Sudoku puzzles can be brainteasers, but one man's brain had an unusual response to solving the numerical grid puzzles: He developed seizures.
The 25-year-old German man didn't always react this way to Sudoku, according to a new report of his case. His problems began after he was trapped in an avalanche during a ski trip. The young man, a physical education student, had been skiing with a friend in November 2008 when an avalanche occurred on the mountain.
The avalanche buried the man in the snow and knocked him unconscious, according to the case report. But he was fortunate to have been skiing with a buddy who was a paramedic, and his friend rescued him and started CPR immediately, said Dr. Berend Feddersen, a neurologist at the University of Munich in Germany, and the lead author of the case report published today (Oct. 19) in the journal JAMA Neurology.
The man suffered a ruptured spleen and hip fracture, Feddersen said. In addition, while he was buried under the snow, his body tissues and brain got too little oxygen, a condition known as hypoxia.
As a consequence of his brain being deprived of oxygen for 15 minutes, the man developed myoclonic jerks, which are sudden muscle twitches. These twitches occurred in the muscles of his mouth when he talked, and they also occurred in the muscles of both of his legs when he walked. [See Video: Man Has Seizures While Doing Sudoku]
In the hospital, the man started having a type of seizure called spontaneous tonic clonic seizures in his left arm, Feddersen told Live Science. This type of seizure involves the muscles stiffening and then jerking rapidly and rhythmically. The doctors prescribed anti-epileptic medication to keep the seizures under control, Feddersen said.
A few weeks later, after the man was moved from the hospital to a rehabilitation facility to continue his recovery, he attempted to solve a Sudoku puzzle, an activity he enjoyed doing in his free time.
But while doing the puzzle, he again began having clonic seizures, or muscle twitches, in his left arm.
Eventually, the doctors figured out that these seizures were triggered because the man had a very intense three-dimensional imagination that activated whenever he solved a Sudoku puzzle. Imagining the numbers three-dimensionally allowed him to sort them and put them in sequence, Feddersen told Live Science.
The seizures did not occur when the man completed other types of math problems, or while he was reading, Feddersen said.
The reason the seizures began only after the avalanche was because the hypoxia had resulted in the death of inhibitory fibers, which slow down brain signaling, in the right centro-parietal region of the man's brain.
Normally, this area of the brain is activated when 3D imagination is used. But with fewer inhibitory fibers in this region, when the man used his 3D imagination, it led to an overactivation of this brain region, which resulted in clonic seizures in his left arm.
The doctors even found that when the man had very strongly activated his 3D imagination while solving Sudoku, the clonic seizures in his left arm were much more intense, Feddersen said.
"When he stopped this 3D imagination, the seizures stopped immediately," he noted. So, the man had no choice but to give up Sudoku.
Feddersen last saw the man in November 2014. He was still affected by the myoclonic twitches brought on by talking and walking, but these symptoms have improved with physical therapy, he said.
The man has been seizure-free for more than five years, thanks to taking anti-epileptic medication regularly — and steering clear of Sudoku.
Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.