Houston Astros Manager Larry Dierker collapsed on June 13th during a baseball game with the San Diego Padres. The game was suspended in the bottom of the eighth inning with the Astros leading 4-1. Dierker suffered a tonic-clonic seizure and was rushed to the hospital, where surgeons operated on his brain. He was in the intensive care unit until the weekend, and then moved to a regular hospital room.

A tonic-clonic seizure (also called a Grand Mal seizure) is a seizure with two parts. First, a person faints and his or her body becomes rigid. In the second part, the body twitches and jerks. Slowly, the person regains consciousness.

With the help of imaging tests such as CT scans, doctors could tell that Dierker had an arteriovenous malformation (AVM). An AVM is a tangle of malformed blood vessels that can disrupt function of the blood supply of the brain. When this tangle of blood vessels is ruptured, a seizure may be triggered. Often the tangles affect the surrounding area of brain and cause scarring. AVMs can occur in the brain and in the spinal cord. They are often not detected until they cause symptoms (in this case, seizures).

Dr. Rob Parrish of Methodist Hospital in Houston performed the surgery on Dierker, which took more than five hours. The surgical team cut a window in Dierker's skull, then removed the AVM, which was in the front part of his brain. Parrish described the AVM as "significant, 4-by-3 centimeters ... bigger than a walnut, smaller than a melon - maybe a lime, or a really big jalapeno." It was sent to the lab to make sure there was no tumor involved. Test results determined that there was no tumor.

The surgeon also removed a small part of Dierker's brain near the ruptured vessels that also had some malformed vessels. How can they just remove part of the brain? Well, surgeons first must tell which part of the brain the damage is in, and then weigh how important that brain region is to a person. The area where Dierker's AVM was located was considered "non-eloquent," meaning an area not essential for daily function. Also, his AVM was a grade "one" on a one-to-five scale, meaning it was the least severe.

After the surgery, doctors examined an angiogram, an imaging technique with which doctors can see blood vessels. They wanted to check that Dierker's normal blood flow in the brain had been repaired.

Dierker was able to watch the game against the Atlanta Braves from his hospital bed on June 15th. The Astros won.

The Astros-Padres game will resume July 23. Bench coach Matt Galante will take over for Dierker in the interim. Dierker, the 1998 National League Manager of the Year, is expected to make a full recovery.