In November 2008, a 25-year-old German physical education student went on a ski trip. An avalanche buried him under snow for 15 minutes. A friend dug him out and performed CPR. He survived, but the oxygen deprivation had done damage.
After recovering in the hospital, the man developed involuntary muscle jerks. His mouth twitched when he talked. His legs jerked when he walked. But his arms seemed fine.
Then, weeks later while in a rehabilitation center, he tried to do something he’d always enjoyed: Sudoku puzzles. His left arm started seizing.
The seizures stopped the moment he put down the puzzle.
Dr. Berend Feddersen, a neurologist at the University of Munich, had never seen anything like it. According to NBC News, there was nothing in the scientific literature about Sudoku-triggered seizures. But after studying the patient’s brain scans and watching what happened when he played the game, Feddersen figured it out.
The 15 minutes of hypoxia had caused widespread brain damage, particularly to structures called U fibers in the right centroparietal region. These are inhibitory neurons that help regulate brain activity. When they were damaged, the patient lost the ability to suppress certain neural responses.
The specific trigger was how the man solved Sudoku. He didn’t just work through trial and error. He visualized the puzzle in three dimensions, arranging numbers around a central point in his mind.
“When he solves Sudoku, one of his strategies is to arrange the numbers in some 3D manner,” Feddersen said. “That’s very interesting, because when I do Sudoku, I just make trial and error.”
That 3D visualization activated the exact part of his brain that had been damaged. Functional MRI showed overactivation of the right central parietal cortex when he played. The result: clonic seizures of his left arm.
This is what doctors call reflex epilepsy. According to a study in Neurology, around four to seven percent of patients with epilepsy experience reflex seizures triggered by external stimuli like playing games, reading, doing math, even bathing in warm water.
For this patient, Sudoku was the trigger. But reading, writing, and even math alone? No seizures. Chess and card games? Seizures. Crossword puzzles? Totally fine.
“Fortunately, he can do crossword puzzles. He never had problems with those,” Feddersen said.
The man stopped playing Sudoku. Doctors prescribed anti-epileptic medication. By the time Feddersen published the case in JAMA Neurology in 2015, the patient had been seizure-free for more than five years. He was working as a journalist, though he still had difficulty with speech and walking.
The case is unusual because the injury was targeted to a specific brain region, and the trigger was so specific. Most people with reflex epilepsy have seizures triggered by broader activities. This man’s brain damage created a situation where one particular mental task, performed one particular way, caused a seizure.
He got to keep crosswords. But Sudoku was done.
