Brief Answer:
Read below.

Detailed Answer:
I read your question carefully and I understand your concern.

Twitching may be due to many different causes ranging from metabolic alterations such as magnesium, sodium, potassium changes, thyroid dysfunction etc or to neurological conditions.

When it is in the setting of a neurological condition though (I suppose that is what worries you most) there are other associated symptoms such as weakness, atrophy etc. So to be more precise some more information would be useful such as:
- the precise location,
- does the location change or is it always the same,
-exacerbating factors such as dehydration, sun exposure, previous physical exertion etc,
-muscle weakness, muscle atrophy, wasting in the area
-any recent blood tests you might have done

I remain at you disposal for further questions, possibly providing the requested information as well.

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Brief Answer:
Read below.

Detailed Answer:
Thank you for the additional info.

The fact the location varies and is widespread is in a way heartening because in the case of threatening issues such as ALS (mentioning it as it's what most patients fear), symptoms start usually in one region, with weakness and atrophy as more prominent symptoms, widespread fasciculations (twitching) would be in last stages. So no indication of it really. Technically to make sure a neurological physical exam may be done to check for weakness, atrophy, altered reflexes etc, but from your description I am positive it won't evidence any such issue.

The phrenic nerve issue is not related. The herniated disc can produce fasciculations but only in the territory covered by the nerve compressed (if the disc compresses a nerve at all that is), so again the changing location excludes that.

So most probably these fasciculations are in the setting of what is called benign fasciculations syndrome (BFS). It can often be in the setting of metabolic/hormonal issues or anxiety, but at times no cause can be found at all.
To check for identifiable causes, electrolytes (including calcium, magnesium, potassium), creatine kinase and thyroid hormone tests are necessary. If the blood tests you have had include these and are recent, then it's fine, do not have to do them again, but please check they have all been part of your work up.
If at the end of the day all is normal and you exclude anxiety, then management depends on how much they affect you. I have had good results in some patients with magnesium supplements even when tests were normal. Should also have a regular sleeping and eating schedule, as well as avoid stimulants like coffee or energy drinks. If really affecting your quality of life despite all these measures medication may be used such as Gabapentine....but really would avoid that unless really necessary.

Let me know if I can assist you further.

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Brief Answer:
You're welcome

Detailed Answer:
Thank you for your kind words, I hope you will feel better soon.

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