Temporal lobe abscess in a patient with isolated fungal sphenoiditis.

Pathology References Isolated sphenoid sinusitis accounts for 2-3% of all sinus infections evaluated by radiologic imaging. Fungal sphenoiditis is present in approximately 5% of isolated sphenoiditis. The most common presenting symptom is frontal/retro-orbital headache; this occurs in roughly 70% of cases. Nasal obstruction is the next most common symptom presenting in 30% of cases. Noninvasive fungal sphenoid sinusitis rarely presents with serious complications. However, diplopia and/or transient vision loss have been the most severe reported complications and have been seen in up to 3% of cases. Intracranial extension and cerebral abscess is another serious complication of fungal sphenoiditis, and to our knowledge has not been reported until now. Intracranial extension from sinusitis is a rare but potentially fatal disease characterized by bony erosion of the skull base and fungal extension into the adjacent cavities, such as the orbit or cranial vault. It is usually associated with acute fulminant invasive fungal sinusitis (AFIFS) in the immunocompromised population, such as patients who have undergone hematopoietic stem cell transplantation or solid organ transplant, those with HIV/AIDS or diabetes mellitus, or those who are undergoing treatment with chemotherapy or immunosuppressants.3, 4 However, this complication has now been shown to very rarely occur in immunocompetent individuals as well, and seems to be increasing in frequency in this population.4-7 Of the approximately twenty pathogenic fungi, the three most common fungal infections in the nasal sinuses are the opportunistic genera of Aspergillus, Mucor, and Candida, of which Aspergillus is the most prevalent organism.1, 8 While rare, each of these can invade the adjacent structures, with Mucor being the most invasive and requiring the most aggressive surgical treatments. Intracranial extension and abscess formation most commonly occurs from the frontal sinus to the frontal and frontoparietal areas of the brain. 4 The rarest occurrence of invasive fungal sinusitis is seen in the sphenoid sinus, due to only 2.7% of all sinus infections occurring there.9 The rarity of this infection in comparison to other sinuses is because of both the anatomical orientation of the sphenoid sinus receiving little directed airflow, and because the sinus mucosa is lined by relatively few glands, producing less mucus to serve as a reservoir for infection.10 When invasion does occur from the sphenoid sinus, it can occur through one of two mechanisms: retrograde thrombophlebitis through diploic veins of the skull, or by direct extension through normal anatomic pathways or wall erosion.11 The fungus can either enter the frontoparietal areas of the brain similar to extension from the frontal and ethmoid sinuses, or it can extend into the cavernous sinus, causing visual defects secondary to destruction of cranial nerves III, IV, V, and VI. Another potential site of invasion is the temporal lobe, which has rarely been documented.10, 11 Case Report