MRI-Guided Repetitive Transcranial Magnetic Stimulation to the Dorsomedial Prefrontal Cortex

Begin with a patient diagnosed with depression wearing a headband with a lateral marker clip to facilitate neuronavigation.

Load the pre-processed magnetic resonance imaging scan into the neuronavigation program to identify the dorsomedial prefrontal cortex for precise targeting.

Turn on the camera.

Position the repetitive transcranial magnetic stimulation coil over the dmPFC under MRI guidance, ensuring close scalp contact.

Orient the coil laterally and stimulate the left hemisphere.

Re-orient the coil and stimulate the right hemisphere, maintaining the vertex fixed over the dmPFC scalp site.

The coil delivers high-frequency electromagnetic pulses that penetrate the skull and generate electric currents in cortical neurons.

This process increases excitatory neurotransmitter release and enhances cortical excitability.

However, the high-frequency pulses also cause scalp pain.

Gradually increase the stimulation intensity and assess pain tolerance using a verbal analog scale after each stimulation period.

This adaptive titration approach minimizes pain and discomfort during rTMS-based depression treatment.

Use the 120 degree angled fluid cooled coil and parameters described here for stimulation in each treatment session. First, ensure that the patient and operator wear earplugs or other hearing protection during treatment. Then, place the coil over the dorsomedial prefrontal cortex target under MRI guidance using the neuronavigation system.

For 10 Hz stimulation, use a duty cycle of 5 seconds on, 10 seconds off, for a total of 60 trains, or 3,000 pulses per hemisphere per session. Perform this protocol on the left hemisphere, then on the right by orienting the coil laterally. If performing treatment with theta burst stimulation, use a duty cycle of 2 seconds on, 8 seconds off, for a total of 600 pulses per hemisphere per session.

Also perform this protocol on the left, then right hemisphere. During initial sessions, adaptively titrate upwards from an initial value of 20% maximum stimulator intensity. Titration of the rTMS stimulus intensity is to allow the patient to habituate to the pain and scalp discomfort associated with stimulation. Adjust stimulation intensity by 2% to 5% on each train of stimulation as tolerated.

After each train of stimulation is delivered, assess tolerability by having the patient rate pain on a verbal analog scale from 0 to 10, with 0 meaning no pain and 10 being the limit of tolerability without emotional distress. For each session, begin with a higher stimulation intensity using a level associated with moderate tolerability from the previous session. Do this until the patient can start at the target intensity of 120% resting motor threshold for each hemisphere.

Be sure to maintain a verbal analog scale of less than 9 throughout treatments during this titration process, typically completed in two to five days. Monitor the patient for any adverse effects during treatment. The most common treatment-interrupting adverse effect is a syncopal episode arising during the first or second session of treatment in approximately 1% of patients. Although these events are rare, also monitor the patient for seizure activity. Use video monitoring so that an episode can be reviewed by a neurologist at subsequent assessment if necessary.