TMS (Transcranial Magnetic Stimulation) is a neurostimulation technique that uses magnetic field generators (in the form of coils) to emit targeted electrical currents that stimulate the cortex. TMS is believed to improve neurological functioning via stimulating activity in hypoactive regions of the brain that are contributing to a particular pathology. For example, individuals with depression often exhibit hypoactivation of the left prefrontal cortex.
Targeting the left [dorsolateral] prefrontal cortex with high frequency TMS tends to activate neurons in this region, ultimately upgregulating cortical activity. The upregulation of cortical activity and release of neurotransmitters facilitates mood improvement. For this reason, the FDA approved the first TMS device called the “NeuroStar” in 2008 for the treatment of depression.
Many individuals find TMS for depression appealing due to the fact that it isn’t associated with significant side effects such as dry mouth, weight gain, and sexual dysfunction – as are commonly experienced on pharmaceutical drugs. While TMS is often an effective non-pharmacological treatment for those with depression, it doesn’t work for everyone. Furthermore, despite the fact that TMS doesn’t involve ingestion of exogenous drugs, the technique can still cause (potentially unwanted) side effects.
Factors that influence TMS side effects
It is important to consider several factors that influence side effects of TMS. These factors include: the type of TMS therapy, parameters, and competency of the TMS practitioner. In addition, it is important to understand that individual variation (genetics, habits, lifestyle) may indirectly influence the intensity, duration, and number of side effects that you experience.
TMS Device Settings
Most TMS devices are preprogrammed with ideal parameters for stimulation. These preprogrammed parameters make it relatively easy for professionals to follow in terms of administration. As of present, there is solely one device called the “NeuroStar” approved for the treatment of depression, and specific parameters must be followed by professionals.
However, assuming one of these parameters is slightly adjusted and/or a new type of TMS stimulation is being tested – there may be more (or less) likelihood of side effects. For example, most research suggests benefit of stimulating the left prefrontal cortex with high frequencies for depression, but another set of parameters involving stimulation of the right prefrontal cortex with low frequencies has demonstrated efficacy; these tactics may yield different side effects.
- Coil types: Expect there to be some diversity of TMS coils on the market in forthcoming years. The variation in the types of coils used are known to generate slightly different effects on the brain, contributing to different side effects. Coil types are subject to variation based on their shape (structure), materials, and specific pulses they emit. Examples of different types of coils include: H-coils, figure-eight coils, and iron-core coils.
- Duration of session: For TMS to elicit a therapeutic antidepressant effect, sessions are typically conducted between 20 and 60 minutes. The longer the session, the increased likelihood of side effects due to increased length of neural stimulation. The shorter the session, the less likely you’ll be to experience long-lasting side effects.
- Frequency: Some believe that the higher the frequency of stimulation, the greater likelihood of side effects. High frequency stimulation is typically conducted on the left hemisphere, and an example of a frequency used for stimulation could be 10 Hz. Low frequency is typically conducted on the right hemisphere, and an example could be something like 1 Hz. It is important to note that as of 2015, solely the 10 Hz frequency has been approved by the FDA for the treatment of depression. All other frequencies are deemed “off-label” until they are proven effective.
- Intensity: The intensity of the magnetic pulses can be programmed, but in many cases they are preprogrammed. For experimental research, the recommended intensity output is between 50% and 70% of maximum capacity. Some researchers have worked with higher degrees of intensity, possibly increasing the reported rates of side effects.
- Localization: Prior to the procedure, professionals should locate the precise region of the brain that is being stimulated. Due to individual differences in anatomy, an expert should not simply “guess” where to place the coil for the TMS procedure. The usage of fMRI neuroimaging is beneficial to pinpoint the specific region that will require stimulation. In some cases the localization is based on “standard space coordinates” which may lack accuracy.
- Pulsation intervals: The intervals between TMS pulsations can be adjusted by professionals conducting experiments. The FDA approved TMS device called the “Neurostar” has a specific interval of pulsations that must be followed. That said, any “off-label” or experimental adjustments in pulsation intervals (milliseconds) may increase and/or decrease likelihood of side effects.
Competency of practitioner
Most practitioners of TMS are well-educated and informed regarding best practices. In other words, they will inform their patients of the potential risks and do everything in their power to minimize risk of side effects and/or adverse reactions for their patients. Prior to treatment with TMS, they will conduct a neurological screening to ensure that the patient is an ideal candidate for treatment based on medical history.
Additionally, the practitioner should know how to properly program and utilize the TMS unit. Improper programming of parameters may result in inadequate therapeutic response, and increase likelihood of side effects and/or adverse reactions. For example, if a practitioner isn’t following a proven protocol such as high-frequency stimulation to the left dorsolateral prefrontal cortex – side effects may be more likely.
Failure to properly position the TMS unit and/or negligence on the part of the professional could increase likelihood of side effects. Therefore, it is imperative to work with a highly-trained, skilled, and seasoned TMS practitioner rather than someone less qualified. Practitioners of lesser competence and/or with poorer attention to detail may increase risk of side effects.
Type of TMS therapy
There are two primary types of TMS that are currently approved for the treatment of psychiatric disorders. Standard, repetitive TMS involves repeated stimulation to the left dorsolateral prefrontal cortex at high frequencies. Sessions with rTMS typically last between 20 and 60 minutes.
By comparison, deep TMS sessions are thought to last 15 to 20 minutes, and penetrate the cortex approximately 3 times the extent of rTMS. The deeper stimulation of cortical regions may trigger more side effects. In addition, rTMS is thought to be more targeted, whereas with deep TMS, the specific regions being stimulated aren’t as well understood – this could lead to slightly different side effects between the two techniques.
- Standard rTMS: Standard TMS stimulates the brain up to 2.5 cm beneath the cortex. This effect is considered targeted, but limited to neurons within the outermost regions of the cortex. It is thought that since neurons deeper within the cortex aren’t directly stimulated, there’s less likelihood of side effects. Therefore standard rTMS may carry less side effects than deep TMS.
- Deep TMS: Deep TMS may trigger different side effects than standard, repetitive TMS due to the fact that it delivers an effect deeper beneath the cortex. Compared to repetitive TMS which only penetrates the cortex up to 2.5 cm, it is suggested that deep TMS penetrates up to 6 cm – stimulating deeper regions of the brain. The fact that deep TMS stimulates portions of the brain that aren’t stimulated by rTMS could trigger different side effects.
It is important to consider that your specific TMS regimen may be responsible for triggering certain side effects. The number of pulsations (stimulations) per session, how frequently you engage in TMS, and total number of sessions may influence side effects. Those that engage in more sessions have stimulated their brain to a greater extent, which could increase (or even decrease) side effects depending on individual neurological changes.
- Pulsations per session: Most practitioners follow an FDA approved protocol for the treatment of depression and deliver the same number of pulsations per session to all clients. That said, despite following a protocol, there could be some variability between number of pulses per session based on how a client feels. In addition, pulses may be tweaked during clinical trials and/or research experiments. It is important to consider that the number of pulsations could influence side effects.
- TMS scheduling: TMS is typically scheduled as a daily treatment for a period of 4 to 6 weeks. Someone who receives treatment daily for several weeks may adapt to the treatment and find that side effects improve over time. In other cases, an increase in the number of TMS sessions may exacerbate existing TMS-induced side effects. Adjusting the scheduling of TMS may aid in reduction of side effects.
Note: Current TMS schedules require daily treatment for 4 to 6 weeks, but should research determine that other scheduling protocols (e.g. every other day or bi-weekly) are effective, perhaps these can be utilized with success among those who dislike daily treatments.
In some cases, two individuals may receive TMS from the same practitioner, targeting the same cortical site (e.g. left DL-PFC), with the same parameters. However, these two individuals may report notable differences in TMS side effects. One person may experience a headache, dizziness, and toothache, while the other may feel a little lightheaded with no other effects.
It is important to consider that individual brain structure, drug interactions, genetics, perception, and even the time of day TMS is administered – may all influence perceived side effects. Two individuals receiving TMS could have very different baseline neurophysiological patterns – one person may be depressed from hypoactivation of the left prefrontal cortex, while the other may exhibit limbic dysfunction causing them to feel depressed.
These differences in baseline neurophysiology may subtly influence side effects that a person experiences. Certain patterns of neurological activity based on neuroimaging may be more (or less) likely to experience substantial side effects. Moreover, it is also important to consider that the side effects attributed to TMS may be due to another factor (e.g. medication).
TMS Side Effects & Adverse Reactions (List)
Below is a comprehensive list of side effects and adverse reactions that have been reported after transcranial magnetic stimulation (TMS). Keep in mind, most people do not experience every single side effect listed below and some people experience no side effects at all. Most common side effects associated with TMS are headaches and scalp discomfort – both of which tend to subside after the first week of treatment.
- Anxiety: The idea of getting your brain jolted with electricity generated by magnetic pulses may provoke a bit of fear prior to treatment. It is common to feel anxious before your first treatment, and especially during the first week of treatment. Most people find that the TMS improves their level of anxiety, but certain side effects and/or the thought that your brain is getting jolted may trigger anxious thinking. As you become more comfortable with the treatment, anxiety levels should diminish.
- Discomfort: For certain individuals, the neurostimulation from TMS therapy is uncomfortable. This discomfort is generally most intense across the scalp region and may linger after each of your sessions. While it is rare for discomfort to become extreme, a small percentage of individuals discontinue TMS because their scalp burns, they have a headache, and notice skin irritation. Coil positioning and stimulation settings can often be tweaked to minimize likelihood of discomfort.
- Dizziness: Many patients report dizziness during the TMS procedure and following each session. The dizziness is generally transient and may fade within minutes and/or hours after administration of TMS. Others may notice that dizziness lingers for a longer duration, but as they adapt to the stimulation, the feelings of dizziness subside.
- Eye pain: It is estimated that eye pain occurs in less than 5% of all patients receiving TMS. Some people report transient pain behind their eyes that tends to subside after several weeks. This pain is thought to be at its peak immediately after treatment, and gradually gets better with time. Others may notice that they experience pain in just one eye, which could be related to the portion of the cortex receiving stimulation.
- Facial pain: Despite the fact that your face isn’t being directly stimulated by the TMS unit, the neural stimulation may have widespread effects which could impact your face. For this reason, many individuals report facial pain following a TMS session. The facial pain is usually mild to moderate intensity and not severe. The sensation of facial pain is thought to last a week or two before diminishing.
- Facial twitching: Some sources estimate that 1 out of 3 individuals experience “facial twitching” during and/or after TMS sessions. This twitching in the facial muscles is caused by intense electrical stimulation that penetrates the cortex. Most people are able to tolerate a bit of twitching and find that the twitches improve over time.
- Fainting: Another extremely rare adverse effect from TMS is the risk of fainting. Fainting may be caused by a variety of things including: intense pre-TMS anxiety, neural stimulation and cascade effects, and/or drops in blood pressure during treatment. It should be reiterated that fainting is highly unlikely to occur during TMS.
- Headaches: Among the most common side effects reported by those receiving TMS is that of headaches. The headaches experienced as a result of TMS are usually of mild to moderate intensity, but in rare cases may be severe. For most individuals, headaches are most intense during the early stages of treatment and improve after several weeks. It is important to mention that some people notice improvement of preexisting headaches after TMS.
- Hearing loss: The pulses generated by the TMS coils are thought to range from 80 decibels to 92 decibels – depending on the programmed settings. Therefore, it is highly recommended to wear earplugs (or some form of hearing protection) to minimize likelihood of noise-induced hearing loss. Most professionals require patients to wear hearing protection throughout the procedure so that they can walk away with normal hearing. Should you fail to properly insert your ear plugs and/or not wear them at all – you run the risk of TMS-induced hearing loss.
- Lightheadedness: A fairly common side effect associated with TMS is lightheadedness. The lightheadedness may be accompanied by a headache and dizziness. It could occur during TMS therapy or may emerge after a session. It may also occur during therapy and linger for awhile after each session. Most people don’t have an issue tolerating temporary bouts of lightheadedness.
- Mania: Most studies suggest that TMS isn’t likely to provoke mania in an individual suffering from the depressive phase of bipolar disorder. That said, an extremely rare potential adverse reaction is “mania” triggered by TMS. Understand that mania or hypomania could theoretically emerge temporarily among individuals without bipolar disorder. As the brain recalibrates itself following TMS, the mania may be transient. That said, should you or a practitioner notice mania, it is important to seek professional help.
- Memory impairment: Some reports have documented the possibility of temporary memory impairment as a result of TMS. Understand that memory impairment is considered a rare adverse reaction and transient in nature. In other words, even if your memory is temporarily jumbled from TMS, there’s no evidence to suggest that this effect will linger. In fact, some reports suggest TMS may improve memory.
- Nausea: Some people end up feeling nauseated as a result of TMS. This nausea is thought to be more common in the early weeks of treatment due to the fact that the brain is not accustomed to the external stimulation. A combination of side effects such as lightheadedness, dizziness, and headaches could exacerbate these temporary bouts of nausea. The nausea is generally not severe enough to provoke vomiting.
- Numbness: TMS may cause a person to feel numbness in the head and/or facial regions during (or after) treatment. While tactile sensation isn’t usually lost, a person may feel as if it is blunted, particularly in the area of the head exposed to the TMS. In rarer scenarios, individuals may notice that the numbness affects other regions of the body.
- Scalp pain: You may notice that your scalp feels incredibly painful during TMS and/or post-procedure; this is an extremely common side effect. This pain may be concentrated in the area of the head positioned beneath the coil, but may also be prominent across a wider portion of the scalp. The pain may be of moderate severity, but could be more intense for certain individuals.
- Seizures: The risk of experiencing a seizure from TMS therapy is approximately 0.1% – meaning it is highly unlikely. That said, assuming you have epilepsy and/or a history of seizures, it is important to discuss this with your TMS practitioner. In a clinical trial of over 10,000 TMS treatments – no seizures were reported. Therefore, seizures should be considered an extremely rare adverse reaction.
- Skin pain: A relatively odd sensation that some people notice during TMS and/or after the procedure is skin pain. This skin pain may be accompanied by irritation, and most commonly occurs in the location of the scalp subjected to the stimulation. However, for other individuals the pain may be more widespread.
- Spasms: Some people experience facial spasms and/or spasms in other bodily regions as a result of TMS. These spasms may be uncomfortable for certain individuals, but they are generally not a major concern. Spasms in certain regions such as the face are fairly common, but do not typically persist for an extended duration of time.
- Tingling: It is possible to notice a tingling sensation throughout your head during TMS and after the procedure. This tingling is a side effect of small-scale electrical stimulation and neurological changes facilitated by the TMS procedure. Tingling sensations are generally well-tolerated and subside after a person has completed treatment.
- Tinnitus: An adverse effect of TMS is that of tinnitus or “ringing in the ears.” Some individuals find that TMS actually helps preexisting cases of tinnitus, but it may exacerbate it in others. Obviously the primary culprit for tinnitus as a result of TMS could be due to improper installation of hearing protection (ear plugs) or failure to wear hearing protection. Protect your ears throughout treatment and this adverse effect is usually avoided.
- Toothache: If you notice that you develop a toothache (or all of your teeth ache) following TMS, you are not alone. A small percentage of those engaging in TMS notice that their teeth feel funky and/or start to hurt after the stimulation. This is a side effect that occurred in clinical trials at double the rate of a placebo (sham-TMS), but only affects less than 5% of people.
- Vision problems: Temporary changes in your visual field may be noticed immediately after TMS. These visual abnormalities aren’t thought to be actual problems with your eyes, rather changes in brain functioning as a result of the TMS. Alterations in regional activation and neurotransmission may trigger things like blurred vision and/or eye floaters – both of which normalize in time.
How long do TMS side effects last?
Most evidence supports the idea that side effects from TMS are most prominent during the first 2 weeks of treatment. Individuals receiving TMS often notice that side effects emerge and are most intense within the first week of treatment. After a full week of treatment, many report that side effects have significantly diminished and/or completely subsided.
In other cases, side effects may linger for 2 to 3 weeks, but clear up halfway through the 4 to 6 week treatment schedule. It is relatively uncommon for severe side effects to persist throughout an entire 6 week treatment protocol. Even then, many of these individuals notice that the side effects diminish quickly upon completion of the full 6-week treatment protocol.
Assuming you are experiencing severe TMS-induced side effects, it is important to communicate them to your practitioner. Some people find that taking an over-the-counter medication can combat certain symptoms, especially headaches. Proper sleep, diet, and exercise can also be extremely helpful for recovery from and prevention of side effects.
Do the benefits of TMS outweigh the side effects?
Most people who partake in TMS therapy end up completing an entire 4 to 6 week protocol of daily sessions. Only a very small percentage of those who engage in TMS find that the side effects are so intense, that treatment must be discontinued. Assuming you’ve tried TMS for a condition like depression, it is always important to evaluate whether the attained benefits of TMS outweigh the side effects (and financial costs).
If you’ve tried medication after medication without satisfactory symptomatic relief, any improvement in mood derived from TMS may be considered so monumental, that a person may not even care about side effects. Assuming TMS therapy significantly improves your mood, you may be willing to put up with every side effect in the book; it may be a worthy sacrifice. On the other hand, if you only attain marginal mood improvement, side effects may not be justified.
Since most people don’t experience significant or unwanted side effects from TMS, the benefits usually end up outweighing side effects for the majority of individuals. That said, if side effects are severe and minimal (or no significant) benefit is derived from TMS, you may want to pursue other treatment modalities in the future.
Have you experienced any side effects from TMS?
An appealing aspect of TMS is that it isn’t associated with significant side effects. Upon comparison to pharmaceutical antidepressant side effects that can include: weight gain, sexual dysfunction, stomach aches (gastrointestinal pain), constipation, diarrhea, and dry mouth – TMS side effects are considered relatively benign. For this reason, many people are often willing to give TMS a shot over pharmacological options.
Assuming you’ve used transcranial magnetic stimulation for the treatment of depression, mention whether you’ve experienced any side effects in the comments section below. If you experienced side effects, discuss: when you first noticed them, whether they persisted throughout treatment (or diminished), as well as their intensity. Also share whether the side effects lingered after the 4 to 6 weeks of treatment and/or whether you ever contemplated discontinuing TMS as a result of side effect severity.