Resting tremor vs action tremor in Parkinson’s: same label, different beast

Tremor in Parkinson’s comes in two flavours. Resting tremor is the classic shaking when a hand or leg is relaxed. Action tremor appears when you hold a posture or move, for example when you hold a cup or type. A large study followed 301 people who had deep brain stimulation in the subthalamic nucleus. Everyone was assessed at surgery and again one year later. Smaller groups were seen again around ten and fifteen years after surgery. The researchers measured resting and action tremor separately, both on and off medicine and with DBS on and off, so they could see how each type behaved over time. The headline result is that resting and action tremor are not the same. Both improved with levodopa and with STN DBS, but resting tremor improved more and stayed steadier over the years. Action tremor improved at first, then slowly crept back in many people a decade or more after surgery. This drift was most obvious in people whose Parkinson’s was tremor dominant at the start. The study also found that action tremor had some links with slowness and stiffness, while resting tremor did not show the same pattern. That hints that each tremor type leans on partly different brain circuits. Why the difference. STN DBS acts directly on the basal ganglia circuits that drive resting tremor, so it tends to quieten that shaking very well. Action tremor draws more on a route that runs from the cerebellum through the thalamus to the cortex. STN DBS touches that pathway less. That is why someone can have a calm hand at rest after STN DBS yet still see shaking when holding a spoon or reaching out. What does this mean if you are considering DBS. First, ask your team to score your resting and action tremor separately and to show you how each responds to a levodopa dose test. If resting tremor is the main problem, STN DBS is often an excellent choice and the benefit is likely to last. If action tremor is your bigger issue, set expectations early. STN DBS may help but may not clear it fully, and it can return years later. In that situation it is sensible to discuss other targets that are better for action tremor, such as the thalamus (often called Vim) or the dentato rubro thalamic tract. Some centres add a thalamic lead later as a rescue if action tremor persists after STN DBS. Focused ultrasound to the thalamus is another option for selected people who fit the criteria. Careful programming still matters a great deal, but sometimes a different target is simply the right tool for the job. The practical takeaway is to match the target to the tremor. Go into DBS with clear goals for rest and action tremor, agree how your team will measure each one before and after surgery, and talk through a back up plan if action tremor remains a problem. This makes outcomes more predictable and helps you choose an approach that gives you steadier hands for the tasks that matter day to day.