Neuro

Question 1

How is autonomic dysreflexia/hyperreflexia defined?

Answer 1

• A BP increase 20mmHg above baseline in someone with a spinal cord injury, usually when the damage has occurred above the T6 level
• It can manifest as a hypertensive crisis with severe complications

Question 2

Aetiology of autonomic dysreflexia/hyperreflexia?

Answer 2

• Disruption to the inhibitory descending pathways to the sympathetic preganglionic neurons below the level of the injury
• When a stimulus below the level of injury occurs there is widespread uninhibited VC of this vasculature leading to severe HTN
• This leads to diffuse vasoconstriction, typically to the lower two-thirds of the body, and a significant rise in blood pressure despite maximum parasympathetic vasodilatory efforts above the level of injury. In an intact autonomic system, this increased blood pressure activates the carotid sinus and aortic arch baroreceptors leading to a parasympathetic response slowing the heart rate via vagal nerve activity and causing diffuse vasodilation to correct the original increased sympathetic tone
  — generalized vasoconstriction affecting the splanchnic, muscular, vascular, and cutaneous arterial circulatory networks
  — The compensatory vagal and parasympathetic stimulation leads to bradycardia and vasodilation, but only above the level of the spinal cord injury

Question 3

Prevalence of autonomic hyperreflexia? What level of injury is needed and how soon after initial injury does it occur?

Answer 3

90% of patients with injuries at or above T6

As soon as within 2-3 weeks. Usually within 1 year in affected individuals

Question 4

What important structures are in the posterior fossa

Answer 4

Brainstem (midbrain, pons, medulla)
Cerebellum
3rd-12th CN nuclei
Ascending & Descending tracts
Vertebrobasilar vascular system
4th ventricle
Aqueduct of sylvius (cerebral aqueduct)

Question 5

Volume of CSF in paediatrics?

Answer 5

• can be more than 10mL/kg in neonates
• 4mL/kg in infants weighing <15kg
• 3mL/kg in children
• 1.5-2mL/kg in adolescents and adults

Question 6

At what ICP does focal ischaemia occur? And at what ICP does global ischemia occur?

Answer 6

> 20mmHg
50mmHg

Question 7

Compare plasma to CSF (appearance, protein, K+, Cl, Mg, Ca2+ , glucose, pH, pCO2, specific gravity)

Answer 7

Plasma: higher protein, K+, Ca2+, Glucose, pH, specific gravity

CSF: higher Cl-, CO2