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Unilateral Symptomatic Palatal Myoclonus: MRI Evidence of Contralateral Inferior Olivary Lesion

單側症狀性顎肌陣攣症:對側下橄欖核病變之磁振攝影變化

摘要


顎肌陣攣(palatal myoclonus)為一種少見的節段性肌陣攣症候群。此種不自主的肌陣攣跳動,主要發生在軟顎肌;此外,也可影響如咽、喉、眼、臉、上臂與橫膈膜部的肌肉。從臨床觀察、透像(fluroscopy)攝影與肌電圖結果,我們可將顎肌陣攣症分為單側性或雙側性,而其肌躍動之頻率為每分鐘100到180次。 臨床上,根據患者有否合併其他中樞神經病變或異常之神經檢查結果,我們可將顎肌陣攣再分為症狀性和原發性兩大類。症狀性顎肌陣孿症患者幾乎都合併有〝齒狀核一紅核一橄欖體〞路徑(dentato-rubro-olivary pathway)的病變,而且在病理學上也大多可見下橄體有退化性肥大現象。因此神經路徑在後結合臂交叉之故,所以小腦齒狀核與上小腦腳病變會造成對側橄欖體肥大,而中央被蓋路徑病變則引起同側肥大。雖有上述病理變化的差異,但就單側性顎肌陣攣患者而言,退化性肥大一定發生在肌躍動的對側橄欖體。以往均而解剖檢查才能得知;近年來,因磁振攝影技術的發展,使我們可以在早期便能偵測出此種特殊之橄欖體肥大現象。 本文報告兩例單側症狀性顎肌陣攣的病例,兩者在臨,除了不自主的單側性軟顎肌躍動外,均合併有同步性的同側咽喉和臉部肌肉跳動與旋轉性眼顫現象。其中一例甚至有間歇性單側橫膈肌躍動。首例為急性左側橋腦被蓋出血,一個月後,患者出現右側眼顎肌陣攣現象。出血三個月後的磁振攝影檢查,在質子與T2為主影像(PDWI & T2WI),顯示左橄欖體有高信號影像變化。第二為進行性基底動脈阻塞症合併橋腦、左側小腦與枕葉缺血性中風。兩個月後的磁振攝影追蹤檢查,出現明顯右側橄欖體肥大與信號變化,然而患者在隔月後才發生左側顎肌陣攣。最後,我們認為(1)齒狀核一紅核一橄欖體路徑病變造成之經越神經退化現象,與(2)病理上橄欖神經原胞質空泡和神經膠質變性造成可動氫核(mobile proton)增加,這兩項可用來解釋顎肌陣孿症患者的磁振攝影變化。

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並列摘要


Symptomatic palatal myoclonus is a rare syndrome of segmental myoclonus which is thought to occur after damage to certain brainstem or cerebellar structures. We report two patients with unilateral PM, who showed hypertrophy of the inferior olivary nucleus on magnetic resonance imaging. In the first patient this was due to a left pontine tegmental hemorrhage, and a right-sided oculo-palato-facial myoclonus developed one month after the episode. The second one had a basilar artery occlusion with ischemic infarcts at the basis pontis, dorso-lateral aspects of the left pons, and left cerebellar dentate nucleus, as well as the occipital lobe. A delayed left oculopalatal myoclonus was recognized 3 months later. Interruption of the 〝dentato-rubro-olivary pathway〞by the lesion with ensuing neuronal loss, cytoplasmic vacuolation, and astrocytic proliferation in the inferior olive, together with an increase of water content as mobile proton may cause the MR signal abnormalities in patients with unilateral symptomatic palatal myoclonus.

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