title: Motor potentials evoked by navigated transcranial magnetic stimulation in healthy subjects.
abstract: Navigated transcranial magnetic stimulation (TMS) is a tool for targeted, noninvasive stimulation of cerebral cortex. Transcranial stimuli can depolarize neurons and evoke measurable effects which are unique in two ways: the effects are caused directly and without a consciousness of the subject, and, the responses from peripheral muscles provide a direct measure for the integrity of the whole motor pathway. The clinical relevance of the method has not always been fully exposed because localizing the optimal stimulation site and determining the optimal stimulation strength have been dependent on time-consuming experimentation and skill. Moreover, in many disorders it has been uncertain, whether the lack of motor responses is the result of true pathophysiological changes or merely because of unoptimal stimulation. We characterized the muscle responses from human primary motor cortex system by navigated TMS to provide normative values for the clinically relevant TMS parameters on 65 healthy volunteers aged 22 to 81 years. We delivered focal TMS pulses on the primary motor area (M1) and recorded muscle responses on thenar and anterior tibial muscles. Motor threshold, latencies and amplitudes of motor-evoked potentials, and silent period duration were measured. The correction of the motor-evoked potential latency for subjects' height is provided. In conclusion, we provide a modified baseline of TMS-related parameters for healthy subjects. Earlier such large-scale baseline material has not been available.
authors.affiliation: Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Laura
authors.initials: L
authors.lastname: Säisänen
authors.forename: Petro
authors.initials: P
authors.lastname: Julkunen
authors.forename: Eini
authors.initials: E
authors.lastname: Niskanen
authors.forename: Nils
authors.initials: N
authors.lastname: Danner
authors.forename: Taina
authors.initials: T
authors.lastname: Hukkanen
authors.forename: Tarja
authors.initials: T
authors.lastname: Lohioja
authors.forename: Jouko
authors.initials: J
authors.lastname: Nurkkala
authors.forename: Esa
authors.initials: E
authors.lastname: Mervaala
authors.forename: Jari
authors.initials: J
authors.lastname: Karhu
authors.forename: Mervi
authors.initials: M
authors.lastname: Könönen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007866:Leg / Q000294:innervation*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation*; D050781:Transcranial Magnetic Stimulation