Neurology

Subdural haemorrhage

Bridging veins shear between the mobile cortex and the fixed dural sinuses, bleeding beneath the dura to form a crescentic collection that crosses sutures but not the falx.

In a nutshell

Subdural haemorrhage is venous bleeding from torn bridging veins into the space between dura and arachnoid, forming a crescentic collection that crosses sutures. Scan on the NICE clock, reverse anticoagulation, and remember the isodense phase between 3 and 21 days, when a bilateral collection can read as a normal scan.

Classic presentation

An 80-year-old on apixaban, three weeks after a fall she barely remembers, with fluctuating confusion, headache, unsteadiness and a new left arm weakness.

Key points

The Glasgow Coma Scale (GCS) scores eye opening out of 4, verbal out of 5 and motor out of 6. The total runs 3 to 15, never 0.
NICE NG232 grades 13 to 15 as mild, 9 to 12 as moderate and 8 or less as severe, and tells you to weight a fall in the motor score.
Subdural crosses sutures but is stopped by the falx and tentorium. Extradural is biconvex and stopped by sutures, but the dural folds do not hold it.
NICE HealthTech guidance HTG706 is interventional procedures guidance IPG779 re-badged in January 2026 with recommendations unchanged, so searching either finds the same research-only advice.
About 85% of adult subdurals are unilateral, but 75 to 85% are bilateral in infants, where non-accidental injury is the leading cause.
Acute subdural is a craniotomy operation with poor outcomes in older people. Chronic subdural is a burr-hole operation. They are different diseases.

First-line investigation

Urgent non-contrast CT head on the NG232 clock: within 1 hour for a GCS score of 12 or less, within 8 hours for an anticoagulated patient with no other indication.

Management

Resuscitate and scan on the clock

ABCDE (airway, breathing, circulation, disability, exposure), protect the cervical spine, assess within 15 minutes of arrival, and record GCS components, pupils and focal signs.^3,4
CT within 1 hour: GCS 12 or less, GCS under 15 at 2 hours, post-traumatic seizure, focal deficit, more than 1 vomit, or open, depressed or basal skull fracture signs.³
CT within 8 hours after loss of consciousness or amnesia plus age 65 or over, a clotting disorder, a dangerous mechanism, or over 30 minutes of retrograde amnesia.³
On an anticoagulant or antiplatelet other than aspirin monotherapy, with no other indication: consider CT within 8 hours, or within 1 hour if presenting later.³

Reverse the bleeding risk

Warfarin with suspected intracranial bleeding: immediate PCC plus phytomenadione (vitamin K) 5 mg by slow intravenous injection. Stop the warfarin, monitor the INR, consider further PCC.^7,8
PCC dosing is weight- and INR-banded. Take the number from the local transfusion protocol or the BNF monograph, never from memory.^7,8
Dabigatran: idarucizumab. Apixaban or rivaroxaban: andexanet alfa, which NICE recommends only for gastrointestinal bleeds. Edoxaban, no authorised agent. Discuss every direct-acting oral anticoagulant (DOAC) reversal with haematology.^6,9
GCS 12 or less with no suspected extracranial bleeding: consider tranexamic acid 2 g intravenous bolus, as soon as possible within 2 hours of injury, before imaging.³

Escalate, transfer and observe

Discuss with neurosurgery regardless of imaging: coma at GCS 8 or less, confusion beyond 4 hours, falling GCS weighting motor, focal signs, seizure, penetrating injury, CSF leak.³
GCS 8 or less: intubate, ventilate and transfer to a neuroscience centre whether or not surgery is planned.³
Once ventilated, target arterial oxygen (PaO2) above 13 kPa, carbon dioxide (PaCO2) 4.5 to 5.0 kPa and mean arterial pressure at least 80 mmHg.³
Observe half-hourly until GCS 15, then half-hourly for 2 hours, hourly for 4 hours, then 2-hourly. Revert to half-hourly on any deterioration.³

Drain the collection

Acute clot with mass effect or deterioration needs urgent craniotomy. Chronic collections are drained through burr holes. Small, asymptomatic collections may be watched.^2,10
Surgery is considered for symptomatic chronic subdural, or minimal symptoms with a large collection causing mass effect such as midline shift over 5 mm.²
Leave a subdural drain on free drainage for 48 hours. It cut repeat surgery from 24% to 9.3% and 6-month mortality from 18.1% to 8.6%.¹¹
Do not give corticosteroids, alone or alongside surgery. Do not offer middle meningeal artery embolisation outside research.^2,10

Prevent recurrence and decline

Consider venous thromboembolism (VTE) chemoprophylaxis 24 to 48 hours after surgery, and 6 hours after any postoperative drain is removed.²
Restarting anticoagulation is an individual risk and benefit decision with neurosurgery and haematology. There is no evidence-based fixed interval.²
Postoperative imaging is not routine. Request it for clinical concern, or to inform a decision about long-term anticoagulation.²
Tell the patient to contact the driver licensing authority, operated or not. Arrange geriatric review if aged 65 or over.²

Exam traps

The isodense phase hides the collection. A bilateral isodense subdural has no midline shift and can read as a normal scan with effaced sulci.
Do not give corticosteroids for chronic subdural haematoma, alone or with surgery. The randomised trials found the harms outweighed the benefit.
NICE recommends andexanet alfa only for gastrointestinal bleeds. Giving it for a DOAC-related intracranial bleed states the opposite of UK guidance.
Aspirin monotherapy is the one exclusion from the anticoagulant and antiplatelet CT limb. Every other antiplatelet and anticoagulant is included.
Presenting more than 8 hours after the injury does not relax the CT clock. It tightens it to within 1 hour.
A normal INR does not exclude a clinically important DOAC effect. Ask the drug, the last dose and the renal function.
New confusion or decline after a fall in an older person is not dementia or delirium until a CT has said so.

Illustrations

Acute subdural haematoma on CTNon-contrast CT showing a hyperdense crescentic collection following the surface of the hemisphere and crossing sutures.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.