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譯者：花人青老師
一個喜歡音樂和攝影的快樂醫生
History: A 67-year-old man presents with sudden-onset hemiplegia and is brought to the emergency room within 30 minutes of onset. Patient has a historyof atrial fibrillation.
病史：67歲男性，突發偏癱，30分鐘內被送至急診室，患者有房顫病史。
Unenhanced CT images and CT angiography (CTA) of the brain are shown below.
顱腦CT平掃及CTA如下所示。
Conventional angiography was performed. Digital subtraction angiography (DSA) images are shown below.
行血管造影，DSA圖像如下所示。
Thombectomy was performed.
行血栓切除術。
Findings 表現
Unenhanced head CT: CT demonstrates poor gray-white differentiation in the right basal ganglia and insular cortex. There is also focal high density in the M1 branch of the right MCA, which may represent acute thrombus.
顱腦CT平掃：右側基底節及島葉皮層灰白質分界模糊，右側大腦中動脈M1段呈局限性高密度，可能代表急性血栓形成。
Head CTA: CTA demonstrates a filling defect at the proximal M1 branch of the right MCA with poor visualization of the distal vasculature.
顱腦CTA：右側大腦中動脈M1段近段見充盈缺損，其遠端血管分支顯示較差。
Cerebral DSA and mechanical thrombectomy: There is a filling defect at the proximal M1 branch of the right MCA without distal perfusion. Following mechanical thrombectomy with a stent retriever ("stentriever") device, there is complete perfusion to the distal vasculature, TICI score of 3.
腦DSA及機械血栓清除術：右側大腦中動脈M1段近段見充盈缺損，遠段無灌注。使用支架取栓器行機械血栓清除後，遠段血管灌注完全，腦梗死溶栓TICI評分為3。
Differential diagnosis：
Embolic infarct
Thrombosis
Vasospasm
Dissection
鑑別診斷：
Diagnosis: Acute right middle cerebral artery embolic infarct.
診斷：右側大腦中動脈急性栓塞性梗死
Key points
Acute middle cerebral artery (MCA) infarct
Pathophysiology 病理生理學
Acute occlusion of the middle cerebral artery, most commonly due to embolic occlusion, resulting in ischemia and infarction of the supplied vascular bed. Other causes include arterial dissection, thrombosis of ruptured atherosclerotic plaque or infection, and vasculitis.
大腦中動脈急性栓塞最常見的原因是栓子堵塞，導致其所供應區域缺血、梗死。其它原因包括：動脈夾層，動脈粥樣硬化斑塊破裂或炎症形成血栓，血管炎。
Demographics 人口統計特徵
Most common in the elderly.
通常見於老年人。
Equal incidence in men and women.
男女發病率相同。
Increased incidence of embolic occlusion in atrial fibrillation.
房顫患者栓子阻塞的發病率較高。
Imaging 影像
Unenhanced CT: May demonstrate mass effect with sulcal effacement and/or midline shift, blurring of the gray-white junction, hyperdense MCA sign demonstrating acute thrombus in the vessel, or relatively hypodense parenchyma.
CT平掃：表現一定的佔位效應，腦溝消失、中線結構移位、灰白質分界模糊、大腦中動脈高密度徵（血管內急性血栓）、腦實質密度相對減低。
CTA: Abrupt occlusion is seen with absent or minimal enhancement of the distal vasculature.
CTA：血管突然閉塞，其遠端分支缺如或少量強化顯影。
Conventional angiography: Similar findings to CTA with abrupt occlusion and possible minimal flow around the occlusion.
血管造影：與CTA表現相同，血管突然閉塞，其周圍血流減少。
MRI: Restricted diffusion seen in the territory of the MCA demonstrated as bright signal on DWI and dark signal on ADC mapping. Findings of mass effect such as sulcal effacement and midline shift may be present. Fluid-sensitive imaging, such as FLAIR, may show hyperintensity. Susceptibility-weighted imaging, such as gradient-recalled echo (GRE), is important to evaluate for blood products.
MRI：大腦中動脈供血區彌散受限，表現為DWI高信號，ADC圖低信號。可見一定的佔位效應，例如腦溝消失、中線移位。水敏感成像FLAIR上，缺血區域呈高信號，磁敏感加權成像GRE序列對於評估有無出血十分重要。
補充知識
大腦中動脈（MCA）是頸內動脈兩個終支中較大的血管，缺血及梗塞最常累及此區。MCA在解剖上一般分成4段或5段，M1=水平段，M2 =腦島段，M3=島蓋段，M4、M5合稱為終末段或皮層支。
1=頸內動脈
2=大腦前動脈
3=Heubner返動脈
4=顳前動脈
5=外側豆紋動脈
6=大腦中動脈分叉處
7=大腦中動脈膝部
8=側裂頂部（環狀溝上限）
M1段：自頸內動脈分叉部起點延伸至側裂，可以看出它包含兩部分，分叉前段及分叉後段。分叉前段是單獨的主幹，分叉後段則可能是單幹，雙幹、三幹甚至更多。
大腦中動脈高密度徵（hyperdense middle cerebral artery sign, HMCAS）的確定標準：
密度：底限——MCA密度高於周圍腦組織，高於對側MCA，高於腦內其他動脈和靜脈；高限——在骨窗片上消失。
部位：單側性，MCA第1段或第2段自發出現密度升高達幾個毫米。
伴隨體徵：對側出現偏癱。
時間：較晚的CT片上，MCA在周圍低密度組織襯託下會顯得密度高一些。因此，宜在6h或3h的CT片上診斷HMCAS，晚於6h應結合其他規定作出診斷。
需排除紅細胞壓積升高、MCA鈣化和外傷等引起的MCA密度升高。
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