Cavernous sinus thrombosis (CST) is a rare condition, most commonly infectious in nature, and the diagnosis on imaging is not always straightforward. It has high mortality and morbidity rates.
CST is rare with ~4.5 cases per 1,000,000 per year 5. It is the least common dural venous sinus thrombosis, accounting for <1.5% of cases 4.
A headache is the most common symptom (85%). Focal neurological signs and/or seizures may also occur 5. Isolated CN III palsy is thought to be an early manifestation.
Orbital signs can include:
- chemosis/peri-orbital swelling
- contiguous spread of infection, typically staph aureus (~55%):
- sinus compression, e.g. trauma, tumour
- procoagulable conditions, e.g. protein C/S deficiency, oral contraceptive use, malignancy
- idiopathic (25%) 5
Cavernous sinus thrombosis is a clinical diagnosis. MRI with contrast is the imaging modality of choice to confirm its presence and to differentiate it from alternatives such as orbital cellulitis, which may have a similar clinical presentation.
- non-contrast: high-density thrombus in affected cavernous sinus (seen in only 25%) 5
- contrast-enhanced: distended cavernous sinus with a non fat density filling defect 4
T1 and T2 5
- absent flow void
- signal characteristics vary depending on the age of the thrombus but will be abnormal
- contrast-enhancement or lack of is not a reliable indicator as organising thrombus can enhance
- diagnosis can generally be made on venography
Treatment and prognosis
The mortality rate is up to 30%. Significant morbidity (e.g. blindness, cranial nerve palsy) in survivors not uncommon 6.
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- 6. Absoud M, Hikmet F, Dey P et-al. Bilateral cavernous sinus thrombosis complicating sinusitis. J R Soc Med. 2006;99 (9): 474-6. doi:10.1258/jrsm.99.9.474 - Free text at pubmed - Pubmed citation