News & Articles

What is Connectivity Guided Focused Ultrasound?

Traditionally, when we are looking for a target within the brain to treat tremor disorders using either focused ultrasound (MRgFUS) or deep brain stimulation (DBS), we have used something called structural magnetic resonance imaging (or MRI for short). MRI is a powerful imaging tool that allows us to visualise the structure of the brain in extreme detail and identify key areas of anatomy.

However, identifying the precise target for focused ultrasound treatment or deep brain stimulation for essential tremor remains a significant challenge, even when using high resolution MRI. When we consider the target that we are trying to identify and treat in the case of essential tremor (known as the ventral intermediate nucleus or Vim nucleus), we are working with a tiny portion of a structure in the deep brain, called the thalamus. The nucleus itself is merely 3mm thick (a quarter the size of a little finger nail) and sits deep within the human brain. Even with the very best structural MRI, this important structure within the thalamus can often be difficult to visualise and differentiate from structures surrounding it. This can make the neurosurgeon’s task more difficult and potentially affect clinical outcomes from treatment.

The role of MR-Connectivity Imaging

However, a more recent MRI technique called diffusion tensor imaging has been fully optimised for MR-guided thalamotomy in Queen Square. Diffusion tensor imaging allows us not only to see the structure of the human brain, but also allows us to see how the brain is connected. In other words, we can pick a spot within the brain and use MR technology and statistical analysis to tell us the probability that one spot in the brain is connected to another spot. The power of ‘connectivity MRI’ is obvious when we consider that the power of the human brain is how its parts are connected to each other. How the different parts of the brain speak to each other, really defines how it functions.

So how does this work in practice to identify a surgical target? Well, as we are now very familiar with the area of the surface of the brain that controls movement, and know which part of the back of the brain (called the cerebellum) controls movement, we can then use diffusion tensor imaging and statistical analysis to see where these two brain regions are most heavily connected, within the thalamus. This then defines the ventral intermediate nucleus, the ‘junction box’ or the ‘motor part’ of the thalamus, not by its structure (as we would try to do using structural MRI alone) but by its connectivity.

Queen Square is leading the way in surgical guidance using MR-Connectivity

Through extensive research performed and published by the functional neurosurgery team here in Queen Square, we’ve been able to publish papers that reliably identify the ventral intermediate nucleus of the thalamus (the motor part that is misbehaving in essential tremor). We have been able to do this not only through connectivity imaging, but we are now also advancing structural imaging sequences to use as high resolution maps, onto which we superimpose connectivity information. This information can be collected during a relatively simple, 30-minute long MRI scan as part of each patient’s pre-assessment.

Therefore, we now have two ways of finding the motor part of the thalamus, which when blended together using powerful computer processing, gives us double the reassurance that we’re going to hit the right target in focused ultrasound thalamotomy and deep brain stimulation procedures. For essential tremor patients, this means that we can maximise the therapeutic benefit and clinical outcomes of treatment and reduce the risk of patients having to make a return visit for repeat treatment. It also means that we can avoid other areas of the brain with our ultrasound beam, vastly reducing the risk of permanent, or even longer term side effects of treatment.

Where can I find further information about focused ultrasound treatment of essential tremor?

MR-guided focused ultrasound treatment for medication-refractory essential tremor is now available in Queen Square to private patients. If you are interested in treatment and would like to find out more, please contact our treatment coordinators at

Additional information is also available at

Professor Ludvic Zrinzo
Consultant Neurosurgeon
More about Professor Ludvic Zrinzo