Jon Oliva, leader of Wild and co-founder of Trans-Siberian Orchestrahas revealed that he has been diagnosed with multiple sclerosis and Ménière’s disease, an inner ear disorder that causes vertigo and severe tinnitus.

As a result of a spinal injury and his aforementioned medical conditions, Oliva was forced to withdraw from Savatage’s upcoming reunion performance at the Brazilian Monsters of Rock festival next year. According to the festival websiteZak Stevens, who fronted Savatage from 1992 to 2000, will take over lead vocals in his place.

Oliva took to social media to address fans and speak openly about his current health issues, stating that he is working with doctors to “get healthy again.” Despite his expected absence, the singer said he is still overseeing the production of Savatage’s upcoming show alongside his bandmates and will be working on new material in the studio in the meantime.

Oliva’s full statement is read (via Facebook):

“Hello Savatage fans, I’m Jon Oliva. I want to make some things clear for everyone. First of all, I’m very excited to have Johnny, Chris, Zak, Jeff and Al playing again. I feel like it’s important for fans to enjoy our music live, and believe me, these guys will.

As far as I go, I was going to do these programs but unfortunately I have encountered more health problems. I want everyone to know that if there was any way I could do these programs, I would do it, but my health problems are more serious than I originally thought.

As most of you know, I fractured my spine in 3 places and was recently diagnosed with multiple sclerosis and Ménière’s disease. My doctors are working with me to get healthy.

I’m working closely with the guys and will be involved in all other aspects of the show. I’m 100 percent behind the guys doing this and I promise to be back (as soon as possible). In the meantime, I’m working in the studio on new material.

I love you all and thank you for understanding my situation, I know my brothers will qualify.

Enjoy the Sava Legions.

Much love to all of you. “Jon Oliva”

Oliva will surely be missed at the upcoming Savatage festival concert, which will be only the band’s second live performance since their hiatus in 2002 (the other was a 2015 show at Wacken Open Air). He is also currently not a touring member of his other notable project, Trans-Siberian Orchestra, with Zak Stevens also filling that role in the progressive metal group’s touring lineup.

See Oliva’s statement, via the “Savatage Legion” Facebook group, below.