Subacute Subdural Hematoma

KEY FACTS

TERMINOLOGY

• Subacute (~ 3 days to 3 weeks) collection

○ In subdural space (between arachnoid and dura or within

inner border cell layer)

○ Partially liquefied clot, resorbing blood products

○ Surrounded by granulation tissue ("membrane")

IMAGING

• Crescent-shaped, iso- to hypodense extraaxial collection

○ Spreads diffusely over hemisphere

○ May cross sutures, not dural attachments

○ May be of same density as underlying cortex

○ Look for inwardly displaced "dots" of cerebrospinal fluid

• MR

○ T1 iso- to hyperintense

○ T2/FLAIR hyperintense (does not suppress)

○ DWI may show double-layer appearance

○ Enhancing membranes may be seen on postcontrast

imaging

• General imaging recommendations

○ NECT initial screen; consider CECT for

membranes/loculations; MR is more sensitive for

subdural hematoma, detecting additional traumatic

brain injuries

TOP DIFFERENTIAL DIAGNOSES

• Other subdural collections: Effusion, hygroma; empyema

• Pachymeningopathies, thickened dura (look for other signs

of intracranial hypotension)

• Chronic dural sinus thrombosis

PATHOLOGY

• Traumatic stretching/tearing of bridging cortical veins as

they cross subdural space

• Trauma may be minor (particularly in elderly patients)

CLINICAL ISSUES

• Can present with headache, seizures, gait abnormalities in

elderly & present weeks after initial minor trauma

(Left) Axial graphic shows a

typical subacute subdural

hematoma (sSDH) ſt. Inset

shows the traversing

"bridging" vein ﬈ and

developing membranes st.

These are often related to

relatively minor trauma in the

elderly. (Right) Axial NECT

scan shows a right sSDH as a

crescentic extraaxial fluid

collection ﬈ that appears

slightly hyperdense compared

with the "dots" of

cerebrospinal fluid (CSF) in the

underlying sulci ﬇.

(Left) FLAIR MR in the same

case shows that the sSDH is

hyperintense ſt and does not

suppress (compared with the

normal "dark" CSF in the

underlying subarachnoid

spaces ﬊). (Right) Coronal T1

C+ MR in the same case shows

enhancing membranes

surrounding the sSDH. The

outer membrane ﬊ is

generally thicker, more

prominent than the inner

membrane ſt.

Trauma, and Stroke

Brain: Pathology-Based Diagnoses: Malformations,

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