Case 42 A 48-year-old otherwise healthy woman was admitted with persistent left-sided blurry vision which began 1 day prior to presentation. She had no vascular risk factors and did not suffer from migraines. Neurologic examination on admission revealed reduced visual acuity restricted to the left side. Left-sided optic neuritis. MRI FLAIR- and T2-weighted images showed no parenchymal lesions. Incidentally, a missing left carotid siphon signal void was noticed on axial T2-weighted images. Subsequently performed intracranial time-of-flight (TOF) and contrast enhanced (ce) MR angiography (MRA) showed agenesis of the left internal carotid artery (ICA). Intracranially, the left middle cerebral artery (MCA) and anterior cerebral artery (ACA) were connected with the left posterior cerebral artery (PCA) via a large posterior communicating artery (PCoA), which was functioning as a “reversed” fetal-type variant. The anterior communicating artery (ACoA) was missing. The external carotid artery (ECA) course was in continuity with the common carotid artery (CCA). In addition, a direct origin of the left vertebral artery (VA) from the aortic arch was present (Fig. B42.1, Fig. B42.2, Fig. B42.3). B-mode imaging revealed no atherosclerotic vascular changes and no signs of vessel dissection. The diameter of the right CCA was larger (5.9 mm) than the left CCA (3.4 mm). The left ICA was completely missing. Doppler spectrum analysis of both CCAs and ECAs revealed normal findings. Blood volume flow (BVF) in the right ICA (320 mL/min) and in the right V2-VA (170 mL/min) was within normal ranges. The left V2-VA BVF yielded raised values of 280 mL/min, resulting in a normal global BVF = CBF of 770 mL/min (Fig. B42.4, Fig. B42.5, Fig. B42.6, Fig. B42.7, Fig. B42.8). Left-sided transtemporal axial insonation revealed a prominent signal in projection of the PCoA with a flow direction toward the anterior circulation. Contralateral insonation also delineated the prominent left PCoA with a blue-coded vessel signal providing blood flow toward the left anterior circulation. Normal blood flow parameters were seen bilaterally in all basal cerebral arteries including the left PCoA. Transorbital insonation showed a normal antegrade flow and flow velocities within normal ranges in both ophthalmic arteries (OAs). Both middle meningeal arteries (MMAs) were examined to analyze their potential roles in supplying the OA. Both vessels were detectable. A higher flow velocity was seen in the left MMA (23/8 cm/s versus 15/6 cm/s) indicating that the ipsilateral MMA supplied the left OA (Figs. B42.9–B42.18). Fig. B42.19 shows a schematic of the patient’s extra-and intracranial brain-supplying arteries. Agenesis of the left ICA with intracranial blood supply of the left MCA and ACA from the left PCA. Left OA blood supply probably via the left MMA. Fig. B42.1 MR T2-weighted image, axial plane. Normal parenchymal imaging but missing signal void of the left carotid siphon (arrowhead). Fig. B42.2 3D TOF-MRA, axial maximal intensity projection (MIP). Prominent vessel in projection of the left PCoA (arrowhead). The left ICA and the ACoA signal are missing. Note that all vessels show normal diameters, indicating anatomic variants rather than vessel pathology. Fig. B42.3 Ce-MRA, coronal MIP. Left CCA with ECA ending and missing left ICA (arrows). Note a compensatory large left VA diameter with VA origin direct from the aortic arch (arrow). As in the TOF-MRA imaging (Fig. B42.2), a prominent communication between the posterior circulation and the left MCA and ACA can be seen (arrowhead). Fig. B42.4 Extracranial duplex, longitudinal plane. B-mode images of the right and left CCA. Note the large diameter difference: right 5.9 mm, left 3.4 mm. Fig. B42.5 Extracranial duplex, longitudinal plane. Left CCA with normal flow parameters despite the reduced diameter (flow velocity 75/19 cm/s). Fig. B42.7 Extracranial duplex, longitudinal plane. Right VA with normal BVF (170 mL/min), diameter 4.3 mm. Fig. B42.8 Extracranial duplex, longitudinal plane. Left VA with increased BVF (280 mL/min), diameter 4.8 mm. Fig. B42.9 TCCS (transtemporal approach), left-sided insonation, midbrain plane. Prominent vessel signal in projection to the left PCoA with a flow toward the anterior circulation (arrow). Fig. B42.10 TCCS (transtemporal approach), left-sided insonation, midbrain plane. Normal flow pattern in the presumed left PCoA (flow velocity 52/24 cm/s).
Left Internal Carotid Artery Aplasia as an Incidental Diagnosis in Optic Neuritis in Lupus Erythematosus
Clinical Presentation
Suspected Diagnosis
Initial Neuroradiologic Findings
Questions to Answer by Ultrasound Techniques
Initial Neurosonologic Findings
Extracranial Duplex Sonography
Transcranial Duplex Sonography
Conclusion