Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 13 Sept 2026Clinical review pending
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Herniation is a clinical and imaging emergency
Declining consciousness, new anisocoria, extensor posturing or abrupt respiratory change can indicate tissue displacement before every radiological sign is fully developed.
Action: Activate emergency neurological support, optimise oxygenation and circulation, elevate and align the head where appropriate, obtain urgent CT when safe, and progress definitive decompression or CSF diversion with neurosurgery.
Synopsis
Recognise CT and MRI signs of raised intracranial pressure, localise mass effect and hydrocephalus, and communicate imaging limits so urgent treatment is driven by the patient and lesion rather than shift alone.
Raised intracranial pressure is a physiological state; CT and MRI show causes and consequences but a normal scan does not universally exclude elevated pressure.
Assess sulci, ventricles, midline, basal cisterns, medial temporal lobes, brainstem and foramen magnum in a fixed sequence before quantifying any single sign.
Mass effect includes sulcal effacement, ventricular compression, cisternal obliteration, shift and herniation; location and rate often matter more than a millimetre value alone.
Key red flags
A falling GCS with a newly dilated pupil or progressive motor asymmetry is an immediate herniation warning; do not wait for the complete Cushing triad.
Effaced basal cisterns, ventricular compression, increasing midline shift or downward tonsillar displacement requires urgent communication even if the report is provisional.
Acute hydrocephalus with drowsiness, vomiting or sixth-nerve dysfunction may deteriorate rapidly and needs neurosurgical assessment for CSF diversion.
A posterior-fossa lesion can obstruct the fourth ventricle and compress the brainstem with little supratentorial shift, so the compartment must be reviewed directly.
Lumbar puncture is unsafe when a space-occupying lesion, obstructive hydrocephalus or evolving herniation creates a pressure gradient.
Sulcal and cisternal effacement
Compare hemispheres and inspect suprasellar, ambient and quadrigeminal cisterns. Loss of normal CSF spaces signals crowding but may be subtle or symmetrical.
Uncal and central descent
Look for medial temporal displacement, asymmetric ambient cisterns, third-nerve compression pattern and progressive brainstem crowding.
Posterior-fossa crowding
Review fourth ventricle, prepontine cistern, brainstem contour and foramen magnum. Beam-hardening artefact on CT can limit confidence and favour MRI after stabilisation.
Obstructive hydrocephalus
Determine which ventricles are enlarged and identify the transition point. Transependymal CSF seepage and clinical decline support an acute pressure consequence.
Investigation priorities
01
Urgent non-contrast CT headFirst step
Identify haemorrhage, oedema, hydrocephalus, mass lesion and gross herniation rapidly.
Management branches
Worked emergency pathwayDeterioration with new anisocoria
A patient with a known intracranial lesion develops reduced consciousness and a unilateral dilated pupil.
Call anaesthesia and neurosurgery immediately, secure oxygenation and circulation, align and elevate the head when appropriate, and avoid hypotension.
Obtain urgent non-contrast CT when transport is safe while initiating specialist-directed temporary pressure rescue.
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 13 Sept 2026; clinical approval remains outstanding.
ENLS Intracranial Hypertension and Herniation Protocol version 6.0Version 6.0, updated September 2024; communication, diagnosis, Tier Zero and Tier One sections read. Multi-aetiology professional consensus for the first hours of an ICP crisis, not a UK national or disease-specific outcomes guideline. Applied specifically to Raised intracranial pressure and mass effect.
NICE NG232 head injury recommendationsPublished 18 May 2023; recommendations on acute assessment, CT criteria, neurosurgical discussion and neurological deterioration read 13 September 2026. This source governs traumatic head injury across ages and was not generalised to spontaneous disease. Applied specifically to Raised intracranial pressure and mass effect.
Brain Trauma Foundation paediatric severe TBI guideline, third editionPublished 2019; neuroimaging, ICP and CPP sections read. Applies only to severe paediatric traumatic brain injury; an initially normal CT does not exclude raised ICP in a comatose child, and adult thresholds were not imported. Applied specifically to Raised intracranial pressure and mass effect.
ESO/EANS 2025 guideline on spontaneous intracerebral haemorrhagePublished 22 May 2025; diagnostic-cause imaging, prognostic-score, blood-pressure, haemostatic, hydrocephalus and surgery sections read. European adult spontaneous ICH guidance; many recommendations are weak and do not govern traumatic haemorrhage. Applied specifically to Raised intracranial pressure and mass effect.