Bottle Neck Sign of the Proximal Portion of the Internal Carotid Artery in Moyamoya Disease

Objective. We investigated morphologic features of the extracranial internal carotid artery (ICA) by carotid ultrasonography in patients with moyamoya disease. Methods. We performed conventional carotid ultrasonography and transoral carotid ultrasonography on 19 ICAs in 10 patients with moyamoya disease (moyamoya group) and 28 ICAs in 14 control subjects (control group). We evaluated whether the diameter was greatly reduced at the proximal portion of the ICA above the bulbus, like a champagne bottle neck, to be less than half that of the common carotid artery and whether the diameter of the ICA was smaller than that of the external carotid artery (diameter reversal) on conventional carotid ultrasonography. We then measured the internal diameter of the extracranial distal ICA by transoral carotid ultrasonography. We compared the incidence of a "bottle neck" appearance, diameter reversal, and the ICA diameter between the 2 groups. Results. The bottle neck and diameter reversal were shown in 14 (74%) and 16 (84%) of the 19 ICAs in the moyamoya group, respectively (χ2 test, P < .0001). However, neither of them was shown in the control group. The diameter of the distal ICA in the moyamoya group was significantly smaller than that in the control group (mean ± SD, 2.4 ± 0.60 versus 4.1 ± 0.52 mm; unpaired t test, P < .0001). Conclusions. These results suggest that rapid internal diameter reduction at the proximal portion of the ICA, characterized by a bottle neck appearance or diameter reversal, is an important morphologic feature of moyamoya disease.