Raised ICP

Question 1

What is the normal ICP in adults?

Answer 1

Normal ICP is <15mmHg

The volume in cranium is fixed so any increase in contents can lead to raised ICP. This can be mass effect, oedema or obstruction to fluid outflow.

Question 2

List some causes of raised ICP.

Answer 2

• Primary or metastatic tumours
• Head injury
• Haemorrhage (subdural, extradural, subarachnoid, intracerebral, intraventricular)
• Infection: meningitis, encephalitis, brain abscess
• Hydrocephalus
• Cerebral oedema
• Status epilepticus

Question 3

What are the signs and symptoms of raised ICP?

Answer 3

• Headache (worse on coughing, leaning forwards), vomiting
• Altered GCS, drowsiness, listlessness, irritability, coma
• History of trauma
• Low HR, high BP (Cushing’s response); Cheyne-Stokes breathing
• Pupil changes (constriction at first then dilation - do not mask these signs but using agents such as tropicamide to dilate the pupil to aid fundoscopy)
• Low visual acuity, peripheral visual field loss
• Papilloedema is an UNRELIABLE sign, but venous pulsations at disc may be absent (absent in ~50% of normal people but LOSS of it is a useful sign)

Question 4

What investigations should you do for raised ICP?

Answer 4

Bloods:

• U&Es
• FBC
• LFTs
• Glucose
• Serum osmolality
• Clotting
• Blood culture
• Toxicology screen

Imaging

• CXR - any source of infection that might indicate abscess
• CT head
• LP - if SAFE (measure the opening pressure - >250mm H20?)

Other:

• optic disc photographs - assess papilloedema
• visual field testing - check for defects