The Hand Motor Hotspot is not Always Located in the Hand Knob: A Neuronavigated Transcranial Magnetic Stimulation Study
Adult
Male
Brain Mapping
Motor Cortex
Middle Aged
Evoked Potentials, Motor
Hand
Magnetic Resonance Imaging
Transcranial Magnetic Stimulation
03 medical and health sciences
0302 clinical medicine
Case-Control Studies
Humans
Neuralgia
Female
Chronic Pain
Aged
DOI:
10.1007/s10548-016-0486-2
Publication Date:
2016-03-18T17:16:04Z
AUTHORS (5)
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.
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