Third Nerve Palsies—Less Frequent but Just as Concerning

In their population-based study of third nerve palsies in Olmsted County, Minnesota, between 1978 and 2014, Fang and colleagues¹ show that the incidence of oculomotor paresis may actually be quite low at 4.2 cases among 100 000 patients. In addition, their data suggest that one of the most concerning causes of third nerve palsy, that of aneurysmal compression, occurs even less often than previous non–population-based studies had suggested, accounting for only 6% of all cases, with most due to cavernous sinus aneurysms, a group whose risk of rupture is low and whose associated morbidity and mortality are much less than those aneurysms within the subarachnoid space. This is good news for Olmstead County, and probably good news that is generalizable, given that population-based assessments are more accurate than retrospective or even prospective studies from specialized centers with referral bias.