3.2 Spinal Cord Injury (SCI)
Key Takeaways
- The ASIA Impairment Scale (American Spinal Injury Association) grades injury from A (complete) through B, C, and D (incomplete with progressively more function) to E (normal motor and sensory function).
- Incomplete SCI syndromes have signature patterns: anterior cord (motor loss, preserved proprioception), central cord (arms worse than legs), Brown-Sequard (ipsilateral motor loss, contralateral pain/temperature loss), and posterior cord (proprioception loss).
- Key muscle motor levels include C5 elbow flexion, C6 wrist extension, C7 elbow extension, L2 hip flexion, L3 knee extension, L4 ankle dorsiflexion, and S1 ankle plantarflexion.
- Autonomic dysreflexia is a medical emergency in injuries at or above T6, presenting with sudden severe hypertension, pounding headache, and sweating/flushing above the lesion — the PTA must STOP activity, sit the patient fully upright, look for the noxious trigger, and call the PT or physician immediately.
- Pressure relief is performed about every 15-30 minutes during sitting (push-ups, leans, or weight shifts) and every 2 hours in bed to prevent pressure injuries over insensate skin.
Classifying the Injury
A spinal cord injury (SCI) disrupts motor, sensory, and autonomic function below the level of the lesion. The neurological level of injury is the most caudal spinal segment with normal motor and sensory function bilaterally. Two distinctions drive treatment:
- Tetraplegia (quadriplegia): cervical injury affecting all four limbs and the trunk.
- Paraplegia: thoracic, lumbar, or sacral injury sparing the upper extremities.
ASIA Impairment Scale
The American Spinal Injury Association (ASIA) Impairment Scale (AIS) standardizes how complete or incomplete an injury is. Sacral sparing (sensation or voluntary anal contraction at S4-S5) is the dividing line between complete and incomplete.
| Grade | Description |
|---|---|
| A | Complete — no motor or sensory function in the lowest sacral segments (S4-S5) |
| B | Incomplete — sensory but not motor function preserved below the level, including S4-S5 |
| C | Incomplete — motor preserved below the level; more than half of key muscles below grade 3/5 |
| D | Incomplete — motor preserved below the level; at least half of key muscles at grade 3/5 or higher |
| E | Normal — motor and sensory function are normal (used when prior deficits have resolved) |
Complete vs Incomplete Cord Syndromes
A complete injury (AIS A) means no sacral sparing. Incomplete injuries spare some function and follow recognizable patterns the exam loves to contrast:
| Syndrome | Mechanism / Pattern | Hallmark Findings |
|---|---|---|
| Anterior cord | Anterior cord/artery damage (often flexion injury) | Loss of motor, pain, and temperature; proprioception and light touch preserved |
| Central cord | Hyperextension, common in older adults | Upper extremities affected more than lower; arms and hands weakest |
| Brown-Sequard | Hemisection of the cord (often penetrating trauma) | Ipsilateral motor and proprioception loss; contralateral pain and temperature loss |
| Posterior cord | Posterior column damage (rare) | Loss of proprioception and vibration; motor preserved |
| Cauda equina | Lumbosacral nerve root injury below the conus | Lower motor neuron signs, flaccidity, bowel/bladder involvement, often incomplete |
Central cord syndrome generally has the best prognosis for ambulation; anterior cord syndrome has the poorest. Brown-Sequard, because hemisection leaves one side largely intact, also has a relatively good functional outlook.
Key Muscle Motor Levels
The NPTE-PTA expects you to connect a spinal level to its key muscle action. Memorize these high-yield levels — they are tested as both "what can this patient do?" and "what level is this?"
| Level | Key Muscle Action |
|---|---|
| C5 | Elbow flexion (biceps) |
| C6 | Wrist extension |
| C7 | Elbow extension (triceps) |
| C8 | Finger flexion |
| T1 | Finger abduction |
| L2 | Hip flexion |
| L3 | Knee extension (quadriceps) |
| L4 | Ankle dorsiflexion (tibialis anterior) |
| L5 | Great toe extension |
| S1 | Ankle plantarflexion |
Functional anchors the exam rewards: C6 tetraplegia allows tenodesis grasp (passive finger flexion when the wrist extends) and independence with many transfers and self-care using adaptive equipment; C7 adds active elbow extension, dramatically improving independent transfers and weight relief; C8-T1 allows hand function and independent living. At T1 and below, the patient typically achieves independent wheelchair-level function.
Autonomic Dysreflexia — A Medical Emergency
Autonomic dysreflexia (AD), also called autonomic hyperreflexia, occurs in injuries at or above T6. A noxious stimulus below the level of injury triggers an unopposed sympathetic surge the body cannot regulate. Common triggers: a blocked or full bladder, bowel impaction, a kinked catheter, tight clothing, a pressure injury, or an ingrown toenail.
Recognize the signs:
- Sudden, severe hypertension (the cardinal sign — systolic can spike 20-40 mmHg above baseline or higher)
- Pounding headache
- Sweating and flushing above the level of injury
- Cool, pale skin below the level of injury, with goosebumps
- Bradycardia, nasal congestion, anxiety, blurred vision
PTA response — memorize this exact sequence:
- STOP the activity immediately.
- Sit the patient fully upright (an orthostatic drop helps lower blood pressure).
- Loosen any tight clothing, binders, abdominal binders, or straps.
- Look for and, if obvious and within scope, address the trigger (for example, unkink the catheter line).
- Call the supervising PT, nurse, or physician immediately and stay with the patient.
Untreated AD can cause seizure, retinal hemorrhage, stroke, or death. Recognizing it and acting fast is squarely within — and required of — the PTA role.
Orthostatic Hypotension vs Autonomic Dysreflexia
Do not confuse the two. Orthostatic (postural) hypotension is the opposite problem: blood pressure drops with upright positioning, producing dizziness, pallor, and fainting. The fix is to recline the patient and elevate the legs — the exact opposite of the AD response. Compression garments, abdominal binders, and gradual position changes prevent it.
Pressure Relief and Skin Protection
Insensate skin cannot warn the patient of tissue damage, so scheduled pressure relief is non-negotiable:
- Sitting: weight shift, lateral lean, forward lean, or wheelchair push-up roughly every 15-30 minutes, held long enough (about 30-60 seconds) to reperfuse tissue.
- In bed: reposition about every 2 hours.
- The PTA teaches and reinforces these schedules, inspects skin during sessions, and reports any new redness or breakdown to the supervising PT.
During a wheelchair mobility session, a patient with a complete T4 spinal cord injury suddenly develops a severe pounding headache, flushed and sweaty skin on the face, and a blood pressure that has spiked well above baseline. What is the PTA's FIRST priority action?
A PTA is reviewing the chart of a new patient with tetraplegia. The patient has full elbow flexion and wrist extension but no active elbow extension. Which neurological level of injury is MOST consistent with this presentation?