Actually he has had brain surgery previously, involving a cyst in his head that had to be drained when it was giving him migraine issues back in 2001 while coaching OSU. He also had a mysterious trip to the hospital at the request of his athletics department staff in 2015 while at LSU. He was fired almost precisely one year later.
For the record, weight gain, unsteadiness, and sedation are common side effects for many migraine meds.
https://www.theadvocate.com/baton_rouge/sports/lsu/article_7ea665f1-05c4-578c-a6be-0889b13261b4.html