The Angiotensin Converting Enzyme (ACE) CSF test measures ACE levels in your spinal fluid to help diagnose neurosarcoidosis, a condition where sarcoidosis affects the nervous system, as elevated levels often signal this inflammatory disease, though it’s not definitive and requires other tests like MRI and spinal fluid analysis for a full picture. ACE helps control blood pressure by narrowing vessels, and high levels in the CSF suggest immune cells (macrophages/epithelial cells) are active in the central nervous system