To report a case series of patients with idiopathic brain stem encephalitis (rhombencephalitis). We review the differential diagnosis, clinical and radiographic features of brainstem encephalitis and describe distinguishing features between different etiologies. We propose a diagnostic approach to brainstem encephalitis.

We searched the medical records of patients treated in the neuroimmunology clinic of our institution for cases of idiopathic rhombencephalitis and extracted clinical data, cerebrospinal fluid (CSF) findings, magnetic resonance imaging (MRI), biopsy results if available, treatment, and outcomes for analysis. Patients with rhombencephalitis based on clinical and imaging criteria, but who did not meet clinical criteria for any known causes of rhombencephalitis were reviewed in detail and included in our report.

Six cases of idiopathic rhombencephalitis were uncovered from our cohort of patients. A specific etiology was not found but thought to be inflammatory or autoimmune. Half of the patients had a CSF pleocytosis and elevated protein and all patients appeared to have some response to immunotherapies like glucocorticoids, azathioprine, mycophenolate, and/or cyclophosphamide.