Mar 212013
 

Twitter is great. It feeds me all sorts of new, sometimes even relevant scientific or medical news.


“Their research shows that autonomic reflex testing, which measures automatic changes in heart rate and blood pressure, consistently shows changes in people who suffer concussions.” (Ashik Siddique, Medical Daily, 20 Mar 2013)

Neurologists at the Mayo Clinic in Arizona were looking for a biological marker for concussion and found this connection. But what is an autonomic reflex?

Reflexes are like neuronal loops. Stimulus of your knee, for example, sends an impulse up a bunch of nerves to your spinal cord and brain, and they send a signal back, and your leg jerks or not. One reason it may not jerk is because you’ve used your brain to over-ride that reflex. You control it. But an autonomic reflex is a loop through your autonomic nervous system, which controls your heart and blood circulation. Just as you cannot tell your heart to beat or your blood pressure to drop, you cannot control the reflex. Plus it’s all internal. You can’t stick a reflex hammer inside and tap your heart. And so it’s a bit difficult to test it.

According to the Cleveland Clinic’s description of cardiovascular autonomic testing, testing includes four activities:

  1. Blow air into a small tube. This is called a Valsalva test.
  2. Put your hand in ice water for two minutes. This is called the Cold Pressor Test.
  3. You are given phenylephrine to increase blood pressure, and your heart rate and blood pressure will be recorded.
  4. You are given amyl nitrite to lower blood pressure, and your heart rate and blood pressure will be recorded.

I had a variation of this test back in 1989/90. Mine included a tilt table (which from what the doc says in the video below sounds like was also done in the research testing). I had it done because I had blood pressure that would drop like a stone under stress and was chronically low. The brilliant woman who tested me and diagnosed what I had died a few years later. Unfortunately, after my brain injury — and even though I was chronically complaining of a permanently racing heart and a yo-yoing blood pressure — I never met anyone as brilliant as she was. And so I didn’t have this kind of test done (not that I would’ve volunteered for it again, as having a needle stuck in your arm for two hours, blood pressure cuff going off all the time for 2 hours, having ECG leads on, putting your hand in ice, and being tilted is awful).

If I had, I wonder what my results would have shown?

The researchers in their video talk about the assumption that post-concussion dizziness is due to vestibular issues. I did have ear and vestibular testing to see if that was the reason for my dizziness. Nope. All peachy keen, and my hearing was excellent too. The researchers dispute vestibular causation and suggest that the symptoms are due to an hyperadrenergic state — basically, too much adrenaline — which I think is a different way of saying the sympathetic system is on overdrive cause of the injury. Yup, that’s me, even 13 years post-injury. Gah! Oh, hey, lookee what they also mention: tachycardia!!! Yup, that’s me. And considerable blood pressure variability!! Oh gee, what a surprise.

They postulate a centrally-located impairment of the adrenergic nervous system (um, I believe that’s the sympathetic nervous system) caused by the brain injury, aka, concussion. And they postulate that the dizziness represents autonomic nervous system impairment, whose symptoms include — wait for it — exercise intolerance!!!! And only a trainer was able to recognize and tell me that people with brain injury can have exercise intolerance. Now neurologists are figuring this out. Double gah!

They suggest autonomic nervous system impairment is common in “these patients” — that includes me. OMG. I’m about to have a heart attack that mainstream brain doctors are actually recognizing what to date only the psychologists and psychiatrist at the ADD Centre and the trainer I met in 2009 have recognized!

Of course, being researchers, they’re only interested in this finding as a biomarker for brain injury. What I want to know is: what now? How does one treat this, FFS?

*Crickets* Sigh. Well, at least a major US centre now recognizes it. Next step is to duplicate the findings with a larger sample size (cause 21 is rather small) and then, you know, work on a remedy.

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