Earlier today Dana White tweeted the following:
White was diagnosed with Meniere's disease -- "a disorder of the inner ear that can affect hearing and balance to a varying degree. It is characterized by episodes of vertigo, low pitched tinnitus, and hearing loss" (per wikipedia) -- earlier this year and has been trying to get his doctor to perform surgery for some time.
Surgery for Meniere's disease is risky and can risk permanently impaired ear function and even worsened vertigo. The recovery time can be substantial.
In June White explained that he was at odds with his doctor who preferred conventional treatments to the surgery which would cut the nerve and require three weeks of intensive rehab. White has spoken of his fear of having flare-ups happen when he's in a foreign country where doctors might not be familiar with how to treat it.