Risks and Side Effects
While rare, seizures have been known to occur in association with TMS treatment. The estimated average risk is approximately 1 seizure per 50,000–60,000 sessions in patients without seizure risk factors such as brain lesions or epilepsy (Rossi et al., 2009; Lerner et al., 2019). Although this risk is low, it is not entirely preventable, even in low-risk populations. To further minimise the risk, patients must inform staff of any changes in their alcohol or drug use, significant reductions in sleep (less than 4 hours per night), or excessive caffeine intake. These factors can increase the likelihood of a seizure and may require adjustments to the treatment protocol. Failure to disclose this information may increase the risk of complications
As per the RANZCP 2024 guidelines, "There are minimal risks with rTMS and any side effects are usually mild, transient and/or can be easily managed. The most commonly reported side effects with rTMS include local scalp pain or discomfort, headache, fatigue and facial muscle twitching during stimulation. The rate of clinical trial discontinuation due to adverse effects across 93 randomised controlled trials was 2.5% in patients receiving active, compared to 2.7% in patients receiving sham stimulation, supporting an excellent safety profile (Zis et al., 2020). "
About 1 in 3 patients undergoing this procedure may experience scalp or facial discomfort at the treatment site. If this occurs, please inform your TMS clinician, who may adjust the magnetic field dose or reposition the coil to help alleviate it. Some patients may experience temporary headaches, temporary fatigue, temporary insomnia or lightheadedness. Often a change in the position of the coil can alleviate this. Facial muscle twitching during treatment sessions (not afterwards) is common and normal given the proximity of the coil to your facial muscles. Rarely, patients may experience referred facial/tooth/jaw/ocular pain. If this occurs please notify your clinician and they will change the position of the coil.
Some patients experience an exacerbation or recurrence of previous symptoms during the early phase of treatment, presenting as "dips in mood" or mood changes (for example). There is also a small risk of inducing mania, particularly but not limited to those patients with a history of bipolar affective disorder. If either of these events occur, please notify your TMS clinician and they will assist you.
TMS should not be used by anyone who has magnet-sensitive metal in their head or within 30 cm of the TMS coil that cannot be removed. Failure to follow this restriction could result in injury. Please inform your psychiatrist if you have any metal objects or devices in your body that may be sensitive to magnets. These may include, but are not limited to, aneurysm clips, brain stents, implanted stimulators, electrodes, ferromagnetic implants in the ears or eyes, shrapnel in the head or neck area, or any other metal implants in the head.
There have been isolated case reports in the medical literature of exacerbated and persistent tinnitus, chronic headaches, prolonged photophobia, and retinal detachment following TMS. While these events are considered very uncommon, their exact frequency is not known, particularly with the newer theta burst or accelerated protocols, which have been less extensively studied compared to traditional TMS protocols. While no definitive causal relationship has been established, patients with pre-existing retinal conditions or a history of eye surgery are advised to discuss this risk with their treating psychiatrist prior to commencing treatment. If any visual disturbances occur during or after treatment, patients should notify their psychiatrist immediately.
It is important to notify your TMS psychiatrist if you are pregnant. The risk-benefit analysis for continuing TMS may change. TMS may be continued in certain circumstances, but how it is conducted may also change. Therefore, the TMS psychiatrist must be informed of any pregnancy as soon as possible, and treatments should be paused until a discussion with the psychiatrist takes place.
Effectiveness and Patient Experience
It is not possible to provide any guarantee that the TMS treatment will be successful. TMS treatment is not a cure, and future relapse remains possible. Treatment outcomes will also vary between individuals.
Clinical experience indicates that most patients who respond positively to a course of TMS are likely to respond similarly in the future. However, this is not guaranteed for all patients, and individual responses to repeat treatments may vary.
For most patients, the repeat course of TMS will be administered in a manner similar to the original treatment. As a result, the patient's experience, including potential side effects, is likely to resemble what they experienced during their initial TMS treatment.
The TMS team will apply their professional skill and judgment, but like many medical treatments, TMS comes with an inherent degree of risk that cannot be removed entirely.
Accelerated TMS protocols (aTMS)
In certain circumstances, we may conduct more than one TMS session per day. This is known as an Accelerated TMS protocol. While aTMS can provide similar clinical outcomes to standard TMS protocols in a shorter timeframe, it may increase the likelihood of experiencing certain TMS-related risks or side effects. According to the 2024 RANZCP guidelines:
“Several studies have indicated that accelerated forms of rTMS and TBS can achieve similar clinical outcomes requiring fewer treatment sessions. Accelerated TMS (aTMS) studies had similar seizure and side effect incidence rates to those reported for once daily rTMS.”
“Accelerated TMS (aTMS) studies had similar seizure and side effect incidence rates to those reported for once daily rTMS. One seizure was reported from aTMS (0.0023% of aTMS sessions, compared with 0.0075% in once daily rTMS). The most common side effects were acute headache (28.4%), fatigue (8.6%), and scalp discomfort (8.3%), with all others under 5% (Caulfield et al., 2022).”
However, patients should be aware that aTMS involves a higher intensity of stimulation in a shorter period, which may lead to a greater accumulation of side effects, such as increased fatigue or headaches, compared to the standard protocol.
While the safety profile of aTMS is promising, less research overall has been conducted on aTMS compared to the standard protocol. As a result, its evidence base is less robust, and certain long-term risks remain less well understood. Further research is ongoing to determine the safest and most effective accelerated protocols.
Hearing
Protection
TMS machines emit a loud click with each magnetic pulse. Although quieter than models used in the past, there is still a risk to hearing that can be mitigated using hearing protection. As per Rossi 2021 et al , " When hearing protection was used, as in the majority of studies, no change in hearing sensitivity after TMS has been reported (Pascual-Leone et al., 1992; O’Reardon et al., 2007; Janicak et al., 2008). When changes in hearing have occurred in the past, studies such as Kujawa and Liberman et all have suggest the effects on auditory systems were temporary."
Wearing ear protection, specifically earplugs, is therefore a required part of the TMS treatment protocol. Patients are strongly advised to use the earplugs provided during all TMS sessions. If you choose to decline the use of ear protection, you do so against medical advice. By declining ear protection, you acknowledge and accept full responsibility for any potential adverse outcomes, including but not limited to the worsening of tinnitus, hearing loss, or other auditory complications.
If you choose to decline ear protection, you will be required to sign a waiver confirming your decision and assumption of all associated risks. Please notify your TMS nurse or clinician immediately if you experience any auditory discomfort or changes during or after the treatment