Intracranial Internal Carotid Artery Calcification: a Predictor of Stroke in the Next Five Years
WCS Chan, WL Poon, WS Wan
Hong Kong J Radiol 2012;15:143-8
Objective: The fact that calcification in the coronary artery is associated with ischaemic heart disease is well-known. Calcification is also very common in the transcranial and intracranial segments of internal carotid arteries. Previous studies on the association of calcification in the intracranial segment of the internal carotid arteries with stroke have yielded controversial conclusions. In this study we aimed to investigate the relationship between calcification of the transcranial and intracranial internal carotid arteries and the five-year stroke risk.
Methods:This was used as a case-control retrospective cohort study designed to avoid recall bias and allow more aggressive risk factor evaluation. Consecutive patients aged 50 to 80 years referred for computed tomography of the brain over a five-week period in 2005 were studied. The computed tomography images were reviewed by two radiologists blinded to clinical outcomes to assess the presence and degree of calcification in the transcranial and intracranial segments of both internal carotid arteries semi-quantitatively. Each artery was given a calcium score to reflect the calcium burden (none = 0, dot calcification = 1, thin or thick calcification affecting one side of the wall / thin calcification affecting both sides of the wall = 2, thick calcification affecting both sides of the wall = 3). The scores of both arteries were summed and thus patients with no internal carotid artery calcification had 0 scores and those with the highest calcium load scored 6. Each patient was categorised into two groups reflecting the calcium burden in these arteries, namely low calcium score (0-2) and high calcium score (3-6). Clinical records were reviewed over the subsequent five-year period to identify the development of a clinical acute stroke. The age, gender, history of smoking, diabetes mellitus, hypertension, hyperlipidaemia, and previous stroke were documented. Patients with the presence of an intracranial mass, extra-axial haemorrhages, or previous intracranial radiotherapy were excluded. Multiple logistic regression was applied to determine the association between incident acute stroke in the study period and internal carotid artery calcium scores and other stroke risk factors. The odds ratios for stroke and internal carotid artery calcium score and other risk factors were calculated and statistical significance was set at 5%. Possible multicollinearity among the factors was checked by the correlation matrix method and examination of tolerance.
Results:A total of 678 patients underwent computed tomography of the head over a five-week period between July and August 2005, and 461 (aged 50 to 80 years; 240 males, 221 females) were included in our study. In all, 271 (58.8%) patients were designated a low calcium score and 190 (41.2%) a high calcium score. Fifty-four patients developed a new onset of clinical stroke in the subsequent five-year period, resulting in a five-year stroke incidence of 11.7%. Binary logistic regression analysis revealed that those with high calcium score had a statistically significant higher incidence of stroke over that period compared to those with a low calcium score (adjusted odds ratio = 2.70; p < 0.05). This was independent of age, gender, smoking history, diabetes, hypertension, hyperlipidaemia, and previous stroke.
Conclusions: The presence of high rather than low calcium burden in the transcranial and intracranial segments of internal carotid arteries is an independent predictor of a higher clinical stroke risk in the ensuing five-year period. The odds (risk) ratio of five-year incident stroke in patients with a high score was 2.7-fold that of those with low scores.
中文摘要
顱內頸動脈鈣化：五年內中風的預測因子
陳煥章、潘偉麟、溫詠雪
目的：眾所週知，冠狀動脈的鈣化與缺血性心臟病有關。而經顱及顱內的頸內動脈出現鈣化很常 見。過往有關顱內頸動脈鈣化與中風關係的研究結果有爭議。本文探討經顱及顱內頸內動脈鈣化情 況與患者五年內中風的風險是否相關。
方法：為避免病人偏差以及積極地評估風險因素，本研究採取病例對照的回顧性研究。研究對象為 2005年的連續五個星期內被轉介作腦CT的所有50至80歲的病人。兩名不知道病患預後的放射科醫生 回顧CT影像，並為病人經顱及顱內的內頸動脈是否出現鈣化以及鈣化程度來作半定量分析。他們為 每根動脈評價其鈣化積分來反映血管的鈣化程度：0=無鈣化、1=點狀鈣化、2=厚或薄鈣化並影響一 邊血管壁，或薄鈣化影響兩邊血管壁、3=厚鈣化現象影響兩邊血管壁。然後把兩根血管的鈣化積分 加起來。因此未有發現頸內動脈鈣化的病人的鈣化積分會是0，而鈣化積分為6的病人的血管鈣化負 荷為最高。再按每位病人血管的鈣化負荷分為兩組：低鈣化積分（即0至2分）及高鈣化積分（即3 至6分）。從2005年開始檢閱病人五年間的病曆紀錄找出他們是否有急性中風的情況。臨床紀錄記載 了病人年齡、性別、吸煙紀錄、糖尿病、高血壓、高血脂和中風紀錄。而有顱內腫瘤、神經軸外出 血、及曾接受顱內放射治療的病人則不被列入研究範圍內。利用多重邏輯回歸分析決定研究期間急 性中風的發生與內頸動脈鈣化積分以及其他中風危險因素的關係，並計算其比數比，5%為達至統計 顯著性。再用相關係數矩陣及檢測限差的方法找出多項因素的多元共線性。
結果：2005年7月至8月的五個星期內共678名病人接受腦CT檢測，其中461人被納入研究範圍（年齡 介乎50至80歲的240男性及221女性）。271人（58.8%）屬低鈣化積分，另190人（41.2%）屬高鈣化 積分。54人在其後的五年內出現首發中風，即五年中風率為11.7%。二元變數邏輯回歸分析顯示鈣化 積分高的病人比鈣化積分低的病人的中風率明顯高（調整後比數比=2.70；p < 0.05）。這點獨立於病 人年齡、性別、吸煙紀錄、糖尿病、高血壓、高血脂和中風病史。
結論：經顱及顱內的內頸動脈有高度鈣化的情況是患者五年內中風風險的一項獨立預測因子。鈣化 積分高的病人五年內中風的風檢是鈣化積分低的病人的2.7倍。