Conventional Repetitive Transcranial Magnetic Stimulation for Depression: A Step-by-Step Protocol

We describe conventional methods for therapeutic use of RTMS for treatment-resistant depression through precise and patient-centered protocol enhancing safety, comfort, and reproducibility. Recent advances include accelerated RTMS protocols, neuronavigation-based targeting, and personalized targeting using individual level functional brain connectivity, which are thought to improve treatment outcomes. While exciting developments are occurring for the use of RTMS to treat depression, establishing even the more conventional protocols can be challenging in some settings.

To begin, place a lycra cap on the patient to mark areas of interest on the scalp. Confirm that the cap is aligned with the patient's eyebrows and the upper part of the ears to ensure consistent reference points for future sessions. Provide earplugs to the patient to minimize discomfort caused by stimulating sounds.

Wear your own earplugs before beginning the transcranial magnetic stimulation procedure. Record all preparatory steps and safety measures in the patient's clinical chart. To determine the motor hotspot, identify the stimulation hotspot for the primary motor cortex of the hand region in the left hemisphere, using a measuring tape measure and mark the mid sagittal line extending from the nasion, which is the top of the nose bridge, to the inion, which is the prominent bump at the back of the skull.

Now mark the intertragus line by placing one end of the measuring tape at one tragus, which is the point just in front of the ear, and stretching it across to the opposite tragus. Identify the intersection of the midsagittal and intertragus lines as the cranial vertex. Use this point as the reference from which additional measurements will be taken to locate the motor cortex hotspot.

Next, draw a triangle by extending a line five centimeters to the left along the intertragus line, and another five centimeters anteriorly along the midsagittal line. Both starting from the cranial vertex. Connect the free ends of these two lines diagonally to form a triangle.

The starting reference point for locating the hand motor hotspot is positioned 2.5 centimeters along this diagonal line measured from the leftmost vertex of the triangle. Then mark four additional points located 0.5 centimeters, anterior, posterior, lateral, and medial from the reference point. To allow detailed exploration during hotspot identification, use these five points as the designated positions where the anterior edge of the transcranial magnetic stimulation coil will be placed during the motor hotspot detection procedure.

Before initiating the search for the motor hotspot, instruct the patient to rest their arms and hands on the armrests of the chair or on their lap, ensuring that both are visible and relaxed. Place the handle of the figure of eight transcranial magnetic stimulation coil on the patient's head at a 45 degree angle relative to the sagittal midline with the handle directed posteriorly and to the left. Apply transcranial magnetic stimulation pulses while maintaining the coil in the previously described position.

To help the patient become accustomed to the procedure, deliver the initial pulses at a lower intensity, approximately 20%to 30%of the maximum output, while assessing the patient's sensory experience. Confirm the visible muscle contraction in the contralateral hand muscles. If no motor response is observed at the initial intensities across the marked reference points, increase the stimulation intensity in 5%increments until a motor response defined as a visible contraction of the right hand is obtained.

Once a motor response is detected, test the remaining marked points to identify the location that produces the strongest contraction. Mark additional reference points as necessary at new positions spaced approximately one centimeter apart to refine the search. Identify the motor hotspot as the point that produces the largest and most consistent muscle contraction.

After locating the optimal stimulation site, trace a concave line along the anterior edge of the coil and mark the midpoint of this line to indicate the precise hotspot location. Now, confirm the identified motor hotspot at regular intervals. If refinement is required during a session or treatment cycle, mark the new hotspot on the patient's cap and record the reason for adjustment in the clinical chart.

To determine the resting motor threshold, begin assessment after allowing the patient a short accommodation period. Deliver transcranial magnetic stimulation pulses at percent of the devices maximum output, and confirm that visible muscle contractions of the contralateral hand occur in at least five out of 10 pulses. If visible contractions in at least five of 10 pulses are not achieved, increase the stimulation intensity in 2%increments until this response criterion is met.

Once the criterion is achieved, decrease the intensity by 1%to identify the minimum level that still elicits a motor response in at least five of 10 pulses. Record the resting motor threshold in the patient's clinical chart for use in upcoming treatment sessions. If reassessment of the resting motor threshold is required, record the new resting motor threshold value along with the reason for reassessment.

After identifying the motor hotspot and determining the resting motor threshold, proceed to locate the treatment site. This procedure focuses on non-neuronavigated approaches based on scalp measurements as these methods are commonly used in clinical practice. Using the five centimeter rule method, extend a parasagittal line anteriorly from the midpoint of the concave line drawn after determining the motor hotspot.

Mark the stimulation point for the left dorsolateral prefrontal cortex at a position between five and six centimeters, most commonly 5.5 centimeters along this line. Then position the coil on the treatment site. Alternatively, use the Beam-F3 method to locate the F3 position from the 10-20 electroencephalogram system on the scalp as an alternative landmark For the left dorsolateral prefrontal cortex.

Input the specific head measurements of the patient into a freely available software that provides instructions for marking F3 according to head size. Using a tape, measure the nasion-inion distance from the top of the nose bridge to the bump at the back of the skull. Second, measure the intertragus distance from one ear's tragus to the other.

Third, measure the head circumference by passing the tape over the eon at eyebrow level. Input the three measurements into the software to generate two output distances. The first output, Point X, provides the distance to the left of the midline along the head circumference, and the second gives the distance from the vertex along a line intersecting Point X.Use these two distances to mark Point Y on the patient's scalp as the left dorsolateral prefrontal cortex treatment site.

Finally, confirm the treatment site at regular intervals. If refinement is necessary, mark the updated treatment site on the patient's cap and document the reason for adjustment in the clinical chart, whether by protocol or due to other factors. After determining the treatment site, initiate the TMS protocol.

A total of 35 treated patients were included in this study of real world evidence. Mean MADRS total score decreased significantly after six weeks of treatment compared to baseline. The mean reduction in MADRS was 9.13 points, demonstrating a statistically significant antidepressant effect after the treatment period.

Following treatment, 56.7%of patients achieved partial response. 46.7%met the criteria for response, and 43.3%reached remission. We provided a standardized RTMS protocol that may improve treatment consistency, reliability, and comfort, supporting effective depression therapy across clinical settings.

Conventional RTMS has paved the way for research focusing on optimizing stimulation parameters, refining strategies for cortical targeting, and evaluating the long-term effectiveness of RTMS for depression.