A lung tumor in the upper most aspect of the lung can grow upward into the brachial plexus and injure the nerves. This would result in predominantly
handHand or foot spasms
Hand tremor weaknessWeakness. An MRI of the brachial plexus should be able to examine this possibility for you. Also having this evaluated by a neurologist who specializes in neuromuscular conditions would be reasonable. They can perform an EMG (muscle/nerve test) and determine which nerves are actually affected. If you would like to search for this on the internet, search for Pancoast Tumor. This is the descriptive word for a lung tumor which invades the brachial plexus. Good luck.