Abstract
Abstract: :
Purpose: To determine the incidence and etiology of sixth nerve palsy/paresis in a population-based study, with particular emphasis on associated co-existing medical conditions. Methods: All new cases of sixth nerve palsy/paresis were identified among residents of Olmsted County, Minnesota, USA, between January 1, 1978 and December 31, 1992 by using the Rochester Epidemiology Project medical records linkage system, which captures virtually all medical care provided to residents of the county. The entire medical record of each patient was reviewed to confirm the diagnosis, document county residency, and to determine the most likely cause and associated medical conditions. We used stringent predetermined criteria to define diabetes mellitus and hypertension as associations. Cases with no apparent cause were defined as undetermined. Incidence rates were adjusted to the age and sex distribution of the 1990 white population in the United States. This study differs from published series by combining a population-based approach with rigorous definitions of coexisting medical risk factors. Results: In our defined population, 137 cases of sixth nerve palsy were identified over the 15-year period. The age- and sex-adjusted annual incidence of sixth nerve palsy was 11 per 100,000 (95% confidence interval, 9 to 13 per 100,000). In order of frequency, causes and associations were: undetermined (26%), hypertension (19%), diabetes mellitus (15%), trauma (12%), multiple sclerosis (7%), cerebrovascular accident (4%), neoplasm (4%), post-neurosurgery (3%), and aneurysm (2%). Where sixth nerve palsy was the presenting sign in cases of neoplasm (n=1) and aneurysm (n=3), history and examination revealed the presence of other neurologic symptoms or signs. The peak incidence of sixth nerve palsy was in the 7th decade of life when the most common causes and associations were undetermined (34%), diabetes (23%), and hypertension (20%). Conclusions: We provide population-based data on the incidence and etiology of sixth nerve palsy that may be less influenced by institutional referral bias than previous series. Associated medical conditions differ from previous institution based series, with a notably lower incidence of neoplasms and higher incidence of diabetes and hypertension. These data are useful in guiding medical evaluation of such patients.
Keywords: 590 strabismus: etiology • 354 clinical (human) or epidemiologic studies: prevalence/incidence • 400 esotropia and exotropia