Spinal cord injuries Flashcards
Basic facts on SCI
C5 is the most common level of injury
Most common cause of death is pneumonia, followed by heart disease and septicemia (usually from pressure ulcers, UTI, LRTI)
Highest complete SCI level that can live independently is a C6 tetraplegia but less than 20% are.
T6 and above: at risk of AD and orthostatic hypotension.
T8 and above: cannot regulate “temp-EIGHT-ture”
Blood supply to the Spinal Cord
Blood supply come from 1 anterior (supplies anterior 2/3) and 2 posterior spinal arteries that originate from the vertebral artery.
The artery of Adamkiewicz provides the major blood supply to lumbar and sacral cord. It arises from the LEFT intercostal or lumbar artery (T9-L3) and is the major supply to the lower 2/3 of the cord.
Lower thoracic region (T4-6) is most affected by low blood flow “watershed area”.
Central cord syndrome
More commonly seen with hyperextension mechanism of injury. Likely to be an incomplete injury with UL weaker than LL and variable bowel and bladder function changes.
Myotomes
C5: biceps - elbow flexion C6: ECR - wrist extension C7: Triceps - elbow extension C8: FDP - finger flexion T1: Abductor digiti minimi - small finger abduction L2: Iliopsoas - hip flexion L3: Quads - knee extension L4: Tib ant - ankle dorsiflexion L5: EHL - big toe extension S1: gastrocnemius - ankle plantarflexion
Level of injury
Sensory level: most caudal segment with normal 2/2 sensory function on both sides for both pinprick and light touch.
Motor level: most caudal key muscle group graded as grade 3 or higher with all segments above graded 5/5 - determined for each side.
Neurologically complete vs incomplete SCI classification is dependent on sacral sparing (either voluntary anal sphincter contraction or S4-5 dermatome sensation).
ASIA impairment level
A = complete B = Sensation preserved. Motor complete (no function more than 3 levels below the level on either side)
If there is sparing of motor functions more than three levels below.
C = More than half muscles below neurological level have muscle grade <3 (0-2)
D = at least half muscles below the neurological level have muscle grade >3
E = normal
Spinal shock
Temporary loss or depression of all spinal reflex activity below the level of the lesion.
- Delayed plantar response (with relaxation)
- Bulbocavernosus reflex returns after planar response (stimulation of anal sphincter contraction), if not present by 24 hours, suspect LMN injury
Brown-sequard syndrome
Results from a lesion that causes a relative hemisection of the spinal cord. Present with ipsilateral motor and proprioceptive loss, but contralateral pain loss and decreased temperature. Plus syndrome is associated with additional findings involving the eyes, bowel or bladder.
Conus medullaris versus cauda equina syndrome
Conus medullaris: L1-2 vertebral level. Normal motor function of lower limbs unless S1-S2 (sacral cord) or LMN lumbar root involvement. Symmetrical. Saddle distribution sensory loss and if high lesion, bulbocavernosus reflex may be present. may be hyperreflexic.
Cauda equina: below involving lumbar-sacral nerve roots. Pain and asymmetry more prominent. Bulbocavernosus reflex absent in lower lesion. Hypo/areflexic with sensory loss in root distribution
Autonomic Dysreflexia - lesions T6 and above
Syndrome of imbalanced sympathetic discharge due to loss of central control of the splanchnic outflow (T5-L2) and hypersensitivity of receptors below the lesion.
Noxious stimuli increases spinal reflex causing regional vasoconstriction, headaches and hypertension. Peripheral baroreceptors respond via vagus nerve with bradycardia, sweating and flushing, pupil constriction
Complications of autonomic dysreflexia
Retinal haemorrhage CVA / SAH Seizure Myocardial infarction Atrial fibrillation Death
Nerve supply to bladder
Parasympathetic: pelvic nerves from S2-4 levels = contraction and emptying.
Sympathetic: T11-L2 travel through hypogastric nerve to B2 receptors in body (SM relaxation) and A1 in urethra (SM contraction) = urine storage.
Somatic: pudendal nerve (S2-4) to external urethral sphincter to prevent leakage
Urodynamics
Volume estimate = (age+2) x 30 mL.
Detrusor Sphincter Dyssynergia (DSD): 1. brisk bulbocaveronsus reflex. 2. Bladder capacity is reduced . 3. And persistently high intravesical pressure during contraction (hyperreflexic). 4. With inappropriate pelvic floor muscle and external sphincter hyperactivity.
Result: small, overactive, spastic bladder with failure to empty and under high voiding pressures.
Risks: Vesicoureteral reflux, increased residual volumes and risk of UTI.
Rx: anticholingeric, botox, alpha-blockers, IC.
