SAN FRANCISCO • An ex-girlfriend has set in motion a legal battle over whether 92-year-old billionaire Sumner Redstone, who controls Viacom and CBS, is able to make his own healthcare decisions.

Manuela Herzer claims he is a "living ghost" obsessed with sex and steak, and out of touch with his surroundings. He has trouble controlling bodily functions and grasping what doctors tell him, she said in a legal filing on Tuesday.

She is asking - after being ousted from his home last month - that the court leave her in charge of his healthcare decisions on the basis that he was not competent enough to sign a directive assigning a new person to the task.

"Sumner Redstone is a tragic figure in the waning days of an accomplished life," Herzer, 51, said in a civil suit asking for a California state court hearing on the matter to be hastily convened. "He is now unable to communicate competently to manage his own healthcare."

Redstone's attorneys said in court documents that her filing is part of a "financial agenda" angling for a share in his estate.

Establishing that Redstone was not competent to make legal decisions about his healthcare could provide a foundation for a court challenge to any recent changes made to his will.

Forbes has estimated his worth at about US$5.5 billion (S$7.7 billion). Redstone is receiving "superior" healthcare and help from a dear friend, according to his attorneys.

Herzer's filing maintained that Redstone's health declined last year after hospitalisations for aspiration and pneumonia.

His condition worsened after a split with his partner of five years, Sydney Holland, last August, when Redstone became "a living ghost", Herzer claimed. They dated for about two years, with the relationship ending in 2001.

The legal wrangling fuels speculation about the health of the person who still officially heads the boards of directors at media giants CBS and Viacom.

Last year, Redstone had told The Hollywood Reporter: "I will not discuss succession. You know why? I'm not gonna die. So why should I discuss succession?"

AGENCE FRANCE-PRESSE