Bayesian - I

I learned a new word today.

“Bayesian”

While more commonly associated with statistics, BBC released a cute video about what it means within the context of logic and reasoning. To quote:

Fundamentally, Bayesian ideas reflect what it means to be human. We live in a world of uncertainty, but we always have prior expectations for what might happen next, and we revise that uncertainty as we learn from experience.

An example: You want a churro, so you go to the churro stand. You see a very, very long line. You think, “aw man, this is gonna take forever!”. But then, against all odds, the churro man is dispensing churros at an incredible rate. You think he must be a churro Olympian.

You update your prediction at how fast the line will move and decide to wait it out. You walk away happy with a fresh, toasty churro.

The point of this blog post isn’t meant to be about churros, nor is it about British statisticians improving our vocabularies. This post is about what it’s like to have Functional Neurological Disorder (FND) from the patient perspective.

Disclaimer: I am not a medical professional of any kind. I’m a random techie from the tech world who finds mental health (especially her own) fascinating.

What is it? #

So what is FND? The Mayo Clinic is wonderful, and I recommend their summary as the polite, conservative explanation for the layman.

Without getting too deep into it here, I would characterize my own manifestation as two subtypes¹: “functional seizures” and “functional movement disorder”. Their powers combined, it looks like:

• Absence seizures, but not.
• Mind blanks.
• Sudden severe lethargy and dropped head.
• Effortful speech and difficulty fetching words. (It’s way more distressing for me than observers, I’ve found.)
• Confusion.

If you ask your neighborhood neurologist, apparently it’s a disorder they commonly see¹. And yet, not a single person I know outside of the medical field has heard of it by any of its names. (I have my own theories on why this is, but that’s for a different post.)

The coolest thing about this disorder, however, is that it vanished the moment I was diagnosed. For like ten months.

Predictive Processing #

The current favored framework for understanding FND is well-summarized by Hallett et al.²:

Functional neurological disorder is arguably what might be expected to happen when predictive processing in the brain goes awry.

When we think of our brains in the Bayesian sense, we theorize that our mush noodle is constantly creating a “mental model” of the world. When we see the Olympian Churro Man, we feel surprise; feedback in our brains called a prediction error rises, and if it “weighs” enough, we’re less likely to jump to impatience at the next long line. Perhaps that line will be faster than expected, too.

(There’s more nuance in the literature and I’m simplifying, but you get the gist.)

One of my favorite papers on the subject is by Wendy Phillips, “Pathophysiology of functional neurological disorder for the general neurologist”³. I’m no neurologist, but I found the paper highly accessible, and I was floored when I read it as I reflected on my own experiences (which I’ll get into in Part II).

I was reminded of the rubber hand illusion, where a person with normal brain function could be influenced to experience a rubber hand as if it was their own.

An excerpt from Wikipedia:

The experiment showed that if the two hands were stroked synchronously and in the same direction, the subjects began to experience the rubber hand as their own. When asked to use their right hand to point to their left hand, most of the time they pointed toward the rubber hand. If the real and rubber hands were stroked in different directions or at different times, the subjects did not experience the rubber hand as their own.

The subject consciously knows the rubber hand is not theirs. The subject isn’t feigning nor pretending that they are experiencing the rubber hand. In fact, using fMRI, experimenters could see the area of the brain that anticipates pain (the anterior cingulate cortex) light up when the rubber hand was threatened with a needle.

Cannot Unsee #

Another thing I like about that paper³ is Figure 4:

Some information is more generally salient than others—the tendency to see faces, for example, and once we ‘see’ something in a shape, the prediction has become established, and it is difficult to ‘unsee’.

Try as you might, you ain’t unseeing these handsome guys.

Back in 2021, I had my first “seizure-like” experience. It was unique from every other episode I had. In fact, thanks to family history, I actually thought I might have had a TIA (transient ischemic attack) or mini-stroke. When my mother was alive, she claimed she had her first mini-stroke in her late 20s, so it did not feel outside the realm of possibility in my panicked mind.

I was working from home at the computer, and noticed that I started to lose vision. At first, it looked like the kind of blurriness you’d have when you’re just waking up, but concentrated to a small circle in the middle of my vision.

Me, being 29, thought nothing of it at the time. But in a manner of minutes, blurry vision became missing vision. Not like a black splotch of nothingness, but as if part of my vision became indiscernible, and part of the computer screen disappeared. My head felt so heavy and like my neck lost all strength.

At this point I slowly turned around in my swivel chair and, in some manner I cannot remember, tried to convey to my partner at the desk behind me that something was wrong.

It’s kind of blurry (ha) after that. I remember it being very difficult to talk, and distinctly, hearing myself say words that were different than what I intended to speak. I tried to stand up and collapsed onto the nearby bed, but did not lose consciousness. At some point there was also a long, red streak of light that stretched across my vision. It persisted even when I closed my eyes.

Interestingly, my partner recalls it a differently: At first, I wasn’t verbally responding at all. Soon after, my speech was effortful, but my words were coherent even when I thought I was saying nonsense.

Long story short, I made a very 29-year-old decision and delayed going to the ER (if it somehow was a stroke, time-critical stroke treatments only work in the first few hours). After getting a stern talking-to from the Urgent Care nurse, my partner transported me to the nearest hospital. Ultimately, I was discharged with specialist referrals, a directive to take baby aspirin every day, and no answers.

In hindsight, it may have simply been a migraine with aura. Way more harmless, but also way more confounding – it’s incredible how little we know about how migraines happen. I never really had migraines before, so it didn’t even cross my mind. Seizures and the aura for a migraine can be very reminiscent of each other, even leading to differentiation challenges in medical settings⁴.

The four years following that is also a long story – one filled with episodes that were misattributed to seizures by an old neurologist who had misdiagnosed me. That first event is the only time I ever had issues with my vision. Confusion, lethargy, and issues with speech prevailed. There was a story behind it all that was starting to concrete itself in my mind, accurate or not: I had a stroke that resulted in epilepsy. After all, I had a family history, and post-stroke seizures is a known phenomenon.

The idea of having had a stroke got me a rumination head-start on my own mortality.

What if the way my “pseudo-seizures” started was getting a little too spooked when an anxiety-ridden day at work led to difficulty focusing, after such a scary event? What if I just couldn’t unsee the mysterious and unsolved problem with my brain, and watching closely made the benign a real experience, just like the rubber hand?

I now believe that 2021 event was my “cannot unsee” event.

Wait for the Drop #

I spent chunks of 2024 trying to figure out why my “seizures” were getting worse. I would look at Slack or code at work, recognize individual words on the screen, but then suddenly couldn’t piece them together to make sense. Cue head drop. Cue non-optional lunchtime nap and an update on the timecard.

I love my job, but I found that trying to manage the symptoms while getting stuff done was making it miserable. I felt guilty to my teammates, convinced I was working too slow and causing burden to the team. I continued going back to my old neurologist for answers, and eventually he verbally shrugged with a “maybe your anti-depressant is too high a dose. You should talk to your psychiatrist.”

My psychiatrist is a charming man who loves to explain how things work. I’ll never forget his skeptic reaction to my neurologist’s latest idea, but we tried it anyway. We cut my SSRI by a quarter, and against all expectations… my “seizures” improved. And as I type this very sentence, I now wonder if it improved because the new dose shifted my mind’s pre-conscious predictions of what would happen. Totally speculative, but I’ll never know for sure; too many factors that come into play. Drat.

Anyway, it was nice while it lasted, but as more stress started to accumulate in my life (I’m also a caretaker), the “seizures” eventually came back. By then, I felt desperate, and my therapist asked me if I considered going to Mayo Clinic for a second opinion on my seizures. After all, I was only an hour and a half from their Phoenix location. Not bad at all.

Mayo Clinic #

In May 2025, I was scheduled to spend a week at Mayo Clinic in the Epilepsy Monitoring Unit (EMU). They are truly incredible over there and make you feel taken care of. I had videos and resources telling me exactly what to expect before we even rolled into the parking lot. They attached all kinds of sensors to me that were not going to come off until after a week.

I have the best partner in the world, and he stayed by my side every day and nearly every night, even when I assured him he didn’t have to. He slept in a hospital chair that could convert into enough of a bed for a back-sleeper. Unfortunately for him, he’s not a back sleeper.

If I needed to use the bathroom, I had to ask a nurse for help. They would attach me to a rail on the ceiling (fall prevention system) and I would waddle my way six feet over to the small, private restroom. No closed door, though. The nurses would have their forearms sticking through the door, holding onto my “leash”, while we both pretended we were anyplace else. Well, I did, anyway. For them, it was just another Tuesday. I eventually got used to it though, and as I would make my way back and forth, I imagined an elderly, crippled Tarzan in a hospital gown in my head.

The doctors, nurses, and staff were incredible and attentive. The nurse to patient ratios were small, and all the staff seemed to be genuinely taken care of. It was a huge contrast from other experiences I’ve had with hospitals.

And then came the testing. They cold turkey’d me off my prescribed seizure medication. They blasted me with flashing lights. They kept me awake to ungodly times for sleep deprivation. They did all kinds of maniacal things to try and trigger a seizure on purpose. However, my “episodes” were milder than when I was home in Tucson, and they would manifest at unusual times, not at times they were “supposed” to.

One of the professionals I saw a couple days in a row, and she administered some mental health-related evaluations, as well as an IQ test. I was so convinced that I underperformed at the IQ test that I started to cry at a couple points, distressed I was losing my marbles. Funnily enough, despite being convinced I was significantly slower and foggier than ever, I ended up getting nearly the same scores I did a couple years back.

After enough testing, they were able to make a diagnosis, and it wasn’t seizures.

Poof! #

It was like magic. The team of physicians that had been supporting me throughout the week walked into my hospital room. Recalling specifics is a little fuzzy now, but I remember one thing clearly: how gently, kindly, and carefully they delivered the FND diagnosis.

They did everything right, and I truly believed them when they said it was a real disorder that wasn’t just “in my head” – an important factor in a patient’s prognosis. They validated that the level of chronic stress I had in my life was making me sick.

This moment is so critical for patients and physicians that literature deep dives on it (for example, see the “Treatment Barrier 1: Challenges of the FMD Diagnosis” section⁵).

In fact, I was already undergoing treatment. Per Mayo Clinic’s standards, which are echoed in most resources you’d find on FND:

Symptoms may get better after an explanation of the condition and reassurance from your health care provider that symptoms are not caused by a serious underlying neurological or other medical disorder. For some people, education and reassurance that they don’t have a serious medical problem is the most effective treatment.

When I left that day, my “seizures” nearly entirely vanished. For a time, anyway. If the patient receives the diagnosis well, they have a much better chance of remission, and I was lucky enough to be one of those patients.

What did it feel like? It felt like I had a near-death experience, but without any of the danger. I suddenly had permission to change my relationship to the parts in my life that were bringing me toxic, chronic stress. It was sporadic, but I had moments of precious emotional peace throughout the day that I would try to grasp and hold onto. It felt like there was My Life Before Mayo and My Life After Mayo. I started to learn more about modern theories on where FND comes from, and through those frameworks, found my circumstances could be reframed through the lens of childhood trauma⁶. As if it were a bright, neon OPEN sign blaring from the front window, I saw “Life doesn’t have to be this way!” I, too, deserved to be healthy. And to be healthy, things had to change.

A team of esteemed medical doctors uniting to say “you must start putting yourself first” is a profound kind of catharsis. It was like I was riding a high for a few weeks after I got home. Eventually things leveled out, and I noticed something important: my primary symptoms did not come back. No seizures.

Instead, I uncovered a reality that the way I was living, and its resulting chronic stress and daily retriggering of unresolved trauma, was not sustainable.

…Unpoof? #

Problem solved, right? And cut. Epilogue. Sayonara. So long, and thanks for all the fish!

I guess it isn’t actually that straightforward.

Part II coming soon.

Usage of AI #

An LLM was used to format and verify citations/footnotes.

An LLM was used as a proofreader/editor, but did not write or directly edit any of the content above.

Further Reading #

• Hallett M. (2022). Free Will, Emotions and Agency: Pathophysiology of Functional Movement Disorder. In LaFaver K, Maurer CW, Nicholson TR, Perez DL (eds), Functional Movement Disorder: An Interdisciplinary Case-Based Approach (Current Clinical Neurology). Humana, Cham. https://link.springer.com/chapter/10.1007/978-3-030-86495-8_2