Incidence and Causes of Acquired Third-Nerve Palsy: Population-Based Study
JAMA Ophthalmology, January 2017
There are many causes of third-nerve palsy, including life-threatening aneurysms. Fang et al. used a population-based approach to determine the etiologies and presenting characteristics of third-nerve palsies and found a higher incidence of presumed microvascular third-nerve palsies and a lower incidence of aneurysmal compression than observed in non–population-based studies.
Using data from the Rochester Epidemiology Project, the authors identified all cases of acquired third-nerve palsy diagnosed in Olmsted, Minn., from 1978 through 2014. Medical records were reviewed to confirm the diagnosis and to record etiology and presenting signs. Incidence rates were adjusted to the age and gender distribution of the 2010 white population of the United States.
There were 145 newly diagnosed cases of acquired third-nerve palsy. The age- and gender-adjusted annual incidence was 4.0 per 100,000 (95% CI, 3.3-4.7 per 100,000). The annual incidence was greater for patients aged >60 years than for younger patients (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 etiologies were presumed microvascular causes (42%), trauma (12%), compression from neoplasm (11%), post-neurosurgery sequelae (10%), and compression from aneurysm (6%).
Pupil involvement was present in 43% of the study patients, including 16 with compressive palsy (64%) and 10 with microvascular palsy (16%). Although the likelihood of pupil involvement was greater for compressive lesions, pupil involvement did not exclude a microvascular origin, and the lack of it did not rule out a compressive cause. Ptosis was present in 86% of patients; its incidence was similar for the various causes. Pain occurred in 69% and varied substantially by cause.
In conclusion, this study suggests that the incidence of presumed microvascular third-nerve palsy is higher, while the incidence of aneurysmal compression is lower, than in previous reports. Because microvascular and compressive origins cannot be differentiated by clinical characteristics alone, neuroimaging is recommended for all cases of acquired third-nerve palsy that lack an obvious known cause.
The original article can be found here.