Pachymeningitis is an inflammatory condition that causes chronic thickening of the dura mater. It is associated with many underlying causes, but here we discuss its rare association with a systemic inflammatory syndrome – rheumatoid arthritis (RA).

We present the case of a 78-year-old man with no prior history of epilepsy who developed abnormal involuntary movements which progressed to a generalized tonic-clonic seizure. His course also included several stroke-like episodes which were often MRI-negative. He was hospitalized repeatedly in the ensuing year for encephalopathy and medication-refractory seizures.

Serial MRI scans over the course of several hospitalizations demonstrated persistence of dural thickening along the bilateral frontal poles with leptomeningeal and pachymeningeal enhancement as well as progressive parenchymal FLAIR changes. Autoimmune labs were notable for elevated ANA titers, rheumatoid factor, and anti-CCP antibodies. CSF analysis across multiple visits was significant for lymphocytic pleocytosis, elevated protein, and positive oligoclonal bands. EEGs were consistent with diffuse cerebral dysfunction and seizure which muscle artifact obscured evaluation of epileptiform discharges. Patient underwent meningeal biopsy which demonstrated chronic inflammation and foci of necrosis consistent with a probable diagnosis of RA-associated meningoencephalitis. The patient was treated with pulse dose steroids and chronic immunotherapy with significant improvement in mentation and seizure frequency.

Pachymeningitis as sequelae of systemic inflammatory diseases such as RA is rare, and recognition of its features are paramount. It can be an insidious, progressive cause of epilepsy and encephalopathy, and should be considered in older adults with new-onset epilepsy and no clear precipitating factors, even without a known history of systemic inflammatory disease. This condition is highly responsive to steroids and immunomodulatory therapy and should be suspected when drug-resistant epilepsy develops in the setting of clinical or lab-supported rheumatologic disease. Pachymeningitis can carry significant morbidity and mortality, therefore prompt treatment can greatly improve patient outcomes.