| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (GK) Class of 2022, Baylor College of Medicine, Houston, Texas |
| Transcript |
So, today we're going to be talking about sarcoidosis, and sarcoidosis is one of those great mimickers that can have any neuro-ophthalmic finding, either on the afferent side or the efferent side. So, we really aren't going to talk about every single thing that sarcoid can do but just the general principles of when should you be thinking about sarcoid. And you should be thinking about sarcoid in any unexplained neuro-ophthalmic deficit because it is the great mimicker. It's like syphilis in that way- it can do anything it wants to do, but the characteristic feature is it's normally associated with inflammation. And that inflammation in the eye manifests as uveitis. That uveitis can be in the front of the eye (anterior uveitis), it can be in the middle of the eye (intermediate uveitis), and it can be the back of the eye, (posterior uveitis). So, in any patient, who has active or prior evidence of anterior, intermediate, or posterior uveitis who has any unexplained neuro-ophthalmic findings, you should be thinking about sarcoidosis. Now sarcoidosis requires a biopsy and what we're looking for is a non-caseating granuloma. And what that means is we have to have the typical features pathologically of a granuloma (multinucleated giant cell), as well as the lack of necrosis is what that caseation means. So, a non-caseating granuloma plus evidence of uveitis in a patient with an unexplained neuro-ophthalmic finding is the established diagnostic test for sarcoidosis, and we would call that neuro-sarcoid once it's in the neuro-ophthalmology realm. However, what if you don't have evidence for a biopsy or a lymph node or hilar lymphadenopathy or something that you could biopsy. Then you're going to have to rely upon the granulomatous features of the uveitis to help us make the diagnosis of sarcoid. So, what we're looking for in the granulomatous disease causing uveitis is mutton-fat keratic precipitates. The mutton-fat looks like greasy blobs of fat because mutton is a very fatty animal. It's going to be globbed onto the back of the endothelium, and the mutton-fat KP associated with granulomas, nodules on the iris, either close to the margin or far from the margin. If it's close to the margin, then KP nodule, and if its far, Busacca nodule. And we're going to be looking for evidence of synechiae, usually tent-like synechiae, broad-based synechiae. So, the presence of these broad-based synechiae are going to be the features that we're going to be looking for in granulomatous uveitis. And so any patient who has unexplained optic neuropathy or unexplained diplopia or unexplained cranial neuropathy, we're going to be looking for evidence of prior or active uveitis in the anterior segment, the intermediate segment (pars plana, snowballs, vitreous opacities), and in the posterior segment (choroidal nodules, peri-phlebitis, candlewax drippings, and optic disc edema, including optic disc granuloma). If we see any of those, you should really be thinking about sarcoidosis. And our typical workup is going to start with imaging in the chest because sarcoidosis has predilection for the chest. Chest x-ray is a reasonable start. CT of the chest would be our next test, and if we are really concerned about sarcoidosis, either a PET scan or a gallium scan so we can look and find a lymph node to biopsy. If we have neuro-ophthalmic findings, we're going to be doing a lumbar puncture looking for CSF pleocytosis. And in the laboratory studies, the angiotensin-converting enzyme, liver function studies, lysozyme - these are the typical tests that we're going to be looking for for sarcoidosis. So, you should be thinking about sarcoidosis- a non-caseating granuloma, causing an unexplained neuro-ophthalmic finding, producing inflammation in the anterior, intermediate, or posterior segment, characterized by uveitis (a granulomatous form of uveitis). We're going to be testing the patient with imaging directed to the chest. If they have a neuro-ophthalmic finding, we're doing MRI, and that MRI is looking for the inflammation, which is going to manifest as gallium enhancement. Enhancement of the nerve, enhancement of the meninges, and sarcoidosis has a predilection for the hypothalamic pituitary axis. So those are the key radiographic features: enhancement of the nerves. We're going to do laboratory tests (ACE, liver function studies, lysozyme), and that's why sarcoidosis is often included as one of our "usual suspects" because it's always a suspect in unexplained ophthalmic disease. |
