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
- spontaneous intracranial hypotension
Crescentic CSF density/signal accumulation of CSF in subdural space that does not extend into the sulci. Vessels rarely cross through the lesion in contrast enhanced studies (see cortical vein sign).
Imaging differential considerations include:
- chronic subdural haematoma: MRI may required to differentiate as they can have an identical appearance on CT
- cortical atrophy/involutional change with enlargement of the subarachnoid space: a positive cortical vein sign may indicate this instead
- benign enlargement of the subarachnoid spaces in infancy: a positive cortical vein sign may indicate this instead
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- 2. Deltour P, Lemmerling M, Bauters W et-al. Posttraumatic subdural hygroma: CT findings and differential diagnosis. JBR-BTR. 1999;82 (4): 155-6. - Pubmed citation
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