The cavernous sinus, with its central location and many direct and indirect vascular connections, is particularly vulnerable to septic thrombosis from the face, nose, tonsils, teeth, and ears. A valveless system of sinuses and veins allows for easy spread of bacteria. Bacterial infection of the orbital structures is more frequent in pediatric patients, secondary to the increased frequency of upper respiratory tract and paranasal infections . The most frequently encountered organisms are Staphylococcus aureus (35%), Streptococcus pneumoniae and other streptococci species, Gram-negative bacilli, and anaerobes [2–4]. Other infections, such as mucormycosis and aspergillosis, are of greater concern in diabetics, the immunocompromised, and other high-risk patient populations.
The source of infection in our first patient was likely sinusitis. The second patient's bacteremia placed her at risk of septic thrombophlebitis. Initial imaging in both girls showed inflammation of the paranasal sinuses, a common source of bacteria. The oropharynx is another source of septic thrombi. F. necrophorum, a commensual anaerobe found in the oropharynx, is responsible for the thrombophlebitis seen in Lemierre's syndrome and has caused rare cases of CST . This organism was identified on our second patient's blood cultures, along with the more commonly implicated streptococcus species and likely contributed to her multiple thromboembolic events. Mastoiditis is an increasingly rare infectious source for CST due to widespread adoption of the 7-valent pneumococcal conjugate vaccine .
After a comprehensive history and physical exam, neuroimaging is one of the most useful tools for evaluating the orbits. High-resolution MRI is the modality of choice in CST. It can detect all stages of thrombus formation, whereas CT can be inconclusive secondary to bone artifact . Filling defects within the cavernous sinus and expansion of tributary veins and venous sinuses are seen in cases of CST. However initial scans can be negative, so evaluating physicians must be diligent in cases where the suspicion is high for a vascular obstruction. Venous dilation can also be seen in carotid-cavernous fistulas, Graves orbitopathy, orbital pseudotumor, and meningiomas. Therefore, CT angiography or MRA may also be used to identify the cause of presenting symptoms [1, 8].
The prognosis and clinical course of CST have been dramatically changed by prompt recognition and treatment with antibiotics . Intravenous corticosteroids have been theorized to rein in the prothrombotic state seen in orbital infections. They are first-line therapy for cases of idiopathic orbital inflammation, where they have proven efficacy in reducing perivascular inflammation and improving cranial nerve dysfunction . However, their use in conjunction with antibiotics has not been shown to improve outcomes in orbital cellulitis [11, 12]. Their role in CST is not known. The role of anticoagulation for septic thromboemboli has not been examined in randomized controlled trials. However, heparin administration in the early period of hospitalization has been associated with a reduction in diplopia from cranial nerve dysfunction and blindness secondary to optic nerve damage [13, 14]. Four to 6 weeks of anticoagulation with warfarin is recommended after initial heparin therapy.
We presented two cases of patients ultimately diagnosed with septic thromboembolic disease. After presenting with one or more cranial nerve palsies and with imaging that revealed sinusitis, antibiotic therapy failed to improve their courses. Despite the concerted efforts of a multidisciplinary team comprising ENT, infectious disease, critical care, and ophthalmology, both girls worsened. CST is thought to be a rare diagnosis with today's widespread use of antibiotics for oropharyngeal infections. However, a low threshold for repeatedly considering septic thromboembolism was vitally important in the decision to rescan each girl and should be regarded as a crucial and astute step leading to their recovery. Every subspecialist who encounters a patient with cranial nerve palsies and sinusitis must consider CST and maintain a low threshold for rescanning.