Spinal cord injury

Question 1

What are the features of vertebrae?

Answer 1

Vertebral body - weight bearing component, lined with hyaline cartilage
Vertebral arch - forms foramen for the vertebral canal
Spinous process - each has a single spinous process, centred posteriorly
Transverse processes - each has two that extend laterally and posteriorly, articulate with ribs
Pedicles - connect vertebral body to the transverse processes
Lamina - connect transverse and spinous processes
Articular processes - form joints between one vertebra and its superior and inferior counterparts

Question 2

What are the classifications of vertebrae and what are their unique features?

Answer 2

Cervical:
C1 and C2 are uniwue, but others have bifid spinous process, transverse foramina for vertebral arteries, triangular vertebral foramen
Thoracic:
Each body has two demi facets on either side to articulate with ribs, costal facet on transverse processes, spinous process extends below body
Lumbar:
very large vertebral bodies, no transverse foramina, costal facets or bifid processes. Spinous process doesn’t extend below body

Question 3

What ligaments are around the lumbar vertebrae?

Answer 3

Anterior and posterior longitudinal ligaments: run the length of the vertebral column, covering the bodies and intervertebral discs
Ligamentum flavum: connects laminae of adjacent vertebrae
Interspinal ligament: connects spinous processes of adjacent vertebrae
Supraspinous ligament: connects tips of spinous processes

Question 4

What are the features of the spinal cord?

Answer 4

• Continuation of the medulla oblongata
• At L2, cord tapers off forming conus medullaris
• Spinal nerves that arise from the end are bundled together = cauda equina
• Cervical enlargement - caused by origin of brachial plexus
• Lumbar enlargement - origin of lumbar and sacral plexi
• Meninges - dura mater, arachnoid mater, pia mater

Question 5

What is the arterial supply of the spinal cord?

Answer 5

Anterior spinal artery
Paired posterior spinal arteries

Question 6

What are the features of the cross section of the spinal cord?

Answer 6

Dorsal horn - location of sensory synapses
Dorsal root ganglion - transmits signals from the PNS to the CNS
Ventral horn - location of motor synapses
Lateral horn - central component of sympathetic division of the ANS

Question 7

What are the different types of vertebral fractures?

Answer 7

Compression fracture: vertebral body collapses, usually caused by osteoporosis
Axial burst fracture: bone crushed in multiple directions usually due to fall or impact
Chance fracture: flexion-distraction injury, usually at thoracolumbar junction results in horizontal fracture through spinous processes, pedicles and vertebral body

Question 8

What are symptoms of a spinal fracture?

Answer 8

Pain in back or neck
Tingling or numbness
Weakness or paralysis of limbs
Uncontrolled muscle spasms
Loss of urinary or bowel control
Loss of consciousness due to high energy trauma

Question 9

What information does the DCML transmit?

Answer 9

Fine touch, proprioception, vibration

Question 10

Where does the DCML travel?

Answer 10

Signals from upper limb (T6 and above) – travel in the fasciculus cuneatus (lateral part of dorsal column)
Synapse in the nucleus cuneatus of the MO
Signals from lower limb (below T6) – travel in fasciculus gracilis (medial part of dorsal column).
Synapse in the nucleus gracilis of the MO
2nd order neurons originating in the cuneate nucleus or gracilis, decussate in MO and travel in medial leminiscus to thalamus
3rd order neurons travel from thalamus to ipsilateral primary sensory cortex through internal capsule

Question 11

What sensory information does the spinothalamic tract carry?

Answer 11

Anterior spinothalamic - crude touch and pressure
Lateral spinothalamic - pain and temperature

Question 12

Where does the spinothalamic tracts travel?

Answer 12

1st order neurons arise from sensory receptors in the periphery
Enter spinal cord, ascend 1-2 vertebral levels, synapse at tip of dorsal horn (substantia gelatinosa)
2nd order neurons originate in substantia and decussate in MO and form distinct tracts:
crude touch and pressure - anterior spinothalamic tract
pain and temperature - lateral spinothalamic tract
Synapse at thalamus
3rd order neurons carry signals from thalamus through internal capsule to ipsilateral primary sensory cortex of the brain

Question 13

What information does the corticospinal tract carry?

Answer 13

Receive inputs from primary motor cortex, premotor cortex and supplementary motor area and somatosensory area (regulates activity)
For voluntary control of musculature of the body

Question 13

Where does the corticospinal tract travel?

Answer 13

UMN originate from the cortex, neurones converge, descend through internal capsule, through crus cerebri of the midbrain, the pons and medulla
Tract divides into two within the MO:
fibres in lateral corticospinal tract decussate, descend into spinal cord, terminating in ventral horn
LMN go on to supply muscles of the body
Anterior corticospinal tract remains ipsilateral, descend into spinal cord. Decussate and terminate in the ventral horn of the cervical and upper thoracic segmental levels

Question 14

What are the different types of causes of spinal cord injury, and give examples?

Answer 14

Trauma: violence, penetrating wounds, whiplash
Demyelinating disease: MS, spinal muscular atrophy
Infection: spinal meningitis, AIDS
Metabolic disorder: vitamin B12 deficiency
Vascular: anterior spinal artery occlusion
Tumour: primary or secondary cancer

Question 15

What are the different types of incomplete SCI?

Answer 15

Central cord
Anterior cord
Posterior cord
Brown-sequard

Question 16

Central cord SCI

Answer 16

Central cord:
Damage to cervical spine, in the centre of the cord. Usually due to hyperextension, and compression of cord occurs
Corticospinal and spinothalamic tract affected.
Weakness affecting upper limbs. Loss of pain and temp sensation below level of injury

Question 17

Anterior cord SCI

Answer 17

Usually due to compromised BF from anterior spinal artery.
Spinothalamic and corticospinal tract affected - loss of pain and temp sensation, weakness/paralysis below level of injury

Question 18

Posterior cord SCI

Answer 18

Rarely due to trauma - normally infection or metabolic causes
Dorsal columns - loss of tactile and vibratory sensation, proprioception
Spinothalamic and corticospinal tracts unaffected

Question 19

Brown-sequard SCI

Answer 19

Right or left sided transection of the cord due to penetrating injuries
Corticospinal and DC tracts: ipsilateral loss of motor function, tactile and vibratory sensation and proprioception below level of injury
Spinothalamic tract: contralateral loss of pain and temperature sensation below level of injury

Question 20

What effect does complete transection of spinal cord have?

Answer 20

Complete bilateral loss motor function, pain sensation, temperature sensation, proprioception, vibratory sensation, tactile sensation below level of injury

Question 21

What can SCI lead to? 6

Answer 21

Reflex bladder: bladder muscles contract to release urine and the person cannot control or feel when this happens
Non-reflex bladder: when bladder is not able to empty urine through reflex
Quadriplegia: paralysis affecting all limbs and body from the neck down
Paraplegia: paralysis of the lower body
Horner’s syndrome: due to damage to hypothalamospinal tract at T1 or above. Presents with partial ptosis, miosis and facial anhidrosis
Poor trunk control: loss of control of abdominal, chest back muscles

Question 22

What is spinal shock syndrome?

Answer 22

Absence of reflexes and motor or sensory function below the level of injury which occurs usually from the time injury as sustained up to 24 hours after, followed by reflex return

Question 23

What is the process of spinal shock syndrome and afterwards?

Answer 23

1-2 days:
neurons become less responsive to sensory input, resulting in full or partial loss of spinal cord reflexes - hyporeflexia
1-3 days:
First return of some reflexes
1-4 weeks:
hyperreflexia - unusually strong reflexes occur, result of new nerve synapse growth and is normally temporary
1-12 months:
hyperreflexia continues and spasticity may develop. Due to changes in neuronal cell bodies and takes much longer than other stages

Question 24

What is the micturition reflex?