Primary leptomeningeal sarcomatosis; a pathology proven case with challenging MRI and clinical findings.

A 20-year-old male patient admitted with intractable seizures and progressive dementia is presented. Magnetic resonance imaging (MRI) examinations revealed diffuse leptomeningeal thickening, enhancement especially in the basal cisterns and multiple cystic formations in the brain stem, temporal lobes and basal ganglia. The pathologic examination from the right temporal lobe was consistent with leptomeningeal sarcoma. Marked regression of the symptoms and MRI lesions were detected following radiotherapy.