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I read your question carefully and I understand your concern. Movement disorders are perhaps the most difficult part of neurology, as there are many disorders presenting in similar ways and often lab and imaging tests are not that helpful for the diagnosis.

Now reading at that description of jerky unilateral tremor, not at rest, which has remained unilateral for 5 years I would say that Parkinson's doesn't look to be a likely cause. As you seem to have done your research it is a rhythmic rest tremor, initially unilateral but usually in 2-3 years spreads to the other side. However there are atypical cases so it can not be completely ruled out. I wounder if you have ever tried levodopa, the main drug used for Parkinson's. Even when not used as regular therapy often a single levodopa taking is used as a diagnostic test. A single dose is given and patient is tested several times ofer the next few hours. If there is substantial improvement that would speak in favor of Parkinson's.

Regarding your other question about this being caused by medication you took for depression I do not think that to be the case either. Mirtazapine has tremor as a side effect but a very rare one (and would be bilateral), actually more often it improves tremor in some studies, probably as it improves anxiety. As for Clonazepam that is actually a medication which also improves some types of tremor so not a side effect of the medication. Only scenario it might cause tremor may be if it is an withdrawal symptom, may appear at times with long use as the patient develops tolerance and the dosage is not enough, needs a higher one, but still doesn't look to be your case as typically would be bilateral. You do not mention any antipsychotics which are the common cause of extrapyramidal syndrome.

As for the ferritin deposits. Some iron deposition are often found with age even in people with no symptoms, may also be found in many extrapyramidal disorder including Parkinson's, so in itself I do not agree it to be against that diagnosis. If the deposits though are very marked then perhaps a condition called neuroferritinopathy must be considered, characterized by deposition of iron and ferritin in the brain. However the 5 year reasoning applies to that as well, it is a progressive neurodegenerative condition and should have progressed. Blood tests may help the diagnosis by showing low ferritin levels, but if normal do not exclude the disease. There are some other movement disorders due to excessive iron deposition but they either manifest since childhood or have manifestations in other organs (like pantothenate kinase-2 associated neurodegeneration, aceruloplasminemia, infantile neuroaxonal dystrophy). I wonder if you could provide the MRI report in order to judge for the scale of iron deposition and the sequences which have been used (MRI has different techniques,sequences, some more appropriate for iron deposits like SWI or GRE).

As for other causes, the lack of urinary symptoms, orthostatic hypotension, psychiatric, cerebellar or eye movement symptoms etc, even after 5 years makes other extrapyramidal conditions like multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration unlikely as well.

So in conclusion I realize that perhaps I haven't offered the definitive diagnosis you might have been hoping for. Apart from not being able to physically examine you, that is often the case with movement disorders, at times the cause may not be identified even if all is done as it should be. Unless typical Parkinson cases, they often necessitate long term periodic follow-up for new symptoms which may orient the diagnosis. Repeat MRI may be done for the evolution of iron deposits. In some research centers PET or SPECT scanning may be be done as well. At times anxiety may be the culprit although atypical unilaterally. For the moment given that many of these conditions are degenerative ones with no treatment I would be heartened by the fact symptoms have not progressed and are improved from Clonazepam and Propranolol.

I remain at your disposal for further questions.

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Thank you for the additional info. For some reason the site shows you to be from Florida, US. Now that you mention the DAT scan thing I checked the IP and it turns out you're writing from Venezuela.
Parkinson's seems less and less likely from what you tell, though no harm trying levodopa test.
Reading at your description of weakness and atrophy I would say that electrophysiological studies (nerve conduction studies and electromyography - EMG) are also necessary to search for a neuromuscular disorder.
Also, perhaps it's been already done, but a blood count with a peripheral blood smear is necessary to search for the presence of acanthocytes, sort of spiky red blood cells, which are part of some movement disorders which may manifest with dystonia. A metabolic panel including electrolytes and thyroid function is also necessary if not already done.
While I said that Mirtazapine is an unlikely cause, it still should be considered as there are a few (rare) reports of it causing dystonia or tremor. So if the issue appeared while you were using it and you still are, and all tests result normal, I would consider its gradual interruption for a while to see if symptom will improve (or perhaps worsen if due to anxiety).
While your worry is understandable, shouldn't be in such a state of terror. The fact that it has been 5 years is really heartening in excluding a degenerative progressive disorder.

I hope to have been of help.

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Detailed Answer:
Thank you very much for your kind words XXXXX

I imagined things were not great in Venezuela, but didn't think that bad, if there is no Sinemet (or other levodopa alternatives like Madopar), then obviously levodopa test can't be done. Perhaps you have difficulties with the other tests I mentioned as well but at least you have had the MRI which has excluded issues such as stroke or tumor which might well have been at the origin of that unilateral, that is heartening together with the response to Clonazepam and Propranolol and lack of progression.

If you want to contact me again later on in the future, just search my name here, on my profile there is a "Ask me a question" tab below my photo, simply click that to go on with the question.

Wishing you good health.

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Thank you

Detailed Answer:
Thank you again for your kind words XXXX. Let me know if I can further assist you.

You can close the conversation and rate our exchange as you see fit.

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