During the study period, 110 patients were selected according to our inclusion criteria in the study centers. Of the 110 patients, 51 were from CHU-Kara (46.4%) and 59 from Hôpital Dogta-Lafiè (53.6%). The age of the patients included in our study ranged from 28 to 85 years, with an average of 62.1 ± 12.6 years. The most common age group was 55 to 65 (39.5%). The sex ratio M/F was 1.4.

Forty-nine (40.9%) patients had at least one major cardiovascular risk factor. In isolation, hypertension was present in 44 patients (40%) and diabetes in eight (14.5%). Thirty-eight (34.5%) patients had elevated total cholesterol levels (above 2 g/L), including 81.8% with LDL-cholesterol levels above 1.5 g/L. Eight patients (21.5%) had low HDL cholesterol (<0.35 g/L). Eighteen patients (16.4%) had a history of ichemic stroke. There were no smoking patients in our series. Thirty-four (30.9%) patients had at least two major cardiovascular risk factors.

Vascular lesions on Doppler ultrasonography of the cervical and encephalic arteries were present in 88 patients, or 80% of ischemic stroke cases. Significant stenoses were found in 60 patients (55%) and occlusions in 28 patients (25%) on all echodopplers. The lesions were tight stenoses (80.9%) and occlusions (19.1%) on atheromatous plaques or post-dissection. Figure 1 and Figure 2 show examples, on the one hand of carotid stenosis by atheromatous plaque and on the other hand an occlusion by thrombus on a carotid dissection.

Ultrasound lesions were right (35%), left (23%) and bilateral (42%). In isolation, lesions were located cervically in 52 patients (59.1%), intracranially in 36 patients (40.9%) and both cervically and intracranially in 18%. The carotid bulb accounted for 38.7% of lesion sites and the middle cerebral arteries for 26.1% ( Table 1 ). Significant stenoses and occlusions involved the carotid system in 78.6% and the vertebro-basilar system in 21.4%. In the cervical region, bulbar carotid and post-bulbar stenoses accounted for 61.5%. In the encephalic region, stenoses of the middle and posterior cerebral arteries accounted for 61.1% and 30.5% of lesions respectively ( Table 2 ). In this study, hypertension was significantly associated with the occurrence of occlusion. There was also a significant association between diabetes, dyslipidemia and the occurrence of stenosis ( Table 3 ).

ACM Middle cerebral arteries ACP Posterior cerebral arteries TB Basial trunk.

ACM Middle cerebral arteries ACP Posterior cerebral arteries.

Ischemic stroke in our study involved patients with an average age of 62.1 ± 12.6 years. This average age is similar to that reported in 2015 by Belo in Togo 2015 (60.3 ± 12.8 years) [3] and Mboup in Senegal (63.4 ± 15.8 years) [10] . In developed countries, on the other hand, DALYs occur 10 years later with a mean age of 73.7 ± 2 years and 73 years [11] .

This disparity seems to be linked to the higher life expectancy in industrialized countries, on the one hand, and the early detection of cardiovascular risk factors and their early and appropriate management, on the other.

In our study, men predominated, with a sex ratio M/F of 1.4. Belo and Goeh-Akoue in Lomé [3] [12] , Baldé [13] in Conakry 2018 had made the same observation. We can note that ischemic strokes affect men more than women on the African continent.

The ischemic stroke is favored by certain cardiovascular risk factors. The four predominant cardiovascular risk factors in our study were arterial hypertension (40%), dyslipidemia (34.5%), diabetes (14.5%) and a history of stroke (9.1%). Belo in 2015 in a study in Lomé reported hypertension as the main risk factor (86.6%), followed by total hypercholesterolemia (54.3%) and diabetes in 10.8% of cases [3] . Similar findings have been reported in Guinea and Morocco [13] [14] . A history of ischemic stroke was found in 9.1% of patients, as in Morocco 9.2% [14] and Guinea [13] , confirming that a history of ischemic stroke constitutes a high risk of ischemic stroke recurrence. The absence of a precise lesion search for ischemic stroke, as well as the lack of adequate management of these lesions, would be sources of ischemic stroke recurrence.

Doppler ultrasonography of the cervical and encephalic arteries in our patients revealed vascular lesions in 80% of cases. The carotid system was three times more affected in this study. According to Rénou, lesions of the supra-aortic trunks involved the carotid territory in eight out of two cases, compared with the vertebro-basilar territory [15] . The anatomy of the bulbar portion of the carotid artery may explain this peculiarity.

In our study, transcranial Doppler ultrasound revealed lesions, whereas Doppler ultrasound of the cervical vessels was normal in 21 patients (23.9% of cases). These results show the importance of coupling transcranial Doppler with Doppler ultrasound of the cervical arteries in the etiological diagnosis of AVCI. In addition, the effects of lesions in the cervical arteries are also felt in the brain, and it is essential to assess their importance both for initial treatment and for follow-up.

It is also essential to assess the completeness of the polygon of Willis, and the quality of bypass conduits such as the anterior and posterior communicantes in the event of significant stenosis or upstream occlusion. Today, Doppler ultrasonography of the cervical arteries without transcranial Doppler at the encephalic level is inconceivable. Moreover, Purroy reported that a patient with moderate to severe intracranial or extracranial stenosis on Doppler ultrasonography of the cervical vessels had a threefold increased risk of ischemic stroke [16] . Doppler ultrasonography of the supra-aortic trunks (TSA) of the cervical and encephalic arteries could thus be used not only as a means of exploring the etiology and lesions of ischemic stroke, but also as a means of monitoring patients with risk factors for ischemic stroke, and as a prognostic tool for patients who have already suffered a ischemic stroke. For our part, the essential thing would be to detect these plaques, monitor them, especially in high-risk patients, and offer them endoluminal or surgical treatment before a genuine ischemic stroke occurs. This decision can only be taken with the help of hemodynamic data on lesions and, above all, on downstream intracranial lesions. Hence, once again, the need to couple transcranial Doppler with Doppler ultrasound of the cervical arteries.

In our study, hypertension, dyslipidemia and diabetes were associated with the existence of vascular lesions on Doppler ultrasound. Debette et al. in 2011 reported an association between hypertension and the presence of vascular lesions in patients with ischemic stroke (odds ratio = 1.67; 95% confidence interval = 1.32 to 2.1; p < 0.0001) [17] . An association between hypertension and the occurrence of occlusive dissection was demonstrated in this study. Similarly, an association between diabetes and the occurrence of stenosis was demonstrated, with p = 0.009. Other authors such as Goeh-Akue, Baldé and Belo have made similar findings [11] [13] [18] . There is every reason to believe that diabetes is more conducive to stenoses, while hypertension is more likely to cause occlusions. Dyslipidemia has been associated with both stenosis and occlusion. This shows how often it is necessary to be aggressive in terms of diet and medication for dyslipidemia, while following and respecting recommendations for patients according to their risk level.

Follow-up of patients at high cardiovascular risk should therefore systematically include supra aortic trunk Doppler ultrasonography. The frequency of Doppler ultrasonography of upraortic trunk may be quarterly, semi-annually or annually, depending on the level of risk and, above all, on the results of the first supra aortic ultrasonography.