Pupil-Involving Third Cranial Nerve Paresis at High Altitude

Although sixth cranial nerve palsies are a well-recognized entity at high altitude, other cranial nerve palsies due to altitude are much more uncommon. A case of a 55-year-old woman is presented who flew from Dallas, Texas (elevation 176 m) to Breckenridge, Colorado, where she hiked up to 3600 m above sea level. She developed a pupil-involving right third cranial nerve paresis that resolved over the next 3 months. In the absence of significant abnormalities on neuroimaging and serum laboratories, the etiology is presumed to be due to high altitude.