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Day-to-day variability in motor threshold during rTMS treatment for depression: Clinical implications
Gonçalo Cotovio1, Albino J Oliveira-Maia2, Carter Paul3
1Berenson-Allen Center for Noninvasive Brain Stimulation, Division of Cognitive Neurology, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, 02215, MA, USA; Champalimaud Research & Clinical Centre, Champalimaud Centre for the Unknown, Lisbon, Portugal; Department of Psychiatry and Mental Health, Centro Hospitalar de Lisboa Ocidental, Lisbon, Portugal; NOVA Medical School, NMS, Universidade Nova de Lisboa, Lisbon, Portugal.
Motor threshold (MT) for repetitive transcranial magnetic stimulation (rTMS) treatment in depression varies daily, impacting treatment intensity. Regular MT assessments, daily or weekly, are recommended for safer and more effective rTMS therapy.
Area of Science:
- Neuroscience
- Clinical Psychology
- Medical Technology
Background:
- Repetitive transcranial magnetic stimulation (rTMS) is a treatment for medication-refractory depression.
- Treatment pulse intensity is individualized using motor threshold (MT).
- Current FDA-approved protocols often acquire MT only on the first treatment day.
Purpose of the Study:
- To assess daily MT variability throughout an rTMS treatment course.
- To simulate the impact of different MT assessment schedules on treatment intensity.
Main Methods:
- A naturalistic retrospective study of 374 patients undergoing therapeutic rTMS for depression.
- Daily MT measurements were collected.
- Simulations were performed to evaluate the effects of varying MT assessment frequencies.
Main Results:
- MT varied by over 5% from baseline in nearly half of sessions for most patients.
- Variability was minimally affected by different technicians.
- Simulations indicated that a single MT measurement could lead to significant intensity deviations in many sessions.
- Weekly MT measurements showed improved outcomes.
Conclusions:
- Daily MT variability is significant and not solely due to measurement error.
- This variability has implications for rTMS safety and efficacy.
- Regular MT assessments (daily or weekly) are suggested to optimize rTMS treatment.
