Availability and usefulness of peripheral nervous system tests

Hi everyone,

I’m keen to know if any forum members have knowledge – or personal experience – of the role of peripheral nervous system tests in ME/CFS diagnosis and in symptom-specific treatments (examples: electromyography and nerve conduction studies; skin biopsy to evaluate epidermal nerve fibre density; thermoregulatory sweat tests). I have fibromyalgia and mild/moderate CFS: allodynia is the most debilitating of the symptoms – pain and swelling (e.g., face and sinuses) caused by wind or air conditioning forces me indoors most of the time. As such, although I’m generally wary of seeing doctors after years of managing this illness, I’m eager in principle to dig deeper into the neuropathic pain angle (if nothing else to determine whether any treatments are available to soften the allodynia symptoms a little). I’m grateful in advance for any thoughts on which tests might be helpful, and also on any neurology specialists/neurology units based in the UK which might be familiar with FM, ME/CFS and the role allodynia can play as part of the symptom picture.

I’m new to this forum and forums generally, so apologies if this thread is in the wrong place.

Thanks.

 

(I am a professor of medicine.) I don't think electrophysiological tests are any use for the face. There are no electrophysiological abnormalities in ME/CFS or fibromyalgia that I am aware of. Electrical tests on limbs are chiefly of use to excuse other things - and their use is quite limited.

There has been a story that skin biopsies show small fibre neuropathy in fibromyalgia but I am pretty sceptical. Counting nerve fibres in biopsies is about the most subjective pathological analysis you can do. Moreover, it does not really fit since an absence of nerves would not fit with hypersensitivity much.

I don't think there are many units that use tests like this in the context. I think there may be one in the UCH/National Hospital for Nervous Diseases group but I would be wary of units that enthuse about tests that others have not found useful.

 

Something to consider, and I'm not recommending anything at all...

Low (and high) vitamin B6 can cause peripheral neuropathy.

 

Thanks for the swift reply. From your assessment, it seems clear that there's little value in going down this avenue from a general ME/CFS diagnosis or treatment pathway point of view. But I wonder if there might still be some value in the context of a less ambitious goal: figuring out why allodynia is so prominent among my symptoms (literally a moderate breeze will make me sick) and whether there might be treatments to explore that mitigate this specific symptom, even if the PEM and shopping list of other symptoms remain unchanged. Grateful for any thoughts on this, and please do be blunt: if this approach also seems misdirected, better to know now before spending time/money. Thanks again.

 

Thank you.

 

In general I have a rule not to advise individual people on their health problems but I try not to follow that just for the sake of it.

A general comment that comes to my mind is that swelling following stimulus is not a feature of allodynia, but of some sort of tissue sensitivity. Allodynia (e.g. hand or foot) can be associated with permanent swelling but that is a very different situation. Facial swelling can be associated with complement activation or mast cell effects and of course also with tear duct and sinus problems. Sympathetic innervation in the face is also rather unusual its effects (e.g. flushing).

I don't know much about known syndromes otherwise but distinct patterns of facial pain are recognised and there are specialists who deal with facial pain. Whether they have anything useful to offer I don't know but there might be specific tests of e.g. autonomic function in the trigeminal area that might at least put symptoms in a known category with a known prognosis.

 

Years ago I used to go on group hikes with a trigeminal neuralgia sufferer, whose pain could be triggered by any light touch on his face (including wind). Battling against a freezing easterly on the Yorkshire coast didn't seem to be a problem; he always said it was more likely to be set off by a gentle summer breeze across the garden.

I don't recall him mentioning swelling, though, so it may be a completely different condition to yours. Just thought it was worth mentioning in case it's vaguely helpful in some way – I really hope you manage to find some solutions.

 

Thanks for this perspective. Perhaps trigeminal neuralgia should join the short-list of things to check for/rule out. The sheer strangeness of the symptom (I don't read of many mild to moderate ME/CFS patients who suffer it to the same degree) makes me feel there's a chance something like TN might be at play, and could be partially treatable even if the CFS symptoms are not. Thanks again.

 

It's eye opening to know that face and sinus pain/swelling in response to light stimulus could be driven by something other that allodynia. I'd stuck with that term as a GP used it years ago, but I now see that it may be misleading for the various reasons you suggest. Anyway, I take note of your rule of thumb re: not diving into individual health problems. If I do pursue this line of enquiry and learn something of general interest, I'll report back; otherwise, thanks again for the context above - it's appreciated.

 

Hi @Jacob Richter,

In my experience getting these sorts of investigations done (or anything, really) won't happen with ME/CFS as the indication. Best to leave that diagnosis at the door and focus on the specific problems.

I've no experience going down this route with a Fibromyalgia diagnosis, but you can certainly get these sorts of tests done via certain autonomic clinics. If you experience POTS or some other sort of orthostatic intolerance it can lead to these tests in some cases.

Personally I've had IENF density biopsy and sympathetic microneurography investigations, arranged by cardiology and peripheral neuropathy teams at KCH. Both seemed very interested in the pain components of small fiber neuropathy, so they might look at "just" Fibro patients without autonomic problems, I couldn't say for sure. Incidentally I've also had SFEMG & nerve conduction studies + other bits in their myopathy clinic, but that wasn't related to allodynia.

In terms of usefulness: not much right now. My allodynia & nerve pain symptoms are quite sporadic & bearable, so I was only advised to try lidocaine patches during flares. If it progressed I was told drugs could be introduced, presumably stuff like gabapentin and pregabalin. Thankfully they have kept me on the books for follow-up each year, so that's reassuring at least. Hopefully they have one eye on the progress being made elsewhere with immunotherapy for these sorts of overlapping conditions.

 

Thanks for sharing your experience - some helpful pointers here. The more I look into this avenue, the larger the "so what?" question looms. If, for example, extensive tests by a peripheral neuropathy team were to show possible evidence of small fiber neuropathy, would this deepen understanding of the overall illness/root cause or open up new treatment options? I'm skeptical, partly for the reasons Jonathan Edwards outlines further up this thread, and partly because - to the best of my knowledge - the available weapons in the arsenal for treating for small fibre neuropathy are already on the radar for ME/CFS, namely pregabalin/Lyrica and IVIG. The pros/cons and question marks regarding these treatments have been well covered on this forum (the mechanism of action and efficacy for IVIG seems particularly unclear to me). So in my case I think it may boil down to seeking specific tests in the trigeminal area (in case there are identifiable localised symptoms worth addressing with specific treatments) and then just keeping an eye, as you say, on the good progress being made in immunotherapy in the hope that cross-over applications emerge one day for the subset of ME/CFS patients where nerve pain/swelling/tissue sensitivity symptoms are especially prominent... applications that bear greater scrutiny, under proper trials tailored to the ME/CFS disease profile, than what's currently on the table. Sorry, bit of a ramble, but thanks again for posting.

 

No problem at all @Jacob, I wish you luck with whatever you choose. Do keep in mind that you won't get very far with local care, usually you need to target specific doctors at teaching hospitals to find people willing to take on complicated patients - from my experience and from most reports I hear, anyway.

Anecdotally I'm aware of one patient that experienced trigeminal neuralgia and ended up with an unexpected Sjogren's diagnosis - they lacked many of the red flag Sjogren's symptoms but had autonomic dysfunction and SFN, which prompted the investigation because there's growing awareness of this association in specialist clinics. There's a number of other diseases that are acknowledged as often associating with SFN, though I imagine some would contend that too!

Aside from the probably quite slim chance of stumbling across a smoking gun as a result of confirming SFN, there are some promising related RCTs underway looking at SFN more generally:

Dr Vernino has an IVIG trial underway, specifically for POTS patients with suspected autoimmunity (with SFN being considered a feature of that). Hopefully this will back up the positive results from previous IVIG case studies in this patient group.
IVIG (Gamunex-C) Treatment Study for POTS Subjects - Full Text View - ClinicalTrials.gov

Dr Systrom has a Pyridostigmine trial underway, more generally for syndromic patients (ME/CFS/Fibro/POTS etc.), which he expects have underlying SFN. This follows on from previous smaller positive studies in POTS subsets.
The Exercise Response to Pharmacologic Cholinergic Stimulation in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome - Full Text View - ClinicalTrials.gov


SFN and if/how it fits in with our issues is clearly contentious but I cannot stress enough the value of being under the care of motivated doctors in clinics that have the resources to champion your case and investigate/refer onward as required. The level of care compared to anything we normally get under the ME/CFS umbrella is a different level entirely. I don't think its unreasonable to say that any opportunity we have for framing a problem as not being ME/CFS related will lead to different, and sometimes better, outcomes.

 

This is again very helpful, thank you. Good to know of these RCTs - they'll join my Excel tracker. Your final point also chimes with my experience; it's a sad reflection on where we are with ME/CFS and how far the medical world has to go, but no less true for that.