What Is Neuronavigation in TMS and Why Does It Matter?

Introduction

Transcranial Magnetic Stimulation (TMS) is a non-invasive treatment that uses magnetic pulses to stimulate specific brain regions. First cleared by the FDA in 2008 for treatment-resistant depression (O'Reardon et. al., 2007) TMS is now also approved for obsessive-compulsive disorder (FDA, 2018) and other indications such as smoking cessation, and migraine with aura (FDA, 2020).

For depression, TMS typically targets the Left Dorsolateral Prefrontal Cortex (DLPFC), a region involved in mood regulation. Current standard methods for locating this target rely on manual measurements of the scalp and other landmarks. This can lead to inaccuracy due to individual differences in brain anatomy. Furthermore, a TMS treatment course includes multiple sessions (usually between 30 to 50), so consistent and accurate coil placement is critical. Neuronavigation helps address this by improving targeting precision and ensuring reproducibility between sessions, even when structural brain imaging is not available. In the sections that follow, we explore how neuronavigation works and what evidence supports its use in clinical practice.

The Basics of TMS Targeting

TMS for depression typically targets the left dorsolateral prefrontal cortex (DLPFC), a brain region involved in mood regulation. Since this area cannotbe directly seen, clinicians estimate its location using external landmarks and scalp measurements.

Two common methods are:

• The 5-cm rule, which places the coil 5 cm forward from the motor cortex (the motor cortex is easier to detect, as stimulating it will result in movement such as a hand twitch), and

• Beam F3, which uses head measurements to approximate the DLPFC location based on distances from landmarks on the head and face area.

These methods are usually done by hand using a treatment cap, introducing room for human error. More importantly, studies show that brain anatomy varies widely across individuals, and these techniques can miss the intended target by several centimeters (Mir-Moghtadei, 2015).

This variability makes a strong case for more precise tools like neuronavigation to improve accuracy and consistency.

What Is Neuronavigation?

Neuronavigation is a technique that improves the precision and consistency of TMS by guiding coil placement relative to the brain’s anatomy. There are two main types: non-imaging-based and imaging-based neuronavigation.

Non-Imaging-Based Neuronavigation

This form of neuronavigation does not require an MRI. Instead, it uses a standardized head model aligned to each patient’s scalp using a dataset. The system tracks the position and angle of the TMS coil in real time and helps the clinician place the coil in the same location and orientation across sessions. This greatly reduces inter-session variability and improves day-to-day reproducibility, even without individualized brain images. It’s like measuring your foot to determine which shoe size and width from what is available in store fits you best.

Imaging-Based Neuronavigation

When a structural MRI is available, neuronavigation can go a step further. The patient’s actual brain anatomy is loaded into the system, and the desired treatment targets, such as the left dorsolateral prefrontal cortex (DLPFC), can be precisely defined. The system then guides the coil directly to that personalized location. This approach offers the highest spatial accuracy and can reduce the chance of stimulating the wrong area due to anatomical variability. To use the same shoe analogy, this is like having a shoemaker make a custom shoe that precisely fits your feet.

How Neuronavigation Enhances TMS

The effectiveness of TMS depends not just on the strength of the magnetic pulses, but also on whether those pulses reach the correct brain region, consistently and accurately.

Neuronavigation enhances TMS in several key ways:

• Improved accuracy: Whether using MRI or a head model, neuronavigation helps ensure that the coil is positioned over the intended brain region rather than an approximation based on scalp measurements.

• Consistency across sessions: Because TMS is delivered over multiple sessions, consistent coil placement is critical. Neuronavigation allows the operator to replicate the coil’s location and angle with precision each time.

• Real-time feedback: The system shows the coil’s position and orientation live on screen, so adjustments can be made immediately if there's drift or movement during a session.

• Reduced operator variability: With manual methods, placement can vary between technicians or even within the same session. Neuronavigation standardizes this process and reduces human error.

In short, neuronavigation does not change the TMS pulses themselves—but like switching from a paper map to GPS, it ensures that those pulses consistently reach the right spot. These advantages can lead to more reliable dosing of stimulation and potentially improved clinical outcomes.

Clinical and Research Evidence Supporting Neuronavigation

Research suggests that neuronavigation can improve the precision of TMS and potentially lead to better outcomes, especially in treatment-resistant depression.

Studies have shown that traditional scalp-based methods can miss the intended target by over 1 cm on average, sometimes more (Trapp et. al., 2020). This spatial error may contribute to variable results. In contrast, TMS with neuronavigation has been linked to stronger engagement of brain regions associated with antidepressant response, such as the subgenual cingulate cortex (Cash et. al., 2019).

Some randomized trials and meta-analyses have found that MRI-guided targeting can improve clinical response and remission compared to standard methods, though results vary based on methodology and population (Herbsman et. al., 2009; Fitzgerald et. al., 2020).

Regulatory and Professional Perspectives

Neuronavigation is not required by the FDA for TMS, and most insurance plans may not cover new brain imaging (MRIs) specifically for this purpose, since it’s not considered mandatory. However, professional groups such as the Clinical TMS Society acknowledge its potential to improve precision and reproducibility. While not standard everywhere, neuronavigation is increasingly used where accuracy is prioritized.

Is Neuronavigation Necessary for Effective TMS?

TMS can be effective without neuronavigation; most FDA-cleared protocols were developed using standard scalp-based methods. However, neuronavigation can offer meaningful advantages in certain cases.

It may be especially helpful in:

• Treatment-resistant depression

• Patients with atypical anatomy or prior neurological conditions

• Or when aiming for greater consistency across sessions or providers

Importantly, MRI-less neuronavigation does not require brain imaging and does not add to the patient’s cost, making it a low-barrier way to improve precision and reproducibility. While not strictly necessary, neuronavigation, (especially non-imaging-based systems, or systems that can utilize previously obtained imaging) offers clear benefits with little downside.

Conclusion

TMS is a proven, non-invasive treatment for depression and other conditions, but its success depends heavily on targeting the right area of the brain consistently and accurately. Neuronavigation enhances this process by improving precision, reducing variability, and helping ensure the treatment is delivered the same way each time.

While not required for effective care, neuronavigation, especially systems that don’t require a new MRI, can offer added value without additional cost. In a field where consistency and accuracy matter, and every bit of symptom reduction translates directly into better quality of life, it's an increasingly important tool for clinics aiming to deliver the highest standard of care.