Pathophysiology of Raised Intracranial Pressure Flashcards
What is the normal range for intracranial pressure?
5-15 mmHg
What is the definition of raised intracranial pressure?
Pressure >20 mmHg for more than 5 minutes
What can cause natural variations in ICP?
Rise in arterial pressure- heart rate
Rise in venous pressure- coughing, sneezing, laughing
Describe the Monroe-Kellie Theory
The cranium is a fixed volume so the volume must remain constant. If the mass inside the cranium starts to increase, it must be compensated for by a loss of venous blood and CSF.
What happens after the critical volume of the cranium is reaches and the cranium mass is still increasing?
The intracranial pressure starts to rise
Why should a lumbar puncture never be done on a patient with suspected raised ICP?
Can cause coning- tonsillar herniation, leading to increased pressure on the brainstem and therefore death of the brainstem.
What may make a raised ICP headache worse?
Lying down, leaning forward
Worse in the morning
Give 4 potential signs in the eye of raised intracranial pressure
Papilloedema
3rd nerve palsy
6th nerve palsy
Loss of vestibulo-ocular reflex
Give 4 non-eye signs of raised intracranial pressure
Confusion Reduced GCS UMN signs Decorticate or decerebrate posture Cushing's reflex
Explain the Cushing’s reflex
Raised intracranial pressure leads to ischaemia of the brain. To compensate, the heart rate is increased which increases the blood pressure. The increase in blood pressure is detected by the baroreceptors and so the respiratory rate is reduced resulting in bradycardia.
Give 5 causes of a raised intracranial pressure
Hydrocephalus Haemorrhagic stroke Tumour Infection Trauma Abscess Meningioma
Give the 3 reasons why hydrocephalus can occur
Excess CSF production
Disruption of CSF flow
Disruption of CSF absorption by the arachnoid granulations
