Edward M. Kennedy Jr. arrives at Mass General Hospital to visit his father, yesterday

Seizures, like the one Sen. Edward M. Kennedy reportedly suffered yesterday, are a fairly common occurence affecting about 10 percent of the population and often are precipitated by a stroke, according to a stroke expert.

“Stroke is probably the most common cause of seizure in American adults,” said Dr. David Thaler, director of Tufts Medical Center Comprehensive Stroke Center.

According to Epilepsy Foundation figures, 22 percent of stroke survivors will have seizures. Two or more after a stroke is labeled a seizure disorder or epilepsy.

Last October, Kennedy underwent an hourlong procedure to remove a blockage from his left carotid artery. The procedure often is performed to prevent stroke.

Seizures are divided into two major categories: generalized and partial, Thaler said.

A partial seizure is an electrical discharge that affects one part of the brain. A generalized seizure is caused by an electrical discharge that affects both sides of the brain simultaneously. It’s a more serious condition that causes convulsions.

Patients can undergo an MRI, CAT scan or electroencephalogram (EEG) to determine the cause of the seizure, Thaler said.

He described anti-seizure medications as “safe and effective.”