Association between frontal-sinus size and syringohydromyelia in small-breed dogs

To determine whether frontal-sinus size is associated with syringohydromyelia. Medical records and magnetic resonance images of 62 small-breed dogs. Medical records and magnetic resonance images were reviewed retrospectively for evaluation of frontal-sinus size and syringohydromyelia. A Yates-corrected 2-tailed chi2 test was used to determine whether an association existed between absent or miniscule frontal sinuses and syringohydromyelia. The strength of the association was evaluated by means of prevalence and odds ratios. Absent or miniscule air-filled frontal sinuses were detected in 28 of 62 (45%) dogs, and syringohydromyelia was detected in 12 of 62 (19%) dogs. Syringohydromyelia was detected in 10 of 28 dogs with absent or miniscule frontal sinuses (prevalence, 36%; 95% confidence interval, 16% to 55%) and in 2 of 34 dogs with larger frontal sinuses (prevalence, 6%; confidence interval, 0% to 15%). The probability of detecting syringohydromyelia in dogs with absent or miniscule air-filled frontal sinuses was significantly greater than the probability of detecting it in dogs with larger frontal sinuses. The prevalence ratio was 6.1, and the odds ratio was 8.9. An association between frontal-sinus size and syringohydromyelia was identified in small-breed dogs, suggesting that the pathogenesis of syringohydromyelia in some instances may involve abnormal development of the entire or supratentorial part of the cranium, as opposed to being limited to the infratentorial part.