Neurogenic shock results from damage to descending sympathetic pathways in the cervical and upper thoracic spinal cord resulting in loss of vasomotor tone and cardiac sympathetic innervation
This leads to hypotension and bradycardia, or absence of appropriate tachycardia as vagal tone dominates
Hypotension may not be corrected by fluid resuscitation alone and may require the use of vasopressors
Spinal shock
Spinal shock refers to flaccidity and areflexia seen after spinal cord injury
It may occur completely non-functional although the cord is not necessarily destroyed
The duration is variable
Specific types of spinal injury
Mechanisms of injury
Axial loading
Flexion
Extension
Rotation
Lateral flexion
Distraction
Atlanto-occipital dislocation
Mechanism: severe traumatic flexion and distraction
Most patients die of apnoea or will have severe neurological impairment eg quadriplegia
Common cause of death in shaken baby syndrome
Atlas (C1) fractures
Jefferson fracture
Burst fracture of both the anterior and posterior rings of C1 with lateral displacement of the lateral masses
Mechanism: axial loading
Axis (C2) fractures
Odontoid peg fractures
Type I: fracture through the tip of the peg
Type II: fracture through the base of the peg
Type III: fracture through the base of the peg into the lateral masses of C2
Hangman’s fracture
Fracture of the posterior elements of C2
Mechanism: hyperextension
C3-7 fractures
Fracture-dislocations
Thoracic spine fractures
Anterior wedge compression injuries
Mechanism: axial loading with flexion
Burst injuries
Mechanism: vertical-axial compression
Chance fractures
Transverse fractures through vertebral body
Mechanism: flexion about an axis anterior to vertebral column eg from wearing lap belts inappropriately high and not over the pelvic girdle
Fracture-dislocations
Clinical features in spinal trauma
General features
Neck pain/tenderness
Back pain/tenderness
Weakness
Absent sensation/sensory level
Absent reflexes (initially)
Urinary incontinence or retention
Loss of anal tone
Neurogenic shock
Hypotension
Bradycardia/absence of appropriate tachycardia
Spinal cord syndromes
Brown-Sequard syndrome
Caused by hemisection of the spinal cord
Results in ipsilateral weakness and sensory deficit with contralateral loss of pain and temperature
Central cord syndrome
Caused by vascular compromise of the spinal cord in the distribution of the anterior spinal artery, usually due to hyperextension injuries
Results in upper limb weakness greater than lower limb weakness (upper limb motor fibres lie more centrally) and a variable, ‘cape-like’ sensory deficit
Anterior cord syndrome
Caused vascular insufficiency of the anterior spinal artery
Results in bilateral paraparesis and loss of pain and temperature with preservation of dorsal column function
Clinical assessment in spinal trauma
Dermatomes
A dermatome is an area of skin innervated by sensory axons of a particular spinal nerve root
Key dermatomes are
C2: posterior head
C3: neck
C4: shoulder
C5: lateral upper arm
C6: lateral forearm & thumb
C7: middle finger
C8: medial hand and little finger
T1: medial forearm
T2: medial upper arm
T4: nipples
T8: xiphisternum
T10: umbilicus
T12: pubic symphysis
L1: groin
L2: anterior thigh
L3: anterior knee
L4: medial shin
L5: dorsal foot and first web space
S1: sole and lateral foot
S2: posterior leg and thigh
S3: ischial tuberosity
S4-5: perianal
Myotomes
A myotome is group of muscles innervated by motor axons of a particular spinal nerve root
Key myotomes are
C5: shoulder abduction, deltoid
C6: elbow flexion, biceps
C7: elbow extension, triceps
C8: wrist and finger flexion
T1: finger abduction, interossei
L2: hip flexion, iliopsoas
L3-4: knee extension, quadriceps
L4-S1: knee flexion, hamstrings
L5: ankle and hallux dorsiflexion, extensor hallucis longus
