後顱窩蜘蛛膜囊腫 — 病例報告

顱內蜘蛛膜囊腫，約佔全部顱內腫瘤的1%。主要是由於先天性發育異常或後天性創傷及感染，造成腦脊髓液流量增加引起局部壓力上升，使得正常的蜘蛛膜往外膨出分離而成。臨床症狀可依其囊腫發生位置及大小之不同或對小腦及腦幹壓迫程度，而有所不同。本院於1999年7月間經歷一34歲男性病例。主訴最近2個星期以來，屢次發生位置性頭痛、持續性頭暈、步態不穩、眩暈、視力模糊併複視、嘔吐、兩側聽力障礙及耳鳴等。一般理學及腦神經學檢查正常。但耳神經學檢查呈現視標追跡測驗顯示原形波呈樹冰狀波（atactic pursuit）。視運動性眼振檢查左右呈現解發不良及右眼overshot。聽力檢查呈兩側感覺神經性聽力障礙。眼振影像圖檢查（videonystagmography）顯示異常水平解離性眼球運動，懷疑小腦及腦幹部位有病灶，安排核磁共振攝影，結果發現在小腦後有一蜘蛛膜囊腫。因此當眼振錄影圖檢查出現異常水平解離性眼球運動及電氣眼振圖（electronystagmography；ENG）出現上述異常徵狀時，須懷疑中樞性病灶，安排影像檢查以證實之。病患術後門診追蹤至今約1年，頭痛、頭暈、嘔吐、眩暈、耳鳴等症狀皆已改善。

關鍵字

後顱窩蜘蛛膜囊腫；解離性眼球運動

並列摘要

Arachnoid cysts account for approximately 1% of all intracranial tumors. Developmental of congenital malformations and traumatic or infectious lesions are the main causes of arachnoid cysts. In both cases, the CSF-filled cavity is surrounded by split layers of arachnoid membrane, caused by increased local pressure due to increases in CSF flow. Clinical symptoms differ according to the location and size of the cyst, as well as the degree of any cerebellar or brain stem compression. In July 1999, we saw a 34-year-old male patient complaining of a postural headache, persistent dizziness, gait disturbance, vertigo, hearing impairment, and tinnitus. An otoneurologic eye-tracking test identified atactic pursuit. This, along with dissociation of optokinetic nystagmus and dissociated eye movement with videonystagmography, led us to suspect a lesion of the cerebellum or brain stem. An MRI was performed which identified a retrocerebellar arachnoid cyst. Accordingly, whenever videonystagmography shows dissociated eye movement or electronystagmography shows the previously described signs, a central lesion should be suspected and MRI should be arranged to confirm the diagnosis. The patient’s condition has been monitored regularly during outpatient visits over the year following surgery, and the symptoms of headache, dizziness, vomiting, nausea and tinnitus have improved considerably.

並列關鍵字

arachnoid cyst ； posterior fossa ； dissociated eye movement

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後顱窩蜘蛛膜囊腫 — 病例報告

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