Patient specific information acquired preoperatively may contribute to target planning, e.g. in thalamus neurosurgery. Information on thalamo-cortical connectivity patterns may refine target volumes, or information on the precise course of white matter pathways (subthalamic zone) may be used for designating new target locations. Is this technique ready to be applied in the neurosurgical practice?
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Atlases cannot cater adequately for individual anatomical variability. Atlases are a product of a time where the brain could not be imaged in vivo. However, they remain an excellent educational tool.
Specific structural stereotactic MRI sequences are the only modality that have been shown to be associated with long term clinical outcome after STN DBS.
MRI connectivity techniques have promise in refining structural targeting but evidence is lacking at present.
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Hi András, you raise a couple of questions.
Firstly, patient specific data must be used for preoperative mapping. Registering a patient's image to an atlas can help with providing anatomic names for regions of interest, but there is too much inter-patient variability to rely on an atlas alone.
Secondly, mapping for surgical application leverages information from many techniques, not just preoperative MRI. For instance, a combination of image guided surgery, microelectrode recordings, and clinical responses to macrostimulation of the region surrounding the STN is now common clinical protocol in the US.
Regarding the most current diffusion weighted MRI protocols, I have not seen better images than what's currently used by the human connectome project: http://www.humanconnectomeproject.org/publications/documents/
-Reese
Here are some relevant links:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3958735/
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=1525182
http://www.humanconnectomeproject.org/publications/documents/
Hello Andras and Reese
May I generate some debate on this topic? Just because a clinical protocol is common practice in the US does not mean it is the logical thing to do! One could argue that invasive multi track mapping with MER is a relic of a bygone era when the pioneers of functional neurosurgery could not see the target they were aiming for, let alone verify the anatomical location of their intervention.
In the 21st century, MRI can be used for intraoperative verification and not just preoperative surgical planning. MRI-verified DBS has MANY advantages over microelectrode (MER) mapping including:
1. There is more published data linking lead location on MRI to long term clinical outcome , both in optimising improvement in UPDRS scores (e.g.: Wodarg 2012, Aviles-Olmos 2014) and in minimising adverse effects, for example dysarthria (Tripoliti 2014). Even if particular MER signals could be linked to good long term clinical outcome (I am not aware of any paper that has done so convincingly) there is no way of replicating recordings in subsequent patients.
2. MRI-verfied DBS carries significantly less risk of haemorrhage causing stroke or death (Zrinzo 2011)
3. MRI-verified procedures can be performed under GA and patients do not have to stop medication completely prior to surgery making for quicker recovery and less perioperative complications (Nakajima 2011)
4. Shorter operative times with MRI-verified DBS allow us to perform two complete bilateral DBS implants with IPG in one day with time to spare at Queen Square (london, UK)
5. MRI-verified surgery is significantly less expensive - to the tune of 'buy one get one free" (McClelland 2011)
After being rather provocative, I would add that there is no "BEST" way to perform DBS. Each surgeon should adapt his/her technique to the local infrastructure, personal training and experience. It would be a real pity if every DBS service around the world performed surgery in exactly the same way!
Best wishes to both!
Ludvic
Obviously, biases can be very strong. Unfortunately, even the most precise pulse sequences with very long acquisition times (unsuitable for the clinic) are still many steps away from actual neurobiology and neurophysiology. Electrophysiological monitoring is much closer to the action of cells and is certainly aided by MRI.
Of course biases can be very strong. I often wonder why it is essential to advance micro electrodes over micrometer scales when a 1.27mm diameter lead is finally implanted. What is important to the patient is the clinical outcome not the action of cells ...
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