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.
Herniation syndromes and emergency neurosurgical referral
Essential points for quick revision.
2 min synopsisUK scopeSources checked 13 Sept 2026Clinical review pending
Saved on this device
!
Brain herniation is a brain code
An acute fall in consciousness, new pupil abnormality, posturing or focal deficit can mark brainstem, cranial-nerve or vascular compression and may become irreversible within minutes.
Action: Call critical care and neurosurgery immediately, secure airway and perfusion, elevate and align the head, treat seizures and give protocol-led osmotic rescue while urgent CT and definitive evacuation, CSF diversion or decompression are organised.
Synopsis
Recognise compartment-specific brain herniation early, localise the likely shift without over-relying on a classic triad, and organise resuscitation, imaging and neurosurgical referral in parallel.
Herniation is tissue displacement driven by intracranial compartment pressure gradients; it can occur with or without a recorded global ICP above a threshold.
Uncal herniation classically causes falling consciousness, an ipsilateral dilated pupil and contralateral weakness, but false-localising ipsilateral weakness can occur from contralateral peduncle compression.
Central descent produces progressive coma, evolving pupil and motor abnormalities and respiratory failure; tonsillar descent threatens the medulla and can cause abrupt apnoea and cardiovascular collapse.
Key red flags
A unilateral enlarging or fixed pupil with reduced consciousness, especially with opposite-sided weakness, is uncal herniation until an urgent assessment proves otherwise.
Progressive drowsiness, small then mid-position fixed pupils, abnormal flexion or extension and irregular breathing suggests descending central transtentorial herniation.
Sudden apnoea, bradycardia, neck stiffness or flaccidity in a patient with posterior-fossa disease suggests tonsillar compression of the medulla.
Leg-predominant weakness with major midline shift can reflect subfalcine displacement and anterior cerebral artery compression before obvious brainstem signs.
Do not wait for the complete Cushing response of hypertension, bradycardia and irregular respiration; ENLS describes the concurrence as uncommon and often late.
A normal earlier CT does not neutralise falling GCS, new anisocoria, a seizure without recovery or progressive focal signs; lesions and oedema evolve.
Uncal transtentorial
Acute reduced consciousness with an ipsilateral enlarging pupil and usually contralateral weakness reflects third-nerve and peduncular compression. Posterior cerebral artery compromise can add occipital infarction.
Central transtentorial
Progressive drowsiness advances to coma, pupils evolve from small reactive to mid-position fixed, motor responses progress from flexion to extension, and breathing becomes abnormal as the brainstem descends.
Tonsillar descent
Inferior cerebellar tonsils compress the lower brainstem, producing neck stiffness, altered consciousness, irregular respiration, apnoea, bradycardia and circulatory collapse, especially with a posterior-fossa lesion.
Investigation priorities
01
Immediate serial neurological examinationFirst step
Identify the evolving syndrome and provide a response baseline without delaying resuscitation.
Management branches
Emergency pathwayClinical brain herniation
Acute consciousness decline with new pupil, motor, posturing or respiratory abnormality suggesting intracranial tissue shift.
Activate critical care, anaesthesia and neurosurgery; assess airway, oxygenation and circulation, obtain IV access, elevate the head above 30 degrees and keep the neck midline without delaying cervical-spine protection where relevant.
Correct hypoxia, hypotension, fever, seizure and severe sodium disturbance; give protocol-led hypertonic sodium or mannitol rescue chosen from the patient's physiology while preparing definitive treatment.
Key medicines
Hypertonic sodium chlorideUse the institution's adult neurocritical-care emergency bolus concentration and volume, selected for venous access and physiology; no single regimen applies across traumatic, vascular, tumour and posterior-fossa causes.Monitor sodium, chloride, renal function, acid–base state, volume status and access; avoid uncontrolled sodium loading and do not delay evacuation or CSF diversion after transient improvement.
Mannitol intravenous solutionUse a local adult emergency weight-based bolus protocol; ENLS v5 describes 0.5–1 g/kg over 5–15 minutes, with repeat dosing governed by response and safety rather than a fixed schedule.Correct hypotension and hypovolaemia, follow urine output, creatinine, volume status and osmolar gap, and avoid automatic repeat dosing when clinical or pressure response is absent.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 13 Sept 2026; clinical approval remains outstanding.
Emergency Neurological Life Support Intracranial Hypertension and Herniation ProtocolNeurocritical Care Society ENLS version 6.0, last updated September 2024; communication checklist, diagnosis, Tier Zero, Tier One, Tier Two and Tier Three scope read 13 September 2026: crisis recognition, head elevation, SpO2, hyperosmolar treatment, short rescue hyperventilation, CSF drainage and definitive cause control. This multi-aetiology professional consensus protocol requires adaptation to age, aetiology, access and local critical-care protocol and does not make adult severe-TBI thresholds universal. Chapter-specific use: herniation syndromes and emergency neurosurgical referral.
NICE NG232 head injury assessment and early managementPublished 18 May 2023; recommendations 1.4.15–1.4.16, 1.8.4–1.8.16 and 1.9.9–1.9.17 read 13 September 2026: neurosurgical discussion, stabilised transfer, age boundaries, neurological observations and deterioration. Applies to traumatic head injury; observation schedules are not asserted for non-traumatic or postoperative patients. Chapter-specific use: herniation syndromes and emergency neurosurgical referral.
Brain Trauma Foundation severe TBI guideline, fourth editionCurrent BTF severe TBI recommendation index, fourth edition 2016 with 2020 decompressive-craniectomy update, read 13 September 2026: hyperosmolar therapy, ICP and CPP monitoring, thresholds, ventilation and CSF drainage. Applies to severe traumatic brain injury; older third-edition mannitol statements are explicitly identified by BTF as not supported by evidence meeting fourth-edition standards. Chapter-specific use: herniation syndromes and emergency neurosurgical referral.
Neurocritical Care Society cerebral oedema guidelineCook et al., Neurocritical Care 2020, body read 13 September 2026: methodology and population limits; TBI recommendations; disease-specific SAH, ischaemic stroke, ICH and hepatic encephalopathy sections; hyperosmolar safety and infusion considerations. Adult studies were used and paediatric studies were excluded. Recommendations are mostly conditional with low or very-low-quality evidence. Chapter-specific use: herniation syndromes and emergency neurosurgical referral.