The sequence of altered mental status and ataxia (stumbling, uncoordinated gait) does not matter. And/or by definition, although, unknown to us, a "premorbid" non-altitude condition could be a factor.
Just to follow-up on my own comments here....
That fact that he was able to continue on up, even with assistance, and return, suggests it was
not HACE ( even though the criteria were met) but rather a premorbid condition.
Morbid does not mean the same as mortal. Premorbid just means he brought an illness or condition
into the setting and was aggravated there (high altitude). I wonder if a premorbid neurological condition was in play. A common one might have been the use of sleeping pills, alcohol or other agents the day or night before.
