Is TMS effective even without MRI neuronavigation?
Short answer: YES. Long answer below!
MRI is used in research facilities to pinpoint the exact location of the best region at which to apply TMS. Recent effective trials like SAINT had very high response rates (79-90%) and used MRI in this way. This leads to the question of whether the response rate was due to MRI, or other factors in the TMS protocol.
In small, private, personalized offices like mine, we don't yet have the capability to have an MRI on site and it would be a challenge for patients to go get one on their own.
Since the advent of TMS for general clinical use, other accessible methods have been used instead to pinpoint the right location. The original method, referred to as the "5cm rule," was only an approximation and not entirely reliable. Luckily, two innovative researchers found us a new option.
Will Beam and Jeff Borckardt proposed a new simple and dedicated method called the ‘‘Beam F3” algorithm (Beam et al., 2009). Their procedure locates the left/right DLPFC at the F4/F3 sites using the 10–20 EEG System. The system estimates the scalp location of the F3 site (the desired TMS target for depression) using three measurements over the skull. Beam and Borckardt even went on to develop a free web interface calculator based on their method, which we use in my office.
Most importantly, other researchers decided to study the Beam F3 method and see if it is indeed accurate. In 2015, Dr Mir-Moghtadaei and his colleagues compared the MRI-determined location versus the Beam F3- determined location on 100 patients to see how well the two lined up.
What they found is really great news for everyone who wants to make TMS widely accessible without huge associated costs to patient and facility! They confirmed that Beam F3 can acceptably estimate neuronavigation when MRI is unavailable. In a majority of their patients, the discrepancy in location between the two sites was less than 0.065cm, which is not clinically relevant when compared to the size of the target.
Bottom line: The method I currently use to determine your treatment location has been scientifically proven to be accurate, and is comparable to MRI-guided neuronavigation. Additionally, during your treatment we will be closely tracking your progress. If there is any evidence that you are not responding as expected (i.e., that we may be treating in a slightly wrong location), we will adjust the treatment location in 0.25cm increments until we have optimized your response.