POTS & Functional Neurology: Why the Brain Is the Missing Piece

If you have POTS, you know the routine. You stand up, your heart races, you get lightheaded, foggy, exhausted. A cardiologist confirms the 30-beat threshold, hands you a beta blocker, tells you to drink more water and add salt, and wishes you luck.

Nobody explains why your heart rate spikes. Nobody measures what is actually happening in your brain when you stand. And nobody asks the question that actually matters: what broke the regulation?

The syndrome nomenclature isn't really that useful. You have a lot of different syndromes that have similar overlapping symptoms but different causes. The mechanism of why is more important than the symptoms themselves.

Your Heart Rate Is Not the Problem

Postural Orthostatic Tachycardia Syndrome is a description. Your heart rate goes up when you change posture. That is the observation. It is not the mechanism.

Your heart rate is trying to save the day. When cerebral blood flow drops — when your brain is not getting enough blood — the heart does the one thing it can do quickly: beat faster to push more blood upward against gravity. That is not a malfunction. That is an intelligent compensation for a real problem.

The system that allows you to stand up and keep blood in your head is a multi-sensory, multi-motor output. You have parasympathetic systems, sympathetic systems, skeletal motor systems, respiratory systems, and multiple sensory inputs — all coordinated by the brain in real time. When any of these inputs degrade, the brain's output degrades with them. The tachycardia is what happens when the system can't do its job cleanly.

Think about it as energy efficiency. If your system is cranking over 100 beats per minute just so you can eat an orange on the couch, that's not efficient. The question is not "is your sympathetic nervous system overactive?" The question is: how much energy are you burning to do basic things, and why?

Cerebral Blood Flow: The Error Point

Most of the symptoms people experience — the fog, the dizziness, the fatigue, the sense that your brain just isn't working — are symptoms related to cerebral blood flow. That is the thing. That is the error point.

This is measurable. Ocon et al. used transcranial Doppler during tilt testing in POTS patients and measured a 19.5% drop in cerebral blood flow velocity — nearly double the 10.3% drop seen in controls. Both dynamic and static cerebral autoregulation were impaired (Ocon et al., Am J Physiol, 2009). Van Campen et al. found that 90% of 429 ME/CFS patients — a population with extensive POTS overlap — demonstrated abnormal cerebral blood flow reduction during tilt, even when heart rate and blood pressure appeared normal (van Campen et al., Clin Neurophysiol Pract, 2020).

And it is not only a standing problem. A 2025 brain SPECT imaging study found that 61% of POTS patients had abnormal cerebral perfusion even while lying down. The lateral prefrontal and sensorimotor cortices were the most affected, and the number of hypoperfused regions accounted for 51% of the variance in patient health scores (Seeley et al., Sci Rep, 2025). Wells et al. demonstrated the same pattern during seated cognitive testing — CBF velocity and psychomotor speed both declined under cognitive load, even without orthostatic challenge (Wells et al., JAHA, 2021).

A standard tilt table test measures heart rate and blood pressure. It never measures whether blood is actually reaching the brain. Transcranial Doppler combined with capnography during tilt shows exactly what happens in the brain's arteries and CO2 levels the moment a patient goes from lying to standing. That is where the mechanism becomes visible.

The Sympathetic Nervous System Is Not One Thing

POTS tends to be linked to this idea that the sympathetic nervous system is overactive. That's actually a really unuseful way to look at it.

The neurophysiologist Wilfrid Jänig demonstrated that the sympathetic nervous system operates through functionally distinct pathways — including separate systems for muscle vasoconstriction, cutaneous vasoconstriction, sudomotor control, cardiac output, and gastrointestinal motility, among others (Jänig & McLachlan, Trends Neurosci, 1992). They do not fire as a single unit. You can have one pathway overactive and another underactive at the same time — just like you can move your index finger without moving your whole hand.

Saying "the sympathetic system is overactive" is like saying "your muscles are too strong" without specifying which one. It tells you nothing useful. The question is: which pathway, and why is it doing what it is doing?

This is not an academic distinction. When elevated norepinephrine shows up in "hyperadrenergic POTS," you have to ask: is that the problem, or is that the ambulance showing up at the accident? Cerebral perfusion is dropping, so the brain floods the system with norepinephrine to drive the heart faster and constrict vessels to push blood back upward. Tremulousness, palpitations, sweating, a sense of impending doom — those are the things you should feel when your brain is losing blood flow. That is a normal response to the problem, not a separate pathology.

How Do You Find What's Actually Causing POTS?

If the tachycardia is compensatory and the brain orchestrates the postural response, the question becomes: where in the system is the regulation breaking down? The answer is different for every patient.

The body operates as a multi-sensory, multi-output system. You can't fix it by looking at one output. The regulation of blood flow to the brain when you stand involves pathways at every level of the central nervous system — from spinal cord circuits to brainstem nuclei to cerebellar integration to cortical processing. Within that system, there are tracts, nuclei, and processing nodes that each handle different aspects of the postural response. Disruption at any level can produce the same downstream picture: symptoms that look like POTS.

Beyond the neurological domain, the full picture spans three interacting systems:

Underneath all three sits the metabolic foundation — nutrient status, thyroid function, energy production. These domains interact. A structural problem can corrupt neurological input, which disrupts vascular regulation. You cannot address one in isolation and expect the others to resolve.

This is why the conventional subtypes — neuropathic, hyperadrenergic, hypovolemic — fall short. They describe downstream features but never explain the upstream mechanism. In practice, patients across all subtypes tend to receive roughly the same protocol: beta blockers, salt, fluids, compression. If these were truly different conditions, treating them all the same way should bother you.

What Needs to Be Measured

Standard POTS workup: tilt table, heart rate and blood pressure monitoring, sometimes catecholamines. That confirms the label. It does not explain the mechanism.

A mechanism-based evaluation asks different questions and uses different tools:

Each of these tools evaluates a different input to the postural response. Transcranial Doppler shows whether blood is reaching the brain — regardless of what the arm cuff says. Capnography reveals whether CO2-driven vasoconstriction is silently choking off perfusion. Stewart demonstrated that in a subgroup of hyperventilating POTS patients, restoring CO2 levels via rebreathing normalized heart rate, blood pressure, cardiac output, and systemic vascular resistance to control values (Stewart et al., JAHA, 2018). Reilly et al. found that 84% of 100 POTS patients referred for respiratory assessment were diagnosed with dysfunctional breathing (Reilly et al., Auton Neurosci, 2020). This is not a rare comorbidity. It is the rule.

Vestibular testing evaluates the fastest postural reflex pathway. The vestibulo-sympathetic reflex adjusts vascular tone within 50–100 milliseconds of a position change — faster than baroreceptors can respond (Yates et al., Compr Physiol, 2014). Kim et al. directly measured otolith function in POTS patients and found augmented oVEMP responses that independently predicted POTS diagnosis — the first direct measurement linking vestibular organ function to POTS hemodynamics (Kim et al., Clin Auton Res, 2023).

Oculomotor assessment provides a window into brainstem function. The nuclei controlling eye movements share neural real estate with the nuclei regulating autonomic output. When saccades, pursuit, or convergence degrade, it tells us that the brainstem circuits coordinating cardiovascular responses may be compromised as well.

Cognitive dual-task testing reveals where the brain runs out of bandwidth. Many POTS patients can tolerate standing still but crash when they add a cognitive task — talking, reading, navigating a store. Stewart's group showed N-back task performance dropped from 78% to 33% during tilt in POTS patients while controls maintained 89% (Stewart et al., Hypertension, 2015).

Can Functional Neurology Treat POTS Instead of Just Managing It?

The conventional approach is symptom management. Slow the heart rate. Increase blood volume. Wear compression garments. These are not wrong — for many patients, medications provide real relief from the worst symptoms. Beta blockers can reduce the pounding heart and the anxiety-like sensations that make daily life unbearable. That relief matters. But there is a ceiling. Medications make the dysfunction more tolerable without restoring the function itself.

This approach, grounded in principles from functional neurology, targets the regulation failure itself. For many patients, medications continue alongside rehabilitation — they provide stability while the system is being rebuilt. The goal is not to rip away something that is helping. The goal is to restore enough regulation that the body no longer needs as much pharmacological support. When the brain systems that coordinate the postural response recalibrate, symptoms resolve because the brain no longer needs to compensate.

The research supporting each individual tool is substantial. Vestibular rehabilitation retrains the balance system's input to the brainstem. Oculomotor retraining drives activity in brainstem circuits that overlap with autonomic control centers. Cervical proprioceptive work restores accurate positional data flowing from the spine to the brainstem — and a randomized controlled trial confirmed that restoring cervical alignment produced significant normalization of autonomic function maintained at long-term follow-up (Moustafa et al., J Athl Train, 2021). CO2 and pH sensitivity retraining addresses hypocapnic vasoconstriction by restoring the brainstem's ability to regulate breathing automatically — not through willpower, but by recalibrating central respiratory integration so the system automates properly again.

Exercise is dosed to cerebral blood flow data. Most POTS patients have been told to exercise more and found that exercise makes them worse. The problem is dose, not concept. When we have transcranial Doppler data, we know exactly how much hemodynamic stress the brain can currently tolerate. Right dose, right time — that is how patients who could not walk around the block begin rebuilding capacity without crashing.

The nervous system's capacity to change is not theoretical. The Nobel laureate Eric Kandel demonstrated that learning physically changes synaptic structure — repeated, specific stimulation grows new synaptic terminals that persist over time (Kandel, Science, 2001). That capacity does not disappear because you have POTS. It just needs to be harnessed correctly — the right inputs, at the right intensity, targeting the specific circuits that have degraded.

Who Benefits from This Approach

This approach tends to produce the strongest outcomes for patients who:

• Plateaued on medication — tried beta blockers, salt, fluids without meaningful improvement in function
• Symptoms beyond heart rate — brain fog, exercise intolerance, or cognitive issues alongside the tachycardia
• Clear trigger event — concussion, whiplash, neck injury, or neurological infection preceding POTS onset
• Overlapping diagnoses — told they also have FND, EDS, or anxiety alongside POTS
• No one has explained why — doctors described the diagnosis but never identified the mechanism driving it

Why Treating the POTS Label Instead of the Mechanism Keeps Patients Stuck

POTS groups patients by a shared observation: heart rate rises too much on standing. But just like "headache" groups migraines, tension headaches, and brain tumors under one symptom label, POTS groups patients with fundamentally different mechanisms under one syndrome name.

We do not treat the label. We identify the specific mechanism driving that particular patient's presentation — through the layered evaluation of metabolic foundations, organ function, and the interplay between neurological, structural, and vascular systems. The central nervous system has depth. The evaluation needs to match it.

That is the difference between managing a syndrome and solving the problem underneath it.

Dr. Keiser is a board-certified chiropractic neurologist (DC, DACNB, FABBIR), not a medical doctor (MD/DO). This content is for educational purposes and does not constitute medical advice. It is not a substitute for professional medical evaluation, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. Medication decisions should be made with your prescribing physician.

← Back to Blog