Kennedy, hospitalized at Massachusetts General Hospital since suffering a seizure at the family compound in Hyannis Port Saturday, had undergone testing to determine the seizure's cause.

In a statement, doctors treating the Kennedy patriarch said, "Preliminary results from a biopsy of the brain identified the cause of the seizure as a malignant glioma in the left parietal lobe," CNN reported.

The customary treatment course includes a combination of radiation and chemotherapy, doctors said.