Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you or obtain a history, I can not tell you what the cause of your pain and
numbnessNumbness and tingling are. However, I will try to provide you with some information regarding possible causes.
NumbnessNumbness and tingling in the
handHand or foot spasms
Hand tremor and arm with pain is most likely of
neurologicFocal neurological deficits
Multiple system atrophy cause. Where the nervous system is affected depends on the exact distribution of your symptoms. The nerves to the arm come off the spinal cord, go through the bones of the spine, join at the upper neck/shoulder/armpit area to form a plexus of nerves, then individual nerve branches break off to supply various different parts of the arm. Irritation to a nerve at any point along this path could lead to symptoms in the arm. Some examples of potential causes are as follows.
Arthritis is a very common condition. Arthritis can affect the bones of the spine, and little spurs (also called osteophytes), which are sort of bony growths, can develop. These can press on nerves as they exit the spinal column, leading to your symptoms. Often, not only is there numbness and pain but also some weakness of the muscles in that area. Also, a herniated disc in the spine can similarly press on the nerves as they exit the spinal column, causing symptoms. In this case, the type of injury is what would be called a "radiculopathy", what is often referred to in lay terms as a pinched nerve. With a radiculopathy, not only is there numbness and pain but also some weakness of the muscles in that area. The level that might be affected in your case would be probably the C6 nerve, or C5. Involvement of the spinal cord itself is also a possibility but is less likely.
Another cause of nerve irritation/damage is obviously trauma. Recent trauma leading to fracture can of course lead to nerve injury as well. Remote trauma can contribute to arthritis, which can then impinge on nerves as above.
Finally, a neuropathy, or nerve problem, can affect the nerve in the arm itself (as opposed to the nerves coming out of the spinal cord, in which case the diagnosis would be a radiculopathy). Since your symptoms are predominantly in your hand and forearm, one possible nerve that could be irritated is the median nerve. If your symptoms were predominantly in your hand, carpal tunnel syndrome, due to compression of the median nerve as it passes through the wrist, is a possibility. The pain of carpal tunnel syndrome can sometimes spread up the forearm but would not tend to reach the shoulder.
As you can see, the nervous system is complicated and localizing exactly where the problem is requires a detailed history and examination. You would benefit from evaluation by a general practitioner who can then determine after examining you what further testing you will need and whether or not you need referral to a neurologist. Tests that could potentially be ordered include an MRI of the cervical spine (the neck area), to look for arthritis or herniated discs that are pressing on the nerves as they exit the spinal cord. Another test that could be ordered is abbreviated as EMG/NCS, it tests how well electricity is conducted along the nerves and how the muscles respond to electricity coming from the nerves.
Thank you for the opportunity to answer your questions, I hope you find this information useful, good luck.