A survey of Moyamoya disease in Hawaii

Moyamoya disease (MMD) is a rare entity in the US with a few retrospective series and sporadic cases reported in the US and North America. Although it is known that MMD exists in all races, there is a predilection for people of Asian origin. Because of the relatively high percentage of Asians living in Hawaii, it was hypothesized that the estimated prevalence of MMD would be higher in Hawaii than the remaining US. All practicing neurologists, neurosurgeons, neuroradiologists and major hospitals in Hawaii were surveyed for MMD patients treated during the past 10 years. Medical records and angiograms (when available) were reviewed and the diagnostic guidelines for MMD from the Ministry of Health and Welfare of Japan applied. There were 53 records reviewed in 42 patients; 21 fulfilled the criteria for definite Moyamoya disease which were the focus of this study. In Hawaii, the prevalence of MMD was higher in patients of Japanese descent compared to Caucasians (P=0.012) and higher than in the remaining US (P<0.001). Non-Japanese Asians and Pacific Islanders had a higher incidence of MMD than Caucasians that was not statistically significant. There was no difference in MMD among Japanese living in Hawaii or Japan. Males had an equal percentage of hemorrhage and infarcts; females tended to have a higher incidence of ischemic events rather than hemorrhage. Age and sex distribution of our series were similar to larger reported MMD studies. Our results suggest that: (1) Moyamoya disease in Hawaii has a higher incidence and prevalence than the rest of the US, largely due to the larger percentage of Asians, particularly Japanese, living in Hawaii; and (2) genetic rather than environmental factors may explain the increased MMD in Hawaii.