Deep TMS vs TMS2018-10-03T12:05:33+00:00

Is deep TMS different from TMS?

The simple answer is Yes.

But searching for information on our treatment can be confusing – you will likely find information on TMS, rTMS, or deep TMS, and you might see adjectives like superficial, shallow, or repetitive. The following seeks to clarify the differences between Transcranial Magnetic Stimulation (TMS) treatments. 

There are two main types of TMS treatment – both fall under the rTMS, or repetitive TMS category – the first is simply called TMS, while the second is deep TMS. While both can, and are, used for Major Depressive Disorder treatment, research literature indicates a few crucial differences between the two. 

Standard TMS

is often described as being superficial or shallow and uses a figure-8 shaped coil; this coil can reach about 1.1 cm beneath the brain’s surface, and stimulates around 3 cm3 of brain volume1.

Deep TMS

utilizes an H-coil patented by Brainsway that can reach up to 2.8 cm beneath the brain’s surface, and stimulates around 17 cm3 of brain volume1. These numbers have been confirmed by studies that suggest that in order for the figure-8 coil to “reach similar depths…stimulator output would have to be increased beyond safety limits, causing pain and increasing risk of seizure”1. Simply put, in order for TMS to stimulate the same amount of your brain as deep TMS would stimulate, treatment intensity would have to be increased to a dangerous amount.

“in order for TMS to stimulate the same amount of your brain as deep TMS would stimulate, treatment intensity would have to be increased to a dangerous amount.”

This graph shows how the electrical fields produced by TMS (Figure-8 coil) and Deep TMS (H1-coil) decay in the brain. The space above the yellow line indicates effective neuronal stimulation; everything below the yellow line indicates ineffective stimulation to the brain. Where the individual coil lines of decay intersect with the yellow line is the maximum depth for which the depression treatment is effective. 

Studies show that “in an animal model of depression…symptom relief…was critically dependent on the depth of stimulation,”1. The structures that play a large role in depression are situated deep within the brain’s prefrontal cortex, so when the electric field is deeper, the “antidepressant effects of TMS” are enhanced1.

 

Figure 21: This image shows a map of the electric field distributions induced by the Deep TMS and TMS treatments. The measurements come from a study done on simulated human heads (model heads filled with a saline solution similar to that which is found in the brain). The fields were adjusted to meet, but not exceed, 120% of the motor threshold. The red coloring indicates that portion of the electric field is sufficient to induce neuronal activity. The lighter colors show the decreasing effect of the electric field on neurons. 

Figure 31: This image, similar to Figure 2, also measures the strength of the electric field within the brain. However, this model accounts for the “structural and physiological complexities of the skull and brain” while still utilizing the physiological saline solution used before1. Once again, red coloring indicates that the electric field interacts sufficiently with neurons, while the lighter coloring indicates the decay of the electric field and its lessening effect on neurons. 

There are no studies that have been conducted to actively compare deep TMS and TMS. However, to gain FDA-approval, each therapy underwent similar large-scale clinical trials. The results from the “two trails are not strictly comparable, [but] they provide an idea of the general degree of response seen with each intervention”1. 

Response and Remission rates are used to determine how effective a depression treatment is. Response is achieved when a patient has their depressive symptoms improve by at least 50%. Remission is achieved when a patient reaches the point when their symptoms are considered normal mood disturbances or mild. Both Response and Remission are measured using standardized scales. At Prime TMS, we use both Beck’s Depression Inventory (BDI) and the Patient Health Questionnaire (PHQ-9) to measure clients’ improvements during their treatment course.

Because both the BDI and PHQ-9 are recognized as standardized scales, Prime TMS considers both when identifying if clients have achieved Response or Remission. With that in mind, Prime TMS is currently producing a Response rate of 88.2% and a Remission rate of 52.9% from its Lawrence facility (n=17).

Although we have our own results, we encourage potential clients to look at the original studies which granted both TMS and deep TMS FDA-approval. These studies report different numbers than our individual facility, and both were done in a clinical setting that allows them a more direct comparison. 

Both the TMS and deep TMS studies reported their subjects’ Remission rates after receiving 4 weeks of treatments. Exactly 32.6% of the deep TMS therapy subjects who were receiving the actual treatments (not the placebo treatment) reached Remission, while only 7.1% to 9% of the subjects receiving TMS therapy reached Remission1. The TMS study did not report their rates of Response, but in the deep TMS study, a Response rate of 38.4% was achieved1. Using these numbers, we know that 71% of the subjects in the original deep TMS study had between 50% and 100% relief from their depressive symptoms. 

Due to the smaller range of TMS and the figure-8 coil, its targeting is much more localized, and one study indicates that because of that localization, the “target area in as many as two-thirds of clinical trial subjects” is missed1. This would indicate that almost 70% of people who receive superficial TMS treatment (vs. deep TMS) aren’t receiving stimulation in the area that would help alleviate symptoms. 

Comparatively, the H-coil stimulates a broad enough area to “assure to stimulate the relevant prefrontal TMS target areas consistently”1. Both treatments use the same targeting procedure, however, treatments using deep TMS are much more likely to hit the necessary brain structures that would allow for an antidepressant effect. 

In addition to the decreased likelihood of targeting the correct structures, the figure-8 coil is prone to “small displacements of the coil during treatment,” which would then decrease its antidepressant effects even more1. Deep TMS treatment minimizes coil movement and prevents loss of contact between the coil and the client’s head because of the coil being “fitted into a helmet with adjustable straps to fasten the coil securely to the patient’s head,”1. This, paired with the H-coils “deeper and broader” field, make dTMS a far more effective depression treatment.

 

Figure 41: This figure displays an evaluation of TMS targeting accuracy using the standard 5-cm rule, which includes finding the motor cortex and then targeting 5-cm anterior to that initial point. The black dots indicate the initial points found in the motor cortex, the colored dots indicate where the treatment targeted after accounting for the 5-cm rule. The yellow dots indicate a correct targeting of the dorsolateral prefrontal cortex (DLPFC), which is where TMS therapy needs to stimulate in order to be an effective depression treatment. In this study, only 7 subjects received accurate targeting, while the remaining 15 would have received treatment at an ineffective location of the brain1.

Prime TMS is currently producing a Response rate of 88.2% and a Remission rate of 52.9% from its Lawrence facility (n=17).

In Conclusion…

Prime TMS has one mission — provide better depression treatment. Insurance plans have general TMS policies that vary depending on the insurance company. They do not distinguish between TMS and deep TMS, and the treatment regimens are the same. This means that…

either treatment (TMS or deep TMS) will cost the same amount to the client through their insurance; if you are considering trying TMS and there’s no difference in treatment plan or how much it will cost you, wouldn’t you want the best?