What is the best imaging modality for diagnosing cavernous sinus thrombosis (CST)?

From the Guidelines

The best imaging for cavernous sinus thrombosis is contrast-enhanced MRI with MR venography (MRV). This recommendation is based on the most recent and highest quality study available, which highlights the superiority of MRI in detecting cerebral venous thrombosis, including cavernous sinus thrombosis 1. The combination of contrast-enhanced MRI and MRV provides detailed visualization of the cavernous sinus anatomy, any filling defects indicating thrombosis, and surrounding soft tissue inflammation.

Key Considerations

• MRI offers excellent soft tissue contrast resolution, ability to detect subtle vascular changes, and capacity to identify complications such as cerebral infarction or abscess formation 1.
• MRI can distinguish between thrombosis and other cavernous sinus pathologies like tumors or inflammatory conditions.
• Time is critical in suspected cavernous sinus thrombosis, so imaging should be obtained emergently, as delayed diagnosis significantly increases mortality risk.
• Clinical correlation with symptoms like orbital pain, ophthalmoplegia, proptosis, and cranial nerve deficits remains essential for proper interpretation of imaging findings.

Alternative Options

• CT with contrast is an acceptable alternative when MRI is unavailable or contraindicated, though it offers less sensitivity and detail 1.
• When ordering these studies, specify the clinical suspicion of cavernous sinus thrombosis to ensure appropriate protocols are used.

Evidence Summary

• A study from 2020 found that MRI without and with IV contrast is preferred over CT/CTV for serial examinations in diagnosing and following cortical vein and dural venous sinus thrombosis 1.
• Gradient-echo T1-weighted postcontrast MRI has been shown to have slightly greater sensitivity and specificity compared with unenhanced MR venography (MRV) for the demonstration of dural venous sinus and cortical venous thrombosis 1.

From the Research

Imaging Modalities for Cavernous Sinus Thrombosis

• Computed Tomography (CT) scan: has a limited role in the diagnosis of cavernous sinus thrombosis, with a sensitivity of 14.6% 2
• Magnetic Resonance Imaging (MRI): is a more sensitive modality, with a sensitivity of 70.7% 2
• Magnetic Resonance Venography (MRV): is useful in diagnosing cerebral venous sinus thrombosis, including cavernous sinus thrombosis, and can detect thrombosis even when CT or MRI is normal 3
• Contrast-Enhanced MRI (CEMRI): plays a crucial role in the evaluation of cavernous sinus thrombosis, providing qualitative and quantitative parameters for diagnosis 4

Diagnostic Criteria

• Cavernous sinus diameter ≥ 10 mm, Superior Ophthalmic Vein (SOV) diameter ≥ 2.9 mm, and Internal Carotid Artery (ICA) flow void diameter ≤ 4.2 mm are suggested cut-off points for diagnosis 4
• Qualitative parameters such as bulging lateral walls of the sinus, heterogeneous signal intensity with filling defects on post-contrast images, abnormal dural enhancement, and orbital apex involvement can aid in diagnosis 4

Clinical Context

• Cavernous sinus thrombosis is a serious condition with high morbidity and mortality, emphasizing the need for timely and accurate diagnosis 5
• Imaging diagnosis is critical, and MRI or MRV are recommended as initial investigations in suspected cases of cavernous sinus syndrome 2