Ask anyone who has experienced a seizure like the one suffered by U.S. Supreme Court Justice John Roberts, and it is very likely that all they will recall from the episode will be a brief, missing chunk of time -- and waking up with a pounding headache.
Ask someone who has witnessed one as a bystander, however, and they will recount a much more vivid event.
"The people look strange, as if they have been 'seized' by something; they lose control," said Dr. Shlomo Shinnar, director of the Comprehensive Epilepsy Management Center at the Albert Einstein College of Medicine's Montefiore Medical Center. "It is a frightening event."
"Most people who see it will equate it with a brush with death," said Dr. Giuseppe Erba, professor of neurology at the University of Rochester. "Seizure is one of the most frightening experiences to look at."
Now, however, many neurologists hope that Roberts' experience will provide an opportunity to dispel the widespread public fear surrounding seizures -- and highlight the fact that seizures like the one Roberts experienced are relatively harmless and often do not indicate any severe underlying health problems.
"Judge Roberts doesn't have any disease, other than that his brain is more excitable than yours or mine," Erba said. "It is a benign condition."
Throughout the centuries, seizures have been viewed as a worrisome omen. Some 3,000 years ago, the ancient Babylonians proposed that demon possession was to blame for the episodes.
The ancient Romans also adhered to this idea, believing that people who experienced the episodes regularly were contagious -- forcing many with the condition to live solitary existences.
The stigma associated with epilepsy, a condition normally defined as a tendency to experience seizures, has led many to hide their condition in the past.
Dr. James Grisolia, senior vice president of the Epilepsy Foundation of San Diego, said this stigma persists until today.
"The idea that people with epilepsy have something really scary goes all the way back to classical times," he said. "Even today, many still have this notion that people with epilepsy might have something spiritually or emotionally wrong with them."
Experts remain split as to whether Roberts' condition should be defined as epilepsy or not. But it is a fact that epilepsy is common condition worldwide. Up to 3 percent of people in the general population experience the condition at some point in their life.
But individual cases of epilepsy can vary widely. And even individual seizures can vary greatly, ranging from a blank stare that lasts for a few minutes to a complete and sudden loss of consciousness.
Seizures in general are caused by abnormal surge of activity within the brain's cerebral neurons. Some doctors have likened the condition to an "electrical storm" within the brain.
It may be a fitting analogy, since in the same way that electrical storms can overwhelm the circuitry of electronics and household appliances, a seizure can interfere with the brain's sensitive circuitry, albeit temporarily.
"By definition, epileptic seizures occur as a result of abnormal electrical discharges in the brain," noted Dr. Dileep Nair, fellowship director for epilepsy and clinical neurophysiology at the Cleveland Clinic Epilepsy Center.
Occasionally, people who are about to have a seizure experience warning signs leading up to the event. Shinnar explained that this is more often a characteristic of a partial seizure, which starts in one side of the brain and later spreads to involve the entire brain.
Hours, or even days, before one experiences a full-blown seizure, he or she may experience a prodrome, commonly referred to as an "aura." This phase often involves anxiety, irritability, difficulty concentrating or sleep disturbances.
In general, seizures like the one experienced by Roberts can be broken down into three phases.
The first phase, known as the tonic phase, involves a contraction of the muscles of the back and arms, leading to a rigid posture and increase heart rate and blood pressure. This phase can last between 10 and 20 seconds.
The next phase is known as the clonic phase and encompasses much of what is traditionally associated with seizures -- rapid convulsions and a clenching of the jaw muscles.
Though the seizure sufferer may appear to be in pain, they are actually completely unaware of their condition.
"When you are in a general convulsive stage, everyone around you may be scared, but you are not conscious," Shinnar said. "You don't feel anything."
During the final phase, known as the postictal stage, the person who has experienced the seizure will gradually regain consciousness.
"After a seizure, one will basically have a bad headache, kind of like a hangover," Shinnar said. "Basically, you are washed out. Your brain has run a marathon, and it is tired."
But even though those who experience seizures may not worry at the time of their episode, they may live in fear of the implications of their condition -- particularly the danger of harm to themselves or others.
"Very prolonged seizures can cause damage, if they last on the order of 20 to 30 minutes," Shinnar said. "But a seizure that's brief is basically not in and of itself considered dangerous; the main risk of a brief seizure is being in the wrong place at the wrong time."
This could be behind the wheel of a car, at the top of a staircase -- or even by a placid lakeside, where drowning is a possibility.
While physicians can be fairly certain as to what Roberts went through during his episode, the exact causes for his seizure remain unclear.
"In many cases when seizures occur in older adults, we never find out the underlying cause," said Dr. Jerome Engel, director of the Seizure Disorder Center at UCLA.
"You can reconstruct it," Erba said. "But it is so important to do good detective work when you do a history. You have to be imaginative."
One possibility is that the sun reflecting off of the lake close to Roberts could have created a strobe effect, setting off what is known as a photosensitive seizure. Another possibility is that extreme stress or lack of sleep in preceding days may have led to the event.
The results of Roberts' electroenchalography, or EEG, tests will likely help determine what might have brought his most recent seizure about -- and whether he will require treatment to avoid future episodes. Fortunately for Roberts, serious potential causes such as tumors and stroke have been largely ruled out by tests.
Regardless of the cause, Grisolia said the incident highlights the fact that seizures are a common -- and often controllable -- problem.
"We have people as high-functioning as Justice Roberts and other people who are really quite impaired," he said. "There is a big spectrum in terms of the kinds of people who can have [seizures]."
ABC Medical Unit Researcher Dr. Sharon Bord contributed to this report.