Naslov
Identification of somatomotor and motor speech-related cortical areas using nTMS.

Autori
Deletis, Vedran ; Rogić, Maja

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Abstracts from the 4th International Symposium on Navigated Brain Stimulation in Neurosurgery / - , 2012, 3-4

Skup
4 th International symposium on Navigated Brain Stimulation in Neurosurgery,

Mjesto i datum
Berlin, Njemačka, 16.11.2012. - 17.11.2012

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
motor speech related cortical areas; nTMS

Sažetak
Various cortical areas in the frontal cortices have been found to be involved in inducing speech arrest by electrical or magnetic stimulation, including the opercular part of Broca’s area and the primary motor cortex (M1) for laryngeal muscles. It has been shown that M1 for laryngeal muscles is responsible for controlling the muscles for vocalization, whereas the opercular part of Broca’s area is involved in motor planning and control of speech. Functional connections have been shown between the M1 for the laryngeal muscles and the opercular part of Broca’s area by cortico-cortical evoked potential recordings (1). The M1 for laryngeal muscles can clearly be differentiated from the opercular part of Broca’s area, due to significantly different latencies of evoked potentials recorded from laryngeal muscles (cricothyroid and vocal muscles). Stimulation of the M1 for laryngeal muscles generates a short latency response (SLR) while the stimulation of the opercular part of Broca’s area generates a long latency response (LLR) (2, 3, 4, 5). It has been proposed that transient speech disruptions elicited by stimulation of these cortical spots produces evoked potentials in laryngeal muscles and can be regarded as a marker to depict motor speech-related areas (5). Stimulation of the cortical spot which generates LLR produces speech arrest, while stimulation of the cortical spot which generates SLR produces dysarthric speech. In anesthetized patients, without using muscle relaxants, mapping of the M1 for the laryngeal muscles and the opercular part of Broca’s area, has earlier been achieved by endotracheally inserting a hook wire electrode in the vocal muscle. In awake patients, the hook wire electrode can be placed in the cricothyroid muscle percutaneously. Short trains of electrical stimuli over the opercular part of Broca’s area and M1 for laryngeal muscles activate the corticobulbar tract for the vagal nucleus (directly when stimulating M1 and indirectly, via M1, when stimulating Broca’s area) generating a LLR and a SLR in the laryngeal muscles, respectively. Recently, it has been shown that non-invasive navigated transcranial magnetic stimulation (nTMS) can locate the representation area of the cricothyroid muscle in the M1 and the opercular part of Broca’s area using a modified, patterned rTMS protocol (NBS System, Nexstim Oy, Finland) (6). The SLRs (corticobulbar motor evoked potentials) and LLRs are recorded by 76 μm hook wire electrodes inserted in the cricothyroid muscle, indicating that, in healthy subjects, the M1 for cricothyroid muscle is located approximately 25 mm more lateral with regard to M1 for the hand muscle (abductor pollicis brevis muscle) (7). There has been progress in the techniques available for non-invasive localization of motor speech-related cortical areas. Having reliable neurophysiologic markers for these areas would significantly contribute to the selection of surgical candidates and planning of safer access to lesions. Additionally, such information would help to preserve motor speech-related cortical areas in anesthetized patients. Mapping of M1 for cricothyroid muscle might represent an important neurophysiologic marker for motor speech-related cortical areas due to the proximity of motor cortical representation of the laryngeal muscles and the opercular part of Broca’s area. The nTMS is a powerful diagnostic tool which will probably in the future have the potential to finely map cortical regions for which we do not yet have a methodology.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

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