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.
The vast majority of patients are asymptomatic, however some symptoms uncommonly reported include 5:
- changes in mental status
- nausea and vomiting
- focal neurological deficits
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
A subdural hygroma radiographically appears as a crescentic CSF density/signal accumulation in the subdural space that does not extend into the sulci and rarely exerts mass-effect 5. Vessels rarely cross through the lesion in contrast enhanced studies (see cortical vein sign) 1.
Treatment and prognosis
The vast majority of patients with subdural hygroma are asymptomatic without radiographic evidence of mass-effect, and thus neurosurgical intervention is rarely required 5. In cases where mass-effect is radiographically demonstrated, then neurosurgically evacuated 5.
Imaging differential considerations include:
- chronic subdural haematoma: MRI may required to differentiate as they can have an identical appearance on CT
- cerebral 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
- 1. Mccluney KW, Yeakley JW, Fenstermacher MJ et-al. Subdural hygroma versus atrophy on MR brain scans: "the cortical vein sign". AJNR Am J Neuroradiol. 13 (5): 1335-9. AJNR Am J Neuroradiol (citation) - Pubmed citation
- 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
- 3. Zanini MA, De lima resende LA, De souza faleiros AT et-al. Traumatic subdural hygromas: proposed pathogenesis based classification. J Trauma. 2008;64 (3): 705-13. doi:10.1097/TA.0b013e3180485cfc - Pubmed citation
- 4. Kabir SM, Jennings SJ, Makris D. Posterior fossa subdural hygroma with supratentorial chronic subdural haematoma. Br J Neurosurg. 2004;18 (3): 297-300. - Pubmed citation
- 5. Lee KS. The pathogenesis and clinical significance of traumatic subdural hygroma. Brain Inj. 1998;12 (7): 595-603. - Pubmed citation
- 6. Hosten N, Liebig T. CT of the Head and Spine. TIS. ISBN:B005R1PB8S. Read it at Google Books - Find it at Amazon