Common Carotid Artery Diaphragm presenting as transient syncope

Carotid diaphragm usually can cause artery stenosis essentially affecting the internal carotid artery (ICA) beyond the bulb segment. Patients are often middle aged and the onset of symptoms typically begins with syncopes leading to ischemic stroke. More than 50 cases have been reported in which all lesions showed as stenosis located in the ICA, in this article, we report a rare common carotid artery (CCA) diaphragm revealed in a 59 year-old female suffering from transient syncopes. This is the third case reported in the literature.

cm/second with turbulent color jet were detected at the level of proximal carotid web ( Fig. B ), suggesting a greater stenosis then 70%. Velocities in the left internal carotid artery were normal, excluding stenosis. An aneurismal dilatation with approximately 5 cm length was also detected at the lesion. Subsequently under further evaluation, it was confirmed by computed tomography angiography (CTA) ( Fig. C and D ) showing a transverse, low density strip on proximal part on the right CCA causing lumen stenosis, with post aneurismal enlargement.   A carotid stent placement was refused by the patient. The aneurysm location in the proximal CCA increased the technical difficulty of a carotid endarterectomy operation. Medical therapy with anti-platelet (aspirin or clopidogrel bisulfate) was a good alternative.
Our patient benefits from a regular follow up and experienced no more neurologic effects.

Discussion
After searching in the MEDLINE/Pub Med/Embase databases using combinations of the keywords diaphragm, common carotid, carotid stenosis, and atypical fibro muscular dysplasia (FMD), there were only two case reports of CCA diaphragm  reported discovered by ultrasound reported in the literature [1 ,2] .
Carotid diaphragms are a non-atheromatous arterial cause of ischemic stroke, especially in people under 65 years old. This anomaly is more common in the African or African-American population [3] . This cause of cerebro-vascular accident (CVA) results from a non-atheromatous overgrowth of the intima of the arterial wall which appears in imagery as an endoluminal web causing carotid stenosis [3 ,4] . Patients with carotid diaphragms can lead to locally formed thrombi that can cause recurrent embolic stroke [4] .
Carotid diaphragm has been considered as a subtype of FMD with non atherosclerotic and non-inflammatory histopathology. FMD is a disease of the musculature of the arterial wall that leads to aneurysm, dissection, stenosis or occlusion [5][6][7] .
Intimal dissection and atheromatous plaque are the two main differential diagnoses of the carotid diaphragm. However, the appearance of a membrane implanted on a regular non atheromatous wall and the absence of any other localization of atheroma distinguish au authentic diaphragm from a focal atheromatous plate. In addition, the very proximal localization of the diaphragm, in the CCA, does not suggest a dissection, which is usually localized downstream of the bulb [6] .
Carotid diaphragm mainly occurs in the ICA and the vertebral artery . . All carotid diaphragms were typically in the carotid bulb or in the proximal-to-middle segment of the ICA. Only two case reports of CCA diaphragms have been reported [1 ,8] .
Most carotid diaphragms reported earlier were initially diagnosed by CDU. The characteristic of ultrasound finding is described as a membranous appearance or a linear band tissue. We report a case of carotid diaphragm, atypical by its rare localization at the level of the CCA on one hand and by the association with an aneurysm of the downstream carotid on the other hand. In addition, aneurysm is not common in the extra-cranial carotid artery caused by the carotid diaphragm [8] . In fact, we believe that the local CCA stenosis may cause localized resistance of blood vessels, hemodynamic disturbance and high pressure on the vessel wall which can lead to its widening.
Management of carotid diaphragm varies depending on patient's symptoms. Medical treatment with antiplatelet is typically used for asymptomatic patients. For several symptomatic patients, Carotid endarterectomy or carotid artery stenting can been proposed as an alternative treatment. The anatomic aneurysm location in the proximal to the middle of CCA in our patient made this alternative technically difficult.

Conclusion
We presented an unusual case of CCA's diaphragm with an accompanying aneurysm, first detected by CDU and subsequently confirmed by CTA.
To our knowledge, this is the third reported CCA diaphragm that is also possible FMD.
This case detailed ultrasound features of carotid diaphragm, so that clinicians can be more mindful with such ultrasound findings in the future particularly while exploring syncope in young adults.