Describe a case of worsening pachymeningitis with an unusual etiology.

Pachymeningitis, thickening of dura mater and increased meningeal signal intensity, has a broad differential including infectious, autoimmune, inflammatory, and neoplastic etiologies.

77 year-old woman with a history of diabetes, bilateral malignant otitis externa (2015), and chronic headaches after head trauma (2018) underwent brain MRI demonstrating pachymeningitis in July 2018. On examination she was well-appearing with no new neurologic deficits. Outpatient evaluation including LP was unrevealing. In March 2019 MRI brain and orbits demonstrated progression of pachymeningitis into the orbital apex and a ring-enhancing lesion in the left frontal lobe for which she was admitted to the hospital. She reported sensitivity to light and worsening of left eye vision. Exam revealed new left disc pallor with rAPD, proptosis, ophthalmoparesis, and visual loss.

Broad infectious workup including repeat LP was unremarkable. Rheumatologic studies demonstrated elevated ESR and CRP, positive anti-SS-A and elevated IgG4 subclass. CT chest/abdomen/pelvis and CSF cytology/cytometry were negative. She underwent a dural-based biopsy which demonstrated hyphae consistent with a fungal organism and abundant IgG4-positive plasma cells. IgG4+ staining and elevated IgG4 levels were thought to be due to an immune response to a fungal infection as opposed to IgG4-related disease. The patient was started empirically on amphotericin and voriconazole. While the culture showed no growth, fungal PCR resulted as Aspergillus flavus. Repeat MRI showed improvement in pachymeningeal thickening and size of abscess.

There are only four case reports in the literature of Aspergillus flavus causing pachymeningitis. All four cases involved a history of either diabetes, otitis media, or both. In this case, dural biopsy elucidated the etiology and directed treatment. Clinicians should consider fungal etiology in patients with progressive pachymeningitis, especially in a patient with diabetes and history of otic disease.