摘要
小腦橋腦角腫瘤最常見的是聽神經瘤與腦膜瘤。原發性中樞神經淋巴瘤較常出現於大腦半球，在小腦橋腦角則為罕見，且淋巴瘤常會被誤診為其他疾病。診斷上需要先切片證實以提供治療計畫的擬定，而非直接廣泛性切除。本部於2009年3月間經歷1名58歲男性病患，主訴左側耳鳴並伴隨左側耳辨音困難數日，偶有複視與臉麻情形，此外並無頭痛、（口惡）心、嘔吐、無力、不自主運動，感覺異常或意識障礙。聽力檢查發現左側耳聽力僅高頻率略差，平均閾值則正常。在頭顱Stenver's view下兩側內聽道並無異常。然而聽性腦幹反應顯示左側明顯無反應，且數日後病患出現Bruns-Cushing眼振與向左側傾斜的步態不穩，磁振造影顯示左側小腦橋腦角有一2×2cm的病灶。經外科實施枕骨下顳骨後顱內切片手術(suboccipital retromastoid craniotomy with biopsy)，病理報告為瀰漫性大型B細胞淋巴瘤(diffuse large B-cell lymphoma)，後續的放射線治療及化學治療效果良好，腫瘤消失。臨床診療上，細究單側耳鳴的病因相當重要，可避免誤診而錯失治療之時機。
並列摘要
Primary central nervous system lymphoma is reported to be a rare tumor and commonly appears at hemisphere of the brain. It is rare to be found at cerebellopontine angle (CPA) where the most common tumors are acoustic neuroma and meningioma and likely to be misdiagnosed. It is also important to take biopsy of the tumor to set up the therapeutic plan. A 58-year-old man had suffered from left-side tinnitus with poor discrimination, intermittent diplopia and left facial numbness for several days in March, 2009. The pure tone audiometry showed mild loss at the left 4 k and 8 k Hz, however, with normal threshold. Stenver's view showed symmetric internal auditory canal, bilaterally. However, auditory brainstem response (ABR) revealed no response at left-side ear. Later, neurologic exam disclosed Bruns-Cushing nystagmus and dysequilibrium tilting to left side. The brain magnetic resonance imaging (MRI) demonstrated a 2×2 cm homogenous enhancing mass in the left CPA region. Suboccipital retromastoid craniotomy with biopsy was performed by neurosurgeon, and diffuse large B-cell lymphoma was histopathologically diagnosed. After a series of tumor surveys, the patient received chemotherapy and radiotherapy for CPA lymphoma. The remission was achieved and the patient was still alive 12 months after initial therapy. It is very important to find the etiology of unilateral tinnitus clinically, in order to avoid misdiagnosis.