Facial Numbness is NOT a Common Side Effect of TMS
Facial numbness is not reported as a common adverse effect of transcranial magnetic stimulation (TMS) treatment. The most frequently reported side effects are headache, scalp discomfort at the stimulation site, and local muscle twitching—not facial numbness 1.
Common Side Effects of TMS
The well-established side effect profile of TMS includes:
- Headache (23-50% of sessions): Typically mild to moderate, transient, and responsive to simple analgesics 2, 3, 4
- Local scalp discomfort/pain at the stimulation site (17% of sessions) 2, 4
- Muscle twitching (43% of sessions): Local to the stimulation area, transient 2, 4
- Fatigue (50% of sessions) 4
- Dizziness 5
These side effects are generally mild, occur most commonly during or immediately after the first few sessions, and resolve spontaneously 2, 3.
Why Facial Numbness is Not Expected
The mechanism of TMS involves electromagnetic induction that stimulates neurons beneath the coil placement 1. The ancillary effects include auditory and somatosensory responses from the clicking sound and mechanical vibrations, and potentially activation of cranial nerves depending on coil location 6. However, numbness—which would indicate sensory nerve dysfunction or blockade—is not part of the expected physiological response to TMS.
Important Caveat: Facial Nerve Stimulation
While facial numbness is not a typical side effect, TMS can cause facial muscle activation when the coil is positioned near facial motor areas. One case report documented trigeminal autonomic cephalalgia (headache with autonomic features like lacrimation) after rTMS 5, but this involved pain and autonomic symptoms, not numbness.
If a patient reports facial numbness during TMS treatment, consider alternative explanations such as coincidental Bell's palsy, anxiety-related paresthesias, or positioning-related nerve compression during the treatment session. This symptom warrants clinical evaluation separate from the TMS procedure itself, as it is not causally linked to the stimulation 1.
The safety profile of TMS across over 10,000 treatment sessions shows no pattern of facial numbness as an adverse event 3, and comprehensive safety guidelines do not list this as a concern requiring monitoring 1.