Research project The overall aim of this research is to address gaps in our understanding of how stereotactic neurosurgical treatment, deep brain stimulation and focused ultrasound, can be optimized for people with essential tremor.
Through new analysis methods that combine motion analysis and neuroimaging, our multidisciplinary research team aims to map the relationships between electrode location, stimulation settings, treatment outcomes and the patient’s specific movement difficulties at the level of both brain and body.
Essential tremor (ET) is a common neurological condition that causes involuntary, rhythmic shaking, mainly in the hands and arms, and can have a major impact on daily life. When medication does not provide enough relief, deep brain stimulation (DBS) or focused ultrasound (FUS) may be treatment options. DBS effectively reduces tremor by electrically stimulating specific parts of the brain network involved in the shaking. Stimulation is delivered through electrodes implanted using stereotactic surgery. At the University Hospital of Umeå, FUS treatment is also available. This treatment instead inactivates a small part of the same network by heating it locally using focused ultrasound.
It is still unclear why the effects of DBS diminish over time in some patients and why stimulation can cause side effects such as balance and coordination difficulties. FUS is a relatively new treatment, and more knowledge is needed about its long-term effects and which brain areas are best suited for treatment. Studies suggest that walking and balance problems may be more common after FUS than after DBS, but the reasons remain unclear. There is ongoing debate about whether ET may encompass different neurological variants (ET subtypes). This could help explain why treatment effects and side effects vary between patients and over time.
We also lack precise clinical tools to identify which patients are at risk of developing these disabling problems. Current assessments rely on clinical rating scales, which do not provide a sufficiently detailed and precise picture of the patient’s movement difficulties. A common view is that coordination difficulties caused by stimulation (known as stimulation-induced ataxia) can be mistaken for a loss of tremor control. This may lead to inappropriate stimulation settings that further worsen these side effects.
To address these knowledge gaps, we will use methodologies based on combined motion analysis and brain imaging, to map and better understand the relationships between motor function, brain activity and treatment effects.
1. Identify ET subtypes based on motor function. Using wearable motion sensors, we measure whole-body movements and analyze tremor, coordination difficulties, and walking and balance problems. We also investigate whether subtype can predict treatment outcomes by comparing motor function at different DBS settings. This experimental cross-sectional study compares people receiving DBS treatment for ET with healthy individuals.
2. Map the relationship between motor function and brain activity in healthy individuals and people with different ET subtypes. We combine functional magnetic resonance imaging (fMRI) with simultaneous recording of three-dimensional arm and leg movements using specialized optical cameras. This allows us to analyze brain activity and movements together. The technology is available at only a few laboratories worldwide and has not yet been used to study ET.
3. Identify the long-term effects of DBS and FUS treatment by measuring motor function and related brain activity. In a longitudinal study, we follow people with ET from before treatment until one year after the procedure and compare them with healthy, age-matched controls.
The illustration shows a gait analysis using wearable motion sensors. The recorded movement data is used to set up a segment model and calculate movement measures.
Image Helena Grip
The figure illustrates a research measurement in which the participant performs a pointing movement while lying in the MRI scanner, while both brain activity and finger movement recorded. The data is used to analyze brain activity in relation to tremor and hand function.
Image Helena Grip
