Subdural hygroma

Case contributed by Karina Dorfman
Diagnosis almost certain


Head trauma

Patient Data

Age: 80 years
Gender: Female

C- head CT at admission


Extra-axial collection with CSF-density on the left hemisphere, causing mild mass effect. Bridging veins that transverse medially to the collection confirm that the collection is located in the subdural space (negative cortical vein sign).  No signs of acute intracranial hemorrhage, or bony injury.

These findings raise a differential diagnosis between subdural hygroma and chronic subdural hematoma.

Additional findings:

  • chronic small vessel ischemia signs and old lacunar infarcts in the left lentiform nuclei and left caudate nucleus body
  • signs of age-related cortical atrophy
  • partially calcified falcine meningioma in right frontal location, with mild vasogenic edema around

Previous CT a wk before the...


Previous CT a wk before the current presentation

On a recent CT scan, that was performed just a week before the patient current presentation (also for evaluation of head trauma), there was no abnormality in the left subdural space, lowering the possibility of chronic subdural hematoma. Mild subcutaneous hematoma in the left parieto-occipital area.

Based on this comparison with the previous study, a confident diagnosis of left subdural hygroma was done.

FU CT 3 days after the...


FU CT 3 days after the initial presentation

A follow-up CT scan showed a stable size of the left subdural hygroma, without evidence of hemorrhagic transformation. The right frontal meningioma with mild vasogenic edema is also unchanged. The patient was discharged from hospitalization to outpatient follow-up. 

Case Discussion

Subdural hygroma and chronic subdural hematoma are both included in the differential diagnosis of a hypodense subdural collection in the elderly patient and share common pathophysiological mechanisms. As it is hard to differentiate between these two entities on CT, it is extremely helpful to review recent examinations, when they are available, for making a confident decision. However, in the absence of such examinations, the diagnosis cannot be done easily on CT.

Subdural hygromas may potentially lead to bleeding in subdural space and transform to a subdural hematoma. Therefore, close imaging follow-up is necessary.

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