Raised Intracranial Pressure Flashcards
What 3 things determine normal ICP?
Volume of;
- Blood
- Brain
- CSF
State the approximate values for normal ICP for Adults, Children and Term Infants
Adults: 5-15mmHg
Children: 3-7mmHg
Term Infants: 1.5-6mmHg
(A good rule of thumb is: >20mmHg = raised ICP)
Describe the Monro-Kellie Doctrine
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
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?
CSF and Venous blood since they are at the lowest pressure
How do you calculate Cerebral Perfusion Pressure
CPP= MAP-ICP
Mean Arterial minus Intracranial
State the normal CPP, MAP and ICP
CPP: >70mmHg
MAP: 90mmHg
ICP: 10mmHg
What happens if MAP increases?
Causes CPP to increase, triggering cerebral autoregulation (vasoconstriction)
What happens if ICP increases?
Causes CPP to decrease, triggering cerebral autoregulation (vasodilation)
Why can’t cerebral flow be maintained if CPP<50mmHg?
Cerebral arterioles are maximally dilated (so no increase in cerebral blood flow)
Describe the capability of maintenance of ICP
Can be maintained at a constant level as an intracranial mass expands, up to a certain point.
Beyond this point, ICP rises very rapidly
How can brain damage affect autoregulation?
Can impair or abolish autoregulation
Describe Cushing’s Reflex/ Response/ Triad
- 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
What are 2 types of consequences of raised ICP
- Clinical features
- Brain herniation
List and describe 5 types of Brain herniation
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
List 8 clinical features of raised ICP
- Headache (Constant, Worse in morning, bending, straining)
- Nausea & Vomiting
- Confusion
- Diplopia
- Seizures
- Difficulty concentrating/ drowsiness
- Papilloedema
- Focal neurological signs
Suggest 4 types of causes of raised ICP
- Too much blood within cerebral vessels (rare)
- Too much blood outside of cerebral vessels
- Too much CSF/ Hydrocephalus (Congenital or Acquired)
- Too much brain
What are the 3 signs of raised ICP
These are late stage signs
- Hypertension
- Bradycardia
- Irregular breathing
Suggest 2 ways having too much blood within cerebral vessels can lead to Raised ICP
- Raised Arterial pressure (e.g Malignant hypertension, Systolic >180 or Diastolic >120)
- Raised Venous pressure (SVC obstruction e.g compression by a lung tumour)
Suggest 5 ways having too much blood outside of the cerebral vessels can lead to Raised ICP
Haemorrhage;
- Extradural, Subdural, Subarachnoid
- Haemorrhagic stroke
- Intraventricular haemorrhage
Either Acquired or Congenital causes of having too much CSF can lead to raised ICP
List 2 types of Congenital causes of Hydrocephalus
- Communicating
- Obstructive/ non communicating
Suggest 2 Obstructive and 2 Communicating causes of Congenital Hydrocephalus
Obstructive Congenital Hydrocephalus;
- Neural tube defects
- Aqueduct stenosis
Communicating Congenital Hydrocephalus;
- Increased CSF production
- Decreased CSF absorption
List 3 clinical signs of Hydrocephalus
- Bulging head with circumference increasing faster than expected
- Neurological deficits
- Sunsetting eyes/ Downward gaze (due to orbital compression + CNIII involvement)
Suggest 4 Acquired causes of Hydrocephalus
- Meningitis/ Infection
- Trauma
- Haemorrhage (E.g after SAH)
- Tumours (Cerebral aqueduct compression-> Stenosis)
Suggest 4 ways ‘too much brain’ can cause raised ICP
- Cerebral Oedema (4 major pathophysiologies/ types)
- Tumour
- Cerebral abscess
- Idiopathic Intracranial Hypertension (IIH)
