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Subdural hygroma

Subdural hygromas refer to a cerebrospinal fluid (CSF) accumulation in the subdural space. In many cases it is considered an epiphenomenon of head injury when it is called a traumatic subdural hygroma


They generally occur along the supratentorial cerebral convexities; occurrence in the posterior fossa is generally rare 4.

  • idiopathic: in paediatric patients
  • trauma: secondary to tear in the arachnoid mater
  • post surgical, e.g. haematoma evacuation, ventricular drainage

Radiographic features


Crescentic CSF density/signal accumulation of CSF in subdural space that does not extend into the sulci. Vessels may cross through the lesion in contrast enhanced studies.

Differential diagnosis

Imaging differential considerations include

  • chronic subdural haematoma: MRI may required to differentiate as they can have an identical appearance on CT
  • atrophy/involutional change with enlargement of the subarachnoid space

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