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

    • –

      Suggest unstable subdural hematoma prone to rehemorrhage

• General imaging recommendations

  • NECT initial screen; consider CECT for membranes/loculations; MR is more sensitive for subdural hematoma, detecting additional traumatic brain injuries

• Early MR is favored, as most concurrent injuries will be more conspicuous in early subacute phase rather than in chronic phase

Top Differential Diagnoses

• Other subdural collections: Effusion, hygroma; empyema

• Pachymeningopathies, thickened dura (look for other signs of intracranial hypotension)

• Chronic dural sinus thrombosis

• Tumor

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

TERMINOLOGY

IMAGING