以腦幹聽覺誘發電位來證實肉毒桿菌注射於局部肌張力不全者的遠端效應

以腦幹聽覺誘發電位來證實肉毒桿菌注射於局部肌張力不全者的遠端效應 中文摘要 局部肉毒桿菌素注射用來治療局部肌張力不全者，如頸肌張力不全，顏面神經痙攣及眼肌痙攣症，肉毒桿菌素經由阻斷神經肌肉間膽鹼的傳導，來減少局部肌肉的痙攣，同時也可對注射的遠端肌肉產生合併的舒緩效用，此種遠端效應的真正機轉並不清楚。很多假設試圖去解釋這種遠端效應，包括有1.局部擴散至遠端肌肉 2.經由血流循環 3.神經軸突的逆向傳導。 本研究乃是利用腦幹聽覺誘發電位的變化來證實其遠端效應，我們收集了16個頸部肌張力不全（9女10男），11個（7女4男）眼肌痙攣症及顏面神經痙攣的病人，在其接受肉毒桿菌注射前及注射後兩週，分別給予腦幹聽覺誘發電位檢查，結果顯示第一波的振幅在眼肌痙攣症這一組病人有明顯的增加（P＜0.01），而第五波的振幅在頸肌張力不全這組有明顯增加（P＜0.05），這可能的解釋，肉毒桿菌素可藉由臉部肌肉經由第七對神經的軸突逆向傳導，而致使蹬骨肌肉鬆馳，而使得在眼肌痙攣症這一組病人的第一波增強，而頸肌張力不全這一組的第五波增加可能由於肉肌梭纖維（Intrafusal fiber）的無力，而調控的感覺傳入腦幹上升徑路產生的變化所引起的，本研究正是以此來證實局部注射肉毒桿菌素所引發的遠端效應。

Brainstem Auditory Evoked Potential Evidence Of Distant Effects Of Botulinum Toxin In Focal Dystonia Abstract Local injection of botulinum toxin (BTX) are recognized as treatment of choice for for cervical dystonia and hemifacial spasm , blepharospasm. By long term blockade cholinergic neuromuscular transmission, BTX reduced localized muscle spasms, and can also produce effect at a distance from the injection site such as resolution of associated facial and oromandibular muscle contractions. However , the exact mechanism of these distant effect is still not clear . In the present study , we studied brain stem auditory evoked potential (BAEP) in n 16 patients（9 F,7 M）injected with BTX for spasmodic torticollis（ST）, and in 11 patients（7F, 4 M）treated for idiopathic blepharospasm or hemifacial spasm（IB/HFS）. BAEP were recorded twice before, and two weeks after the BTX injection. After BTX, mean amplitude values of the BAEP wave I increased in IB（p＜0.01）, while they were slightly reduced in the ST group. Wave V amplitudes tended to increase after BTX in both IB and ST group（p＜0.05）. Retrograde axonal transport of BTX from facial muscle via the 7th nerve can provoke weakening of stapedius muscle and thus induce the BAEP wave I amplitude increase in IB/HFS group. BTX induced intrafusal fibers paralysis within neck muscles may modify sensory afferent input control on the brain stem level resulting the wave V amplitude increase. We conclude the BAEP changes observed after BTX injection reflect distal effects of this treatment on the brain stem ascendant pathway and reflex