Raised Intracranial Pressure Flashcards
What is the intracranial and spinal vault enclosed by?
Dura mater and bone
What does the intracranial and spinal vault contain?
- Neural tissue (brain and spinal cord)
- Blood
- CSF
What is intracranial pressure?
The pressure within the intracranial space
What is the normal ICP?
5-15mmHg
What occupies the intracranial space?
- CSF
- Blood
- Brain
How is blood flow to the brain regulated in an healthy individual?
- Autoregulation
- Chemoregulation
How does autoregulation of blood flow to the brain occur?
- Vasoconstriction
- Vasodilation
How does chemoregulation of blood flow to the brain occur?
Vasodilation in response to a low cerebral pH
What is the result of adaptation of the brain, blood, and CSF?
It can maintain ICP to a degree, even in disease states
Describe the steps in the pathophysiology of a brain injury?
- Reduction in blood supply to brain cells, e.g. compression by intracranial tumour
- Cytotoxic cellular oedema
- Further swelling and compression, so further reduction in blood supply to brain cells
What are the signs and symptoms of raised ICP?
- Headache
- Vomiting
- Visual disturbances
- Depression of conscious level
What are the features of the headache caused by raised ICP?
- Generalised ache
- Worst on awakening in the morning
- May awaken patient from sleep
- Severity gradually progresses
Why is the headache from raised ICP worse in the morning?
As a result of hypoventilation during the sleeping hours
What factors aggregate the headache caused by raised ICP?
- Bending or snooping
- Coughing or sneezing
Describe the vomiting caused by raised ICP
Nausea and vomiting that progresses to projective vomiting
What visual disturbances might occur with raised ICP?
- Blurring
- Obscurations
- Papilloedema
- Retinal haemorrhages
What are obscurations?
Transient blindness upon bending or posture changes
When will raised ICP patients get retinal haemorrhages?
If the rise in ICP has been rapid
How might slowly increasing intracranial pressure present in infants?
As slowly increasing head size
What happens if raised ICP is not treated, and continues to rise?
You get herniation through the foramen magnum
What is the clinical relavance of herniation through the foramen magnum?
It is a poor prognostic sign
What is Cushing’s reflex?
A last effort to perfuse the brain, whereby there is;
- Increased blood pressure
- Irregular breathing
- Bradycardia
What causes the bradycardia in Cushing’s reflex?
Ischaemia at the medulla leads to sympathetic activation, which causes a rise in blood pressure and tachycardia. Baroreceptors react, causing bradycardia
What causes the low respiratory rate in the Cushing’s reflex?
Ischaemia at the respiratory centres in the pons/medulla
What are the categories of causes of raised intracranial pressure?
- Increased cerebral blood volume
- Cerebral oedema
- Increased CSF
- Space occupying lesion