Neuroradiology, ICP and CBF,

Question 1

what are common indications for a CT scan in neurology?

Answer 1

• stroke
• headache (subarachnoid haemorrhage)
• tumours
• head trauma

Question 2

what are contraindications for CT scans in neurology?

Answer 2

• epilepsy

- no significant symptoms post head trauma

Question 3

what are common indications for MRI scans in neurology?

Answer 3

• CNS tumours
• demyelination
• spine compression (slipped disc)
• epilepsy
• TIA
• headaches
• pediatric neurology

Question 4

what are contraindications for MRI scans in neurology?

Answer 4

• metallic pacemakers/implants/devices

- claustrophobia/pregnancy/tattoos

Question 5

what do CT or MRI perfusion scans measure?

Answer 5

amount of blood flowing in volume of tissue in certain amount of time

Question 6

what indications are cerebral angiograms carried out for in neurology?

Answer 6

• aneurysms
• arteriovenous abnormalities
• carotidocavernous fistula
• persistent epistaxis

Question 7

what would a CT perfusion scan show in 1. tumours, and 2. stroke?

Answer 7

1. increased perfusion - angiogenesis around tumour

2. decreased perfusion - blood vessel blocked or in spasm

Question 8

what are common indications for PET scans in neurology, and what do they show?

Answer 8

show glucose usage by cells
indications:
- tumours
- inflammation
- infection

Question 9

what are four among the common neurology emergencies which may require imaging?

Answer 9

• head trauma
• stroke
• subarachnoid haemorrhage
• cauda equina syndrome

Question 10

what is the estimation of cerebral perfusion pressure?

Answer 10

55-60ml/100g/min

Question 11

what is the volume of cerebral perfusion pressure below which ischaemia occurs?

Answer 11

less than 20ml/100g/min

Question 12

what is the average volume of a normal brain?

Answer 12

1400g

Question 13

what is the added volume of blood and CSF to the volume of an average brain?

Answer 13

150mg blood + 150mg CSF

Question 14

what does cerebral autoregulation consist of?

Answer 14

the ability of maintaining a constant blood flow to brain tissue despite changes in cerebral perfusion pressure changes

Question 15

above which level of cerebral perfusion pressure is autonomic regulation lost?

Answer 15

150mmHg or above

Question 16

what equation gives the cerebral perfusion pressure (CPP)?

Answer 16

MAP - ICP

Question 17

list the three main factors which affect cerebral blood flow

Answer 17

• CPP
• arterial PCO2
• arterial PO2

Question 18

what are the physiological reactions to low or high CPP in the brain?

Answer 18

low CPP - vasodilation of arterioles to increase blood flow

high CPP - vasoconstriction of arterioles to reduce blood flow

Question 19

what are the three possible types of cerebral oedema? name a cause for each

Answer 19

• vasogenic (tumour, late stage of infarction)
• cytotoxic (water poisoning, early infarction)
• interstitial (communicating hydrocephalus)

Question 20

what is the blood brain barrier?

Answer 20

it’s a physical barrier between brain tissue and circulation to keep brain tissue under tight regulation

Question 21

what is the blood brain barrier made up of?

Answer 21

tight junctions between vascular endothelial cells

tightly packed astrocytes around the brain arterioles

Question 22

which nutrients can get through the BBB, and through what means?

Answer 22

lipids - passive diffusion

amino acids and sugars - gated channels

Question 23

what does the Monro-Kellie doctrine explain?

Answer 23

it defines the relative compensation of brain pressure in response to a change in volume

Question 24

what two concepts does the Monro-Kellie doctrine use? what are the equations for each?

Answer 24

compliance = volume/pressure
elastance = pressure/volume

Question 25

according to the Monro-Kellie doctrine, which components of total brain volume are used to initially compensate for a change in volume?

Answer 25

• CSF

- venous blood

Question 26

what are the components of the brain which make up its total volume?

Answer 26

• brain tissue
• arterial blood
• venous blood
• CSF

Question 27

what is the triad of symptoms called which can occur as a result of raised ICP?

Answer 27

Cushing’s reflex

Question 28

what are the three main signs of Cushing’s reflex?

Answer 28

• hypertension
• bradycardia
• irregular breathing

Question 29

explain, in short, the cause of each symptom of Cushing’s reflex

Answer 29

• hypertension: raised MAP in attempt to counter raised ICP and get enough blood through constricted arterioles
• bradycardia: vagal response to sympathetic action which caused the tachycardia and hypertension
• irregular breathing: medulla malfunctioning as a result of raised ICP and MAP

Question 30

what are the three main stages of the ICP waveform? what do they reflect?

Answer 30

1 - percussion wave - systolic pressure
2 - tidal wave - brain tissue resistance to systolic blood volume
3 - dicrotic wave - aortic valve closing

Question 31

how are the waveforms of ICP measured?

Answer 31

through a manometer attached to an external ventricular drain

Question 32

what is the management of raised ICP?

Answer 32

• raise bedrest
• hyperventilation to increase CBF
• inject mannitol/hypertonic saline
• surgical decompression
• barbiturate coma to reduce cerebral metabolism

Question 33

what clinical event can follow Cushing’s reflex?

Answer 33

brain herniation

Question 34

what are the varying types of ICP waveforms called?

Answer 34

Lundberg waves A, B and C

Question 35

what are Lundberg waves A?

Answer 35

temporary sustained rise in ICP, associated with raised cerebrovascular volume due to vasodilation

Question 36

what are Lundberg waves B and C?

Answer 36

short temporary increases in ICP, related to breathing pattern and systemic blood pressure