Acute Subdural Hematoma

KEY FACTS

TERMINOLOGY

• Acute blood between inner border cell layer of dura,

arachnoid

IMAGING

• NECT as initial screening study

○ Use both bone, soft tissue algorithms

○ Use both standard brain, wide windows (150 HU)

○ Coronal, sagittal reformatted scans best for detecting

small subdural hematomas (SDHs)

• Crescentic hyperdense extraaxial collection

○ Spreads diffusely over cerebral convexity

○ Often extends along falx, tentorium

• Inward displacement of cortical veins, sulci

• May cross sutures, not dural attachments

TOP DIFFERENTIAL DIAGNOSES

• Other subdural fluid collections

○ Mixed SDH (acute on chronic/subacute SDH):

Hyperdense foci in pockets of iso-, hypodense fluid

○ Subdural hygroma: Clear CSF, no encapsulating

membranes

○ Subdural effusion: Near CSF density

○ Subdural empyema: Peripheral enhancement,

hyperintensity on FLAIR; restricted diffusion on DWI

• Acute epidural hematoma (typically crescentic)

PATHOLOGY

• Common: Tear of bridging cortical veins

• Nontrauma (spontaneous) more common in elderly

CLINICAL ISSUES

• Mental status & focal neurological changes can have rapid

deterioration

DIAGNOSTIC CHECKLIST

• Multiplanar reconstructions, wide windows best for subtle

acute SDHs; inform clinician if unsuspected finding

(Left) Graphic shows acute

subdural hematoma (aSDH)

st compressing the left

hemisphere and lateral

ventricle, resulting in midline

shift. Coexisting cortical

contusions ﬈ and axonal

injuries ﬉ are common in

aSDHs. (Right) Axial NECT in a

58-year-old woman with head

trauma shows a classic aSDH

st extending over the left

convexity and compressing the

underlying subarachnoid space

﬇. The subtle hypodense foci

﬈ within the hyperdense

aSDH represent unclotted

blood and risk for rapid

hematoma expansion.

(Left) Occasionally, aSDHs are

isodense to the underlying

brain. Note the aSDH ſt with

mass effect, inward

displacement of the

underlying gray-white

interface ﬇, and left-to-right

subfalcine herniation of the

lateral ventricles st. (Right)

More cephalad NECT scan in

the same patient again shows

the isodense aSDH ſt. The

underlying sulci are

completely effaced. Compare

this appearance of "absent

sulci" with the normalappearing cerebrospinal fluidfilled sulci ﬇ over the right

hemisphere.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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