Isolated Meningitis Is a Unique Clinical Phenotype of Myelin Oligodendrocyte Glycoprotein Antibody-associated Disease
Albert Aboseif1, Nabeela Nathoo1, John Chen2, Laura Cacciaguerra1, Nisa Vorasoot1, Samantha Banks1, Jan-Mendelt Tillema1, Deena Tajfirouz2, Smathorn Thakolwiboon3, Michel Toledano1, Sean Pittock1, Eoin Flanagan1
1Department of Neurology, 2Department of Opthalmology, Mayo Clinic, 3Department of Neurology, Mayo Clinic Health System
Objective:
To describe individuals with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) manifesting with isolated meningitis/meningoencephalitis.
Background:
Cases of meningitis have rarely been described in MOGAD, and such patients may not fulfill the 2023 MOGAD diagnostic criteria.
Design/Methods:

We reviewed the medical records of 346 patients in our MOGAD cohort and identified those with isolated meningitis attacks. Inclusion criteria were: 1) Meningeal symptoms or signs; 2) Cerebrospinal fluid (CSF) pleocytosis; 3) Absence of an infectious etiology; 4) MOG-IgG positive; 5) Initial brain imaging lacking parenchymal involvement.

Results:
Twenty patients were included (representing 6% of our total MOGAD cohort), with a median titer of 1:100 (interquartile range[IQR], 100–1000). The median age was 18 years (IQR, 9.6–33.2) and 13 were male (65%). The meningitis attack occurred at onset in 12 (60%) and as a relapse in 8 (40%). Presenting features included headache (n=20, 100%), fever (n=14, 70%), nausea/vomiting (n=13, 65%), photophobia (n=12, 60%), encephalopathy/meningoencephalitis (n=7, 35%), nuchal rigidity (n=6, 30%), and seizure (n=4, 20%). Increased intracranial pressure was present in 9/10 analyzed (90%; median=34 mmH2O; IQR, 26–40). CSF analysis revealed an elevated white blood cell count (WBC) in 20 (100%; median WBC 50/µL; IQR, 39–137; 67% lymphocytic; 18% neutrophilic). Two had leptomeningeal enhancement (10%). Fourteen (70%) received antimicrobials for presumed infectious meningitis. Only 3 (14%) episodes were initially attributed to MOGAD. Within the attack, 14 (70%) evolved into a characteristic cerebral core demyelinating event with parenchymal brain lesions detected on repeat imaging (n=11, 55%) or developed concurrent myelitis (n=3, 15%) or optic neuritis (n=3, 15%) at a median of 15 days (IQR, 11-20) from symptom onset.
Conclusions:
Isolated meningitis or meningoencephalitis is a unique clinical phenotype of MOGAD that is under-recognized and mimics infectious meningitis.  Future iterations of MOGAD diagnostic criteria could consider incorporating this clinical phenotype.   
10.1212/WNL.0000000000205621