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Neurology > ICP & Hydrocephalus > Flashcards

ICP & Hydrocephalus Flashcards

1
Q

The brain makes up 80-85% of the head and blood and CSF make up the extra 20-25%. How much in mls is there approx of each?

A

Brain - 1300-1750ml
Blood - 100-150ml
CSF - 100-150ml

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2
Q

What is the normal ICP at rest and when may it be physiologically negative?

A
  • 7-15mmHg

- when in vertical position

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3
Q

explain the Monro-Kellie-Doctrine

A

Compensatory mechanism for expanding masses - immediate compensation is decrease in CSF by moving it out of foramen magnum and decreased in blood volume by squeezing sinuses. Delayed compensation is decrease in extra cellular fluid

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4
Q

Approx. How much CSF is secreted a day?

A

500mls/day

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5
Q

What is the cerebral perfusion pressure equation?

A

Mean arterial pressure - intracranial pressure

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6
Q

What is the equation for cerebral blood flow?

A

Cerebral perfusion pressure divided by cerebral vascular resistance

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7
Q

What state would cause the cerebral perfusion pressure to be
MAP 100 - ICP 20 = CPP 80

A

Cushing’s response - MAP high because raised BP in Cushing’s, your ICP is high because reacting a lot

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8
Q

What state would cause the cerebral perfusion pressure to be

MAP 50 - ICP 20 = CPP 30?

A

Hypotension - MAP low because hypotensive and ICP high because pain maybe

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9
Q

What state would cause cerebral perfusion pressure to be

MAP 90 - ICP 10 = CPP 80?

A

Normal state

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10
Q

What is the normal at rest ICP and in what non-pathological state can it be negative?

A
  • 7-15mmHg

- in vertical position

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11
Q

What is the easiest substance to release first according to Monro-Kellie doctrine? (CSF/venous blood)

A
  • CSF first

- then venous blood

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12
Q

Through what foramina does CSF move from 4th ventricle into the subarachnoid space?

A
  • two lateral foramina of Luschka

- medial foramen of Magendie

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13
Q

How does body auto regulate cerebral blood flow?

A
  • pressure autoregulation - arterioles dilate/constrict in response to changes in BP or ICP
  • metabolic autoregulation - arterioles dilate in response to chemicals e.g. lactic acid/CO2
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14
Q

Up to what mmHg can body autoregulate ICP?

A

50-150mmHg

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15
Q

What are the four mechanisms of raised ICP?

A

mass effect
brain swelling
increase in central venous pressure
problems with CSF flow

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16
Q

Give examples of mass effect causes of raised ICP.

A 
tumour
infarct
contusions
haematoma
abscess
17
Q

Give examples of causes of brain swelling that raises ICP. (5)

A 
ischaemia/anoxia
acute liver failure
encephalopathy
IIH
hypercarbia
18
Q

Give examples of causes of increase in central venous pressure.

A

venous sinus thrombosis
heart failure
obstruction of jugular veins

19
Q

Give examples of causes of CSF flow problems causing raised ICP. (3)

A

obstruction (obstructive hydrocephalus) e.g. masses/chiari syndrome,
increased production e.g. choroid plexus papilloma,
decreased absorption so arachnoid granulations are blocked (communicating hydrocephalus) e.g. SAH, meningitis, malignant meningeal disease

20
Q

What is treatment for choroid plexus papilloma and who tends to present with these tumours?

A

acetazolamide

children

21
Q

What is normal newborn ICP?

A

1.5-6mmHg (often <0)

22
Q

What is normal ICP in young children?

A

3-7mmHg

23
Q

What is normal ICP in older children?

A

10-15mmHg

24
Q

What are early signs & symptoms of raised ICP? (5)

A
  • decreased consciousness level (bit drowsy)
  • headache
  • pupillary dysfunction +/- papilloedema
  • changes in vision
  • nausea and vomiting
25
Q

What are later signs & symptoms of raised ICP? (6)

A 
coma, 
fixed, dilated pupils, 
hemiplegia,
bradycardia -> Cushing's triad, 
hyperthermia,
increased urinary output
26
Q

What are interventions for raised ICP? (7)

A 
maintain head in midline,
loosen tube ties/collars etc,
Head of bead 30-45 degrees elevation to facilitate venous flow out ,
avoid gagging, coughing ,
decrease environmental stimuli 
treat hyperthermia
maintain normal fluids, electrolytes
27
Q

What is medical management for raised ICP? (4)

A

diuretics e.g. hypertonic saline (sometimes mannitol, furosemide, urea),
barbiturate coma (last resort),
antiepileptics (prophylactically),
surgical decompression

28
Q

What is another description for hydrocephalus?

A

water on the brain

29
Q

What is the difference between communicating/non-communicating hydrocephalus?

A

Communicating is where CSF can still flow at the ventricles

Non-communicating is where CSF is blocked at the ventricles

30
Q

What is arrested hydrocephalus?

A

Hydrocephalus where patient has no symptoms because its compensated for

31
Q

Which type of hydrocephalus (communicating/non-communicating) will appear with enlargement of lateral, 3rd and 4th ventricles?

A

Communicating

32
Q

Which type of hydrocephalus (communicating/non-communicating) will appear with enlargement of frontal horns, temporal tip dilation , rounded 3rd but normal 4th ventricles?

A

Non-communicating

33
Q

What is treatment for hydrocephalus?

A

Shunt - commonly ventriculoperitoneal shunt

34
Q

What is the classical presentation of normal pressure hydrocephalus?

A
  • elderly

- present with Hakim’s triad (wet, wobbly and weird)

35
Q

What are the 3 symptoms of Hakim’s triad?

A
  • abnormal gait
  • urinary incontinence
  • dementia
36
Q

What is thought to be the cause of normal pressure hydrocephalus?

A

possibly decreasing brain elastance i.e. stiff tissue

37
Q

What are investigations for normal pressure hydrocephalus?

A
  • LP
  • lumbar drain test
  • lumbar infusion studies
38
Q

What is treatment for normal pressure hydrocephalus?

A
  • VP shunt

- medium-low or low-pressure valve

Neurology (34 decks)

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