Session 9 - Raised Intracranial Pressure Flashcards
What is the range for normal intracranial pressure?
5-15 mm Hg
How is blood flow to the brain regulated in healthy individuals?
Autoregulation:
- vasoconstriction
- vasodilation
Chemo-regulation:
- vasodilation in response to low cerebral pH e.g. high pCO2
These can maintain ICP to a degree even in diseased states
What are the signs and symptoms of raised intracranial pressure?
Headache Vomiting CN VI palsy Visual disturbances Depression of conscious level In infants, slowly increasing intracranial pressure may present as a slowly increasing head size.
Describe the headache experienced by patients with raised intracranial pressure.
Generalised headache Worst on awakening in the morning (result of hypoventilation during sleep and increased venous pressure in the head when lying down) May awaken patient from sleep Aggravated by bending, stooping Aggravated by coughing or sneezing Severity gradually progresses
The nausea and vomiting experienced by patients with raised intracranial pressure will eventually progress to what?
Projectile vomiting
What visual disturbances are experienced by patients with raised intracranial pressure?
Blurring
Obscurations - transient blindness upon bending or posture changes
Papilloedema in some patients
Retinal haemorrhages if the rise in ICP has been rapid
Why do patients with raised intracranial pressure experience depression of conscious level?
Ischaemia of the reticular formation
What are the three kinds of brain herniation?
Subfalcine herniation
Uncal herniation
Tonsillar herniation
Which kind of brain herniation is the most common?
Subfalcine herniation
What are the symptoms of a subfalcine herniation?
May be asymptomatic
Symptoms can include headache and contralateral leg weakness if anterior cerebral artery affected.
Midline shift on CT
How is the brain displaced in an uncal herniation?
The uncut (medial part of the temporal lobe) is displaced across the tentorial opening.
What are the symptoms of uncal herniation?
As the herniation progresses, the uncus puts pressure on the midbrain. This leads to
Ipsilateral oculomotor nerve (parasympathetic fibres) - ipsilateral dilated pupil
Compression of cerebral peduncle - contralateral leg weakness
Above signs may be false localising if the midbrain is pushed against the opposite side of the tentorium.
Decreased level of consciousness.
What is a tonsillar herniation?
The cerebellar tonsils herniate through the foramen magnum.
What are the symptoms of a tonsillar herniation?
Compression of medulla and upper spinal cord.
Brainstem affected - cardiac and respiratory dysfunction
Decreased level of consciousness
What is Cushing’s reflex?
If raised ICP is untreated and continues to rise you get a triad of:
High BP
Bradycardia
Low respiratory rate - altered breathing pattern
Poor prognostic sign. If left untreated - death.