rTMS Safety: Side Effects, Precautions and Clinical Assessment

The overall safety picture

When delivered with standard protocols and proper screening, rTMS has a well-characterised and generally favourable safety profile. It has been studied for decades and used clinically across tens of thousands of patients worldwide. That said, it is an active stimulation treatment — 'non-invasive' does not mean 'risk-free', and safety depends on the assessment done before the first pulse is delivered.

Common, usually temporary effects

The most frequent side effects are local and short-lived:

These effects typically reduce over the first few sessions as the scalp adapts and protocol settings are adjusted.

• Scalp discomfort or pain at the stimulation site during or shortly after sessions
• Headache, usually mild and responsive to simple analgesics
• Facial muscle twitching during stimulation
• Occasional lightheadedness or temporary fatigue
• Rarely, mild hearing discomfort if ear protection is not used

Rare but serious risks

The most serious known risk of rTMS is an induced seizure, which is rare — estimated on the order of well under 1 in 1,000 treatment sessions when modern safety guidelines are followed. Other rare events include transient hearing changes (prevented with ear protection) and mania induction in patients with bipolar disorder, which is a known consideration in any activating treatment for mood disorders.

International safety guidelines, most comprehensively the expert consensus published in Brain Stimulation (2021), define safe limits on frequency, intensity, session duration and inter-session intervals for a wide range of populations. A specialist service plans treatment within these limits.

What screening protects against

Before treatment, a structured safety screen covers:

Most patients pass screening without difficulty. Where risk factors exist, the correct response is protocol modification, additional caution, or — in some cases — a decision that another treatment is safer. That judgment is precisely what specialist assessment exists for.

• Neurological history: seizures, epilepsy, head injury, neurosurgery
• Metal or implanted devices in or near the head — cochlear implants, aneurysm clips, deep brain stimulators, some metallic dental or cranial hardware
• Medications known to lower seizure threshold
• Bipolar history and current psychiatric state
• Pregnancy and other medical conditions