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IMPORTANCE Among cranial nerve palsies, a third nerve palsy is important because a subset is caused by life-threatening aneurysms. However, there is significant disagreement regarding its incidence and the reported etiologies.OBJECTIVE To determine the incidence and etiologies of acquired third nerve palsy using a population-based method.DESIGN, SETTING, AND PARTICIPANTS All newly diagnosed cases of acquired third nerve palsy from January 1, 1978, through December 31, 2014, in Olmsted County, Minnesota, were identified using the Rochester Epidemiology Project, a record-linkage system of medical records for all patient-physician encounters among Olmsted County residents. All medical records were reviewed to confirm a diagnosis of acquired third nerve palsy and determine the etiologies, presenting signs, and symptoms. Incidence rates were adjusted to the age and sex distribution of the 2010 US white population. MAIN OUTCOMES AND MEASURESIncidence and etiologies of acquired third nerve palsies. The secondary outcome was incidence of pupil involvement in acquired third nerve palsies. RESULTSWe identified 145 newly diagnosed cases of acquired third nerve palsy in Olmsted County, Minnesota, over the 37-year period. The age-and sex-adjusted annual incidence of acquired third nerve palsy was 4.0 per 100 000 (95% CI, 3.3-4.7 per 100 000). The annual incidence in patients older than 60 was greater than patients younger than 60 (12.5 vs 1.7 per 100 000; difference, 10.8 per 100 000; 95% CI, 4.7-16.9; P < .001). The most common causes of acquired third nerve palsy were presumed microvascular (42%), trauma (12%), compression from neoplasm (11%), postneurosurgery (10%), and compression from aneurysm (6%). Ten patients (17%) with microvascular third nerve palsies had pupil involvement, while pupil involvement was seen in 16 patients (64%) with compressive third nerve palsies. CONCLUSIONS AND RELEVANCEThis population-based cohort demonstrates a higher incidence of presumed microvascular third nerve palsies and a lower incidence of aneurysmal compression than previously reported in non-population-based studies. While compressive lesions had a higher likelihood of pupil involvement, pupil involvement did not exclude microvascular third nerve palsy and lack of pupil involvement did not rule out compressive third nerve palsy.

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Purpose The objectives of the present study were to evaluate whether investigator bias influenced the Convergence Insufficiency Symptom Survey (CISS) scores of children with normal binocular vision (NBV) in our original validation study, reevaluate the usefulness of the cut-off score of 16, and reexamine the validity of the CISS. Methods Six clinical sites participating in the Convergence Insufficiency Treatment Trial (CITT) enrolled 46 children 9 - <18 years with NBV. Examiners masked to the child’s binocular vision status administered the CISS. The mean CISS score was compared to that from the children with NBV in the original, unmasked CISS study and also to that of the 221 symptomatic CI children enrolled in the CITT. Results The mean (±SD) CISS score for 46 subjects with NBV was 10.4 (±8.1). This was comparable to that from our prior unmasked NBV study (mean = 8.1(± 6.2); p = 0.11), but was significantly different from that of the CITT CI group (mean = 29.8 ± 9.0; p < 0.001). Eighty-three percent of these NBV subjects scored less than 16 on the CISS, which is not statistically different from the 87.5% found in the original unmasked study (p = 0.49). Conclusions Examiner bias did not affect the CISS scores for subjects with NBV in our prior study. The CISS continues to be a valid instrument for quantifying symptoms in 9 to <18 year-old children and these results confirm the validity of a cut-point of ≥ 16 in distinguishing children with symptomatic CI from those with NBV.

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