The incidence of double hypoglossal canal in Japanese: evaluation with multislice computed tomography.

Double hypoglossal canal, namely a hypoglossal canal bridging, is a normal variation of the hypoglossal canal. Racial differences in the prevalence of double hypoglossal canal have been reported. We evaluated the prevalence of double hypoglossal canal in a Japanese population with multidetector computed tomography (MDCT). We reviewed five hundred and ninety consecutive patients (mean age, 61 years: range, 15-94 years: 254 men, 336 women) who underwent computed tomographic angiography (CTA) of the brain for a variety of CNS abnormalities. Two radiologists achieved consensus on the canal being single or double, and measured the sizes of single canals on CT images. Kappa statistics was used to test the reliability between the 2 investigators. A logistic regression was used to evaluate the prevalence of double hypoglossal canal and the following factors: sex, age, and laterality. Student's t-test was used to evaluate the asymmetry of single hypoglossal canal diameters. Statistical significance was accepted at P < 0.05. Double hypoglossal canal was identified in 16.9% of the patients, and was bilateral in 2.2%. Double hypoglossal canal was significantly more frequent on the left side than right (P = 0.004, odds ratio = 1.79) and in males than females (P = 0.011, odds ratio = 1.67). A larger left or right-sided canal was found in 31.6% and 12.2% of the patients, respectively, following the same side preference as that of double hypoglossal canal. Almost perfect agreement was achieved between the two readers (k = 0.975). In this Japanese population, the prevalence of a double hypoglossal canal was 16.9%, of which 2.2% were bilateral. Double hypoglossal canal was more frequent in males than females, and on the left side than right.