| Transcript |
So we're going to talk about optic atrophy today. So optic atrophy, as you know, is not a diagnosis, it is a description of atrophy of the optic nerve. So the first question is, is it real, or is it pseudo-pallor? A nerve can look pale, but isn't pale. So we would not want to label a nerve as optic atrophy if we didn't have the clinical evidence to support the diagnosis that the nerve is pale. And so the way to do that is by establishing that there is or is not an optic neuropathy. So we want to check the visual acuity and visual field, we want to look for the relative afferent pupillary defect, which may be absent if it's bilateral and symmetric, and we're going to do an OCT of the optic nerve to try and see if we can identify the nerve fiber layer loss that would prove that this nerve is really pale, versus just looking pale. The most common causes of it to look pale are peri-papillary atrophy or pseudophakia, posterior chamber interocular lens. So if it's true that it's pale, and we have an optic neuropathy, then common things are common. And the most common cause of unilateral optic atrophy in an adult, in a vasculopathic patient, is old non-arteritic anterior ischemic optic neuropathy. So if we can get the record to show that this patient had a swollen disc before, has vasculopathic risk factors, and the small cup-to-disc ratio in the fellow eye, then we can be pretty certain that it was old NAION, as long as it doesn't change over time. In a young person, however, optic neuritis is the most common cause of an acute unilateral optic neuropathy. So again, looking at the record and establishing what was the prior diagnosis, it helps save us from doing a full-scale workup on an optic atrophy when a patient just has a common presentation of a common disorder. If, however, we don't have any evidence of NAION or optic neuritis in the past, and we just have optic atrophy, we'd like to know, is it unilateral or bilateral? So in the patients who are bilateral, that usually means that there's a systemic process going on. So the workup for bilateral optic atrophy with a central scotoma in each eye is going to be looking at things like B12, folate, Leber's hereditary optic neuropathy, toxic and nutritional things-these are the common things for the workup for bilateral with the central scotoma. If it's just unilateral, we pretty much aren't going to be doing the vitamin testing, we're not going to be thinking about systemic toxins, we're not going to be thinking about Leber's hereditary optic neuropathy as much, because those are all bilateral. So if it's a strictly unilateral, it's a real optic atrophy, and we've excluded the common things, the highest yield test is going to be doing an MRI. But because the optic nerve has an intraocular portion and an intraorbital portion and intracanalicular portion and intracranial portion, we need to have an MRI of head and orbit with gadolinium and fat suppression sequences. So that is going to provide us a yield of about 20%, so about 20% of people, we're just going to be able to find right away that the cause of the optic atrophy is compression from a neoplasm. So this is the go-to test at the initial stage. The follow-up to a negative MRI, however, is going to be testing for what I call the usual suspects-the lurker infections, the type of infections that can stay inside of you and have no other symptoms. That's the syphilis serology, tuberculosis with a quantiferon and chest x-ray, Lyme disease. These are the common things that lurk inside of you and have no other symptoms, and could just present with optic atrophy. Of the list, syphilis would be the most common. And if that's negative, the workup for that is negative, then we can just follow the patient and see if there's progression. Because it's still probably one of these common presentations of a common disorder--NAION or optic neuritis; if it's bilateral, toxic or nutritional, and if it's unilateral, a compressive lesion that might show later. If it stays the same, we probably stop at what I would call second line testing. However, if it continues to progress, then you have to do more. And if you're getting to this point right here, you probably should refer to neuro-ophthalmology, for proceeding to tertiary testing like NMO, and MOG, and autosomal dominant optic atrophy, and paraneoplastic. These things are probably best left to the experts. So optic atrophy-make sure it's real, not just looks pale but is pale, check and define the clinical parameters of optic atrophy. Is it old optic neuritis or old NAION, because common things are common? Is it unilateral or bilateral? That will drive the decision-making. Image the patient, because 20% of the patients will have a compressive lesion. Test for the usual suspects, follow the patient for progression or stability of the disease, and recognize, triage, and refer when you need help. |
