SPINAL CORD INJURIESAnatomy & Pathophysiology

J C King

Definition

Insult to spinal cord resulting in a change,

in the normal motor, sensory or autonomic function. This change is either temporary or permanent.

Mechanisms:

i) Direct trauma

ii) Compression by bone fragments / haematoma / disc material

iii) Ischemia from damage / impingement on the spinal arteries

Statistics:

National Spinal Cord Injury Database { USA Stats }• MVA 44.5%• Falls 18.1%• Violence 16.6%• Sports 12.7%

• 55% cases occur in 16 – 30yrs of age• 81.6% are male!

South African Statistics (GSH Acute Spinal Cord Injury Unit 2007)

• MVA 56%• Falls 16%• Gunshot Injuries 11%• Blunt Assault 6%• Diving Accidents 5% • Stab Wounds 4%• Sport Injuries 3%

Other causes:• Vascular disorders• Tumours• Infectious conditions• Spondylosis• Iatrogenic• Vertebral fractures secondary to osteoporosis • Development disorders

Anatomy :

Spinal cord:

• Extends from medulla oblongata – L1

• Lower part tapered to form conus medullaris

On the surface :

• Deep anterior median fissure

• Shallower posterior median sulcus

Spinal cord segment :

• Section of the cord from which a pair of spinal nerves are given off

Hence: 31 pairs of spinal nerves:

8 cervical

12 thoracic

5 lumbar

5 sacral

1 coccygeal

• Dorsal root – sensory fibres

• Ventral root – motor fibres

• Dorsal and ventral roots join at intervertebral foramen to form the spinal nerve

Physiology and function

• Grey matter – sensory and motor nerve cells

• White matter – ascending and descending tracts

• Divided into - dorsal

- lateral

- ventral

Tracts :

1) Posterior column:

• Fine touch

• Light pressure

• Proprioception

2) Lateral corticospinal tract :

• Skilled voluntary movement

3) Lateral spinothalamic tract :

• Pain & temperature sensation

• Posterior column and lateral corticospinal tract crosses over at medulla oblongata

• Spinothalamic tract crosses in the spinal cord and ascends on the opposite side

NB to understand this as it helps to understand the clinical features of injury patterns and the neurological deficit

Dermatomes

• Area of skin innervated by sensory axons within a particular segmental nerve root

• Knowledge is essential in determining level of injury

• Useful in assessing improvement or deterioration

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© 2007 Elsevier

Downloaded from: Rosen's Emergency Medicine (on 29 April 2009 06:34 PM)

© 2007 Elsevier

Myotomes :

• Segmental nerve root innervating a muscle• Again important in determining level of injury

• Upper limbs:

C5 - Deltoid

C 6 - Wrist extensors

C 7 - Elbow extensors

C 8 - Long finger flexors

T 1 - Small hand muscles

• Lower Limbs :

L2 - Hip flexors

L3,4 - Knee extensors

L4,5 – S1 - Knee flexion

L5 - Ankle dorsiflexion

S1 - Ankle plantar flexion

Spinal Cord Injury Classification

• Quadriplegia :

injury in cervical region

all 4 extremities affected

• Paraplegia :

injury in thoracic, lumbar or sacral segments

2 extremities affected

Injury either:

1) Complete

2) Incomplete

Complete:

i) Loss of voluntary movement of parts innervated by segment, this is irreversible

ii) Loss of sensation

iii) Spinal shock

Incomplete:

i) Some function is present below site of injury

ii) More favourable prognosis overall

iii) Are recognisable patterns of injury, although they are rarely pure and variations occur

Injury defined by ASIA Impairment Scale

ASIA – American Spinal Injury Association :

A – Complete: no sensory or motor function preserved in sacral segments S4 – S5

B – Incomplete: sensory, but no motor function in sacral segments

C – Incomplete: motor function preserved below level and power graded < 3

D – Incomplete: motor function preserved below level and power graded 3 or more

E – Normal: sensory and motor function normal

Muscle Strength Grading:

• 5 – Normal strength

• 4 – Full range of motion, but less than normal strength against

resistance

• 3 – Full range of motion against gravity

• 2 – Movement with gravity eliminated

• 1 – Flicker of movement

• 0 – Total paralysis

Spinal Shock vs Neurogenic Shock

Spinal Shock : • Transient reflex depression of cord function below level

of injury• Initially hypertension due to release of catecholamines• Followed by hypotension• Flaccid paralysis • Bowel and bladder involved• Sometimes priaprism develops • Symptoms last several hours to days

Neurogenic shock:

• Triad of i) hypotension

ii) bradycardia

iii) hypothermia

• More commonly in injuries above T6

• Secondary to disruption of sympathetic outflow from T1 – L2

• Loss of vasomotor tone – pooling of blood• Loss of cardiac sympathetic tone – bradycardia • Blood pressure will not be restored by fluid

infusion alone• Massive fluid administration may lead to

overload and pulmonary edema • Vasopressors may be indicated• Atropine used to treat bradycardia

Types of incomplete injuries

i) Central Cord Syndrome

ii) Anterior Cord Syndrome

iii) Posterior Cord Syndrome

iv) Brown – Sequard Syndrome

v) Cauda Equina Syndrome

i) Central Cord Syndrome :

• Typically in older patients

• Hyperextension injury

• Compression of the cord anteriorly by osteophytes and posteriorly by ligamentum flavum

• Also associated with fracture dislocation and compression fractures

• More centrally situated cervical tracts tend to be more involved hence

flaccid weakness of arms > legs

• Perianal sensation & some lower extremity movement and sensation may be preserved

ii) Anterior cord Syndrome: • Due to flexion / rotation• Anterior dislocation / compression fracture

of a vertebral body encroaching the ventral canal

• Corticospinal and spinothalamic tracts are damaged either by direct trauma or ischemia of blood supply (anterior spinal arteries)

Clinically:

• Loss of power

• Decrease in pain and sensation below lesion

• Dorsal columns remain intact

ii) Posterior Cord Syndrome:

Hyperextension injuries with fractures of the posterior elements of the vertebrae

Clinically: • Proprioception affected – ataxia and

faltering gait • Usually good power and sensation

iv) Brown – Sequard Syndrome:

• Hemi-section of the cord

• Either due to penetrating injuries:

i) stab wounds

ii) gunshot wounds

• Fractures of lateral mass of vertebrae

Clinically:

• Paralysis on affected side (corticospinal)

• Loss of proprioception and fine discrimination (dorsal columns)

• Pain and temperature loss on the opposite side below the lesion (spinothalamic)

v) Cauda Equina Syndrome:• Due to bony compression or disc

protrusions in lumbar or sacral region

Clinically • Non specific symptoms – back pain

- bowel and bladder dysfunction- leg numbness and weakness- saddle parasthesia

In conclusion;

Spinal Cord Injuries:• Devastating event to both patient and

family.• Huge impact on society• After receiving First – World care in

tertiary institutions, many of our patients return to impoverished communities

• Here they face huge challenges in terms of survival

thank you

References: 1. Andrew T Raftery, et al. Applied Basic Science for

Basic Surgical Training. Second edition 2008;8:219-223

2. ATLS, et al. Student Course Manual. 7th Edition 2004;7:177-204

3. Keith L Moore et al. Clinically Orientated Anatomy. 3rd Edition1992;4:359-369

4. Segun T Dawodu et al. eMedicine Specialities. March 2009

5. K Frielingsdorf, R N Dunn et al. SAMJ. March 2007,Vol. 97,No. 3