By Mandy Oaklander
Updated: October 21, 2015 1:00 PM ET | Originally published: October 19, 2015

In a new report published in JAMA Neurology, a team of doctors discuss one of their more puzzling cases: a man who had a seizure when he tried to solve Sudoku.

The patient was a 25-year-old man who had been buried by an avalanche during a ski trip and endured 15 minutes without enough oxygen, a condition called hypoxia. After, he developed involuntary muscle jerks of his mouth when he tried to talk and his legs when he tried to walk—but his arms didn’t seem to have been affected. That changed weeks later, explain the authors, the patient’s team of doctors from the University of Munich in Germany. “He was in the rehabilitation clinic, and he was bored, so he started doing Sudokus,” says co-author and neurologist Dr. Berend Feddersen. When the right-handed patient tried to solve a Sudoku puzzle, he experienced quick muscular contractions—clonic seizures—of his left arm. (Here’s a video of the patient solving Sudoku.) The seizures stopped instantly when he stopped the game.

Feddersen had never seen anything like it, and nothing existed in the scientific literature about Sudoku-caused seizures. But the authors explain it as a case of reflex epilepsy: seizures that can be triggered by external stimuli like playing games, reading, doing math, touching and bathing in warm water. For this patient, Sudoku, which involves ordering numbers one through nine in a square grid, was such a trigger. Reading, writing and even math alone didn’t have an effect. But visualization-spatial tasks, in which the patient sorted numbers in ascending order, did. “When he solves Sudoku, one of his strategies is to arrange the numbers in some 3D manner,” Feddersen says. “That’s very interesting, because when I do Sudoku, I just make trial and error.”

After analyzing his brain imaging data, the patient’s doctors concluded that the oxygen deprivation caused damage throughout the brain, especially to the U-fibres found all around the brain that contribute to inhibition. “When these kinds of neurons are dying, then you have not enough inhibition, so a loss of U-fibres leads to an overactivation,” Feddersen says. “For him, luckily it was this kind of Sudkoku thing which was the activation, and not another one he does in his daily life.” When the patient stopped solving Sudoku puzzles, the seizures stopped, too. “[He] has been seizure free for more than 5 years,” the study authors write.

Write to Mandy Oaklander at mandy.oaklander@time.com.

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