The overall goal of this initial transcranial magnetic stimulation treatment visit is to determine the patient's motor cortex location and stimulation intensity necessary for the patient's TMS treatment, which targets their treatment-resistant depression. So, the main advantage of this device over other current FDA-approved devices is that the unique coil design, it's able to produce a wider and a deeper stimulation over the cortical-targeted area in the brain. In randomized controlled studies, significant improvement has been demonstrated with shorter sessions and fewer pulses than with other FDA-approved devices.
TMS treatment should only be performed by personnel adequately trained and certified by the device manufacturer. Prior to these procedures, have the patient complete a TMS Safety Questionnaire to ensure that TMS treatment is both safe and appropriate, and have them review and sign an Informed Consent document detailing the procedure. To begin preparation, have them sit in a chair that is positioned in front of the TMS machine's cart and ensure that they're at an appropriate angle for the coil to be positioned comfortably on the head.
At this point, the patient should remove any eyeglasses or other metal on the head. Also, provide earplugs and ensure they are properly positioned to protect hearing. To facilitate locating anatomical landmarks in the patient's head, use a stretchable cap with a chinstrap and black-and-red flexible rulers.
Slide the cap on to the patient's head, with the front over the forehead just above the eyebrows. The cap's red stitch midline should be along the midline. Fold the ear covers down, stretching the cap firmly around the head, then attach the chinstrap.
Position the zero-point on the ruler at the nasion, the junction of their nasal bone and forehead. Now attach the black anterior-posterior flexible ruler along the midline of the cap with the cap's red midline positioned directly to the left of the ruler. Next, locate the patient's inion, being the most prominent projection at the lower-rear part of the head.
Then, record this location on the black midline ruler. Pull the cap down snugly and stretch the back peripheral straps up and across the back of the head, and then fasten them on to the back of the cap. Calculate 40%of the distance between the nasion and the inion, and place the red lateral-medial flexible ruler so that it's 25 centimeter mark lines up with this location on the black midline ruler.
The two rulers should now be perpendicular. Then, position the TMS machine's arm at 45 degrees relative to the cart holding the stimulator. For the entire motor threshold procedure, ensure that the zero point on the helmet midline lines up with the cap's midline.
Then, position the front end of the mesh helmet coil cover at seven centimeters on the black midline ruler. Adjust the helmet so the entire front edge of the helmet is level and perpendicular to the midline ruler on the cap. Record the location at which the helmet coil cover meets the red lateral-medial ruler on the left side of the patient's head.
Next, shift the coil cover on the left side of the helmet two centimeters medially along the red lateral medial ruler, while ensuring the coil cover at the front of the helmet remains in place. This positions the coil's maximal magnetic output approximately over the region associated with contralateral hand control. Now, turn on the stimulator, select single pulse, and set the stimulator output to 50%before arming the machine.
Then, position the patient with their right hand resting over a pillow on their lap, palm facing up, so that any finger movement can be easily seen. Next, to locate the motor cortex, use the current location of the coil and stand to the left of the patient. Press down on the helmet with one hand, while supporting the patient's neck with the other, and apply a single pulse by depressing the stimulus foot petal.
Rate any involuntary finger movement on the patient's right hand from zero to five, with zero being no movement detected, and five being a very rigorous involuntary movement. Wait five seconds, then perform this again at the same location. If there is no motor response after two single pulses, increase the stimulator output by increments of 5%Repeat this procedure at several more locations in a systematic grid pattern, first finding the most consistently active location along the midline anterior-posterior access.
Then, move one centimeter at a time along the lateral-medial ruler to, again, find the location that produces the most robust and consistent motor responses. Document the strength and number of elicited responses at each location. Next, with the helmet in the same location, determine the patient's minimum motor threshold by systematically lowering the stimulus intensity in small increments until you reach an intensity which produces at least two, but no more than three, responses out of six administered single pulses being the subject's motor threshold.
When ready for treatment, the coil needs to be positioned so that the magnetic output is concentrated at the targeted treatment region, the left lateral prefrontal cortex. Do this by moving the front edge of the helmet down six centimeters in the midline ruler, or the level of the patient's eyebrow, whichever is higher. Next, secure the helmet coil cover to the patient's head by pulling down on the pad at the back of the helmet.
Then, tighten the knob and adjustment cords, and fasten the helmet's chin strap. Now, turn on the cooling system and wait for the temperature gauge to read below 14 degrees Celsius before starting treatment. Then, press the single pulse button on the stimulator touch screen.
Set the stimulator output to the patient's previously established motor threshold, and set the percent motor threshold to 100. Also, select Repetitive Mode"and enter the treatment parameters as seen here. The number of pulses will auto-populate based on duration and frequency, and power will auto-populate based on the values entered for the stimulator output and percent motor threshold.
Now, select Run Session"and arm the machine. Then, let the patient know they will experience strains of pulses, and verify that they are ready to begin treatment. Once they are ready, count down from three to one loudly and clearly, while visually indicating the countdown with your fingers in front of the patient.
Then, press the yellow start button on the panel to administer the first train. Observe the patient's face and limbs, then, after the first pulse, ask how they feel. If they experience anything more than mild discomfort or facial contractions, the treatment may be stopped and the location may be adjusted up to two centimeters in any direction.
Once the patient is comfortable, begin the first treatment session by administering at 100%power relative to the patient's motor threshold. Stop stimulation after every 10 pulse trains, and titrate the intensity up by 5%of the motor threshold. Do this until 120%of motor threshold is achieved.
Always notify the patient before increasing the intensity, and afterwards, ask if they feel discomfort. At any intensity level, if the patient reports significant discomfort, return to a lower intensity and allow them to further acclimate to the sensation before attempting to increase the level again. During all sessions, continue to monitor the patient for increased motor movement including any signs of facial contractions, limb movement, or inadvertent re-positioning of the helmet.
Once the treatment is completed, first, remove the coil and the cap, and assist the patient out of the treatment chair if necessary. The pattern and time course of improvement in depression symptoms during the course of deep TMS treatment varies across different patients. Here, we see that Patient D first experienced a decrease in depressive symptoms during the fifth week of treatment, Day 28 to 35, which was pushed into a full and sustained remission during the sixth week of treatment, Day 35 to 42, which was sustained through the one month post-treatment follow-up.
Patient S first showed a decrease in symptoms during the end of the second week of treatment, but did not reach a full and sustained remission of symptoms until the end of week four, which was sustained through the three month post-treatment follow-up. With practice, this mapping and motor threshold technique can be done quite efficiently. The success of DTMS for treatment of patients with treatment-resistant depression has paved the way for researchers in neuropsychiatry to investigate TMS as a treatment modality for patients with other psychiatric disorders such as Alzheimer's, OCD, PTSD, substance abuse and bi-polar disorder.
