STEPTRACKERNERVOUS SYSTEM | PATHOLOGY + ANATOMY | HIGH-YIELD REVIEW

Intracranial Hemorrhage & Head Trauma

Bleeding above the dura, below it, in the subarachnoid space or into the brain itself — each with its own vessel, shape and story.

FOCUS ON
Epidural: middle meningeal artery, temporal fracture, lucid interval, biconvex, doesn't cross sutures. Subdural: bridging veins, elderly/alcoholics/shaken infants, crescent, crosses sutures. Subarachnoid: berry aneurysm, "worst headache," xanthochromia, vasospasm (nimodipine). Hypertensive bleeds: Charcot-Bouchard aneurysms in the basal ganglia. Amyloid angiopathy: lobar bleeds in the elderly.
LESION
VESSEL · MECHANISM
FEATURES
CLUE
Epidural hematoma
Middle meningeal artery (from maxillary) torn by a pterion (temporal bone) fracture
Brief LOC → lucid interval → rapid decline; biconvex lens-shaped; doesn't cross sutures
Transtentorial herniation, CN III palsy · emergency evacuation
Subdural hematoma
Torn bridging veins (cortex → dural sinus) with acceleration–deceleration
Crescent-shaped; crosses sutures, not the falx; acute (hyperdense) or chronic (weeks, hypodense, slow confusion)
Elderly (atrophy), alcoholics, anticoagulants, shaken baby
Subarachnoid hemorrhage
Ruptured saccular (berry) aneurysm (ACom most common) or AVM; trauma
Sudden "worst headache of my life," neck stiffness, LOC; noncontrast CT → LP if negative: xanthochromia
Nimodipine prevents vasospasm
SAH — complications
Blood irritates vessels and blocks CSF absorption
Vasospasm (days 3–10) → delayed ischemia; rebleeding; communicating hydrocephalus; hyponatremia (SIADH, salt wasting)
Secure the aneurysm (coil or clip)
Berry aneurysm risk
Congenital weakness of the media at circle of Willis branch points
ADPKD, Ehlers-Danlos, Marfan, coarctation, smoking, hypertension
PCom aneurysm → CN III palsy with dilated pupil
Hypertensive intraparenchymal hemorrhage
Chronic HTN → Charcot-Bouchard microaneurysms of lenticulostriate and other small penetrating vessels
Putamen/basal ganglia (most), thalamus, pons (coma, pinpoint pupils), cerebellum (ataxia, vomiting)
Same vessels as lacunes
Cerebral amyloid angiopathy
β-amyloid deposits in cortical/leptomeningeal vessel walls → fragile
Recurrent lobar hemorrhages in the elderly; microbleeds
Associated with Alzheimer disease
Other causes of brain hemorrhage
Abnormal vessels, coagulopathy, drugs, tumors
AVM (young), anticoagulants, cocaine/amphetamines, hemorrhagic metastases (melanoma, RCC, choriocarcinoma, thyroid), GBM, hemorrhagic transformation
Young normotensive bleed → AVM or drugs
Germinal matrix hemorrhage
Fragile vessels of the germinal matrix in premature infants
< 32 weeks, < 1500 g; intraventricular bleeding in the first 72 h
Hydrocephalus, cerebral palsy
Diffuse axonal injury
Rotational acceleration–deceleration shears axons
Coma after trauma with a near-normal CT; MRI: punctate bleeds at gray–white junction, corpus callosum, brainstem
Axonal swellings (retraction balls)
Cerebral contusion
Brain strikes the skull: coup (impact site) and contrecoup (opposite side)
Frontal and temporal poles
Hemosiderin-stained old scars

Mechanism — why the shapes differ

Arterial bloodBetween skull and dura
→
Dura stuck at sutures
→
Biconvex, fastEpidural
Venous bloodBetween dura and arachnoid
→
Spreads along the convexity
→
Crescent, slowerSubdural

Subarachnoid blood fills sulci and cisterns; intraparenchymal blood forms a round hematoma with surrounding edema.

Epidural vs subdural

FEATURE
EPIDURAL
SUBDURAL
Vessel
Middle meningeal artery
Bridging veins
Injury
Temporal bone fracture
Shearing; minor trauma in elderly
Shape
Biconvex (lentiform)
Crescent
Sutures
Doesn't cross
Crosses
Falx / tentorium
Can cross
Doesn't cross
Course
Lucid interval → rapid decline
Gradual (chronic) or acute

How it's tested

COMMON CONFUSIONA CN III palsy from aneurysm compression dilates the pupil (parasympathetic fibers sit on the outside); a diabetic CN III palsy spares the pupil.
THE TRAPA normal CT doesn't end the SAH workup if the headache began more than 6 hours ago — do an LP and look for xanthochromia.
YOUR APPROACHTrauma or spontaneous → age and BP → imaging shape and location → vessel → complication (herniation, vasospasm, hydrocephalus) → treatment.

If you see… think…

Hit by a baseball, brief LOC, talks normally, then collapses → epidural hematoma
Older alcoholic, weeks of confusion after a fall, crescent on CT → chronic subdural
Infant with retinal hemorrhages and subdural bleeding → abusive head trauma
Thunderclap headache with neck stiffness → subarachnoid hemorrhage
New neuro deficit a week after SAH → vasospasm — nimodipine
ADPKD patient with sudden severe headache → ruptured berry aneurysm
Ptosis, eye down and out, dilated pupil, headache → PCom aneurysm
Hypertensive with sudden hemiparesis and putaminal bleed → Charcot-Bouchard rupture
85-year-old with repeated lobar hemorrhages → cerebral amyloid angiopathy
Comatose after a car crash, CT nearly normal → diffuse axonal injury