Long Covid and Dysautonomia

Using Nerve Express to Personalise Your Health.

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While the spread of severe Covid-19 infections has waned, emerging studies are ascertaining that many people are suffering from a long-lasting sequelae of symptoms following Covid-19 infection and that this is increasingly prevailing. This condition is known as post-acute sequelae of COVID 2019 (COVID-19) (PASC), or Long COVID. Even though PASC is not widely described, it is most commonly defined as COVID-19 symptoms that continue longer than 30 days. PASC can manifest as a wide range of symptoms, many exhibiting autonomic characteristics. An autonomic nervous system illness, postural orthostatic tachycardia syndrome (POTS), strongly connected with a prior viral infection, is the most prevalent autonomic diagnosis correlated with PASC. In fact, one study found that 67% of individuals with Long Covid are developing dysautonomia (Larsen et al. April 2022). This knowledge gives gravitas to the importance of incorporating autonomic nervous system assessment into the treatment plan of all our patients exhibiting post viral symptoms.

From another perspective, if you had the ability to determine which exercise type, intensity and duration to perform that would bring about enough adaptation without inducing fatigue, pain or a “flare up” (if suffering from Long COVID) would you be interested? Would you like the confidence of knowing the exact personalised dosage exercise intervention before embarking on a program? After all, there may be a minutia of difference between optimal adaptation and maladaptation, injury and poor recovery. Nerve express is our greatest gift in determining this by providing insight into our Adaptability level and Functional Capacity level.

Figure 1 above from: Angeles, M. R., Wanni Arachchige Dona, S., Nguyen, H. D., Le, L. K., & Hensher, M. (2022). Modelling the potential acute and post-acute burden of COVID-19 under the Australian border re-opening plan. BMC public health, 22(1), 757. https://doi.org/10.1186/s12889-022-13169-x

Nerve Express vs.Tilt Table testing

When it comes to autonomic evaluation, the gold standard is considered to be tilt table testing. This, however, is extremely rigorous and comes with a high expense, at close to $1000.  In addition, the long wait times needed to get a referral for a neurologist or cardiologist to administer the test make it quite out of reach for the average individual. Furthermore, a tilt table test is very time consuming at approximately two hours duration, and requires copious amounts of preparation and handling. It is not performed often in a cardiology setting unless significantly indicated.

Nerve-Express is a fully automatic, non-invasive computer-based system designed for quantitative assessment of the Autonomic Nervous System (ANS) and level of physical fitness (Fitness Score ) based on R-R interval Variability (HRV) analysis. Nerve-Express is the first and only system to solve the problem of SNS-PSNS quantification based on a method of clusterisation of the relationship between SNS and PSNS status.When we consider Nerve Express as a worthwhile option or precursor evaluation to tilt table testing, we can positively state that it is a non-invasive, time-efficient and cost-effective way to determine the amount of physiological  sympathetic and parasympathetic reserve of the ANS, similar to what would be determined by tilt table testing.

What is Dysautonomia?

Firstly, let’s look at the role of our autonomic nervous system, which branches into the sympathetic and parasympathetic nervous systems.Our sympathetic nervous system is involved in the fight or flight response and delivers fuel to the working muscles and brain. It does this by cardiac acceleration and contractility. Opposing this is the parasympathetic system (rest and digest), which helps with resolving inflammation, repairing tissue and improving the digestive and absorptive function of the gastrointestinal tract. .

Dysautonomia is simply dysregulation of either the sympathetic, parasympathetic system or both. Medications, chronic infections and neuro-inflammation can all affect the output of sympathetic and parasympathetic systems. Each individual may express dysautonomia differently and therefore have a significantly elevated  or depressed sympathetic or parasympathetic tone at rest, supine to standing during breathing holding or deep breathing.

Symptoms may include - dizziness,  lightheadedness, nausea or increased bowel sounds upon standing, balance impairment, noise/light sensitivity, shortness of breath, visual disturbances, large swings in heart rate and blood pressure, migraines or headaches, dehydration, frequent urination, low blood sugar, exercise intolerance, changes in body and skin temperature, fainting/loss of consciousness, ongoing fatigue, difficulty swallowing.

The table below highlights different categories of dysautonomia and associated symptoms:

Types of Dysautonomia 
Elevated sympatheticpallor, significantly elevated heart rate, sweating, trembling and increased BP upon standing. Patients may also complain of pain in the back of the neck and shoulders upon standing.
Depressed sympatheticdizziness and low BP upon standing, exertional fatigue, droopy eyelid/s
Elevated ParasympatheticIncreased nausea and vomiting, malabsorption, urge to urinate, low muscle tone, increased salivation, slowed heart rate.
Depressed parasympatheticconstipation, dry eyes leading to chronic eye infections, dry mouth and slowed GI function leading to maldigestion, malabsorption and consequently Small intestinal bacterial overgrowth

Question: Do you have high energy during bouts of exercise but feel like you ‘crash and burn’ afterwards?  OR do you experience exertional fatigue DURING exercise but seem to recover really well afterwards? Or do you feel that you are fatigued during BOTH exercise AND recovery?

After analyzing the table above you could postulate that if you answered yes to the first question, it may be that you have optimal sympathetic function but declining  parasympathetic function post exercise.

If you answered yes to the second question, it may be that you have poor sympathetic tone during exercise but optimal parasympathetic tone at rest helping you recover. HRV apps don't provide this detailed information whereas Nerve Express can shed significant insight into how well you may initiate, continue, adapt and recover from exercise or a stressor. 

How does HRV assessment compare with Nerve Express?

Most apps that measure autonomic function, do so via heart rate variability (HRV). Whilst HRV has been documented in the literature to provide good information regarding physiological health, it does not  include quantification of blood pressure, or differentiate sympathetic and parasympathetic branches of the nervous system from supine to standing, valsalva or deep breathing, as is possible with Nerve Express evaluation. Whilst HRV apps can assess current status from a single result, this is not always reliable as it cannot accurately predict how much reserve we have in our system. Otherwise simply stated, the amount of currency we have in our ‘bank’ to spend before significant loss or bodily decline cannot be determined by a skewed breath measurement. Multiple ongoing measurements would be required to obtain a more complete picture.

Dysautonomia, Neuroinflammation and Long COVID

Alternatively,  Nerve Express uses more complex algorithms to ascertain various aspects of the different breath states, including heart rate variability monitoring and continuous blood pressure readings, giving an enriched understanding of the underlying functional contribution of each system during each positional and physiological transition state

An example of a patient with very low parasympathetic tone at rest
Example of a patient with POTS as shown by an increase in heart rate in excess of 30bpm from supine to standing

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Many patients suffering from Long COVID have persistent loss of smell and/or taste. The most obvious consequence has to do with diminished drive to eat, with potential for weight loss. This can be harmful, especially in the elderly, where maintenance of muscle mass is a key case objective that influences the quality and duration of the patient’s life. The risk of eating spoiled food is already high in the elderly and any additional loss of smell and/or taste heightens this concern, especially for those elderly patients who prepare their own food.

What we tend to overlook are the neurological consequences of loss of smell or taste. First, eating is a fundamentally pleasurable thing to do. We typically encounter this pleasurable sensory stimulus two or three times per day. This means that the pleasure centres in the brain, the caudate and ventral tegmenjtum, are stimulated systematically multiple times every day. What happens when those pleasure centres are not stimulated? Stress levels go up and the likelihood of depression is increased. This can have substantial negative effects on the immune system and increase inflammatory activation in a way that loops back to sympathetic nervous system activation. So, the first step with a patient who has lost smell and/or taste is to consider their stress and inflammation and provide adaptogenic and immune modulating support. 

The second point, and the one that warrants particular focus, is that taste is a form of neurosensory stimulation. Loss of taste means loss of a potentially crucial increment of sensory stimulation. Taste is a special visceral afferent stimulation provided by three cranial nerves: the facial (CN VII, glossopharyngeal (CN IX) and vagus (CN X) nerves.

So, why does this matter? 

CN V, VII, IX, and X are from the same embryologic origin. That means that when one of them gets activated, they’ll all get activated or more commonly said, nerves that wire together, fire together. But if you lose a bunch of the stimulation that activates them (if your sense of taste has diminished since COVID), you won’t get synonymous activation of the other cranial nerves

In this case, the risk is that your vagal motor outflow may wind down. If that happens, you lose many functions:

  • Diminished inhibition of TNF alpha production in macs in the small intestine and spleen,
  • Diminished inhibition of IL-6 production in the liver,
  • Diminished HCL and digestive enzyme production,
  • Diminished gut motility.

The downstream effects are a more inflamed body, more food antigenicity, and Small Intestinal Bacterial Overgrowth (SIBO) !

So, the take-home message may be that it’s enormously important to consider stimulation of the vagus nerve in patients who have lost their sense of taste post Covid-19.

Symptoms to look for include: worsening food sensitivities, dry eyes (suggesting diminished motor activity in CN VII), constipation, bloating, or other GI dysregulation (suggesting diminished motor activity in CN X).

For treatment, consider the following:

  • transcutaneous vagal nerve stimulation (tVNS) using a TENS device (we administer this in combination with red light therapy in clinic)
  • chew every mouthful of food until it’s liquid (this used to be called Fletcherizing). Chewing drives sensory input to CN V, which will activate V, VII, IX, and X.
  • stimulate the tongue periodically with a bitter taste. Berberine can be used for this, for example. Bitter is the strongest form of taste stimulation, so you may have some ability to get something going with bitter, compared to other tastes.
  • sing at high volume. There is an interesting paper in which patients with sleep apnea were given opera lessons, which greatly improved their apnea. The sensory/motor loop activation involved in control of the throat muscles provided vigorous activation of CN V, VII, IX, and X.

It’s also useful to remember that normal activation of the brainstem pontomedullary reticular formation (PMRF) is provided from the prefrontal cortex. If there is CNS inflammation, prefrontal cortex firing rates are lower, so the extent to which the prefrontal cortex output activates the PMRF is likely to be diminished. So, as usual, attending to body and CNS inflammation is essential.

It’s also essential to identify Genetic polymorphisms in the PEMT and MTHFD1 genes, to identify if you need additional choline support, since vagal motor outflow is cholinergic.

Lastly, taste and smell are typically affected by damage to epithelial cells by the SARS-CoV-2 virus. So it’s useful to take measures to address epithelial repair, using the approaches you would use with the intestines or lungs.

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