Hi NoXfear: Thanks for these infos!
Not much to do with Small Fibre Neuropathy and Stiff Person's Syndrome that sprung to my mind first.
I'll compare using the webpage you quoted:
It shows lots of similarities to fibro - used to be thought of as all in the head / psychological, nothing visible in MRIs and EEGs, mind's signals would correspond to the CSS hypothesis of the cause of FM, symptoms varying between & fluctuating in patients, addition of chronic pains, fatigue, sleep problems, memory symptoms, bowel (IBS) and bladder symptoms, anxiety and depression, also there are triggering factors.
Main differences are that it does seem more in the brain and it seems possible to re-train the brain. Some of the symptoms like numbness, tingling seem like ones many fibromites have, but many others don't. The symptom you describe that it takes time to move a limb isn't at all fibro-like, despite the weakness involved. And especially: It can be diagnosed with the Hoover's test, tremor entrainment test and presence of non-epileptic seizures. As wikipedia says in a very short referral: Movement disorders and blackouts.
It does seem as if people with FND could well have FM, but not so much the other way round, despite the guess that FND is fairly prevalent.
Good to know, as it says not many people have heard about it.
There's a (free) review from 2018 on pubmed comparing FND, FM and CFS as regards their cognitive aspects (brain fog, ADHD-type-distractability): <A unifying theory for cognitive abnormalities in functional neurological disorders, fibromyalgia and chronic fatigue syndrome: systematic review>.
Interesting problem that neither neurologists nor psychiatrists think they should be treating, so this article proposes an integrated approach: <Treatment for Patients With a Functional Neurological Disorder (Conversion Disorder): An Integrated Approach>
BTW actually it's normally against the forum rules to directly hyperlink - in the past spammers have regularly opened and used an account here, unfortunately. So rather you just write e.g. <Functional Neurological Disorder - NORD (National Organization for Rare Disorders)> for us to search for ourselves next time. Don't be irritated if you find your link edited by a moderator soon, nothing personal.