Raised Intracranial Pressure

Question 1

Define raised ICP

Answer 1

normal ICP is 7-15 mmHg; upper limit of normal is 20-25 mmHg.

The volume inside the cranium is fixed. This can be mass effect, oedema or obstruction to fluid outflow.

Question 2

What are the causes/risk factors of raised ICP?

Answer 2

• Space Occupying Lesions:
- Primary or metastatic brain tumours.
- CNS TB
- Brain Abscess
• Head injury
• Haemorrhage (SAH, EDH, SDH, intracerebral, intraventricular).
• Infection: meningitis, encephalitis, brain abscess.
• Hydrocephalus –obstruction to CSF outflow.
• Increased venous pressure: venous sinus thrombosis and congestive heart failure.
• Cerebral oedema.
• Status epilepticus.
• Idiopathic Intracranial Hypertension (IIH).

Question 3

What are the signs and symptoms of raised ICP?

Answer 3

• Trauma
• Headache, worse on coughing and leaning forwards
• Visual Acuity; Peripheral Visual Field Loss
• Neck and shoulder pain
• Papilloedema is an unreliable sign, but venous pulsation at the disc may be absent.
• Vomiting without nausea
• GCS: drowsiness; listlessness, irritability, coma.
• Cushing’s Reflex: Irregular breathing, Systolic Hypertension & wide pulse pressure, bradycardia.
• Cheyne–Stokes respiration: Progressive increase in depth & rate of respiration, then a progressive decrease culminating in apnoea.
• Biot’s respiration: breathing is rapid for a period and then absent for a period, occurs because of injury to the cerebral hemispheres or diencephalon.
• Pupil changes (constriction at first, later dilatation—do not mask these signs by using agents such as tropicamide to dilate the pupil to aid fundoscopy).
• In infants, protruding fontanels may be a sign of raised ICP.

Question 4

What investigations are carried out for raised ICP?

Answer 4

• Funduscopic – Papilledema – can then do an OCT to measure the retinal nerve fibre layer – papilledema
• Snellen’s acuity testing
• CT/ MRI: to visualise the lesion causing intracranial hypertension.
• LP: To diagnose meningitis and encephalitis; once ICP is reduced.
• LP is contraindicated in raised ICP.
• Bloods: FBC, U&Es, Glucose, Clotting Screen and Blood Culture –results can help identify the underlying cause.