Symphony officials earlier this month said “extreme gastric distress” forced the conductor to withdraw from his fall residency and return to Milan for treatment.

On Tuesday, the orchestra said tests determined Muti is suffering from extreme exhaustion as a result of prolonged physical stress. Abdominal pain and other physical symptoms resulted.

Doctors have recommended a month of rest, which Muti has begun at his home in Italy.

The 69-year-old Muti was scheduled to conduct fall concerts from Sept. 19 to Oct. 17. He is still scheduled to return for a winter series Feb. 3 through Feb. 19.