
• Autonomic dysreflexia
  • Medical emergency for individuals with T6 or above injury
  • Caused by a noxious stimulus below the level of injury, which triggers a reflex sympathetic surge and widespread vasoconstriction below the lesion. Descending inhibitory signals from the brain can’t pass the lesion to calm this response, so blood pressure rises sharply. Baroreceptors then trigger a vagal (parasympathetic) response above the lesion, causing bradycardia and flushing above the level of injury.
    • Noxious stimuli can be constipation, catheter malfunction, pressure injuries, tight clothes, or sitting on a sharp object
  • Symptoms: headache, increased blood pressure, bradycardia, flushing and diaphoresis above the level of injury, pallor and piloerection (cool skin) below the level of injury, seizures. If left untreated, it can lead to death.
  • Medical management: stop the activity and sit the patient upright with legs lowered; loosen tight clothing or an abdominal binder; check the catheter, bladder, and bowel for the noxious stimulus; monitor blood pressure every few minutes; notify nursing and the supervising PT
• Spasticity
  • A velocity-dependent increase in resistance to passive stretch (hyperactive stretch reflexes) in the extremities or trunk; leads to range of motion deficits and functional impairment
  • Will only be seen in upper motor neuron lesions
  • Occurs most often in incomplete lesions
  • Utilize the Modified Ashworth Scale to assess
• Heterotopic ossification
  • Abnormal bone growth in the muscle
  • Symptoms: pain with palpation or muscle stretch, warmth, swelling, decreased range of motion
  • Typically occurs around large joints below the level of injury, most commonly the hips, followed by the knees
• Deep vein thrombosis
  • Requires urgent medical attention; can lead to a life-threatening pulmonary embolism
  • Development due to immobility of extremities, which places individuals at increased risk for blood clot development
  • Warning signs: unilateral calf swelling, warmth, redness, or pain
  • If suspected: hold exercise and mobilization and notify the PT/medical team immediately
  • Prevention: graduated compression socks, anti-coagulation medication
• Orthostatic hypotension
  • Defined as a drop of at least 20 mmHg systolic or 10 mmHg diastolic on moving upright; in SCI it results from loss of sympathetic vasomotor tone, with venous pooling in the legs and abdomen
  • Warning signs: dizziness, lightheadedness, or blurred vision on sitting or standing
  • If symptoms occur: recline the patient, elevate the legs, monitor blood pressure, and report to the PT
  • Treatment option: graduated compression stockings, abdominal binder, tilt table, or medication
• Syringomyelia
  • A fluid-filled cavity (syrinx) in the spinal cord that commonly begins in the cervical area and causes a capelike loss of pain and temperature sensation over the shoulders, arms, and back, while light touch and position and vibration sensation are not affected

Distinguishing autonomic dysreflexia from orthostatic hypotension: both cause headache or lightheadedness tied to position or activity in SCI, but the blood pressure change and the correct response are opposite.

Feature	Autonomic dysreflexia	Orthostatic hypotension
Blood pressure	Sharply increased	Decreased
Heart rate	Bradycardia	Usually increased
Key symptoms	Pounding headache, flushing and sweating above the lesion, pale skin below the lesion	Dizziness, lightheadedness, blurred vision
Correct position	Sit the patient upright, legs down	Recline the patient, legs elevated

Intervention considerations

• Follow a pressure-relief schedule (weight shifts every 15-30 minutes) during wheelchair use to prevent pressure injuries
• Avoid stretching the fingers and wrist into extension at the same time in patients with C6-C7 tetraplegia relying on tenodesis grasp, since tenodesis depends on wrist extension creating passive finger flexion
• Use gentle, pain-free range of motion around joints affected by heterotopic ossification; forceful stretching can worsen bone formation
• Progress upright tolerance gradually (for example, with a tilt table) and monitor blood pressure frequently to manage orthostatic hypotension
• Support breathing in patients with tetraplegia using assisted (quad) cough, diaphragmatic breathing or inspiratory muscle training, and an abdominal binder

Wheelchair wheelies

A wheelie is balancing a manual wheelchair on its rear wheels with the casters off the ground. It is the foundation for community skills such as going down a high curb: in a wheelie the rear wheels land first, so the foot supports do not catch the street and pitch the user forward. Going up a curb starts with a caster pop, a brief partial wheelie that lifts the casters onto the curb. Users with full upper extremity strength, such as at a low thoracic level, can learn independent wheelies and curbs.

• The main risk is a backward tip, so the spotter stands behind the chair holding a spotter strap
• Training starts with the rear wheels blocked and on a soft surface, then progresses to free balance and then to curbs
• Rear anti-tip devices may need adjusting for wheelie training, which raises the risk of a backward tip
• Users also learn to recover from a backward tip by flexing the neck and trunk and pulling back on the hand-rims

Levels of independence (for complete injuries)

Key preserved muscles drive these levels: C5 elbow flexors (biceps), C6 wrist extensors, which allow tenodesis grasp, and C7 triceps, which allow push-up depression transfers.

• Transfers
  • C1-C5: dependent transfers
  • C6: independent with sliding board transfers on level surfaces
    • For a sliding board transfer, one side of the board is placed under the upper thigh or buttock, and the board must be firmly placed on both surfaces
  • C7 and beyond: independent with transfers without a sliding board on level surfaces; at C7-C8, uneven-surface transfers may still need some assistance
• Wheelchair use
  • C1-C5: power wheelchair use with head control, mouth control, or joystick
  • C6: manual wheelchair on level surfaces with use of wheel projections and large knobby wheels - independent status
  • C7-C8: manual wheelchair with modified rims, independent indoors and on level outdoor terrain, with some assistance on uneven terrain; T1 and below: independent on all surfaces
• Respiration
  • C1-C3: usually ventilator-dependent, since the phrenic nerve (C3-C5) innervating the diaphragm is lost
  • C4 and below: diaphragm function is typically preserved, but reduced vital capacity and a weak, ineffective cough remain common due to paralyzed abdominal and intercostal muscles

Gait (ambulation potential decreases, and orthosis and energy demands increase, as the level of injury rises):

Definitions

Reciprocating gait orthosis

A series of interconnected braces aiding in ambulation by a lever system attached to the torso; unweighting of the extremity is performed by lateral movement of the torso, causing the swing leg to move forward while the stance leg is pushed backward.