POLL: physical vs cognitive PEM - same or different?

Perhaps we could list our cognitive PEM symptoms. I never understood the meaning of "brain fog".

I can't absorb or process information during PEM, my brain feels ill. I don't have memory issues, but years ago I had to call FED EX back 3 times because I wrote down the wrong phone number and date they gave me. I can't listen and write down information at the same time.

 

I find PEM caused by cognitive exertion a very tricky beast. For me it is most likely to hit immediately or fairly quickly. How quickly it resolved depends on how much I've pushed (assuming I haven't pushed physically).

What I do is as important as how long I do it for - like with physical PEM, I suppose.

It took me a long time to realise that for me there does seem to be an order in which things go south cognitively with cognitive PEM.

Higher functions go first - i think this is roughly the order they go in -more advanced maths skills, ability to map read, getting "lost" in familiar spaces, language skills start to deteriorate but can still hold a basic conversation, spatial awareness, basic maths, difficulty finding common words. Memory & ability to concentrate start to become affected about halfway through the list and continue to deteriorate alongside the others.

It's difficult to observe and record because the self aware or ability to observe & rate oneself also starts to become unreliable and fade somewhere down the list.

For me cognitive problems are more stressful than physical PEM because I never know when extra demand such as benefits review, doctor's appointments will happen and they're often time sensitive. It's always a worry that in dealing with the fallout of those I will be cognitively incapable of dealing with other important things - sorting car tax, car & home insurance and the like.

Also, I worry that if I was alone and incapacitated I could very easily be unable to seek help and support - if there were any available to us anyway.

 

I think we are missing the key symptom of ME: the ability to produce weird, inexplicable symptoms at almost random occasions, with just enough of a hint of a pattern to let us think, mistakenly, that we have cracked it.

 

I know that they are fundamentally the same for me because i cannot do physical and cognitive activity at the same time... if i'm going to read/think/write/have a conversation, i have to be laid down/reclining with legs up & head/neck supported, otherwise there just isnt the juice to fuel both. I am known for saying "i dont know, let me lay down & then i can think to tell you".

So while it is often complex because i find PEM a cumulative problem - ie it's more about how much i do over a wk than how much i do over a day - its sometimes obvious whats caused it because, for example i spent every ounce of energy and more on reading guides to filling in a PIP form & making a few notes, during which time i had to stop all but absolute survival based physical activity & do all the reading whilst laying down.
I am always shocked at how overdoing it cognitively can trigger all my bodily PEM symptoms as well as the cognitive ones, and vice versa.

The only very minor difference is that i do get a cognitive related clue that I'm overdoing it for cognitive exertion - focussing eyes gets more difficult & start making more mistakes, & a physical AND cognitive clue for physically overdoing it -fast heart rate feeling dizzy sick/strong urge to lie down plus feeling confused/mentally slow/speech gets slurry.
If i stop at those signs i usually dont go into major PEM, but if i dont/cant the PEM that results is always identical whichever activity triggered it (including sensory overload), & involves physical and cognitive symptoms.
I think the cognitve symptoms are the ones to show up first though... ie they will be significant even at a low severity PEM/more minor crash, but once the bad body symptoms start i'm almost completely non functional cognitively.


It's so interesting that it isnt the same for everyone - i wonder if that would prove more useful in subgrouping than focus on mere symptoms/onset etc?
It suggests there is a different mechanism for those who dont get PEM after cognitive work.

 

Guilty admission: I haven't voted either. In my own poll! I've started to doubt whether what I thought I knew about my own experience is really correct.

Until recently I would have said my cognitive and physical PEM are much the same with a similar mix of cognitive and physical symptoms but with differences in timing. My cognitive PEM always hits immediately whereas my physical PEM sometimes hits immediately and sometimes after a delay, and cognitive PEM only lasts a few hours whereas physical PEM lasts days or (much) longer. Interestingly this is a pattern coming through in the comments of this thread, too.

But! On reflection I realise that all the PEM episodes I had considered cognitive had actually involved a lot of orthostatic effort which I think is a combination of physical (using muscles to stay upright) and cognitive (lack of blood to brain), and often physical effort as well. Which amounts to a lot of confounding factors.

So, some deliberately provocative questions, to stimulate discussion:

1. Could it be that immediate symptoms, whether from physical or cognitive exertion, aren't PEM at all but the result of our ridiculously exaggerated fatiguability?
2. Does cognitive PEM even exist? Or are the symptoms we call cognitive PEM actually symptoms of fatiguability?
3. Is physical, delayed PEM the only "true" PEM?
4. Are there different pathophysiological processes underlying fatiguability symptoms and "true" delayed PEM symptoms?
5. Do we confuse symptoms from fatiguability and from "true" delayed PEM because most of us get both, and they run and blend into each other?

Finally, what data or observations would it take to properly answer the above questions?

 

I think this would be a really useful thread/ discussion for COVID longhaulers too.
Contrasts and commonalities would be interesting .

 

My bolding answers:

Excellent questions.

 

I agree this is an important distinction and one I often fail to make.

For me it most obvious with orthostatic intolerance (OI), which when at its worse results in headaches, fatigue, brain fog, dizziness, etc within a few minutes. With orthostatic intolerance I have to stop what I am doing at once and lie down, in extreme just lying on the ground wherever I happen to be, so this can mean I don’t actually get to the point where a physical activity triggers PEM the next day.

However it is confused by the fact that PEM worsens the OI. Further too much fighting OI, say lots of short bursts of upright activity, I think can also trigger PEM. However, I have not however done the formal activity recording to be able to clearly say whether too much total time upright, rather than the activities involved, is the trigger for any subsequent PEM.

For me there is also parallel relationship with sensory intolerances, noise and light. In general too much noise or bright light triggers avoidance and any negative consequences are short lived if I get away from the stimulus, but if I can not avoid the source soon enough, there are both the immediate effects to recover from, but also the possibility of delayed PEM.

Further at times when necessary daily activity is regularly triggering PEM, which also lowers the thresholds for fatiguability and for further PEM episodes, you can end up in a continuous malaise where there is no meaningful distinction between the two. Though this is not confined to severe ME as on reflection when my ME was much milder but I was still fighting to continue working I suspect I was in a continuous malaise too.

Perhaps being able to distinguish between PEM and fatiguability is a luxury only available to those whose normal is being able to pace such that exceeding your PEM threshold is not a daily occurrence. So perhaps it is understandable that we have not collectively clearly articulated such a distinction.

(Note. A feature of PEM is that it can get worse over several days, that it’s severity is not proportional to the exertion triggering it, that it is an abnormal process. Presumably however we are saying this distinguishes it from fatiguability which is immediate and proportional to the activity, though more marked than premorbidly, that is fatiguability, though exaggerated by the ME, is a normal process.)

 

At times it may be hard to tell the difference but, for me, there is a difference. Increased fatiguability will certainly lower my PEM threshold and being in PEM will increase my fatiguability so there's a very strong relationship between two different things, I think.

For me, cognitive PEM definitely exists. I may be an anomaly here, but cognitive PEM is more disabling for me than physical PEM. There have been times during the course of my illness when I could still stand up and walk and physically be capable of doing things when supervised but incapable of coherent thought.

When I was still capable of working and before I sought medical "help" I was experiencing cognitive PEM. I had some physical symptoms but initially, for me, the cognitive ones were more marked. Then the physical issues caught up.

​

I don't think we know enough to say. Not that we know much about PEM at all, really. It may be a slightly different mechanism but we don't really know what PEM is. We are really trying to describe what it feels like, when it occurs, how long it lasts and what triggers it. One day, with research, we make look back on these discussions and liken them to primitive man assigning gods to natural phenomenon in an effort to understand.

Possibly, but there definitely interconnected for me as PEM increases fatiguability and increased fatiguability lowers my PEM threshold.


In terms of OI, while I experience it I believe my OI is milder and was much less of an issue earlier on in my illness. I still suffered quite severe cognitive PEM, so while OI will make matters worse, I personally feel that cognitive issues occur anyway independently.

It is impossible to completely carry out any physical activity without some cognitive exertion and vice versa but, even taking that into account, for me both definitely exist. I spent some time working with a physio trying to improve quality of rest and minimise physical symptoms - even when physically well rested my cognitive PEM threshold is never very far away.

 

Haha. No, it was more a case of great minds think alike. I'd drafted my 'provocative' questions but was hesitating to post them because I was a little worried about being misunderstood. I mean, first I create a poll to encourage people to share about their cognitive PEM - and then I go and ask if it's even real!

But what your post in the other thread did do was encourage me to post mine and it looks to have sparked some good discussion, so thanks @Trish and everybody who took my 'provocation' in the spirit it was meant.

 

Clarification:

Just realised that the term "cognitive PEM" is ambiguous.

It could be interpreted as cognitive symptoms of PEM after either physical or cognitive exertion. That's not the way I meant it. I think it's beyond doubt by now that cognitive symptoms can be part of PEM.

I use "cognitive PEM" to mean PEM induced by cognitive exertion. The actual symptoms can be both cognitive and physical.

Language, eh!

Question: What sort of activities do you consider (almost) purely cognitive? I'm still trying to disentangle in my mind the effects of cognitive exertion from those of physical exertion.

 

The thing I currently notice is novel on line activities. I can mange familiar activities like ordering groceries, but struggle with novel activities or activities that I have not do for some time such as renewing my blue badge or ordering a passport.

Subjectively the same amount of time online with familiar activities does not trigger PEM whereas unfamiliar activities does. If my subjective impressions are correct the only difference between the two are cognitive demand.

In parallel with this is telephone calls. I used to have to avoid phone calls altogether as all calls caused subsequent PEM, but how much of this was cognitive issue and how much OI and physical exertion I am not sure. However now I can manage light social calls to chat to people I know well, but business calls, especially requiring sharing information from documents or a screen still trigger PEM. Again the difference between the two would seem to be cognitive exertion.

(Now I have PA support I usually get some one else to do the novel online activities with me, to reduce the cognitive load and avoid PEM. Also for demanding calls I will get someone else to make them for me.)

 

I have severe OI, which means that even sitting up in bed is physical exertion for me. So, I would say thinking while lying in bed. For example:
- reading a book or listening to an audiobook
- planning a project
- making a shopping list
- trying to remember something
- problem-solving
- focussed concentration
- trying to learn or understand something new
- using my imagination
- making a decision or a judgement (weighing pros and cons, comparing etc)
- putting something into words, for example thinking about something I want to write in an email or a text message later
- sudoku, some meditation techniques, trying to decide what to have for dinner, ordering something online, watching TV/films, listening to music, answering questions etc

In other words, anything that requires thinking, attention, language, memory and/or information processing.

I'm not sure of the official definitions, but I think of perceptions as largely cognitive too. Processing sensory input, for example.
- looking at something (watching TV and trying to make sense of what you're seeing, simply allowing daylight into your room can be very draining cognitively if you have light sensitivity, a bright screen, trying to see clearly in a dark room)
- listening (could be intrusive noise from the street outside, receiving info from someone speaking on the phone or in a video, listening to a podcast, or perhaps listening/waiting for some particular sound like a knock on the door)

 

No, there can be such a switch. Physical exertion triggers an abrupt rise in IFN-g ~24 hrs later, and that cytokine can trigger all sorts of effects, such as activating glial cells. T-cells, and maybe others, have pretty amazing timing mechanisms. My ME started with a type IV delayed food sensitivity: my symptoms would abruptly flare up 48 hrs later +/- just a few minutes. T-cells might not be the mechanism for the delay for physically-induced PEM, but it certainly does fit.

My cerebrally-induced PEM had a more variable delay, occurring within hours, or maybe even less than an hour. Driving was one consistent trigger, and the severity of the PEM correlated with the stressfullness of the driving conditions. Driving to town on icy roads with blowing snow at night was very stressful, and gave really bad PEM. Socializing was pretty reliable for triggering PEM too, so I gave that up.

 

I use the terms "physically-induced PEM" and cognitively-induced PEM".

 

My theory on PEM is that it's a neurological switch of some sort. Cognitive exertion can trigger it directly, with minimal delay. Physical exertion triggers the same switch through cytokines, whose release is delayed by how the immune system works.

For me, the type of physical exertion was important. I could do pretty heavy physical activity for hours without triggering PEM, if I used my muscles in ways they were accustomed to, such as walking or cycling. A minute or so of activity that my muscles weren't accustomed to, such as climbing a ladder or washing a window, would trigger PEM. My theory is that the unaccustomed exertion tore some muscle or connective tissue cells, which activated the immune system to clean up the debris, with a consistent delay before large amounts of cytokines were released.

 

Do you have OI or autonomic issues? Lifting my arms above my head gives me a PEM-like feeling. I need to lie down immediately after for an hour to recover.

For me it doesn't make any difference which muscles I use. I can't do any resistance-type exercise except for light weights from time to time when I'm feeling ok. My comfortable exercise is power walking carefully timed.

 

No. I did have a brief period (few months?) where I had what might have been OI (abrupt exertion would drop blood pressure in my head), but that passed.

Another example of what did and didn't trigger PEM: shovelling soil normally (stomp shovel in, toss soil into wheelbarrow) didn't cause PEM even after doing hours of doing that for several days in a row, but a little bit of shovelling using different muscle movements (stabbing the shovel horizontally) did. I assume that the unaccustomed movements would do more tissue damage. I do wonder though, since hours of digging should do some tissue damage, but maybe if it's spread out over hours it doesn't trigger the same level of immune response.

 

Just checking I'm understanding you correctly @Creekside. Are you saying that:

a) an IFN-g rise about 24 hrs after physical exertion is normal and occurs in all people including in in healthy people, and

b) in ME that normal IFN-g rise then causes something abnormal, like excessive activation of glial or T-cells?

(IFN-g, glial & T-cell activation are just cited as examples of a range of possibilities, to illustrate the concept)

So we could have something like this:

1) Physical exertion triggers a normal process but some later product of that normal process triggers something abnormal in the brain which results in PEM symptoms. This could nicely explain delayed PEM from physical exertion.

2) Cognitive exertion triggers the same something-abnormal, but in the brain directly. This could nicely explain the lack of delay in PEM from cognitive exertion.

3) That leaves the question of the immediate symptoms after physical exertion many people report.

We could posit that physical exertion causes PEM via two separate pathways, the indirect one described in point 1 and a direct one which acts immediately on the brain similar to cognitive exertion in point 2. That sounds unlikely to me.

Or we could posit that immediate symptoms aren't PEM at all but fatiguability instead. This seems more likely but still leaves us having to explain two pathological mechanisms, one for excessive fatiguability and one for PEM. Also, IIRC some people report that their immediate and their delayed symptoms are identical, which would be difficult to explain with the fatiguability versus PEM concept. Unless they mean their immediate cognitively-induced symptoms and their delayed physically-induced symptoms are the same, but immediate physically-induced symptoms are different?​

--> Question: which of the following do you get, and which of them are the same and which are different for you?

• immediate symptoms after cognitive exertion
• delayed symptoms after cognitive exertion
• immediate symptoms after physical exertion
• delayed symptoms after physical exertion