Study On Optimal Velocity Of Transcranial Doppler In Diagnosis Of Middle Cerebral Artery Stenosis

Objective:Internal carotid atherosclerosis is the most common cause of ischemic stroke in western population. However, atherosclerotic stenosis of intracranial large arteries occur frequently in stroke patients in Asia. It is considered that 22-26% of ischemic stroke in Asia is contributed to atherosclerotic stenosis of intracranial large artery, especially the middle cerebral artery (MCA). Elderly, hypertension, diabetes and hyperlipidemia were all the risk factors of MCA stenosis. The prevalence escalated quadratically with increasing number of the risk factors, from 7.2% for one factor to 29.6% for four. Among patients with a unilateral marked stenosis, 60.7% had a recurrent stroke or TIA in the territory of the stenotic artery. The rate of recurrence of ischemic stroke is related with the severity of stenosis. The more severity the stenosis is, the recurrence is more possible. So it is important to diagnose and grade stenosis of MCA for the prognosis and treatment of patients. Now, there are several methods to detect intracranial arteries, such as magnetic resonance angiography (MRA), computed tomography angiography (CTA), digital subtraction angiography (DSA), transcranial Doppler (TCD). Up to date, DSA is still the"gold standard"for diagnosing stenosis of intracranial arteries. Today TCD is being applied to clinic more and more often than before for its convenience, rapid diagnosis and noninvasiveness. Now most researches have confirmed the value of TCD to diagnose MCA stenosis. But the diagnostic criteria of MCA stenosis are uncertain. The article will confirm the value of TCD to diagnose MCA stenosis and detect the optimal value of velocity for diagnosing MCA stenosis.Methods:45 patients with MCA stenosis were checked out by magnetic resonance angiography (MRA) from 2006 to 2007 in Shenyang Military General Hospital. 35 patients with MCA stenosis on average of 51 years of old, including 23 men and 12 women, were considered as objective group except for 10 patients with bad acoustic window or with internal carotid artery out of skull stenosis. At the same time, 35 normal subjects on average of 53 years old served as the control group. Then mean velocity (Vm), pulsatility index (PI), the window of cortex and sound of MCA of them were measured. According to the severity of MCA stenosis the normal-mild, moderate and severe stenoses were classified by MRA, and compared among them. Set the Vm as >110cm/s,>120cm/s,>130cm/s, >140cm/s,>150cm/s, the different ROC (receiver operator characteristic) curves were got and determined which cutoff point was the best for diagnosing the MCA stenosis.Results :1 In the case group,the number of vessels of normal-mild stenosis were 32, their mean MCA velocities were 106.92+-16.95cm/s which was faster than the control group(P<0.05). Most of them ,the window exist frequently and the acoustic frequency were clear and soft. 2 of vessels have change of the Pathologic vortex. The number of vessels of moderate stenosis were 20, their mean MCA velocities were 138.11+-10.81cm/s which was more faster than the control group(P<0.05). Most of them ,the window exist frequently and the acoustic frequency were clear and soft. 9 of vessels have change of the Pathologic vortex.4 of vessels have change of the Pathologic vortex with lower noise. The number of vessels of severity stenosis were 18,their mean MCA velocities were 207.12+-50.8 cm/s which was more faster than the control group(P<0.05). 10 of vessels have change of the Pathologic vortex with lower noise. 8 of vessels have change of the Pathologic vortex with high noise. In the control group, the mean MCA velocities were 84.26+-31.2cm/s . The window exist frequently and the acoustic frequency were clear and soft. 2 There was a obvious difference of mean velocity among these four groups, while pulsatility index not. 3 Through calculating the biggest areas under ROC,we concluded the optimaI values of mean velocity for diagnosing MCA stenosis was l20cm/s,and according to this cutoff Point,It is specificity and sensitivity in diagnosing MCA stenosis were 92.59% and 81.25%(P<0.05).4 The false negative rate and the false passive rate of diagnosing MCA stenosis by TCD were 7.41% and 18.75%.5 The accurate ratios in diagnosis of MCA stenosis were the same in the whole between the TCD and MRA.Conclusions:The optimal Vm for diagnosing MCA stenosis was l20cm/s. There should be a good correlation between the TCD and MRA in diagnosing the MCA stenosis. This method provides a noninvasive and reliable method for diagnosing MCA stenosis and allows 1ongitudal monitoring of the relationship between clinical outcome and hemodynamic change.