Skull base allergic fungal sinusitis with abducens palsy in the third trimester

Allergic fungal sinusitis (AFS) usually follows a slow course, but bone erosion including that of the skull base can be seen. Patients may present with intracranial extension mimicking a cranial base neoplasm. We describe a 21-year-old pregnant female initially seen at 27 weeks gestation with a complete right sixth nerve paralysis. MR imaging showed an apparent nasopharyngeal neoplasm invading both temporal lobes. Further evaluation revealed typical findings of fungal sinusitis on both CT and MR images. Biopsy results fulfilled the diagnostic criteria of AFS, and after endoscopic treatment the sixth nerve palsy quickly resolved. Although abducens palsy has been reported with acute bacterial sinusitis and with mucocele, and limitation of eye motility has been described with orbital involvement by AFS, we are unaware of any prior reports of true cranial nerve palsy associated with proven AFS. Our patient had no evidence of mucocele or of bacterial infection. The palsy in this case was presumably the result of compression of the cavernous sinus. The patient's pregnancy made decision making regarding imaging and surgical intervention complex. Mother and child are alive and well 31 months after surgery.