Ethnic differences in syringomyelia in New Zealand

To determine the prevalence of syringomyelia in a defined population in New Zealand and measure the prevalence of syringomyelia in the three main ethnic groups (Maori, Pacific people and Caucasians/others) living in this region.

A retrospective study of all confirmed cases of syringomyelia diagnosed in residents of northern New Zealand from 1961 to 2003.

In all, syringomyelia was diagnosed in 137 patients. The mean age at onset of symptoms was 27.5 years and mean age at diagnosis was 32.6 years. The incidence of new cases increased from 0.76/100,000 a year between 1962 and 1971 to 4.70/100,000 a year by 1992-2001. The prevalence of syringomyelia in 2003 was 8.2/100,000 people: 5.4/100,000 in Caucasians or others, 15.4/100,000 in Maori and 18.4/100,000 in Pacific people (chi2 = 37.0, p<0.0001). Syringomyelia was more often associated with an isolated Chiari I malformation in Pacific people (84.4%) as compared with 42.9% of Maori and 38.2% of Caucasians or others (chi2 = 62.3, p<0.0001).

The prevalence of syringomyelia is higher in northern New Zealand than in studies carried out before the advent of magnetic resonance imaging. The prevalence is particularly high in Maori and Pacific people. The cause of the ethnic differences in the prevalence of syringomyelia identified in this study is unexplained and warrants further investigation.