A 25-year-old female patient visited the neurology outpatient clinic with severe holocranial headache that had persisted for 2 months. The pain was intermittent and relieved by analgesics. Clinical examination was unremarkable.\nComputed tomography (CT) scan of the brain showed absent bony carotid canal on the left side [Figure and ]. Magnetic resonance angiography (MRA) [Figure and ] showed complete absence of the cervical and petrous part of the left ICA. An abnormal vessel was seen arising from the cavernous segment of the right ICA. This vessel was passing across the floor of sella, reconstituting the cavernous and supraclinoid segments of the left ICA, and continuing as the left MCA. Aplasia of A1 segment of left ACA was also observed.\nMagnetic resonance imaging (MRI) showed absent left ICA flow void with an abnormal flow void in the sella [Figure and ]. No evidence of any SAH or aneurysm was seen. The vertebrobasilar system was normal.\nDoppler imaging [Figure –] showed complete absence of the left ICA. The left common carotid artery (CCA) was seen continuous with the external carotid artery (ECA). The left CCA and ECA showed high resistance flow with narrow systolic peak and low diastole. Since the right CCA has to compensate for the absent left ICA, it showed low resistance flow with broad systolic peak and high diastolic flow.\nLateral radiograph of the skull [] and the corresponding sagittal reformatted CT scan [] showed a well-defined lytic area in the anteroinferior aspect of the sella due to the abnormal intercavernous vessel traversing across it.
The patient was a 63-year-old female with hypertension and diabetes. She had no history of smoking or heart disease. She had undergone surgery to clip a cerebral aneurysm 3 years previously and the treating neurosurgeon responsible at the time had reported difficulty with catheterization of cervical arteries. She was examined with Doppler ultrasonography of carotid and vertebral arteries, which showed that the left common carotid artery had a smaller caliber than the right ( ), the left carotid bifurcation could not be observed, and the left common carotid artery only led to the left external carotid artery ( ). Angiotomography was ordered, showing agenesis of the left internal carotid artery ( ). The patient remains asymptomatic and attends regular follow-up consultations.