Cavernous Sinus Thrombosis – Diagnosis and Treatment

Cavernous sinus thrombosis (CST) is a rare condition caused by a blood clot in the cavernous sinus. The thrombosis can be septic or aseptic. Aseptic CST follows surgery or trauma but is far less common than septic CST. Septic CST occurs when an embolus infected with bacteria or fungus reaches the cavernous sinus through its many anastomotic connections. The cavernous sinus is valveless allowing flow in either direction. Typically the cavernous sinus receives blood via the superior and inferior ophthalmic veins, the superficial cortical veins, or the basilar plexus.The cavernous sinus then drains into the petrosal sinuses and ultimately into the internal jugular vein. Septic CST can also result from direct extension of infection from sources in close proximity to the cavernous sinus. Sources include sinusitis, otitis, odontogenic, cellulitis, facial furuncles, and erysipelas.

CST is extremely rare. The estimated annual incidence of cavernous sinus thrombosis is approximately 0.2 to 1.6 per 100,000 per year.^[1]

Historically, CST has been reported to be more common in children and neonates than in adults, although the effects of routine vaccination and frequent use of antibiotics may contribute to decreasing prevalence.

The cavernous sinuses flank both sides of the sella turcica and are connected by intercavernous sinuses which can allow a unilateral thrombosis to spread to the contralateral side. Contralateral spread over a 24 to 48 hour period after presentation is pathognomonic for CST.

The trabeculated sinuses act like sieves, trapping bacteria, emboli, and thrombi progressing from anterior infected sites involving the nose, sinuses, or medial third of the face or retrograde from lateral venous sinuses, ears, or teeth.

The intimate relationship between the cavernous sinus and nearby structures explains the symptoms of CST. The  most critical structures are in close proximity to the cavernous sinus and are highlighted in the figure below:

• Carotid artery
• Sympathetic plexus
• Cranial nerves III, IV, V (V1 and V2 branches), and VI

Anatomy of the Cavernous Sinus

(Coronal View)

(Kasper 2016)^[2] 

Patients with CST present in dramatic fashion with symptoms such as headache, fever, and ocular problems. In patients with headache and cranial nerve findings, it is a diagnosis that one can’t miss – mortality nears 100% if not treated appropriately.

The typical patient may endorse a recent history of sinusitis or a facial furuncle that he or she tried to “pop” at home in the week or two prior to presentation.

The most common signs of CST are related to damage of the nerves that traverse the cavernous sinuses and engorgement of the retinal and orbital vessels caused by impaired venous drainage.

Ophthalmologic examination discloses unilateral or bilateral exophthalmos, chemosis, periorbital edema, proptosis, absent pupillary reflexes, and papilledema. Involvement of the third, fourth, and sixth cranial nerves or the ophthalmic branch of the fifth nerve leads to ophthalmoplegia.

Ocular Findings in Cavernous Sinus Thrombosis

Right periorbital swelling, erythema, proptosis, chemosis, and injection of the conjunctiva. (Pavlovich 2006)[3]	Left CN VI palsy is one of the earliest oculomotor deficits. (Knoop 2016)[4]

Emergency physicians should have a low threshold to workup CST because any delay can lead to significant morbidity and mortality. The constellation of symptoms above along with imaging can confirm the diagnosis.

CT of the head and orbits with IV contrast will show a filling defect in the cavernous sinus along with bulging of the lateral margins of the cavernous sinus. A CT may also show engorgement of the cerebral or superior ophthalmic veins feeding into the cavernous sinus.

Contrast-enhanced High Resolution CT

(Axial View)

Note the marked distension of the right superior ophthalmic vein with a tubular filling defect (white arrow), consistent with thrombosis.^[3]

CT findings may be subtle, and a negative CT cannot rule out CST when the clinical suspicion is high.

CT venogram and MR venogram can detect dilatation of the cavernous sinus, enhancement, and convexity of the lateral wall on coronal views. These images may also show heterogeneous and asymmetric filling defects, increased density of orbital fat, thrombosis in the superior ophthalmic vein or other veins and tributaries leading to the cavernous sinus. An example of of MR findings can be seen below.

MRI Findings in Cavernous Sinus Thrombosis

(Coronal and Axial Views)

(Ahern 2014)^[5] 

Antibiotics are the first line treatment for septic CST. The most commonly isolated organisms are Staphylococcus aureus (about 70%) and Streptococcus species (about 20%).^[1] If there is suspicion of an odontogenic source, anaerobes should be considered as well. An initial approach should include broad spectrum antibiotics such as vancomycin, ceftriaxone, and metronidazole. Typically, a minimum of 3 to 4 weeks of IV antibiotics is required. Special consideration should be given to diabetic or immunocompromised patients, since they are susceptible to fungal infections which are associated with higher mortality. Aspergillus fumigatus is the most common fungal infection. Amphotericin B can be used for fungal infections.

Surgical intervention is primarily for source control of primary infections that require incision and drainage. There is no clear benefit to clot retrieval.

Anticoagulation is often given, however, its use is controversial. The purported benefit is to prevent propagation of the thrombus, but this must be weighed against the risk of hemorrhage, especially if the patient is a candidate for surgery. An argument against the use of anticoagulation is the reasoning that permitting thrombus may confine the septic embolus, thus preventing further dissemination of the infection.

Steroids may have a role in reducing inflammation and swelling, but routine use is also not well established. The possible benefit must be weighed against its potential immunosuppressive and prothrombotic effects.

Visual impairment has been reported in 7% to 22% of cases, with blindness reported in 8% to 15% of cases.^[6]

Further dissemination of the infection may result in meningitis, encephalitis, brain abscess, or pituitary infection.

Extension of the thrombus to other sinuses, such as the petrosal, inferior sagittal and sigmoid, can occur. The dural venous sinuses and the cerebral veins should be carefully evaluated in cases of CST, as up to 90% of patients will have multiple thromboses.^[7] Extension or subsequent ischemia may result in anterior hypopituitarism given that the anterior pituitary’s blood supply is derived from the carotid artery within the cavernous sinus.

CST mortality has decreased from 80-100% in the pre-antibiotic era to 20-30% since 1940.^[1] 

One should consult ophthalmology and infectious disease emergently. If necessary, surgery can be called to assist with source control. Patients with septic CST should be admitted to the hospital with consideration of a critical care setting given the high morbidity and mortality.