A 59-year-old white female presented to the emergency room after slipping and falling on ice. She had a past medical history of hypertension, hyperlipidemia, and asthma. The patient smoked one half pack of cigarettes per day. An axial 3D time of flight magnetic resonance imaging (MRI) scan was performed and identified the absence of the left carotid canal with an absence of flow signal (Figure ). An unusual vessel was also seen to arise from the right cavernous internal carotid artery (Figure ). The vessel traveled in the floor of the sella turcica (Figure ). Additional imaging with 3D reconstruction from a computed tomography (CT) angiography better defined an aberrant origin of the left internal carotid artery (Figure ). CT angiography noted the presence of an anterior communicating artery aneurysm, which was bilobed and measured 7 x 11 mm. The physical examination was unremarkable for any neurological deficits. Angiography found that the aneurysm was not amenable to endovascular treatment. Therefore, the patient underwent a right-sided craniotomy for clipping of her complex aneurysm and was soon discharged home with no complications.
A 42-year-old woman applied to the ophthalmology department with a complaint and history of a half-hour-long visual loss of her left eye one day ago. At clinical examination, both of her eyes were found to have full vision, and also microscopic fundus examinations revealed no pathological conditions. The patient gave a history of a prior application to an outer medical center with the same complaint, and there she had been diagnosed with a left ICA occlusion, following Doppler US and angiographic examinations. The patient applied to our department with the demand of an extracranial carotid Doppler US examination. At Doppler US, the right CCA diameter was found to be 8 mm, whereas the left one came out to be 4 mm (Figures and ). The right CCA bifurcation and the ICA and ECA were found to be normal. At the left side, spectral data for the ECA () and the particular branching which demonstrates that the vessel is ECA indeed were present, whereas there was no Doppler signal and gray-scale findings for the ICA (). Because the left CCA was hypoplastic and there were no findings of atherosclerotic plaques in other arterial segments; it was thought that the left ICA might not be suffering an occlusion at all, but instead it might well be agenetic. Based on the presumption of an ICA agenesis, a computed tomographic (CT) examination of the skull base was performed. CT images revealed a normally appearing right carotid canal but no clear image of the left one (). Then, the previous angiographic images of the patient were reevaluated, and it was then recognized that the left ECA and its branches were well visible, while the left ICA and its branches did not show any filling with contrast (). It was also noted that the filling of the left anterior and medial cerebral arteries was sustained by the patent anterior communicating artery following the injection of contrast into the right carotid artery () and also via the posterior communicating artery following the injection of the vertebrobasilary system (). In addition to the ICA agenesis, another surprising finding was that the right vertebral artery was not stemming from the right subclavian artery but instead was originating from the aortic arch, as its first branch (). It was finally understood that the patient did not have an occlusion of the left ICA, but instead her left ICA was agenetic. She also had an additional aortic arch anomaly. At the end, it was concluded that an ipsilateral CCA hypoplasia might be taken as a valuable clue in the differential diagnosis of ICA agenesis and occlusion.