Raised intracranial pressure
Overview
•Rising ICP → reduced CPP → brainstem ischaemia → sympathetic surge → vasoconstriction and hypertension → baroreceptor-mediated reflex bradycardia + irregular breathing
•Cushing's triad = hypertension + bradycardia + irregular breathing - a late, pre-terminal sign of critically raised ICP
Presentation
•Headache - worse on waking, coughing, straining, or bending forward (ICP peaks during sleep due to increased cerebral venous pressure when lying flat)
•Vomiting - projectile, without preceding nausea; direct medullary stimulation
•Papilloedema - raised ICP transmitted along optic nerve sheath, compressing central retinal vein; fundoscopy shows blurred disc margins, loss of venous pulsations, flame haemorrhages
•CN VI palsy (diplopia) - false localising sign; longest intracranial course, vulnerable to compression regardless of lesion location
•Fixed dilated pupil + ptosis - unilateral CN III palsy = uncal herniation (medial temporal lobe herniates through tentorial notch) = neurosurgical emergency
•Altered consciousness - lethargy → stupor → coma → death
Investigations
🥇 First-line
•CT head - identifies haematomas, hydrocephalus, midline shift, mass lesions, loss of basal cisterns (sign of impending herniation)
•Lumbar puncture - contraindicated if raised ICP suspected until CT has excluded mass lesion or obstructive hydrocephalus; risk of tonsillar herniation (coning)
Management
•Dexamethasone - effective for vasogenic oedema around brain tumour/metastasis; do NOT use in traumatic brain injury or ischaemic stroke oedema (worsens outcomes)
Hydrocephalus in Infants
•Exponentially increasing head circumference - unfused skull sutures allow splaying
•Bulging fontanelles
•Dilated scalp veins
•Sunsetting sign - impaired upward gaze caused by pressure on the tectal plate of the midbrain
•Bradycardia and seizures may also occur