= TRAUMATIC SUBDURAL EFFUSION

= localized CSF-fluid collection within subdural space

Cause:

1. minor trauma results in separation of dura and arachnoid; proliferation of dural border cell layer results in neomembrane with hyperpermeable capillaries + efflux of serous fluid into subdural space
2. traumatic tear in arachnoid with secondary ball valve mechanism

Age: most often in elderly + young children

Time of onset: 6–30 days following trauma

• asymptomatic in majority; headaches, drowsiness
• decreased level of consciousness, confusion
• radiolucent crescent-shaped collection (as in acute subdural hematoma) of CSF density
• NO evidence of blood products (DDx to subdural hematoma)

MR:

• isointense to CSF / hyperintense to CSF on T1WI (← increased protein content)

Prognosis: often spontaneous resorption; may develop into a chronic subdural hematoma

DDx:

1. Enlarged subarachnoid space
2. Subdural empyema
3. Chronic subdural hematoma
4. Brain atrophy