Laboratory Studies
Cavernous sinus thrombosis (CST) is a clinical diagnosis and lab studies are seldom specific. Most patients exhibit a polymorphonuclear leukocytosis, often marked with a shift toward immature forms. Examination of the cerebrospinal fluid is consistent with either a parameningeal inflammation or frank meningitis. Blood culture results generally are positive for the offending organism.
One study by Misra et al showed that a D-dimer may be useful in patients with suspected cortical sinus venous thrombosis (CSVT). [5]
Imaging Studies
Historically, a number of techniques have been used to image cavernous sinus thrombosis (CST), including plain sinus radiography, carotid angiography, and orbital venography. In current practice, computed tomography (CT) scan or magnetic resonance imaging (MRI) with contrast is the modality of choice to confirm the diagnosis of CST and to differentiate it from alternatives such as orbital cellulitis, which may have a similar clinical presentation. [6] The literature suggest using both CT and MRI, particularly diffusion weighted MRI; CT first (since it is generally faster and more available) and then MRI, especially if the CT is not definitive. [7, 8, 9, 10]
MRI with MR venogram (MRV) is the preferred imaging choice as the MRV will show the absence of venous flow in the affected cavernous sinus.
On noncontrast CT, thrombosis of the cavernous sinus can be appreciated as increased density. The introduction of intravenous contrast can reveal filling defects within the cavernous sinus as well as thickening of the superior ophthalmic vein. Nevertheless, CT scan findings may be subtle, and a negative CT scan cannot rule out CST reliably when the clinical suspicion is high.
Carotid angiography can demonstrate narrowing or obstruction of the intercavernous segment of the carotid artery. MRI and CT scan can also show this narrowing and/or obstruction of the carotid artery.
Procedures
Lumbar puncture may be helpful in distinguishing CST from more localized processes (e.g., sinusitis, orbital cellulitis). Lumbar puncture reveals inflammatory cells in approximately 75% of cases.
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Anatomy of cross section of cavernous sinus showing close proximity to cranial nerves and sphenoid sinus.
