A 55-year-old male with no medical history presents with headache which has lasted for the last 8 days. Approximately 2 weeks ago, he had a furuncle adjacent to the right nares drained. This morning he developed fever, diplopia, and right eye ptosis. On examination, he is febrile to 38.4°C, somnolent but arousable, and hemodynamically stable. He has ptosis and proptosis of the right eye, with a dilated pupil. Neurologic examination shows right third and fourth nerve palsy and decreased sensation on the right side of his face. A highresolution CT scan with contrast shows regions of decreased enhancement, thickening of the lateral walls, and bulging of the cavernous sinus.
Which is the MOST likely causative organism of the infection?
A. RhizopusCorrect Answer: B
This patient presents with concern for septic cavernous sinus and thrombosis. The multiple trabecula of the cavernous sinus acts as sieves to trap bacteria and consequently makes it the most frequent dural sinus to become thrombosed. Infections of the face including the orbit (orbital cellulitis), around the nose, and soft palate can spread to the cavernous sinus from the facial veins and the pterygoid plexus. In this patient, bacterial spread likely resulted from the drained furuncle. Cranial nerves III, IV, ophthalmic (V1 ) and maxillary(V2 ) branches of the trigeminal nerve, and VI all travel through the cavernous sinus. Headache and cranial nerve deficits should alert the clinician to the possibility of this condition. CT or MR venography can readily identify septic cavernous sinus thrombosis characteristically demonstrating regions of decreased or irregular enhancement, thickening of the lateral walls, and bulging of the sinus.
The causative organism reflects the primary site of infection. Staphylococcus aureus accounts for 70% of all infections, and communityacquired MRSA is increasingly reported. Less commonly streptococci (Streptococcus pneumoniae) are found. Anaerobes (Fusobacterium, Bacteroides) most often occur with dental or tonsillar infections. Fungal pathogens (Rhizopus) have been reported but are quite rare. High-dose intravenous antibiotics against the most probable organisms should be instituted promptly and continued for a prolonged period (at least 3 weeks) to ensure sterilization.
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