Background

When repetitive transcranial magnetic stimulation (rTMS) is used to treat medication refractory depression, the treatment pulse intensity is individualized according to motor threshold (MT). This measure is often acquired only on the first day of treatment, as per the protocol currently approved by Food and Drug Administration.

Objective

Here, we aimed to assess daily MT variability across an rTMS treatment course and simulate the effects of different schedules of MT assessment on treatment intensity.

Methods

We conducted a naturalistic retrospective study with 374 patients from a therapeutic rTMS program for depression that measures MT daily.

Results

For each patient, in almost half the TMS sessions, MT varied on average more than 5% as compared to the baseline MT acquired in the first treatment day. Such variability was only minimally impacted by having different TMS technicians acquiring MT in different days. In a smaller cohort of healthy individuals, we confirmed that the motor hotspot localization method, a critical step for accurate MT assessment, was stable in different days, arguing that daily MT variability reflects physiological variability, rather than an artifact of measurement error. Finally, in simulations of the effect of one-time MT measurement, we found that half of sessions would have been 5% or more above or below target intensity, with almost 5% of sessions 25% above target intensity. The simulated effects of weekly MT measurements were significantly improved.

Conclusions

In conclusion, MT varies significantly across days, not fully dependent on methods of MT acquisition. This finding may have important implications for therapeutic rTMS practice regarding safety and suggests that regular MT assessments, daily or at least weekly, would ameliorate the effect.

中文翻译：

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rTMS 治疗抑郁症期间运动阈值的日常变异性：临床意义

背景

当重复经颅磁刺激 (rTMS) 用于治疗药物难治性抑郁症时，治疗脉冲强度根据运动阈值 (MT) 进行个体化。根据食品和药物管理局目前批准的方案，该措施通常仅在治疗的第一天获得。

客观的

在这里，我们旨在评估 rTMS 治疗过程中的每日 MT 变异性，并模拟不同 MT 评估时间表对治疗强度的影响。

方法

我们对 374 名来自抑郁症治疗性 rTMS 计划的患者进行了一项自然回顾性研究，该计划每天测量 MT。

结果

对于每位患者，在几乎一半的 TMS 会话中，与在第一个治疗日获得的基线 MT 相比，MT 平均变化超过 5%。让不同的 TMS 技术人员在不同的日子获得 MT 对这种可变性的影响很小。在一小群健康个体中，我们证实运动热点定位方法是准确 MT 评估的关键步骤，在不同的日子里是稳定的，认为每日 MT 变异性反映了生理变异性，而不是测量误差的产物。最后，在模拟一次性 MT 测量的效果时，我们发现一半的训练会高于或低于目标强度 5% 或更多，几乎 5% 的训练会高于目标强度 25%。每周 MT 测量的模拟效果显着改善。

结论

总之，MT 在几天内变化很大，并不完全依赖于 MT 获取方法。这一发现可能对治疗性 rTMS 实践的安全性产生重要影响，并表明每天或至少每周定期 MT 评估会改善效果。