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Original Investigation
January 2017

Incidence and Etiologies of Acquired Third Nerve Palsy Using a Population-Based Method

Author Affiliations
  • 1Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota
  • 2Department of Ophthalmology, First Affiliated Hospital of Anhui Medical University Hefei City, Anhui Province, China
  • 3Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota
JAMA Ophthalmol. 2017;135(1):23-28. doi:10.1001/jamaophthalmol.2016.4456
Key Points

Question  What is the incidence and etiologies of acquired third nerve palsy?

Findings  In this case series in Olmsted County, Minnesota, the age- and sex-adjusted annual incidence of acquired third nerve palsy was 4.2 per 100 000. There was a higher incidence of microvascular and lower incidence of aneurysm than previously reported.

Meaning  Because of its population-based method, this study provides evidence regarding etiologies of acquired third nerve palsies that can be considered by clinicians when evaluating patients with such palsies.


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 Measures  Incidence and etiologies of acquired third nerve palsies. The secondary outcome was incidence of pupil involvement in acquired third nerve palsies.

Results  We 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 Relevance  This 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.