Visualizing the effects of rTMS in a patient sample: small N vs. group level analysis

Area of Science:

• Neuroscience
• Clinical Neurophysiology

Background:

• Transcranial magnetic stimulation (TMS) is increasingly used to measure cortical excitability in various populations.
• Assessing TMS efficacy is challenging due to small sample sizes and response variability.
• Repetitive TMS (rTMS) is a therapeutic intervention requiring sensitive outcome measures.

Purpose of the Study:

• To compare the effectiveness of single-subject statistical analysis versus traditional group-level statistics for detecting changes in cortical excitability.
• To evaluate these statistical approaches in patients with focal hand dystonia undergoing rTMS treatment.

Main Methods:

• A single pulse TMS excitability measure was employed in patients with focal hand dystonia.
• Data were analyzed using both traditional group-level statistics (ANOVA) and single-subject analyses (split middle line analysis).
• Cortical excitability was assessed before and after a course of repetitive TMS (rTMS).

Main Results:

• Single-subject analysis identified significant changes in cortical excitability in 4 out of 5 patients.
• Group-level ANOVA did not detect any statistically significant findings across the patient group.
• Individual data analysis proved more sensitive in detecting treatment effects at the subject level.

Conclusions:

• Single-subject statistical analysis is a valuable tool for assessing cortical excitability changes with TMS, especially in small patient cohorts.
• This approach may help researchers better describe the variable outcomes of rTMS interventions.
• Considering individual responses is crucial for understanding the efficacy of neuromodulation techniques like rTMS.