title: Transcranial magnetic stimulation and brain atrophy: a computer-based human brain model study.
abstract: This paper is aimed at exploring the effect of cortical brain atrophy on the currents induced by transcranial magnetic stimulation (TMS). We compared the currents induced by various TMS conditions on several different MRI derived finite element head models of brain atrophy, incorporating both decreasing cortical volume and widened sulci. The current densities induced in the cortex were dependent upon the degree and type of cortical atrophy and were altered in magnitude, location, and orientation when compared to healthy head models. Predictive models of the degree of current density attenuation as a function of the scalp-to-cortex distance were analyzed, concluding that those which ignore the electromagnetic field-tissue interactions lead to inaccurate conclusions. Ultimately, the precise site and population of neural elements stimulated by TMS in an atrophic brain cannot be predicted based on healthy head models which ignore the effects of the altered cortex on the stimulating currents. Clinical applications of TMS should be carefully considered in light of these findings.
authors.affiliation: Division of Health Sciences and Technology, Harvard Medical School/Massachusetts Institute of Technology, Boston, MA, USA. twagner@alum.mit.edu
authors.forename: Tim
authors.initials: T
authors.lastname: Wagner
authors.forename: Uri
authors.initials: U
authors.lastname: Eden
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
authors.forename: Antoni
authors.initials: A
authors.lastname: Valero-Cabre
authors.forename: Ciro
authors.initials: C
authors.lastname: Ramos-Estebanez
authors.forename: Valerie
authors.initials: V
authors.lastname: Pronio-Stelluto
authors.forename: Alan
authors.initials: A
authors.lastname: Grodzinsky
authors.forename: Markus
authors.initials: M
authors.lastname: Zahn
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
mesh_terms: D001284:Atrophy; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D001931:Brain Mapping; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D006801:Humans; D008959:Models, Neurological; D050781:Transcranial Magnetic Stimulation / Q000379:methods*