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Clinical Neuroscience > Raised Intracranial Pressure > Flashcards

Raised Intracranial Pressure Flashcards

1
Q

What 3 things determine normal ICP?

A

Volume of;

  • Blood
  • Brain
  • CSF
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2
Q

State the approximate values for normal ICP for Adults, Children and Term Infants

A

Adults: 5-15mmHg
Children: 3-7mmHg
Term Infants: 1.5-6mmHg

(A good rule of thumb is: >20mmHg = raised ICP)

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3
Q

Describe the Monro-Kellie Doctrine

A

Any increase in the volume of one of the intracranial components must be compromised by a decrease in the volume of one of the others

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4
Q

According to the Monro-Kellie Doctrine, in the case of an intracranial mass (tumour) what are the 1st components to be pushed out of the intracranial space?

A

CSF and Venous blood since they are at the lowest pressure

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5
Q

How do you calculate Cerebral Perfusion Pressure

A

CPP= MAP-ICP

Mean Arterial minus Intracranial

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6
Q

State the normal CPP, MAP and ICP

A

CPP: >70mmHg
MAP: 90mmHg
ICP: 10mmHg

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7
Q

What happens if MAP increases?

A

Causes CPP to increase, triggering cerebral autoregulation (vasoconstriction)

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8
Q

What happens if ICP increases?

A

Causes CPP to decrease, triggering cerebral autoregulation (vasodilation)

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9
Q

Why can’t cerebral flow be maintained if CPP<50mmHg?

A

Cerebral arterioles are maximally dilated (so no increase in cerebral blood flow)

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10
Q

Describe the capability of maintenance of ICP

A

Can be maintained at a constant level as an intracranial mass expands, up to a certain point.

Beyond this point, ICP rises very rapidly

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11
Q

How can brain damage affect autoregulation?

A

Can impair or abolish autoregulation

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12
Q

Describe Cushing’s Reflex/ Response/ Triad

A
  • Rise in ICP initially-> Hypertension as body increases MAP to maintain CPP
  • Increased MAP detected by Baroreceptors, which stimulate a reflex bradycardia via increased vagal activity. (Can cause stomach ulcers)
  • Continued Brainstem compression-> Irregular breathing
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13
Q

What are 2 types of consequences of raised ICP

A
  • Clinical features

- Brain herniation

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14
Q

List and describe 5 types of Brain herniation

A

Tonsillar herniation/ Coning;
- Cerebellar tonsils through FM, compress Medulla

Subfalcine herniation;
- Cingulate Gyrus pushed under Falx Cerebri (can compress ACA)

Uncal herniation;
- Uncus through Tentorial Notch (Midbrain compression, CNIII palsy, Contralateral Hemiparesis due to Cerebral Peduncle compression)

Central Downard herniation;
- Medial T lobe/ midline structures pushed through T notch

External herniation;
- Through Skull Fracture or Craniectomy

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15
Q

List 8 clinical features of raised ICP

A
  • Headache (Constant, Worse in morning, bending, straining)
  • Nausea & Vomiting
  • Confusion
  • Diplopia
  • Seizures
  • Difficulty concentrating/ drowsiness
  • Papilloedema
  • Focal neurological signs
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16
Q

Suggest 4 types of causes of raised ICP

A
  • Too much blood within cerebral vessels (rare)
  • Too much blood outside of cerebral vessels
  • Too much CSF/ Hydrocephalus (Congenital or Acquired)
  • Too much brain
17
Q

What are the 3 signs of raised ICP

These are late stage signs

A
  • Hypertension
  • Bradycardia
  • Irregular breathing
18
Q

Suggest 2 ways having too much blood within cerebral vessels can lead to Raised ICP

A
  • Raised Arterial pressure (e.g Malignant hypertension, Systolic >180 or Diastolic >120)
  • Raised Venous pressure (SVC obstruction e.g compression by a lung tumour)
19
Q

Suggest 5 ways having too much blood outside of the cerebral vessels can lead to Raised ICP

A

Haemorrhage;
- Extradural, Subdural, Subarachnoid

  • Haemorrhagic stroke
  • Intraventricular haemorrhage
20
Q

Either Acquired or Congenital causes of having too much CSF can lead to raised ICP

List 2 types of Congenital causes of Hydrocephalus

A
  • Communicating

- Obstructive/ non communicating

21
Q

Suggest 2 Obstructive and 2 Communicating causes of Congenital Hydrocephalus

A

Obstructive Congenital Hydrocephalus;

  • Neural tube defects
  • Aqueduct stenosis

Communicating Congenital Hydrocephalus;

  • Increased CSF production
  • Decreased CSF absorption
22
Q

List 3 clinical signs of Hydrocephalus

A
  • Bulging head with circumference increasing faster than expected
  • Neurological deficits
  • Sunsetting eyes/ Downward gaze (due to orbital compression + CNIII involvement)
23
Q

Suggest 4 Acquired causes of Hydrocephalus

A
  • Meningitis/ Infection
  • Trauma
  • Haemorrhage (E.g after SAH)
  • Tumours (Cerebral aqueduct compression-> Stenosis)
24
Q

Suggest 4 ways ‘too much brain’ can cause raised ICP

A
  • Cerebral Oedema (4 major pathophysiologies/ types)
  • Tumour
  • Cerebral abscess
  • Idiopathic Intracranial Hypertension (IIH)
25
Q

List and describe the 4 different types/ pathophysiologies of Cerebral Oedema

A

Vasogenic;
- Disruption of BBB tight junctions

Osmotic;
- Change in osmolarity gradient across BBB, so water enters CSF

Cytotoxic;
- Injury to Bain cells

Interstitial;
- Increased pressure in ventricles, so lining gets damaged-> CSF leaks into brain parenchyma

26
Q

Describe the presentation and epidemiology of Benign/ Idiopathic Intracranial Hypertension (IIH)

A
  • Headache + Visual disturbance

- Obese, middle aged females

27
Q

How is IIH diagnosed?

A
  • CT/ MRI FIRST to rule out herniation
  • Raised opening pressure on LP

LPs are CONTRAINDICATED in RAISED ICP, due to risk of HERNIATION

28
Q

How is IIH treated?

A
  • Weight loss
  • BP control
  • Treat symptoms and prevent progressive nerve damage
29
Q

How is Raised ICP managed?

A
  1. ABCDE approach
  2. Stabilise + neurological exam
  3. Simple measures;
    - Elevate head
    - Avoid pyrexia
    - Analgesia
  4. Specific medical measures;
    - Anticonvulsants
    - Sedation
    - Mannitol/ hypertonic saline

Surgical;

  • Ventricular drainage
  • Decompressive craniectomy (last resort)
30
Q

Describe the management of Hydrocephalus in an acute setting

A

Tapping the fontanelle with a needle

31
Q

Describe the management of Hydrocephalus in the medium-term

A

Use an External Ventricular Drain (EVD);

  • Risk of infection
  • Allows continuous pressure monitoring
  • Used if shunt fails or contraindicated
32
Q

Describe the treatment of Hydrocephalus in the long-term

A
  • Can use a VA or VP shunt (most common)
  • One way valve used to prevent backflow
  • Extra length of tubing is provided to allow growth

(Most shunts will require revision)

33
Q

Compare the routes of VA and VP shunts

What are 2 things VP shunts are vulnerable to?

A
  • VA: Ventricular system to Right Atrium
  • VP: Ventricular system to Peritoneum
  • Infection
  • Kinking

Clinical Neuroscience (19 decks)

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