Vol.:(0123456789) 1 3 Acta Neurologica Belgica https://doi.org/10.1007/s13760-018-0935-7 ORIGINAL ARTICLE Smaller caliber of the internal carotid artery in patients with ipsilateral aplasia of the A1 segment of the anterior cerebral artery: a study with CTA Kenneth Carels 1  · Sandra A. Cornelissen 1  · David Robben 2  · Walter Coudyzer 1  · Philippe Demaerel 1  · Guido Wilms 1 Received: 5 February 2018 / Accepted: 23 April 2018 © Belgian Neurological Society 2018 Abstract To measure the diameter and the transsectional area of the internal carotid arteries (ICA) on CT Angiography (CTA) in patients with aplasia of the A1-segment of the ACA (A1) and in patients with symmetrical A1, the mean diameter and area of the ICA on both sides were measured at a level of 2 cm below the skull base with a commercially available CT software in 41 consecutive patients with aplasia of A1 observed during a 12-month period on CTA and in 41 control patients with symmetrical A1. The mean diameter of the ipsilateral ICA was 3.83 ± 0.60 mm versus 4.86 ± 0.60 mm as mean diameter of the contralateral ICA and versus 4.40 ± 0.60 mm as mean diameter of both ICAs in the control group of patients. The mean area of the ipsilateral ICA was 11.58 ± 3.80 mm 2 versus 18. 82 ± 7.39 mm 2 as mean area of the contralateral ICA and versus 15.29 ± 4.42 mm 2 as mean area of both ICA in the control group of patients. These diferences are statistically highly signifcant. In patients with symmetrical A1, there was no statistical diference between the diameter or area of both internal carotid arteries. In conclusion, in patients with aplasia of A1, the ipsilateral diameter and area of the cervical ICA is smaller than the diameter and area of the contralateral ICA and smaller than the diameter and area of both internal carotid arteries in patients with symmetrical A1. Keywords CT Angiography · CTA · Circle of Willis · Aplasia A1 segment of the anterior cerebral artery · Internal carotid artery Introduction In 1996, Kane et al. [1] reported that in case of absence or hypoplasia of the A1 segment of the anterior cerebral artery (A1), the ipsilateral internal carotid artery (ICA) showed a reduced caliber on Magnetic Resonance Angiography (MRA) of the vessels of the brain obtained with a time-of- fight sequence. This study was performed with MRA on a relatively small number of patients. We wished to repeat this study with Computed Tomog- raphy Angiography (CTA) for three reasons. First, we pre- ferred CTA over MRA, because CT is less sensitive to fow changes, ofers better anatomical landmarks, is less depend- ent on cardiac output, and is more readily available. Second, on CTA, all neck vessels from the aortic arch to the vertex are included. In this way, patients with carotid stenosis are to be excluded from the study. Finally, with the Siemens “Syngo. via”-software in the “CT vascular workfow”, it was possible to measure not only the diameter of the cervi- cal internal carotid artery, but also the transectional area or surface of the vessel, which seems a more robust measure- ment to evaluate the caliber of a blood vessel. The fact that the cursor is automatically positioned perpendicular to the blood vessel also guaranties more accurate measurements. With this study, we wanted to confrm: • That in patients with aplasia of A1, the mean diameter and area of the ipsilateral ICA are smaller than that of the contralateral ICA. • That in patients with aplasia of A1, the mean diameter and area of the ipsilateral ICA are smaller than the mean diameter of both ICAs in patients without aplasia of A1. * Guido Wilms guido.wilms@uzleuven.be 1 Department of Radiology, UZLeuven, Campus Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium 2 ESAT/PSI, Department of Electrical Engineering, KU Leuven, Leuven, Belgium