title: The Hand Motor Hotspot is not Always Located in the Hand Knob: A Neuronavigated Transcranial Magnetic Stimulation Study.
abstract: The hand motor hot spot (hMHS) is one of the most salient parameters in transcranial magnetic stimulation (TMS) practice, notably used for targeting. It is commonly accepted that the hMHS corresponds to the hand representation within the primary motor cortex (M1). Anatomical and imaging studies locate this representation in a region of the central sulcus called the "hand knob". The aim of this study was to determine if the hMHS location corresponds to its expected location at the hand knob. Twelve healthy volunteers and eleven patients with chronic neuropathic pain of various origins, but not related to a brain lesion, were enrolled. Morphological magnetic resonance imaging of the brain was normal in all participants. Both hemispheres were studied in all participants except four (two patients and two healthy subjects). Cortical mapping of the hand motor area was conducted using a TMS-dedicated navigation system and recording motor evoked potentials (MEPs) in the contralateral first dorsal interosseous (FDI) muscle. We then determined the anatomical position of the hMHS, defined as the stimulation site providing the largest FDI-MEPs. In 45 % of hemispheres of normal subjects and 25 % of hemispheres of pain patients, the hMHS was located over the central sulcus, most frequently at the level of the hand knob. However, in the other cases, the hMHS was located outside M1, most frequently anteriorly over the precentral or middle frontal gyrus. This study shows that the hMHS does not always correspond to the hand knob and M1 location in healthy subjects or patients. Therefore, image-guided navigation is needed to improve the anatomical accuracy of TMS targeting, even for M1.
authors.affiliation: EA 4391, Excitabilité Nerveuse et Thérapeutique, Université Paris-Est-Créteil, Créteil, France.|Service de Physiologie - Explorations Fonctionnelles, Hôpital Henri Mondor, Assistance Publique - Hôpitaux de Paris, 51 avenue de Lattre de Tassigny, 94010, Créteil, France.|Neurology Division, University Medical Center Rizk Hospital, Beirut, Lebanon.
authors.forename: Rechdi
authors.initials: R
authors.lastname: Ahdab
authors.affiliation: EA 4391, Excitabilité Nerveuse et Thérapeutique, Université Paris-Est-Créteil, Créteil, France. samarayache@gmail.com.|Service de Physiologie - Explorations Fonctionnelles, Hôpital Henri Mondor, Assistance Publique - Hôpitaux de Paris, 51 avenue de Lattre de Tassigny, 94010, Créteil, France. samarayache@gmail.com.|Neurology Division, University Medical Center Rizk Hospital, Beirut, Lebanon. samarayache@gmail.com.
authors.forename: Samar S
authors.initials: SS
authors.lastname: Ayache
authors.affiliation: Service de Neuroradiologie, Hôpital Henri Mondor, Assistance Publique - Hôpitaux de Paris, Créteil, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Brugières
authors.affiliation: EA 4391, Excitabilité Nerveuse et Thérapeutique, Université Paris-Est-Créteil, Créteil, France.|Service de Physiologie - Explorations Fonctionnelles, Hôpital Henri Mondor, Assistance Publique - Hôpitaux de Paris, 51 avenue de Lattre de Tassigny, 94010, Créteil, France.
authors.forename: Wassim H
authors.initials: WH
authors.lastname: Farhat
authors.affiliation: EA 4391, Excitabilité Nerveuse et Thérapeutique, Université Paris-Est-Créteil, Créteil, France.|Service de Physiologie - Explorations Fonctionnelles, Hôpital Henri Mondor, Assistance Publique - Hôpitaux de Paris, 51 avenue de Lattre de Tassigny, 94010, Créteil, France.
authors.forename: Jean-Pascal
authors.initials: JP
authors.lastname: Lefaucheur
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping; D016022:Case-Control Studies; D059350:Chronic Pain / Q000503:physiopathology; D019054:Evoked Potentials, Motor; D005260:Female; D006225:Hand; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D009437:Neuralgia / Q000503:physiopathology; D050781:Transcranial Magnetic Stimulation
keywords: Motor cortex; Motor hotspot; Navigation; Sulcal anatomy; Transcranial magnetic stimulation