Since you seem to be offline, ill leave a response here which we can discuss later on.
The first thing which comes to mind is definitely parkinsons disease however parkinsons would usually be accompanied by symptoms of bradykinesia and rigidity. This means that your husband would have problems in initiating movements and at the same time would also have stiff arms or legs or even the hands. Now if this is parkinsons then it would need to be diagnosed clinically however in advanced cases a MRI of the brain would be helpful to look atcertain regions of the brain like the basal ganglia. These would show degeneration. Now in parkinsons while there is not a cure there are certainly treatments to help control the disease which can include drugs like levodopa, ropinirole, amantadine etc. Anti cholinergics would also be helpful here.
Another condition which can be possible here is that your husband could be suffering from essential tremors while it is less likely as essential tremors are usually long standing in most patients but they can still occur at any time in some patients. if this is the case then it would simply be treated with various drugs. Yet another possibility is that he could be suffering from the side effects of some drug. Valproic acid is less likely to be culprit but it can be a drug which he has used in the past. Talking about valproic acid, it is possible that your husband has developed a form of epilepsy which is not being controlled with valproic acid. Uncontrollable shaking like this could be indicative of partial seizures which would need another EEG to be done and then treated with another type of drug.
In short i do agree that this can be parkinsons but at the same time it can be a number of other things. Regarding the shoulder surgery, i would like to know as to why shoulder surgery is being done? Do they think there is nerve compression at the shoulder or does he have pain there?
Do you have any more questions?
Please leave a POSITIVE rating by clicking on the stars above, until you do i am not compensated for my time. You can continue to ask follow-up questions even after the POSITIVE rating. You can also ask questions from me directly by going on the link below,