Article
Incidence and anatomical correlation of speech disturbances induced by navigated transcranial magnetic stimulation in brain tumour patients
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Published: | June 4, 2012 |
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Outline
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Objective: Transcranial Magnetic Stimulation (TMS) has been a very reliable process in locating the motor function regarding the tumours located in the eloquent motor areas of the brain. Recently, TMS helps to locate the speech eloquent areas of the brain in patients with tumours in the peri-sylvian regions and aids to justify as well as prepare for their forthcoming awake operations. Further more, the cortical stimulation of the brain through TMS, helps in categorizing the different object naming errors performed during the stimulation and in judging the respective neuro-anatomical correlates as well as its cortical localisation.
Methods: 12 Patients, selected for awake surgery, underwent a cortical language mapping with the help of TMS. Resting Motor Threshold (RMT) for the dominant left hemisphere was defined, patients were shown photos of different objects, a baseline naming of objects without stimulation was evaluated and patients were told to name the respective objects during the stimulation. Intensity between 80–120% of RMT and frequency between 5–10 Hz were varied. Different language errors performed by the patients were categorized as: aphasia, performance, phonological, semantic and neologism.
Results: Altogether 1913 stimulations were performed and 394 errors were noted (20.6%). Among the five gyri stimulated, the error distribution, along with the total number of stimulation were: inferior frontal gyrus 68/377, precentral gyrus 135/608, postcentral gyrus 73/423, supramarginal gyrus 47/225 and supratemporal gyrus 71/280. 73 Aphasia, 98 performance, 26 phonological, 180 semantic and 17 neologism were altogether seen. Semantic was also the dominant error seen in each of the five respective gyri.
Conclusions: TMS can be generally used to specify the language dominant hemisphere and to categorize different language errors by the patients with tumours in the peri-sylvian region of the dominant hemisphere. But the validation of this method is yet to be fully proved and its specification still underlies the direct cortical stimulation.