||Andrew G. Lee, MD, Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, TX; Professor of Ophthalmology, Weill Cornell Medicine; Jeffrey Lee, Baylor College of Medicine Class of 2022
||So, today we're going to be talking about a patient with a homonymous hemianopsia, but a negative MRI with no structural correlate to the homonymous field. And normally the thing that drives the differential diagnosis is how long has the homonymous hemianopsia been there for. So, in a patient who has a homonymous hemianopsia with no lesion, there are basically very few things that that could possibly be. So, if it's short, like minutes, 2 minutes - 2 hours, then the thing we're thinking about is occipital seizure including the post-ictal variety, which is the visual field variant of the Todd's paralysis. So, we have a homonymous hemianopsia after an occipital seizure. If it's medium duration, hours to days, then we're thinking about non-ketotic hyperosmolar hyperglycemia which is a metabolic problem in the occipital lobe. And if it's months in duration, then we really should be thinking about the Heidenhain variant of Creutzfeldt-Jakob disease, and normally those people have other mental status change. They'll develop myoclonic epilepsy type of seizure jerking. They'll have characteristic EEG findings, such as spike-and-wave activity, and CSF analysis might show abnormal proteins including 14-3-3 and tau proteins and other proteins. And if it's years, no, if it's 2 months then we're thinking about Creutzfeldt-Jakob disease, a prion disease. And if it's 2 years, we're really thinking about posterior cortical atrophy. And we should be able to see that on the MRI, so that's the visual variant of an Alzheimer's disease. If it's 2 decades of unexplained, intermittent homonymous hemianopsia, then that's usually a migraine. And of course, that doesn't have a correlate, but it comes and goes. So, when we have a homonymous hemianopsia, but a negative MRI. You should be thinking about the duration as the driver for the differential. If it's minutes to hours, seizure. If it's hours to days, non-ketotic hyperosmolar hyperglycemia. If it's two months, especially if there's myoclonic jerking, mental status change, progressive neurocognitive deficit, think Heidenhain variant of Creutzfeldt-Jakob disease. If it's years, posterior cortical atrophy, the visual variant of Alzheimer's disease. And if it's decades of intermittent come-and-go, that's migraine. Now, homonymous hemianopsia is a very uncommon thing for a non-organic patient to have. So, if someone has a homonymous hemianopsia, you really should be taking that seriously and work your way through this differential. That means EEG, repeat MRI scan, LP, EEG for the Heidenhain variant and PET scan to look for posterior cortical atrophy. Or, just put the clinical pieces together and do neuro-psych testing to make the diagnosis.