Rosai Dorfman

33-year-old female with history of chronic headaches and symptoms of elevated intracranial pressure on clinical examination. Images demonstrate symmetric pachymeningeal thickening over the right and left cerebral hemispheres with corresponding T1 signal which is isointense to gray matter, T2/FLAIR hyperintense, and restricts diffusion on the DWI images. Postcontrast images demonstrate diffuse leptomeningeal enhancement with marked thickening and enhancement of the pachymeningeal surfaces. Differential diagnosis sarcoidosis, extensive dural metastatic disease, hypertrophic pachymeningitis, Erdheim-Chester disease, Rosai-Dorfman disease and numerous diffuse meningioma. This case went to open biopsy at which time a diagnosis of Rosai-Dorfman disease was made. Rosai-Dorfman is a rare benign idiopathic proliferative disease. Presentation is usually in young adulthood with a slight male predominance. Patients typically present with painless massive cervical lymph node enlargement. Headaches and seizures also occur with intracranial involvement. The etiology is unknown but autoimmune and viral causes have been suspected.