The repeatability of corticomotor threshold measurements

Area of Science:

• Neuroscience
• Neurophysiology
• Clinical Research

Background:

• Motor threshold (MT) is a critical neurophysiological parameter in transcranial magnetic stimulation (TMS) studies.
• Assessing the repeatability of MT measurements is essential for reliable longitudinal research and clinical applications.

Purpose of the Study:

• To investigate the repeatability of motor threshold (MT) measurements in healthy subjects over extended time intervals.
• To evaluate the influence of age, threshold magnitude, and test-retest interval on MT repeatability.
• To assess the adequacy of using a fixed stimulation point for measuring corticomotor threshold topography.

Main Methods:

• 82 healthy subjects underwent baseline MT assessment using a figure-of-eight coil.
• Six retest sessions were conducted at intervals ranging from 19 minutes to 1867 days.
• Statistical analysis, including repeated measures ANOVA, was used to determine the significance of MT differences.

Main Results:

• No statistically significant differences in MT were observed across all retest sessions compared to baseline (P > 0.05).
• The 95% confidence interval for MT difference indicated high repeatability, with a measurement error upper limit of 8.
• Repeatability was independent of subject age, MT magnitude, and the test-retest interval; a fixed stimulation point was adequate.

Conclusions:

• Motor threshold (MT) is a stable neurophysiological parameter on both individual and group levels.
• The quantified repeatability of TMS-based MT measurements supports its utility in longitudinal studies.
• A fixed stimulation point is a reliable technique for assessing corticomotor threshold topography.