Taiwan's former President Chen Shui-bian has been granted a one-month medical parole for treatment of neural degeneration, more than four years into his 20-year prison sentence for corruption, the Justice Ministry announced Monday.

Chen, 64, whose election in 2000 ended a 50-year monopoly on power by the island's Nationalists, or Kuomintang, and who moved to expand Taiwan's de-facto independence from mainland China, went on trial shortly after the end of his 2000-2008 tenure.

He was convicted in September 2009 of taking more than $12 million in embezzlement and bribe-taking in what he denounced as a persecution driven by his political opponents.

He has reportedly suffered from depression, sleep apnea, heart ailments and neural degeneration while behind bars, and authorities say he attempted suicide. The one-month medical parole was granted for treatment of his neural degeneration, which was worsening despite efforts at treatment while he was incarcerated, the Justice Ministry said in a statement.

"It is believed that only on medical parole can his life and health be ensured, and the degeneration be prevented from worsening," the ministry said.