I've been trying to get my head around what this thread is about.
We have a secondhand anecdote thus:
I just wanted to share an article that was recently posted to our Facebook group on ME/CFS and structural diagnoses. A woman in it who meets ME/CFS criteria was recently diagnosed with bilateral internal jugular vein stenosis (IJVS). This is considered a congenital condition, however she never had symptoms before contracting Dengue Fever. Her doctor hypothesizes that since Dengue Fever can thicken the blood, her infection took a previously asymptomatic congenital condition and made it symptomatic. This hypothesis is supported by the fact that a drug called Stugeron, a vasodilator, improves her symptoms.
This includes
1. An ME diagnosis
2. A diagnosis by scan of IJVS
3. Speculation by a doctor that this might have become symptomatic due to 'blood thickening' following Dengue fever
4. Secondhand report from the patient that Stugeron improves symptoms.
The paper linked says this:
Extracranial venous abnormalities, especially jugular venous outflow disturbance, were originally viewed as nonpathological phenomena due to a lack of realization and exploration of their feature and clinical significance. The etiology and pathogenesis are still unclear, whereas a couple of causal factors have been conjectured. The clinical presentation of this condition is highly variable, ranging from insidious to symptomatic, such as headaches, dizziness, pulsatile tinnitus, visual impairment, sleep disturbance, and neck discomfort or pain. Standard diagnostic criteria are not available, and current diagnosis largely depends on a combinatory use of imaging modalities.
So we have a condition that has no standard diagnostic criteria or scanning method, and variable symptoms. The symptoms listed include:
dizziness, pulsatile tinnitus, visual impairment, sleep disturbance, and neck discomfort or pain.
And I looked up Stugeron which is a trade name for Cinnerizine.
It is an antihistamine and calcium channel blocker.
Wikipedia tells me this:
It is also known to promote cerebral blood flow, and so is used to treat cerebral apoplexy, post-trauma cerebral symptoms, and cerebral arteriosclerosis. However, it is more commonly prescribed for nausea and vomiting due to motion sickness or other sources such as chemotherapy, vertigo, or Ménière's disease.
So the list of symptoms treated by Stugeron include some of the same symptoms as are listed in the rather vague list for IJVS.
Wikipedia also tells me this:
Cinnarizine inhibits the flow of calcium into red blood cells, which increases the elasticity of the cell wall, thereby increasing their flexibility and making the blood less viscous.
[9] This allows the blood to travel more efficiently and effectively through narrowed vessels in order to bring oxygen to damaged tissue
So maybe it's helping with the inflexible red blood cells Ron Davis is investigating.
Note also if we want to play the symptom overlap game, dizziness, vertigo, tinnitus, nausea, headaches, brain fog possibly due to reduced cerebral blood flow etc. are all symptoms suffered by some people with ME.
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My conclusion from all this is that an anecdote of an individual with an ME diagnosis who finds some of their ME symptoms improved with Stugeron may have no connection with the fact that they have a scan showing previously asymptomatic IJVS. The stugeron may be acting on things other than their jugular veins to produce improved symptoms.
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Now to add an anecdote of my own. I use Stugeron for travel sickness. I was also prescribed it many years ago in the early years of my ME for a bout of labyrinthitis, whose symptoms are vertigo, dizziness and nausea.
I remember being surprised in my early ME days that I coped better than I expected with travelling with ME. Not only did the stugeron help with my travel sickness, but it also relieved my almost constant ME related nausea, and I had less PEM after travelling than I would have expected. Perhaps the stugeron was helping my ME in other ways too! I still use it sometimes when my ME nausea gets really bad.
Edit: I tell this anecdote not to add more to the heap of speculation based on anecdote, but to demonstrate that we can probably all come up with anecdotes and try to make up explanations that probably bear no relation to real biology.
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Edit: On other thing that puzzles me: I looked up Dengue fever and couldn't find any mention of it thickening blood as the individual's doctor hypothesised. All I could find was stuff about a drop in platelets, particularly in the haemorrhagic version, in other words it can thin blood while the individual is infected.