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Abstract(s)
Introdução: A estimulação magnética transcraniana repetitiva (EMTr) permite alterar a excitabilidade do tecido neuronal através da criação de campos magnéticos. A theta burst stimulation (TBS) é um protocolo de EMTr com duas variantes: TBS intermitente (iTBS-estimulação excitatória) e TBS contínua (cTBS - estimulação inibitória). Este estudo tem por objectivo averiguar se a TBS é capaz de produzir alterações na oxigenação cerebral, na pressão arterial e na frequência cardíaca quando aplicada ao córtex pré-frontal dorsolateral esquerdo em voluntários jovens e saudáveis.
Metodologia: A amostra inclui 79 voluntários, 30 dos quais submetidos a estimulação e 49 submetidos apenas à medição dos valores de oxigenação cerebral, todos entre os 18 e os 30 anos. Os 30 indivíduos estimulados foram divididos equitativamente em 3 grupos: cTBS, iTBS e placebo, tendo todos efectuado uma recolha dos valores de oxigenação cerebral, pressão arterial e frequência cardíaca, antes e depois da estimulação. Os indivíduos pertencentes ao grupo controlo da oxigenação cerebral fizeram apenas duas medições de oxigenação cerebral num intervalo de trinta minutos.
Resultados: Verificou-se que a estimulação inibitória (cTBS) produziu uma diminuição significativa (teste t de student, p=0,022) na oximetria do córtex esquerdo e marginalmente significativa na oximetria do córtex direito (teste t de student, p=0,068). No grupo excitatório (iTBS), para o córtex esquerdo, verificou-se que na fase “pós-TBS” a oximetria média foi significativamente superior à do grupo controlo (Dunnett, p=0,012) e que houve um aumento do valor médio da oxigenação na fase “pós-TBS” em relação á fase “pré-TBS”. Para as variáveis “pressão arterial” e “frequência cardíaca”, não se encontraram valores estatisticamente significativos.
Conclusões: Neste estudo concluiu-se que a cTBS aplicada ao córtex pré-frontal dorsolateral esquerdo, diminui a oxigenação do lobo frontal ipsilateral. Estes achados sugerem que a diminuição da actividade neuronal produzida pela cTBS poderá levar à diminuição do metabolismo, havendo uma menor necessidade de aporte de oxigénio à área estimulada. No grupo iTBS, a variação da média e os resultados do teste de Dunnett, levam-nos a supor que perante uma amostra maior teríamos obtido um aumento significativo da oxigenação na área estimulada. Concluiu-se ainda que numa população normal entre os 18 e os 30 anos, a variação de oxigenação num intervalo de 30 minutos não é estatisticamente significativa. Os resultados obtidos para as variáveis “frequência cardíaca” e “pressão arterial”, que não mostraram alterações em ambos os grupos cTBS e ITBS, ajudam a consolidar a segurança da técnica.
Introduction: Repetitive transcranial magnetic stimulation (rTMS) can change the excitability of neuronal tissue through the induction of electromagnetic fields. Theta burst stimulation (TBS) is an rTMS protocol that has two variants: intermittent TBS (iTBS-excitatory) and continuous TBS (cTBS-inhibitory). This study aims to investigate whether TBS is able to produce changes in cerebral oxygenation, blood pressure and heart rate, when applied to the left dorsolateral prefrontal cortex (DLPFC) in healthy young volunteers. Materials & Methods: The sample includes 79 individuals, 30 of whom underwent stimulation and 49 that were submitted only to the measurement of cerebral oxygenation values, all between 18 and 30 years. The 30 stimulated individuals were divided equally into 3 stimulation groups: cTBS, iTBS and sham, all having made a collection of brain oxigenation, blood pressure and heart rate values before and after stimulation. The remaining individuals were allocated to the brain’s oxygenation control group in which only two measurements of oximetry were made, with an interval of thirty minutes. Results: It was found that inhibitory stimulation (cTBS) produced significantly lowered values in left’s brain oximetry (paired t-test, p=0,022) and marginally significant lower values for right brain oximetry (paired t-test, p=0,068). Regarding the iTBS, we noted that in the “afterstimulation” phase the left brain oximetry was significantly higher than in the control group (Dunnett, p=0,006) and there was an increase in the average value, from the “before” to the “after” phase. On the variables “heart rate” and “blood pressure” we found no significant changes. Conclusion: In this study we concluded that cTBS, when applied to the left dorsolateral prefrontal cortex, is able to lower brain´s oxygenation in the ipsilateral frontal lobe. These findings lead us to suggest that cTBS decreases neuronal activity and consequently its metabolism, leading to decreased oxygen delivery to the stimulated area. The iTBS group average variation and the Dunnett’s test result, leads us to believe that if we had a larger sample we could have a significant increase in stimulated area oxygenation. This study also revealed that in a normal population aged 18 to 30 years, variation of cerebral oxygenation within 30 minutes is not significant. The results of “heart rate” and “blood pressure” in individuals undergoing iTBS and cTBS help to consolidate technique security.
Introduction: Repetitive transcranial magnetic stimulation (rTMS) can change the excitability of neuronal tissue through the induction of electromagnetic fields. Theta burst stimulation (TBS) is an rTMS protocol that has two variants: intermittent TBS (iTBS-excitatory) and continuous TBS (cTBS-inhibitory). This study aims to investigate whether TBS is able to produce changes in cerebral oxygenation, blood pressure and heart rate, when applied to the left dorsolateral prefrontal cortex (DLPFC) in healthy young volunteers. Materials & Methods: The sample includes 79 individuals, 30 of whom underwent stimulation and 49 that were submitted only to the measurement of cerebral oxygenation values, all between 18 and 30 years. The 30 stimulated individuals were divided equally into 3 stimulation groups: cTBS, iTBS and sham, all having made a collection of brain oxigenation, blood pressure and heart rate values before and after stimulation. The remaining individuals were allocated to the brain’s oxygenation control group in which only two measurements of oximetry were made, with an interval of thirty minutes. Results: It was found that inhibitory stimulation (cTBS) produced significantly lowered values in left’s brain oximetry (paired t-test, p=0,022) and marginally significant lower values for right brain oximetry (paired t-test, p=0,068). Regarding the iTBS, we noted that in the “afterstimulation” phase the left brain oximetry was significantly higher than in the control group (Dunnett, p=0,006) and there was an increase in the average value, from the “before” to the “after” phase. On the variables “heart rate” and “blood pressure” we found no significant changes. Conclusion: In this study we concluded that cTBS, when applied to the left dorsolateral prefrontal cortex, is able to lower brain´s oxygenation in the ipsilateral frontal lobe. These findings lead us to suggest that cTBS decreases neuronal activity and consequently its metabolism, leading to decreased oxygen delivery to the stimulated area. The iTBS group average variation and the Dunnett’s test result, leads us to believe that if we had a larger sample we could have a significant increase in stimulated area oxygenation. This study also revealed that in a normal population aged 18 to 30 years, variation of cerebral oxygenation within 30 minutes is not significant. The results of “heart rate” and “blood pressure” in individuals undergoing iTBS and cTBS help to consolidate technique security.
Description
Keywords
Estimulação magnética transcraniana - Cortex cerebral Oxigenação cerebral Pressão arterial Frequência cardíaca Oximetria
Citation
Publisher
Universidade da Beira Interior