Secondarily generalized seizures are usually partial seizures evolving into generalized seizures, most often with tonic-clonic convulsions. The partial seizures, which were once limited to one hemisphere of the brain, progress to encompass the entire brain bilaterally. This causes a generalized seizure. The clinical nature of a secondarily generalized seizure usually does not differ from that of the initial, originating seizure.
Secondarily generalized seizures are predominant in 16 percent of all children and 9 percent of all adults with seizure disorders. Most people with complex partial seizures and many with simple partial seizures will experience a secondarily generalized seizure at some point. When they occur frequently, the chances for future partial seizures may be increased.
Secondarily generalized seizures occur infrequently and are easily controlled by anti-epileptic medication.