PEM induced only by sensory/cognitive exertion - what does it indicate about the pathophysiology of ME?

I read an account by a housebound ME patient about being able to handle very short car trips as a passenger, while longer ones flare their symptoms even though they remain as idle as possible.

Such a flare could only plausibly be induced by sensory stimuli during the trip, among which vehicle motion, ambient noise from the vehicle, surrounding vehicles and the road, bumps in the road and sunlight / UVs (when looking through the windows or the windshield).

While it is acknowledged that active cognitive exertion and sensory / passive cognitive exertion are standalone PEM triggers, and that they can provoke PEM of the same intensity as that induced by physical activity, neither has yielded much insight into PEM until now. Few research studies have investigated their involvement in this regard.

First, there does not seem to be a recognition that studying sensory exertion would lead to designing less strenuous repeated exertion tests than the 2-day CPET. They would be less dangerous and more accessible to moderate and severe patients, and they may be as effective -- at least for the needs of research --.

In particular, a simple test with a virtual reality headset could be devised. To minimize physical activity and external sensory stimuli, a patient would lie flat in a calm, dark, temperature-regulated room. With the VR headset, they could then be subjected to scenarii involving varying amounts of sensory exertion, ranging from a dark bedroom to a car trip, a busy urban setting, a concert and so forth. Importantly, such a setup enables choosing the type of sensory stimuli as well as the duration of each scenario.

Second, does the fact that sensory and cognitive exertion are standalone PEM triggers suggest that PEM from physical activity may not originate from a problem with muscles themselves, but rather that the latter results from the involvement of organs and biological pathways that are common to both types of exertion?

Although evidence is suggestive or lacking, the hypotheses of cerebrovascular issues (e.g. cerebral perfusion), cerebral inflammation and neuronal signalling in general come to mind. Under this light, central sensitization may be evoked too, but it does not seem plausible as the onset of PEM is delayed at least by a few hours after terminating exposure to a sensory trigger.

 

My cognitive exertion/sensory can induce physical PEM and vice versa. I went for a 2 hour car ride several years ago and I could barely lift my arms the next day, and I was the passenger.

 

I wouldn't discount the sustained unusual posture associated with a car journey, nor the activities surrounding getting into the car in the first place.

It took me many years to realise that a great deal of the impact of traveling somewhere was in fact related to the unusually timed & compacted routine of eating & showering before leaving the house. These factors aggravated the OI that inevitably followed from sitting in the car.

I like the idea of using a VR headset supine, in the home, to control for this. From my own experience I'd expect someone to handle more stimuli and for longer in that scenario, vs the car journey.

 

Prolonged upright sitting can certainly exacerbate symptoms on its own due to OI. In the account that I read, the patient said they were lying flat at the back of the car, so this would not have been a factor.

Preparation for the car trip can be a confounding factor, although patients are probably aware of this and attempt to adapt it to minimize its impact (e.g. not showering, planning the trip at a time that would not interfere significantly with their normal daily routine).

 

I see rapid fatiguability as relevant here, though this also interacts with the PEM issues.

I rapidly fatigue with sensory over stimulation or being up right, especially in a fixed position, and very quickly experience brain fog, headaches, tiredness, etc. However this is not the same as my subjective experience of PEM. As long as I lie down or remove myself from the stimuli, soon enough, even after these symptoms have emerged, I experience rapid recovery.

In contrast if I persist in the situation this will contribute to triggering PEM, which may be delayed and will persist beyond the removal of myself from the offending over stimulation or offending posture. Further as others point out often sensory overload is accompanied by out of the ordinary physical activity, eg exposure to bright sunlight often goes hand in hand with going outside and doing things and with being upright.

This is further complicated by PEM in turn increasing the rapidness of the fatiguability, and in turn lowering the threshold for further PEM.

Using virtual reality type situations, as @Ryan31337 suggests, might enable teasing these issues apart, as it would allow isolating sensory overload from posture issues from associated physical exertion, and remove the need for showering, dressing, etc prior to entering a social setting. (It does seem particularly hard to get people to understand that say going out in the car as a passenger, also requires a prior shower and changing into clean clothes, that wanting not to smell is not a social phobia or an anxiety issue, but an additional level of exertion associated with the activity.)

Distinguish fatiguability and PEM would in my view require a measurement of the adverse symptoms in some way and looking at the timing of their onset and whether or not they persisted beyond the end of the triggering factors. For me the two are not always easily distinguished by the symptoms involved as there is some symptom overlap, but rather by timing of recovery and rate of recovery.

 

The interesting thing is that I didn't have orthostatic impairment during that time period. That developed several years later.

 

VR systems cause major sensory problems in at least some of us. I am not sure of the numbers. It could be rare. It could be common.

 

Can you be confident there were no orthostatic intolerance issues at that time?

It retrospect I suspect my orthostatic intolerance was present mildly for a good number of years before I recognised it. For a number of years I was aware that there were significant differences between resting sitting upright with my head unsupported, sitting upright with my head supported, reclining with my feet off the ground but my head raises on such as the arm of a sofa, and lying totally flat. I initially thought this related to the varying levels of physical effort required to sustain these poses, and had no explanation why activities involving bending forward (eg weeding) were so exhausting.

However as I worsened, it became apparent that the amount of time up right was becoming a bigger limiting factor than any exertion involved in an activity, about which time I also became aware of the concept of OI, which enabled a better understanding of my limitations than just physical or cognitive exertion alone.

 

I get bad (full body affecting) PEM, from cognitive exertion or sensory stimulation alone - ie while lying completely flat.

Travelling in a car, even while lying down in silence is a very physically demanding thing to do. One doesnt notice it as a healthy person, but it's not all about sensory stimulation by any means. The movement requires many many small muscle adjustments, multiple times a minute as the car turns, even slightly, accelerates, bumps etc.

I am by no means continually bedbound, so it's not OI/positional as 'reclined' is essentially where i spend most of my hours. but a trip to my family 90mins away requires 7 days complete rest prior, including having everything packed 7 days before, not bathing etc. Then just getting dressed & into the car - at which point i feel at my absolute best after 7 days complete rest.

Driven, reclining fully & with drk glasses & shaded windows, very slow steady driving on motorway (not winding roads), & in absolute silence.
When i get there i am so ill i cannot speak, i throw up about 5 mins after car stops, i feel like i still moving for about an hr afterwards, i cannot stand, or work my arms/legs fingers, i am essentially a blob, strangers have suggested an ambulance/thought i had stroke.

This improves slightly but it takes about 5 days of horrible PEM to recover back to 'normal' again.
When the journey is shorter the PEM can sometimes arrive a bit later, sometimes next day or 2 days after, but it always gets me.

I think it's the vibrations. There are machines that are used as exercise/fitness machines that are purely vibration units that you sit on. Its a very physical thing & involves a lot of muscle work without it seeming so, it's much more strenuous than it appears.

But I can also be made just as ill as that, and it take a long while to recover, while lying down in bed, if you start making me watch films made with hand held cameras, flashing lights, and multiple complex sound. And the sensory stimulus will produce many more 'neurological' symptoms much quicker, than physical exertion alone (balance/co-ordination, confusion, crazy-off proprioception etc). I have never understood why too much sensory input (including input that i am really enjoying so it's nothing to do with stress/distress) can make my legs both hurt, and basically stop work, becoming like tree trunks that have no coordination and dont conform to instructions.

Personally i wish research, even just observational as you suggest, would be done into the impact of sensory stimulation. But i think the trouble is that it's got swallowed up into a idea that it's sensitivity to 'sound/light etc, where people see it as something that is distressing or creates anxiety or even something that is not liked. For example i have a friend with anxiet issues who cant cope with sensory overload because it makes her feel panicky... contrast that with my listening too long to my most favourite sound - certain bird song which makes me weep with joy on occasion - and ending up in terrible pain, not able to bathe/get food later, and my brain kind of scrambled - no balance, disoriented,confused, cognitive impairment etc... because of the exertion of processing that sensory input. Listening to something that gives me joy, for too long, makes me ill.

That's got nothing to do with anaerobic threshold, or i'd have thought anything else that's purely energy production related.

 

No, but I was able to sit upright for long periods of time, and didn't have chest/forehead pressure or any other distressful symptoms that I experience now. Maybe there is also something else at play? I started experiencing OI after I had a relapse from taking immune modulators that reactivated HHV6 and EBV, it felt like something 'new'.

I did experience similar OI-type symptoms during PEM back then, but definiately not as distressful as I do now, so it was most likely mild?

 

Incidentally I have found over the years that spreading the journey out, stopping for 30 mins every 20 mins, (ie turning a 90min journey into a 3-4hr one, can lessen the overall effect. But only if a place of absolute silence & dark can be found for those breaks - bright sun shining in through windscreen, traffic noise etc, cold/hot weather requiring engine runnning for heat or a/c, just counteracts the benefits of the breaks.

 

My money is on that it´s a brain disease.

Then there are two possibilities:

a) something is wrong in certain cells.
b) only a whole network has come out of a proper shape.


In case the disease originates in the nerves, b) may be principally fixable by patients themselves. One would only need to somehow understand which stuff is used to induce which action in such a network ... And this would also go along the fact that different, though certain influences, appear to be able to induce the disease.

In case the disease originates in the immune-system it may well require objective knowledge ... though it might be an easy applicable solution.

 

That really depends on the cause. It may be completely unfixable without altering the biochemistry.

 

Ditto.

 

The idea of a VR head set is a total no go area for me! Yikes!

 

I think it depends what was going on, inside it i mean.

I think i would much rather do a 2 Day CPET on a bike, than (for example) a 2day sensory overload assault. I can only walk about 10mtrs, so 5 mins on a bike would be pretty much impossible, but in my experience, pushing through with a purely physical challenge, has a less overall-horrendous effect on me than being forced into a sensory assault. So the idea that they'd be less dangerous(my bolding in quote) is suspect from my POV, although it would certainly be more accessible.

And for some people cognitive exertion/sensory stimulous alone, does not trigger noticably bad PEM so... It'd be interesting to explore though

 

What you say would be my point a), so: No, per definition it would be for each cell within normal biochemistrical range, only for the whole it wouldn´t.

 

I'm one of the folk who's never had noticeable PEM from cognitive activity alone.

Sensory stimulus is different altogether, possibly because I also have autistic sensory sensitivity and my responses to it are very physical – it makes me tense every muscle in my body, toss and turn continuously if I'm in bed, etc.

Travelling in a car, even lying down, can be exhausting even for mildly-affected people, because of the motion, constant vibration, G-forces, sensory onslaught, and the general discomfort – not only the fact that an optimal position is usually difficult to find because of space constraints, but also the frequent need to use slightly crude methods of heating, ventilation, or air-con to maintain a comfortable temperature.

If we're looking for good examples of non-physical triggers for PEM, I'd suggest ruling out all modes of transport, as they're inevitably physically stressful. Even being wheeled through a dark, silent space in a supine wheelchair would have physical impacts for many people, as the motion and the patient's inability to anticipate changes of direction affects the vestibular system.

 

I got PEM from driving. The worse the driving conditions, the worse the PEM. Driving in the dark, in heavy snowfall, on icy roads, triggered severe PEM. The same drive during a sunny dry-road day usually didn't. I think it was the cerebral processing of inputs and the stress of the increased danger.

Chatting with people was another trigger. It may not have been stressful, but it does require a lot of cerebral processing.

I can't remember getting PEM from a video game, either action or strategic.

 

Totally agree with this. I don't get PEM from cognitive exertion or sensory stimulus. I never have. For me it is about overdoing physical activity that sets off PEM.