||Andrew G. Lee, MD, Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, TX; Professor of Ophthalmology, Weill Cornell Medicine; Anna Poliner, Baylor College of Medicine Class of 2021
||We're going to talk about vitamins. Vitamins are vital amines. And what that means is our body can't make them, so we have to eat them. So have you to eat your vitamins. And this can show up to neuro op. And they're lettered, but not all the letters of the alphabet are used. And some of the letters became numbers in the B category. ; ; Vitamin A comes to us in two ways. You can have too much vitamin A, and that can produce idiopathic intracranial hypertension. So one of the medicines we always ask patients about with pseudotumor is if they're taking too much vitamin A or if they're on therapeutic doses of vitamin A to treat leukemia or some other disease. Vitamin A is also used to treat acne, it's isoretinoic acid. In addition, you can have too little vitamin A, usually because you've had gastric surgery or some sort of intestinal surgery. And too little vitamin A produces a very distinctive symptom called nyctalopia, night blindness. So when we hear night blindness, we're thinking about vitamin A, and we're going to do a ERG to test the function of the retina. The optic nerve really doesn't care about night and day, but the retina sure does. The B vitamins are numbered, but not all the numbers are used just like not all the letters are used. And the one that comes to us on the efferent side is B1, which is thiamine. And if you're deficient in thiamine because we don't have good thiamine stores and because thiamine is a pathway cofactor that is so important in metabolic processes, if you have thiamine deficiencies you'll notice right away. It comes to us as ophthalmoplegia ataxia, they might have mental status change. But ophthalmoplegia nystagmus are the ways it comes to neuro op. And that condition is called the Wernicke. The Wernicke syndrome you shouldn't wait for the getting thiamine levels, you should just treat with thiamine. You might image the patient; it might show bilateral medial thalamic hyperintensity or involvement of the mamillary bodies or the ophthalmoplegia is coming from periaqueductal grey, but if the scan is normal still treat with thiamine. And we need high dose thiamine here like 500mg TID, and cofactor of magnesium. And the reason thiamine is important is it is involved in three important enzymatic functions that happen to spell out the mnemonic ATP. In the Krebs cycle, alpha ketoglutarate dehydrogenase; the transketolase pathway, which is in the ribose phosphate shunt, and pyruvate dehydrogenase, which is involved in the entry level of acetyl Co-A into the Krebs cycle. So deficiencies of thiamine will lead to breakdown in ATP production from glycolysis and the entry into the Krebs cycle. It will also be problematic for the transketolase pathway, which is involved in the formation of nucleic acids and NADPH as well as other neurotransmitters and alpha ketoglutarate dehydrogenase in the Krebs cycle also will result in energy failure. B9 and B12, folate look similar to us, they present to us with painless, progressive bilateral central or cecocentral scotoma and that is usually because the person isn't eating enough, usually alcohol abuse or they've had bariatric surgery or they've had hyperemesis gravida and they're vomiting all the time or they're a strict vegetarian and they're not getting enough B12. But it comes to us as painless, progressive bilateral central or cecocentral scotoma. That's B9 and B12. Although the other vitamins can present to us, these are the main ones and we don't have time in today's video to cover all of the vitamins. C is a little bit interesting because it can cause impaired wound healing and we use vitamin C for wound repair, especially in the anterior segment. D is interesting to us because vitamin D deficiency is an immunomodulatory vitamin and so we supplement patients with Vitamin D who have optic neuritis or multiple sclerosis. It's also important in preventing osteoporosis from patients who we are giving corticosteroids to like giant cell arteritis, who might get bone loss from the secondary side effect of corticosteroids. So we do DEXA bone density studies and supplement with vitamin D, calcium, and bisphosphate might be necessary. E deficiency produces ophthalmoplegia, sometimes called the Bosen Cornswag syndrome (??), abetalipoproteinemia. All the letters beyond that are not used except for K, and as you know the vitamin K cofactors are for coagulation. So really the vitamins we really need to know are A for nyctalopia, B1 for Wernicke and thiamine, and B9 and 12 for central scotoma, painless and progressive vision loss.