So How Come They Don't Go Straight To The Spinal Tap?
Posted 24 January 2009 - 10:27 PM
...so I didn't know how to answer... is there a reason they avoid the spinal tap unless absolutely necessary? Is it just because its unpleasant, or is it dangerous? are the results ambiguous?
.. just curious..
Posted 24 January 2009 - 11:31 PM
.. just curious..
*gasp* You know, I have no idea! I mean, if you want to know if someone isn't making hypocretin in their brains, what better way to go directly to the source and find out? Maybe someone else here knows. Because, in research, we did it all the time. Does hypocretin output change over time? Well, let's find out! *poke*
Why not go for that first if N is suspected in humans? Makes sense to me. (and I've never had it done, either, btw...I wish I had but now I'm kinda better so prolly wouldn't tell much if I asked for it.) I mean, what are you going to do, wait until the patient dies and count the hypocretin cells? Ha!
All a genetic test will tell you is maybe whether or not you have a known gene to predispose you to N, not whether you actually have it or not. It's not going to tell you everything, and they don't even know for sure all the genes that might cause N yet. New genes are discovered all the time. And a lot of doctors discriminate against patients without specific genes. God knows I was kicked out of a few offices for not having the "right" genes. Piffle.
I say why beat around the bush? Go for a lumbar puncture. But then, I'm not a doctor. Ho hum. Still working on that song...
Posted 25 January 2009 - 02:42 AM
Posted 25 January 2009 - 09:17 AM
Posted 25 January 2009 - 09:33 AM
What is the cause of narcolepsy?
Recent studies have shown that narcolepsy with cataplexy is usually caused (>90%) by the lack of two related brain chemicals called "hypocretin-1" and "hypocretin-2". The cause of narcolepsy without cataplexy is still under investigation.
So basically a spinal tap would indicate if you had N w/ C.... but if you just had N, then it could possibly miss that diagnosis..
see..ya learn something every day....
Posted 25 January 2009 - 09:39 AM
Yes but with a caveat. No single test will ever be 100% specific for narcolepsy but this test is clearly much more specific than HLA typing. Aproximately 90% of the narcoleptic patients we have tested to date have undetectable hypocretin levels in their cerebrospinal fluid (CSF). All the normal individuals (with or without HLA-DR2 or DQB1*0602) we have tested have detectable hypocretins in their CSF. Having undetectable levels (independently of any other severe medical condition) is thus clearly a strong signature for narcolepsy. We however still need to extend the study before fully assessing the value of the test. For example, we don't know if patients without cataplexy also have abnormal hypocretin levels. Furthermore, it is likely that some (probably rare) patients with narcolepsy will have normal CSF hypocretin levels. In narcoleptic dogs for example, hypocretin CSF levels are normal even so the animals have all the symptoms of narcolepsy. In this case, the receptors for hypocretins are the problem, not the hypocretin molecules (receptors are proteins on which the hypocretins act to produce their effect on cells, like a lock -receptor- and a key -hypocretin-). In the narcoleptic dogs, the hypocretin is present but cannot produce its effect on cells in the brain.
To draw CSF requires a lumbar puncture (spinal tap). This is a safe but not completely insignificant procedure (the main problem is that temporary headaches can occur in about 5% of the cases following the procedure). The procedure is a little similar to an epidural anesthesia (actually safer and easier), is used a lot by neurologists to exclude many neurological problems such as brain hemorrhage, brain infections, multiple sclerosis, etc... We have tried to measure hypocretins in other tissues such as blood but this molecule probably exists in sufficient amount only in the brain and the CSF. Clearly, some effort should be devoted in measuring hypocretin levels more easily.
So I guess that's that...
Posted 25 January 2009 - 09:53 AM
Posted 25 January 2009 - 01:23 PM
I came very close to having one done, but i kept trying to talk my doctor out of it b/c I really didn't think it was that necessary given our overwhelming evidence for N at the time. however, he would contend that there was no way in hell that we would be able to get approved for Xyrem if we didn't have that one additional piece of positive evidence to add to my narcolepsy dx cache. Then, he told me that even if it comes out negative, it doesn't mean I don't have N, it just means that I most likely have N either without or with merely mild cataplexy. When the fluid tests positive it is for N with cataplexy, that is why they use it; for a definitive cataplexy dx.
After I argued that it made no sense for me to undergo such a serious procedure when the results had a potential to be less than effective in furthering my ability to get Xyrem; that if it came back negative for cataplexy, despite the fact that I have dropped 7-8x's in my life and continue to have mild attacks/weakness often, then the entire process would be a ridiculous case of gambling with my well-being for no other reason than to placate the drug company/insurance company. I mean, it's the puncture your spinal column for *BEEP*'s sake! No one should take that lightly, it's a big deal.
So, he thought about it a moment and then realized my point and agreed, so he decided to just have a go at getting Xyrem with the evidence that we already had and whaddya know, we got approved. God forbid he would have just done that in the first place; it would have saved me months of worry and deliberating upon whether or not I would have the spinal done. I mean, I went back and forth with him on this issue for at least 2 months. Frankly, I think the guy was a bit spinal tap happy and looking to do one; he's young and eager.
I'm so very glad I stuck to my guns and didn't have the procedure. You have to be your own advocate.
Posted 25 January 2009 - 01:38 PM
Gee thanks...lol! It sounded awful to me when he first mentioned it too... but he assured me it's really no more painful than having blood drawn, and that they do it right in their office... and he is a very experience neurologist so I'm not really worried about that.
After having three kids, and having three epidurals, I was reading that an epidural is far more dangerous than a spinal tap... so that doesn't worry me that much.. and epidurals are a piece of cake as long as you don't look at the needle.. EEK!
I'm not really worried about it.. and I'm not going to protest it if they want to do it... I have had SOOOOO many misdiagnoses in my life... it feels good to be working with a dr. that wants to be confident we're dealing with the right one. I'm more worried about being given handfuls of drugs for a condition I don't have... see example A:
Posted 26 January 2009 - 05:27 PM
Posted 27 January 2009 - 05:22 AM
Most studies say it's 90% or more but one study shows only 72% of people with N with cataplexy (and if they are also HLA + )having low CSF hypocretin. Sounds like if you've got low hypocretin, that test helps with diagnosis, but if you've not got low hypocretin it doesn't help to rule N out.
But some doctors still use this test to exclude N.
I think there's some studies saying it's 90% and some saying it's 72% because they're using different definitions of cataplexy and they measure the hypocretin differently.
There's a subgroup of pwn with the worst symptoms and total paralysis cataplexy, - it looks like for those of us with it like that we're very likely but not certain to have low/undetectable hypocretin. So it's sort of accurate for the group of people that are the most likely to get diagnosed by history and sleep tests and not need it for diagnosis and there's still some who look like they are in that group but have normal hypocretin.
Haven't found any figures on this but from reading case studies it looks like there's maybe quite a few with N from brain injury and some other illnesses that don't have very low hypocretin, and we don't always have it worked out that it was an injury or other illness triggering/causing it before we get tested.
It's such a big thing to decide about someone's life, so I feel like a test has to be perfect if you're going to turn people away based on the results. I wish they wouldn't ever use it to exclude N at all.
I've heard two doctors and a researcher say - for ethical reasons they would only use spinal tap to see if the person has low hypocretin, as last resort when all other tests are inconclusive, just to see if they could positively diagnose it that way, but that normal results couldn't ever rule out N. I know we're being sold strong drugs, but at some point someone just has to listen to you!!
Posted 27 January 2009 - 05:42 AM
Posted 27 January 2009 - 02:01 PM
.... it is SAD how many people are dealing with dr's that seem to go out of their way to prove there is nothing wrong with them... (then again I've had similar problems.. thankfully not so much with N, but when I was having fertility problems)...
... now I get the confusion.. but I agree.. if it were being used to exclude N as a diagnosis.. then that wouldn't seem a very fair test...