Use Progressive Multifocal Leukoencephalopathy and Neurosarcoidosis to guide the working diagnosis and next step; let the main risk or management issue drive escalation, treatment choice, and follow-up.

Neurological complications develop in only a small minority of individuals with sarcoidosis, affecting approximately 3 to 5% of all cases.; Beyond that, individuals can develop structural hydrocephalus, papilledema driven by elevated intracranial pressure, various hypothalamic-pituitary hormone dysfunctions, and a painful peripheral neuropathy.; Under the microscope, the classic pathognomonic finding is the presence of prominent intranuclear inclusion bodies inside the infected oligodendrocytes, surrounded by widespread patches of naked demyelination.; To lock in a definitive diagnosis, you must obtain a physical tissue biopsy that confirms the presence of characteristic noncaseating granulomas.; Single most frequent clinical presentation is chronic basilar meningitis, which characteristically causes multiple cranial neuropathies, most notably facial nerve palsy, which is often bilateral.