以功能性磁振造影及腦電訊號觀察超音波施於癲癇模型之神經調控效應

Abstract

癲癇是一種神經系統疾病，其特點是不正常的神經放電。目前已有多種治療癲癇的方法，包括迷走神經刺激、深部腦刺激和反應性神經刺激。作為一種替代性神經調控療法，聚焦式超音波（Focused Ultrasound, FUS）被發現具有調控局部大腦興奮性的潛力，並且最近研究表明脈衝式(burst-mode)超音波刺激具有抑制癲癇的效果。在本研究中，我們嘗試使用靜息態功能性磁振造影（resting-state functional MRI, rs-fMRI）和腦電訊號(Electroencephalography, EEG)，來研究藥物誘發癲癇的小動物模型中，聚焦式超音波脈動引起的抗癲癇效應的可行性。 本研究結果展示了在同一癲癇動物模型中，成功整合長期的rs-fMRI監測和EEG記錄，以評估藥物注射後誘發的癲癇信號。EEG結果顯示，不正常放電所引起的尖波(spike)，注射藥物後10分鐘內spike數量由17.5上升至118.8，後續60分鐘內隨時間降低至75.8；fMRI結果顯示功能性連接相關係數(Correlation Coefficient, C.C.)由0.19上升至0.65，後續60分鐘內隨時間降低至0.29。該模型也可觀察FUS對癲癇的抑制效果，在10分鐘的FUS施打後，最高可抑制52.9\%的spike數量；超音波誘導的神經調控引起了腦區與腦區間的功能性連結的變化，rs-fMRI結果顯示在FUS施打後，巴貝茲迴路(Papez circuit)相關腦區，功能性連結C.C.相較於僅有藥物誘發癲癇，最高下降了61.8\%，使原本興奮的腦區趨於靜息態。藥物誘發癲癇可從功能性連結觀察到全腦興奮的現象，而聚焦式超音波誘發的神經調控使得腦區與腦區間的功能性連結發生變化，分析結果在癲癇模型中EEG的spike與fMRI的C.C.呈現高度相關性，根據本研究可得出全腦C.C.平均數高於0.36代表腦呈現癲癇狀態，而FUS治療後C.C.若低於0.31代表癲癇已一定程度被抑制。 綜上所述，本研究建置的模型可藉由rs-fMRI和EEG探究藥物誘發癲癇的生理訊號改變，也可觀察超音波施於癲癇模型的神經調控效應。然而，為了理解利用超音波干預癲癇的機制與背後的聯繫，對於FUS參數的優化、施打腦區的選擇、以及未來可用蛋白染色探討FUS神經調控機制等，尚需更多研究與實驗。

Epilepsy is a neurological disorder characterized by abnormal neuronal discharges. A number of modalities have been developed to interfere with epilepsy, including vagus nerve stimulation, deep brain stimulation, and responsive neurostimulation. As an alternative neuromodulation therapy, focused ultrasound (FUS) has been found to have the potential to modulate regional brain excitability, and recently burst-mode ultrasound stimulation has been shown to have an epileptic suppressing effect. In this study, we investigate the feasibility of utilizing resting-state functional MRI(rs-fMRI) and Electroencephalography(EEG) to investigate the anti-epileptic effect induced by focused ultrasound pulsations in a drug-induced epileptic small-animal model. The results of this study demonstrate the successful integration of longitudinal rs-fMRI monitoring and EEG recordings in the same epilepsy animal model to assess drug-induced epileptic signals. The EEG results showed that the number of spikes caused by abnormal discharges increased from 17.5 to 118.8 within 10 minutes after drug injection and then decreased to 75.8 within the following 60 minutes. The fMRI results showed that the functional connectivity correlation coefficient (C.C.) increased from 0.19 to 0.65 within 10 minutes after drug injection and then decreased to 0.29 within the following 60 minutes. The model also observed the inhibitory effect of FUS on epilepsy, with a maximum suppression of 52.9\% of spike numbers after 10 minutes FUS. FUS-induced neuromodulation resulted in changes in brain region-to-region functional connectivity. The rs-fMRI results showed that after FUS, the C.C. of the Papez circuit-related brain regions decreased by up to 61.8\% compared to drug-induced epilepsy alone, indicating a shift towards a resting state in originally excitable brain regions. Drug-induced epilepsy was observed in functional connectivity as increased brain excitability, while FUS-induced neuromodulation led to changes in brain region-to-region functional connectivity. The analysis showed a high correlation between EEG spikes and fMRI C.C. in the epilepsy model, and based on this study, a C.C. average higher than 0.36 indicated an epileptic state, while a C.C. lower than 0.31 after FUS treatment suggested epilepsy suppression. In summary, the model established in this study can be utilized to explore the biosignal changes caused by drug-induced epilepsy using rs-fMRI and EEG and observe the neuromodulation effects of FUS in the epilepsy model. However, to better understand the mechanism and underlying connections of using FUS intervention for epilepsy, further research and experiments are required to optimize FUS parameters, determine optimal stimulation site, and explore FUS neuromodulation mechanisms using protein staining.