45-year-old woman presented with fever and new-onset intractable headache with meningismus within one week of receiving COVID-19 vaccine. Initial CSF analysis demonstrated leukocytosis with neutrophilic predominance. MRI brain showed mild diffuse leptomeningeal enhancement.
She was empirically treated for bacterial meningitis. CSF cultures and viral studies, including HSV-1/HSV-2 PCR, was negative. During her course, she developed bilateral sensorineural hearing loss, raising concern for Cogan syndrome; however, other systemic findings including interstitial keratitis were negative.
She was readmitted with recurrent fever, worsening headache. Serial lumbar punctures demonstrated dynamic CSF pleocytosis, with neutrophilic predominance during febrile episodes and lymphocytic predominance when afebrile.
Extensive evaluation, including CSF autoimmune encephalitis panel (including GFAP-IgG), MOG antibodies, CSF flow cytometry, PET imaging, and genetic testing for periodic fever syndromes, was unrevealing. Brain biopsy was unremarkable. Evaluation for systemic vasculitis, sarcoidosis, IgG4-related disease, and Behçet disease was negative.
Over time, the patient developed persistent chronic cough of unclear etiology despite negative systemic and pulmonary evaluations, raising concern for neurogenic cough.
The patient demonstrated partial clinical response to corticosteroids but experienced relapses during tapering. Mycophenolate mofetil provided limited benefit. Significant clinical and radiographic improvement was observed following initiation of rituximab.