By Joanne Martelli, PMHNP-BC
TMS mapping, which is also called brain mapping, is one of the first things you’ll hear about if you’re thinking about TMS therapy or if your doctor has suggested it. This first session is a straightforward, exact technique that makes sure the magnetic pulses go to the proper place in your brain with the right amount of power. It’s the basis for a therapy plan that works for you.
As a psychiatric nurse practitioner with more than 12 years of experience treating depression and other mental health problems, I know how life-changing TMS can be when mapping is done right. A TMS mapping session helps us find the proper target area before treatment starts. This makes every session after that more accurate, comfortable, and helpful.
Quick Overview: What Brain Mapping Is and Why It Matters
During your first appointment, doctors use TMS brain mapping to identify two things: 1) the exact location on your scalp that corresponds to the motor cortex (your “motor hot spot”), and 2) the lowest intensity of stimulation that reliably makes your muscles respond. This is called your motor threshold. The treatment team can then use the right coil placement and dose to target the dorsolateral prefrontal cortex (DLPFC), which is a part of the brain that is often targeted for mood and anxiety problems. Doing this right makes TMS more likely to work and less likely to have side effects that aren’t needed.
How Does a TMS Work?
TMS uses a magnetic coil on the head to make short magnetic pulses. The pulses go through the skull without hurting anything and create little electrical currents in the neurons below the coil. The DLPFC can change how brain circuits talk to one another when it gets a sequence of these pulses over and over again throughout sessions. This typically brings activity back to areas of the brain that aren’t working as well as they should be in mood and cognitive regulation. You stay fully awake and attentive during this noninvasive stimulation, which doesn’t require anesthetic or systemic medicines. After a session, most people can drive home.
The global TMS market was worth $256.53 million in 2024 and is expected to rise by almost 10% every year, reaching $594.49 million by 2033. This quick growth shows that more and more people are realizing that TMS is a good option when other treatments haven’t worked.
What to Expect During a Typical TMS Mapping Session
A TMS mapping session normally lasts longer than your follow-up appointments. Plan on it taking about 45 to 60 minutes. You should expect a quiet room, a chair that reclines, and earplugs to block out the clicking sounds. The first steps are:
- Set-up & explanation: The technician or physician will explain the technique and put a soft cap on the head or label the scalp to keep track of where the coil is.
- Finding the motor hot spot: The coil goes over the motor strip, which is across the top of the head. The doctor watches for small twitches in the fingers or thumbs while giving short pulses. The motor hot spot is the place where movement happens all the time.
- Measuring motor threshold: The minimum amount of pulse intensity that reliably causes a muscle response is found by small changes in pulse intensity (usually done using EMG sensors). That % is your motor threshold, which helps you figure out how much DLPFC treatment you need.
- Locating the DLPFC: The doctor uses the motor hotspot as a guide to find the DLPFC for treatment and marks it so that it stays the same across sessions.
- Plan & schedule: You’ll go over the treatment plan (how many sessions and when) and any questions you have about side effects or logistics.
If changes are needed, mapping may be done again later in the course. However, for most people, the first session gives them long-lasting targeting advice.
Why The Motor Hot Spot and Motor Threshold Matter
Two practical reasons:
- Accuracy of targeting. The DLPFC is not a single area; because people have different body shapes and sizes, a “one-size-fits-all” site is not ideal. When physicians use the motor hotspot as a guide, they can put the coil where it will best reach the DLPFC.
- Personalized dosing. The motor threshold tells you how easily your cortex responds to stimuli physically. The team doesn’t guess the dose; instead, they use your motor threshold to create a safe, effective intensity. This is the difference between generic stimulation and brain-mapping treatment that is made just for you.
How Long is Each TMS Session, and How Many Treatments Do People Usually Get?
After the mapping visit, standard rTMS procedures call for follow-up TMS treatments that last about 20 to 30 minutes, but some regimens are different. For major depressive disorder programs, many clinics provide a course of five sessions per week for around six weeks, which adds up to about 36 sessions in total. The actual number of sessions will depend on the protocol utilized and how well you respond to treatment. Your doctor will talk to you about the exact plan and how progress will be measured.
What Does Mapping Feel Like? Is It Painful?
It shouldn’t hurt to map. Most individuals say they feel a tapping or light discomfort on their scalp while the pulses are being sent. A few people get a little headache or sore scalp afterward, but this is usually tolerable with over-the-counter painkillers. Your doctor will utilize the lowest intensity that works to get the motor response. If you still feel pain, the team can change the position of the coil or the stimulation parameters. Serious adverse effects are infrequent (seizures are possible but not common, and are checked for ahead of time).
Who is TMS Appropriate For?
The FDA has approved TMS for several uses, including treatment-resistant major depressive disorder and, more recently, various OCD regimens. People commonly think about it when regular medication and therapy don’t work well enough or when the side effects of the medication are too bad. Your psychiatrist or TMS provider will look at your medical history, including any implants, the risk of seizures, and your medication profile, to make sure that you are a good fit.
Safety Notes and Side Effects
Mild headaches, soreness in the scalp, and temporary twitching of the face muscles are common effects that don’t last long. Seizures and other significant dangers are rare, although they may be more likely to happen if there are risk factors that haven’t been tested for (like a history of epilepsy or particular implants). Clinics do extensive screenings and customize the TMS mapping session to lower the risk. If you have metal implants, are pregnant, or have a history of seizures, tell your doctor right away. They will tell you about safe or other treatment options.
Practical Tips For Your Mapping Visit
- Bring a list of all the medications you’re currently taking, as well as any medical records about seizures, implants, or brain surgery.
- Wear comfortable clothes and stay away from heavy hair products that could get in the way of coil contact.
- The first appointment should last approximately an hour, and short follow-ups usually last 20 to 30 minutes.
- If it matters to you, ask your clinic if they use neuronavigation or MRI guidance.
- Tell the staff if you’re nervous. Most centers will walk you through each process and can slow down or stop if you need to.
Begin Your Personalized TMS Journey with Joanne Martelli, PMHNP
A TMS mapping session is the first step toward a treatment plan that is right for your brain activity if you are thinking about TMS therapy. This method makes sure that everything is correct, comfortable, and works well, which will help you obtain the best outcomes from your TMS sessions.
I’m available for evaluation and consultation if you need a referral or help figuring out if TMS could be right for you. I have been a psychiatric nurse practitioner for more than 12 years, and I help my patients figure out what their options are and how to get better. Call my office at (623) 692-9933 to learn more or set up your TMS appointment. This is the first step toward better mental health.
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