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  • Dr. Nathan Keiser

What a water bottle can teach us about overcoming lightheadedness after concussion.

Lightheadedness is an excellent indicator that you are not yet at full-strength when returning from a concussion.


If you have ever been laying on the couch watching tv and got up quickly, you have no doubt had the experience of feeling lightheaded. You might have felt faint, had blurry vision, tingling in your face, or felt like blood was rushing out of your head.


This sensation can come from many causes including benign ones like dehydration or dysglycemia, and can also be a sign of more concerning issues in the heart or thyroid. If you have begun to experience lightheadedness after sustaining a concussion, it is an indicator that your body is still working very hard to try to heal.


When your body is still healing, you are susceptible to further injury. Other common symptoms are:

  1. foggy thoughts

  2. fatigue with exercise

  3. depressed mood

  4. feeling lethargic

  5. feeling anxious

  6. feeling generally fatigued or worn out.


If you want to understand why you are lightheaded, and how you can use neuroscience to help take control of it, then continue reading.


Lightheadedness after a concussion is most commonly linked to the brain’s inability to maintain normal blood pressure ranges in the brain. When we are healthy, our brain has an amazing system for keeping the blood pressure inside our skull in a very constant range. This is valuable for 2 reasons:

  1. When blood pressure in the body is high, it prevents damage from too much pressure in and around our brain.

  2. When blood pressure in the body is low, it maintains a steady supply of oxygen to keep our brain alive.

So to simplify, no matter what is going on with blood pressure in the body, the blood pressure in the brain should remain constant.


This concept is called Cerebral Autoregulation.


In cases of concussion/mTBI, the lightheadedness that you experience is largely from interruptions in your cerebral autoregulation.


Interruptions in cerebral autoregulation are also part of the clinical picture in several forms of acquired dysautonomia:

  1. Postural Orthostatic Tachycardia Syndrome (POTS)

  2. Orthostatic Hypotension

  3. Orthostatic Cerebral Hypoperfusion Syndrome (OCHOs).


To understand how to solve this problem, we need to understand more about how cerebral autoregulation works.


Grab a bottle of water.


Imagine you are holding an unopened bottle of water in your hand. You’ll notice that it is not completely filled with water, there is a little room at the top. This is a good metaphor for the blood circulating in our bodies. Our blood vessels aren’t completely full all the time either. We rely on our blood vessels to shift blood around to the active cells in our body. We can control our blood flow by changing blood pressure. If the vessels constrict, the pressure increases. If the vessels dilate, the pressure decreases. This amazing process is controlled by the Autonomic Nervous System in our brain(more on that to come).


If you take the same water bottle and gently squeeze it, you can push the water toward the top. Try to apply enough pressure so you can feel the water touch the cap without adding any extra force.


Now relax your grip, dilating the size of the bottle and you will see the water fall away from the cap.

You can think of the autonomic nervous system as the hand that controls exactly how hard to squeeze the bottle. Enough pressure to fill the brain, but too much or there will be damage.


For this example, you were able to use your eyes to see the water moving up and touching the cap. You were able to confirm with the feedback from the sensation in your hand.


If we can't see our blood flow or feel it with our hands, how can we control it?


We have special pressure sensors called baroreceptors in our blood vessels. There are very important baroreceptors in the blood vessels in our neck and in our brain. These receptors tell the brain the exact blood pressure so the autonomic nervous system knows exactly how hard to squeeze.

When you are lightheaded after a concussion, your autonomic nervous system is malfunctioning. It is failing to control blood pressure in the body and the brain.


To carry our water bottle metaphor a step further, imagine laying the water bottle on its side. You have to exert very little if any effort to squeeze water into the top of the bottle. The water will effortlessly flow where gravity directs it to go. Now try to stand the water bottle back up while maintaining the same pressure of water against the cap. You can feel it requires very fine control of the pressure you apply to the bottle. If you don’t squeeze the bottle soon enough, the water will fall away from the top of the bottle. If you over-correct, there is too much pressure against the cap.


When the bottle is laying down, gravity does most of the work, letting water flow to the cap. When you stand the bottle up, gravity is working against you pulling the water down away from the cap.


When applied to a human, the autonomic nervous system is able to relax when you are laying down. Standing then requires a fast response to keep the pressure stable. If the system is too slow or inaccurate, the pressure drops, and blood "falls out" of your head.


Since gravity has a strong impact on our blood flow, the brain uses gravity receptors to help detect changes in pressure.


This job is done by your vestibular system. It senses the position of your head at all times. Accurate head position signals help your autonomic system work with gravity. This feedback loop maintains blood pressure and prevents you from feeling lightheaded.


It is also worth noting that lightheadedness has lasting effects. Long-term cerebral hypoperfusion is associated with stroke, vascular cognitive impairment, and early-onset dementia.


While it might be tolerable to carry on feeling lightheaded and pretend it isn’t there, it is an important signal that your vestibular system and autonomic systems are not communicating effectively in the brain.


Action steps

Start with the basics:

  1. Stay hydrated. There is an excellent calculator here that tells you precisely how much fluid you should take and in what ratios.

  2. Eat regularly. Blood sugar spikes can also cause lightheadedness. Eat a protein-based snack every 2-3 hours to maintain stable glucose levels.

  3. Get Sleep. Get as much sleep as your body requires. Go to bed earlier rather than staying up late and sleeping in.


Once the basics are accounted for:

Gather data. If you are going to fix the problem, you are going to need to measure it.

In the clinic, we have a full autonomic lab that measures your autonomic function through a head-up tilt test, Valsalva test, paced breathing where there is a constant monitor of your heart rate, blood pressure, respiration and heart rate variability.


This test can be approximated outside the clinic if you have access to a heart rate and blood pressure monitor.

  1. Lay down on your back and relax quietly, without moving for 5 minutes. Record your heart rate and blood pressure. These are your baseline numbers.

  2. Stand up in one motion. Immediately record your heart rate and blood pressure again.

  3. Continue to stand without talking or moving for 10 minutes. Measure your heart rate and blood pressure again.


There are 5 simple criteria you can evaluate from this test to determine when you should seek out further testing and help.

  1. You felt lightheaded or dizzy when you stood up.

  2. Your heart rate rose by more than 20 beats per minute on either standing measurement when compared to laying down.

  3. Your heart rate laying down was greater than 90 beats per minute.

  4. Your heart rate at any point was 120 beats per minute or more.

  5. Your blood pressure increased or decreased by more than 20 points on the top number (systolic pressure) or more than 10 on the bottom number (diastolic pressure).


If any of the 5 criteria are met, you should consider a more in-depth workup that includes a full autonomic testing series, vestibular testing, oculomotor testing, and a comprehensive neurological examination.


Now that you know more about how lightheadedness is influenced by your autonomic and vestibular system, you may be interested in reading more about dysautonomia and concussion here.


If you have questions about what you’ve read here, feel free to reach out to our clinic. The phone number is (734) 707-5105.


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