Bony carotid canal hypoplasia in patients with moyamoya disease.

OBJECT: The natural history of moyamoya disease is not well known. We have observed that the bony carotid canal is hypoplastic in patients with adult onset moyamoya disease. Bony carotid canal development should represent internal carotid artery (ICA) development, and may stop with the beginning of ICA stenosis. The purpose of this study was to determine the onset of moyamoya disease by measuring the bony carotid canal.

METHODS: The normal diameter of the bony carotid canal was evaluated on 4-mm thick bone window CT scans of the skull base in 60 Japanese patients aged 20-80 years, who had minor head trauma or headache considered to be unrelated to the skull base or arterial systems. The relationship between age and bony carotid canal development was assessed in a second group of 50 patients aged 0-19 years, including 10 under 2 years, using CT scans with the same parameters. The diameter of the bony carotid canal in 17 Japanese patients with moyamoya disease was measured.

RESULTS: The normal diameter in adults was 5.27 +/- 0.62 mm (mean +/- SD). The bony carotid canal developed rapidly before approximately 2 years of age. After fusion of the bony suture, the bony carotid canal developed slowly. The mean diameter of the bony carotid canal was 3.31 +/- 0.44 mm in 11 adult patients with adult-onset moyamoya disease. According to the apparent curve of bony carotid canal development, ICA stenosis was assumed to start in early childhood.

CONCLUSIONS: Our findings suggest that most cases of Asian moyamoya disease may arise in childhood and that many Asian adult patients with moyamoya disease may develop occlusive vasculopathy in childhood.