Cavernous sinus thrombosis (CST) is septic or aseptic thrombotic occlusion of the cavernous sinus and represents an ophthalmological/neurological emergency. The most common etiological cause is paranasal sinusitis (60-80%, particularly sphenoid and ethmoid sinusitis) and orbital/facial infections (orbital cellulitis, facial furuncle, dental infections). Because facial venous drainage is valveless, infection easily spreads retrograde. Clinically, it presents with rapidly progressive proptosis, chemosis, periorbital edema, ophthalmoplegia (III, IV, VI cranial nerve palsies), trigeminal neuropathy (V1/V2 hypoesthesia), and vision loss. Bilateral involvement (60-80%) occurs through intercavernous sinus connections and is the most distinguishing clinical feature of CST — a critical clue for differentiation from unilateral orbital cellulitis. Untreated mortality can reach 30-50%; early diagnosis and aggressive treatment (broad-spectrum antibiotics + anticoagulation) are life-saving. Contrast-enhanced MRI and MR venography are the gold standard for radiological diagnosis: cavernous sinus expansion, filling defect (thrombus), superior ophthalmic vein dilation, and convex lateral wall are the most important findings.
Age Range
15-60
Peak Age
35
Gender
Equal
Prevalence
Rare
The venous drainage anatomy of the face and paranasal sinuses plays a central role in the pathogenesis of cavernous sinus thrombosis: facial veins (angular vein, superior ophthalmic vein) and the pterygoid venous plexus are valveless, allowing infection to reach the cavernous sinus through retrograde flow — particularly sphenoid sinusitis, ethmoid sinusitis, and orbital cellulitis most commonly serve as sources due to direct anatomical proximity. When infection reaches the cavernous sinus, endothelial damage and Virchow's triad (endothelial damage, stasis, hypercoagulability) trigger thrombus formation; as the thrombus expands, it compresses structures passing through the sinus (III, IV, V1, V2, VI cranial nerves and internal carotid artery) — this compression is the mechanism of ophthalmoplegia and trigeminal neuropathy. Radiologically, thrombus is visualized as a filling defect on contrast-enhanced MRI: acute phase T1 isointense, T2 hypointense deoxyhemoglobin; subacute phase T1 hyperintense methemoglobin. Bilateral spread occurs through anterior and posterior intercavernous sinuses connecting the two cavernous sinuses and carries risk of septic embolism. Superior ophthalmic vein thrombosis leads to venous drainage obstruction, forming the pathophysiological basis of proptosis, chemosis, and orbital edema.
Cavernous sinus expansion with a non-enhancing filling defect (thrombus) on contrast-enhanced MRI combined with bilateral superior ophthalmic vein dilation is the pathognomonic radiological combination of cavernous sinus thrombosis. Lateral wall convexity is an additional supporting finding. This combination is critically important for early diagnosis of septic CST and represents a radiological emergency requiring initiation of urgent treatment.
On contrast-enhanced fat-suppressed T1 MRI, the cavernous sinus is expanded and a non-enhancing filling defect (thrombus) is identified within the sinus. While normal cavernous sinus shows homogeneous enhancement, the thrombosed sinus shows heterogeneous or absent enhancement. The cavernous sinus lateral wall has become convex (normally concave). The internal carotid artery passing through the sinus may appear narrowed (thrombus compression). Peripheral enhancement (non-enhancing thrombus center surrounded by enhancing dural walls) may create an 'empty triangle' or 'delta sign'-like appearance. In bilateral involvement, similar findings are present in both cavernous sinuses. Coronal plane is the section orientation where cavernous sinus anatomy and lateral wall convexity are best evaluated.
Report Sentence
On contrast-enhanced MRI, the ___ cavernous sinus is expanded with a filling defect (thrombus) within the sinus; the lateral wall has become convex; findings are consistent with cavernous sinus thrombosis.
On T1-weighted MRI, thrombus signal characteristics vary according to thrombus age. Acute thrombus (<7 days): T1 isointense or mildly hypointense (intracellular deoxyhemoglobin). Subacute thrombus (7-28 days): T1 hyperintense (intracellular/extracellular methemoglobin) — this is the most diagnostic phase because hyperintense thrombus is visible even on pre-contrast images. Chronic thrombus (>28 days): T1 isointense or hypointense (hemosiderin). Cavernous sinus expansion and lateral wall convexity are seen in all phases. In bilateral involvement, simultaneous signal changes are seen in both cavernous sinuses. Pre-contrast T1 images are mandatory to distinguish the hyperintense methemoglobin signal of subacute thrombus from enhancement — on post-contrast T1, hyperintense thrombus may be confused with enhancement.
Report Sentence
On T1-weighted sequences, an area consistent with thrombus showing ___ signal characteristics is observed within the cavernous sinus; signal characteristics are consistent with ___ stage thrombus.
On T2-weighted MRI, superior ophthalmic vein (SOV) dilation (normal diameter <3 mm) is the earliest and most reliable orbital finding of cavernous sinus thrombosis. The dilated SOV may show tortuous course. When thrombus is present within the SOV, T2 signal change within the vein lumen is seen (acute: hypointense, subacute: heterogeneous). Bilateral SOV dilation suggests bilateral CST. T2 hyperintense edema (preseptal and postseptal) in orbital fat accompanies. Extraocular muscles may appear thickened and edematous (T2 hyperintense). Streaky T2 hyperintense areas in retrobulbar fat indicate infectious/inflammatory changes. Globe shape is preserved but optic nerve sheath edema may be seen. On T2, cavernous sinus thrombus is conspicuous in the acute phase with hypointense deoxyhemoglobin signal, while showing signal increase in the subacute phase.
Report Sentence
On T2-weighted sequences, bilateral superior ophthalmic vein dilation (diameter: ___ mm) is observed accompanied by preseptal and postseptal orbital edema; findings are consistent with venous congestion secondary to cavernous sinus thrombosis.
On contrast-enhanced CT, the cavernous sinus is expanded with a hypodense filling defect (thrombus) within. In the normally homogeneously enhancing cavernous sinus, thrombus appears as a non-enhancing hypodense area. Lateral wall convexity and SOV dilation can also be assessed on CT. CT venography (CTV) allows simultaneous screening of cavernous sinus and cerebral venous system thrombosis. Accompanying sphenoid/ethmoid sinusitis is seen as fluid levels and mucosal thickening. Intracranial complications (cerebral abscess, subdural empyema, meningitis) can be evaluated on contrast-enhanced CT. CT is preferred in emergency situations where MRI is unavailable or in MRI contraindications. Bone window evaluates sphenoid sinus bone erosion (infection source).
Report Sentence
On contrast-enhanced CT, the ___ cavernous sinus is expanded with a hypodense filling defect within; the superior ophthalmic vein is dilated; accompanying ___ sinusitis is present.
On diffusion-weighted imaging, acute cavernous sinus thrombus may show diffusion restriction — this finding is particularly prominent in septic thrombosis. High DWI signal and low ADC values within the cavernous sinus support the presence of thrombus. DWI is critically important for detection of intracranial complications (cerebral abscess, subdural empyema): abscess cavities show marked diffusion restriction (ADC <0.5 × 10⁻³ mm²/s) — this finding distinguishes abscess/empyema from sterile collections. Venous infarct areas (cerebral venous infarct as a complication of cavernous sinus thrombosis) show diffusion restriction on DWI. In case of orbital abscess development, a collection showing DWI restriction may be seen within the orbit. DWI provides additional information to conventional sequences in early diagnosis of septic thrombosis and detection of complications.
Report Sentence
On diffusion-weighted imaging, diffusion restriction is observed within the cavernous sinus consistent with acute/septic thrombus; ___ has been evaluated for intracranial complications.
On non-contrast CT, bilateral (or unilateral) proptosis, preseptal and postseptal soft tissue swelling, SOV dilation, and accompanying paranasal sinus opacification (sphenoid and/or ethmoid sinusitis) are seen. SOV enlargement indicates cavernous sinus outflow obstruction. Streaky densities in retrobulbar fat reflect orbital edema and inflammation. Extraocular muscles may appear thickened. Sphenoid sinus bone erosion indicates the infection source. Non-contrast CT is rapidly obtained as the first imaging modality in emergency diagnosis and shows indirect findings such as sinusitis, orbital complications, and cavernous sinus enlargement. However, contrast-enhanced imaging (CT or MRI) is mandatory for direct thrombus assessment.
Report Sentence
On non-contrast CT, bilateral proptosis, preseptal-postseptal soft tissue swelling, and superior ophthalmic vein dilation are observed accompanied by ___ sinusitis; contrast-enhanced imaging is recommended with preliminary diagnosis of cavernous sinus thrombosis.
Criteria
Infectious etiology (sinusitis, orbital cellulitis, dental infection, facial furuncle); fever, leukocytosis, positive blood cultures; most commonly Staphylococcus aureus
Distinct Features
More rapid course, more severe clinical picture; diffuse inflammatory changes in surrounding tissues; risk of abscess development; marked restriction on DWI (septic material); risk of septic embolism; mortality higher (20-30% with treatment); treatment includes antibiotics + anticoagulation; sinus drainage may be needed
Criteria
Non-infectious etiology: hypercoagulability, oral contraceptives, pregnancy, malignancy, post-skull base surgery, trauma; no fever
Distinct Features
Slower course; inflammatory changes in surrounding tissues less prominent; DWI restriction milder; anticoagulation primary in treatment; antibiotics not needed; prognosis better than septic form; thrombophilia screening needed; accompanying malignancy should be excluded
Criteria
Thrombotic involvement of both cavernous sinuses; spread through intercavernous sinuses; seen in 60-80% of cases
Distinct Features
Bilateral proptosis, chemosis, and ophthalmoplegia; bilateral SOV dilation; bilateral cranial nerve palsies; most important clinical and radiological finding for differentiation from unilateral orbital cellulitis; filling defect and expansion in both cavernous sinuses on MRI
Distinguishing Feature
Orbital cellulitis generally shows unilateral preseptal/postseptal inflammatory changes, no cavernous sinus filling defect, SOV dilation not typical and if present limited to ipsilateral; bilateral involvement not expected in orbital cellulitis — bilateral proptosis and bilateral SOV dilation are distinguishing features of CST
Distinguishing Feature
Thyroid ophthalmopathy shows bilateral extraocular muscle thickening (tendon spared — 'belly sparing'), proptosis may be present but no SOV dilation or cavernous sinus filling defect; clinically shows subacute/chronic course, no fever or septic findings; thyroid function tests are abnormal
Distinguishing Feature
Idiopathic orbital inflammation (pseudotumor) shows diffuse enhancement and inflammatory thickening of orbital structures, steroid response is rapid; no cavernous sinus filling defect, SOV dilation rare; Tolosa-Hunt syndrome (granulomatous inflammation of cavernous sinus/orbital apex) is the most confused entity with CST — steroid response and absence of thrombus in Tolosa-Hunt are distinguishing
Urgency
emergentManagement
medicalBiopsy
Not NeededFollow-up
Serial MRI at 48-72 hours, then weekly until resolution; clinical monitoring of cranial nerve function; ophthalmologic assessment; long-term follow-up for residual cranial nerve deficitsCavernous sinus thrombosis is a neurological/ophthalmological emergency and untreated mortality can reach 30-50%. Treatment must be initiated immediately: broad-spectrum intravenous antibiotics (vancomycin + metronidazole or meropenem — covering Staph aureus and anaerobes) and anticoagulation (heparin infusion — if no contraindication). Antibiotic therapy is continued for minimum 3-4 weeks. Treatment of the source infection (sinus drainage, dental treatment) should be performed simultaneously. Surgical sinus drainage is indicated in cases not responding to medical therapy. Steroid use is controversial but may be considered in severe orbital congestion and optic neuropathy. With early diagnosis and aggressive treatment, mortality can be reduced to 5-10% but permanent cranial nerve deficits are seen in 50% of cases. Vision loss is the most serious complication. Prognosis significantly worsens with intracranial extension (meningitis, cerebral abscess, venous infarct).
Life-threatening emergency. Mortality 20-30% (with treatment). IV antibiotics + anticoagulation is the mainstay of treatment. Septic embolization and intracranial complications (meningitis, brain abscess) may develop.