Subdural haemorrhage

Overview

•SDH = blood between dura mater and arachnoid mater, from shearing of bridging veins (venous, not arterial)

•Collection is crescent-shaped and NOT limited by suture lines (unlike extradural which is biconvex and IS limited)

•Acute SDH = hyperdense (white) on CT; chronic SDH = hypodense (dark) on CT

Presentation

•Acute SDH: severe headache, decreased consciousness, nausea/vomiting, focal deficits (contralateral hemiparesis), ipsilateral pupil dilatation (uncal herniation, CN III compression), seizures (~20%)

•Chronic SDH: insidious headache, cognitive impairment mimicking dementia, personality change, gait disturbance, mild fluctuating focal deficits

•Infant/NAI: seizures (often presenting feature), drowsiness, tense/bulging fontanelle, retinal haemorrhages, unexplained bruising (especially posterior torso)

Investigations

🥇 First-line

•CT head (non-contrast) - identifies crescent collection, acute vs chronic, midline shift

•coagulation screen (PT, APTT, INR) - identify and reverse coagulopathy before surgery

🥈 Second-line

•MRI brain - more sensitive for subacute (isodense) SDH and cortical injury in NAI

•NAI: skeletal survey (mandatory if NAI suspected) + formal dilated fundoscopy (document retinal haemorrhages)

Management

•Urgent neurosurgical assessment for all patients; ABCDE resuscitation, airway protection if unconscious, reverse coagulopathy

•NAI: immediate safeguarding referral to children's social care and police child protection team; do not discharge until safeguarding plan in place

CT appearances - SDH vs extradural

SDH vs extradural haematoma on CT
FeatureSubdural haematomaExtradural haematoma
ShapeCrescentBiconvex (lentiform)
Suture linesNOT limitedLimited by suture lines
Acute densityHyperdenseHyperdense
Chronic densityHypodenseRemains hyperdense
SourceBridging veins (venous)Middle meningeal artery (arterial)
Classic historyAcceleration-deceleration / NAI / elderly fallLucid interval after head trauma

Feature	Subdural haematoma	Extradural haematoma
Shape	Crescent	Biconvex (lentiform)
Suture lines	NOT limited	Limited by suture lines
Acute density	Hyperdense	Hyperdense
Chronic density	Hypodense	Remains hyperdense
Source	Bridging veins (venous)	Middle meningeal artery (arterial)
Classic history	Acceleration-deceleration / NAI / elderly fall	Lucid interval after head trauma

🎯
A hypodense crescent NOT limited by suture lines = chronic SDH. A biconvex hyperdense collection LIMITED by suture lines + lucid interval = extradural haematoma.

Shaken baby syndrome (non-accidental injury)

•Classic triad: retinal haemorrhages + subdural haematoma + encephalopathy (seizures + reduced consciousness)

•Haematoma is SUBDURAL (not extradural) - bridging vein shearing from rotational forces

•Bilateral SDH in ~80% of infant NAI cases (bilateral distribution unusual in accidental trauma)

•Retinal haemorrhages present in up to 85-90% of affected infants

•Rib fractures and long bone fractures may be present in NAI but are NOT part of the triad

⚠️
Rib fractures and long bone fractures can occur in NAI but do NOT replace encephalopathy in the classic shaken baby triad. The haematoma is subdural, not extradural.

Intraventricular haemorrhage (IVH) - key distinction

•IVH mostly affects pre-term infants and can present with irritability and convulsions in the first 2 days of life

•Diagnosed by cranial ultrasound; extradural haemorrhage is unlikely to occur during the birthing process