Motor and phosphene thresholds to transcranial magnetic stimuli: a reproducibility study.
OBJECTIVE
As repetitive transcranial magnetic stimulation (rTMS) is often applied on different days, it is of interest to know whether motor (MT) and phosphene (PT) thresholds are reproducible across time and whether the intensity determined on the first day can be used in subsequent sessions.


METHODS
We studied MT and PT over 5 separate recordings in 10 healthy volunteers using a focal coil and a Magstim(Rapid stimulator. After the initial recording (session 1), the others (2 to 5) were performed respectively after 1 day, 7 days, 1 month and 4 months.


RESULTS
Mean MT at rest were 65.30 +/- 5.54%, 65.7 +/- 7.18%, 60.4 +/- 4.27%, 61.8 +/- 4.34%, and 63 +/- 9.1% at sessions 1 to 5. Mean PT were 71.43 +/- 6.68%, 66.29 +/- 10.67%, 60.71 +/- 8.64%, 60.57 +/- 8.08%, and 68.71 +/- 15.48% at sessions 1 to 5. MT and PT were reproducible (ANOVA analysis), however, as shown by coefficients of variation, variability between the first 3 sessions exceeded 10% for MT in 3 subjects and in 4 subjects for PT.


CONCLUSIONS
It seems preferable to determine thresholds and adapt output intensity of the stimulator at each rTMS session.
Fumal
A
A
Departments of Neurology, Neuroanatomy, University of Liège, B-4000 Liège, Belgium.
Bohotin
V
V
Vandenheede
M
M
Seidel
L
L
Maertens de Noordhout
A
A
Schoenen
J
J
D000328:Adult; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D010719:Phosphenes / Q000502:physiology*; D015203:Reproducibility of Results; D012684:Sensory Thresholds / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*