記住我
CASE REPORT
Year : 2023 | Volume
: 9
| Issue : 1 | Page : 44-47
Importance of multiplanar reformation angiographic images for the detection of carotid web: A case series
Laura Zelada-Ríos1, Danny Barrientos-Imán2, Lourdes Simbrón-Ribbeck3, Carlos Abanto Argomedo2, Jorge Ramírez-Quiñones2, Pilar Calle La Rosa2, Ana Valencia Chávez2, Ricardo Otiniano-Sifuentes4
1 Department of Neurovascular Diseases, Instituto Nacional de Ciencias Neurológicas; San Fernando School of Medicine - Postgraduate Unit, Universidad Nacional Mayor de San Marcos, Lima, Peru
2 Department of Neurovascular Diseases, Instituto Nacional de Ciencias Neurológicas, Lima, Peru
3 Diagnostic Imaging Department, Universidad Peruana Cayetano Heredia, Lima, Peru
4 Department of Neurovascular Diseases, Instituto Nacional de Ciencias Neurológicas; School of Public Health and Administration, Universidad Peruana Cayetano Heredia, Lima, Peru
Correspondence Address:
Ricardo Otiniano-Sifuentes
Jr. Ancash 1271, Barrios Altos, Lima 15003
Peru
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/bc.bc_75_22
Carotid web (CW) is considered a variant of intimal fibromuscular dysplasia. CW represents between 9.4% and 37% of ischemic strokes that were initially misclassified as “cryptogenic.” However, in Latin America, there is a lack of detection. We present 5 cases of ischemic stroke due to CW and discuss the usefulness of multiplanar reformatting (MPR) imaging in computed tomography angiography. The identification of CW with the use of tridimensional (3D) reconstructions and maximum intensity projection was 20%, the rest was misdiagnosed as atherosclerotic plaque. With the MPR, the identification of typical CW findings was improved, such as a thin septum, a shelf-like image, and a mountain shadow-like image. However, one must be alert to changes in the 3D disposition of the carotid bifurcation, as they may mask the typical CW findings. A good practice is to align the internal carotid artery exactly posterior to the external carotid artery in the sagittal plane.
Keywords: Carotid web, cryptogenic stroke, computed tomography angiography, multiplanar reformation
Carotid web (CW) is considered a variant of intimal fibromuscular dysplasia,[1] described as a shelf-shaped filling defect arising from the posterolateral wall of the carotid bulb.[2] CW represents between 9.4% and 37% of ischemic strokes that were initially misclassified as “cryptogenic.”[3],[4],[5],[6] However, in Latin America, there is an underreporting due to many factors, such as the poor recognition of this entity through ultrasonography. Although ultrasonographic studies can detect CW, their detection capacity is operator dependent.[7],[8]
Angiographic studies of supra-aortic vessels, such as digital subtraction angiography (DSA) or noninvasive studies, such as computed tomography angiography (CTA) or magnetic resonance angiography (MRA), allow for the diagnosis of CW based on its location and shape.[2] However, viewing only tridimensional (3D) reconstructions or maximum intensity projections (MIP) can mask CW. We present 5 cases of ischemic stroke due to CW and highlight the usefulness of multiplanar reformatting (MPR) imaging in CTA.
Case ReportBetween December 2020 and April 2021, there were 84 cases of ischemic stroke, in 5 of these patients (6.0%); the etiology was CW [Table 1]. They were three women and two men aged between 35 and 43 years. A previous stroke (transient ischemic attack) was only reported in case 2, which occurred 2 months earlier. Patients had no cardiovascular risk factors; the only antecedent was headache in cases 3 and 5. In all cases, the cerebral infarction was in the territory of the middle cerebral artery, in the M1 (two cases), the M2 (two cases), and M3 (one case) segments. Echocardiogram and Holter studies were normal. Cervical CTA showed CW ipsilateral to the affected hemisphere. In two cases, there were bilateral CWs and one of them also had a thrombus superimposed on one of its membranes (case 5). Discharge treatment consisted of acetylsalicylic acid 100 mg/day and high-intensity atorvastatin. No recurrences were reported in an average of 6 months of follow-up.
The identification of CW with the use of 3D reconstructions and MIP was 20%; the rest was misdiagnosed as atherosclerotic plaque. With MPR, in the axial planes, a septum was identified at the level of the carotid bulb compatible with CW in 60%. In sagittal planes, in all cases, there was a shelf-like image dependent on the posterolateral wall. In the coronal plane, in 60%, an image was found as a mountain shadow. The presence of at least two of these findings was 80%, and the presence of all three was 40% [Figure 1].
Figure 1: Images of 3D and MPR reconstructions by CTA. Yellow circles indicate imaging modalities that correctly identified a typical CW finding. Green circles indicate imaging modalities that did not identify a typical CW finding. Arrows point to the CW. The typical CW finding in the MPR sagittal plane is a shelf-like image that was identified in all 5 cases; In the axial plane, the typical finding is a thin septum dividing the carotid bulb. This was only found in 3 of our cases. Finally, in the coronal plane, the CW is observed as a mountain shadow image, and it was identified in 3 of our cases. In case 5, a thrombus adhered to the right CW is observed in the axial plane of the MPR (white arrows). R: Right, L: Left, CTA: Computed tomography angiography, CW: Carotid web, MPR: Multiplanar reformatting, 3D: Tridimensional Discussion We report clinical and imaging characteristics of 5 cases of CW. We found that patient's characteristics that guided the diagnosis were age group and absence of cardiovascular risk factors. The use of MPR by CTA facilitated the identification of CW compared to MIP and 3D reconstructions. MPR findings were the presence of a thin septum in the axial planes, followed by a shelf-like image in the lateral planes and a mountain shadow-like image in the coronal planes.
Currently, CW can be detected with a comprehensive diagnostic workup; therefore, it is not correct to define CW as a cause of cryptogenic stroke. However, in previous studies, ischemic strokes associated with CW represented up to 37% but were misclassified as cryptogenic strokes, probably because their causal role was unknown.[6] In Latin American countries such as Peru, there are few reports of this etiology.[7] Some clinical characteristics, such as those found in our cases, can guide the diagnosis of CW. In these patients, it is important to perform angiographic studies of supra-aortic vessels such as CTA, MRA, or DSA. However, in noninvasive angiographic studies, CW may be missed if only 3D reconstructions or MIPs are viewed.
MIPs display only the voxels that have the highest contrast intensity in a given projection. This generates a sum of images that gives a depth effect that varies according to the determined slice thickness. If the thickness of the MIP slice is wide, it can hide the CW, especially if it is small. The MPR, on the other hand, gives us images in different planes with a minimum thickness. This allows a better appreciation of the typical characteristics of CW and thus distinguishes them from its main differential diagnoses.
Atherosclerotic plaque can mimic CW because they share a location in the carotid bulb. In our cases, MIP misdiagnosed atherosclerotic plaques instead of CW in 80% of cases. However, MPRs achieved better diagnostic accuracy. The sagittal plane was the one that best-detected findings compatible with CW: A membrane with a smooth edge that protrudes into the lumen giving a shelf-like image dependent on the posterior wall of the carotid bulb. In contrast, atherosclerotic plaque is not usually limited to the posterior wall of the bulb, also compromising the distal common carotid artery and above the carotid bulb. In addition, the plaque surface is usually irregular, with ulcerations, intraplaque hemorrhage, or calcifications.[9]
Another differential diagnosis is carotid dissections; because it also occurs in young adult patients without cardiovascular risk factors and has similar imaging findings. In the sagittal plane, an intimal flap from a dissection might resemble a shelf-like image; while in the axial plane, the double-lumen image of a dissection can be confused with the thin septum of a CW. However, dissections usually spare the carotid bulb and start 2 cm above the carotid bifurcation [Table 2].[1]
The visualization of these three findings, in their respective planes, depends on the anatomical distribution. Normally, the internal carotid artery (ICA) has a posterior-lateral origin to the external carotid artery (ECA); however, since the carotid bifurcation is in a soft and adipose environment, its 3D disposition can vary even with movements of the throat (coughing and swallowing) and mask the CW. For this reason, it is recommended to align the ICA exactly posterior to the ECA in the sagittal plane. This will allow to improve the visualization of typical CW finds in their respective planes.
In our case series, all patients were treated with aspirin, and there was no recurrence. However, we cannot affirm that aspirin is an effective treatment given that our series is very small and has a short follow-up. In addition, stenting and open surgery are also widely recommended in CW due to the high incidence of recurrent stroke in young patients.[3] It is necessary to design studies that identify the population of CW patients that best benefit from invasive treatment.
In conclusion, CW-compatible findings are a thin septum, a shelf-like image, and a mountain shadow-like image. The proper use of MPRs improves the identification of these findings and can increase the reporting of CW in Latin American countries. However, one must be alert to changes in the 3D disposition of the carotid bifurcation, as they may mask the typical CW findings.
Ethical approval
This study was approved by the Ethics Committee of the Peruvian National Institute of Neurological Sciences (No. 026-2021-CIEI-INCN). This case report was performed in accordance with the ethical standards of the Declaration of Helsinki.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
留言 (0)