The country's Supreme Court granted the lesser detention after hearing recommendations from the 82-year-old's doctors.
The country's Supreme Court granted the lesser detention after hearing recommendations from the 82-year-old's doctors, attorney Ezra Angel told AFP.
Noriega, who is increasingly frail, is serving three 20-year sentences for the disappearances of opponents during his 1983-1990 rule.
The United States invaded Panama in 1989, seizing Noriega on drug trafficking and money laundering charges.
After time behind bars in the US then France, he was extradited to Panama in 2011 where he was incarcerated in El Renacer prison on the banks of the Panama Canal.
The tumor was detected several years ago and "has grown pretty rapidly during the time Noriega was here in Panama," Reyes said.
He added that removing the tumor was necessary to avoid "convulsions and even cardio-respiratory arrest."
No date has yet been set for the surgery, according to the lawyer and Noriega's daughter Thays Noriega.
Reyes said authorities would decide after the operation whether Noriega would return to prison or see out the rest of his sentence at home.