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The patient had been in an avalanche and the problems snowballed from there.

Dominik Ehrich, a 25-year-old physical education student from Germany, endured 15 minutes of hypoxia while being buried under the snow during a ski trip, leaving him with posthypoxic intention myoclonus with involuntary myoclonic jerks of the mouth and legs when he was talking and walking.

A few weeks later, he was still in the hospital recovering from his injuries and trying to solve a sudoku puzzle when he developed clonic seizures of the left arm that, well, snowballed, , of the University of Munich, and colleagues .

"I fell out of my wheelchair," Ehrich told 麻豆传媒. "I couldn't move, I couldn't talk or shout for help, so I was on the floor for some time."

Ehrich said he imagined the puzzles in a 3-dimensional manner -- and Feddersen and colleagues pointed to reports in the literature that similar seizures could be elicited by other visual-spatial tasks. Similarly, "reflexive epilepsy" is characterized by seizures prompted by external stimuli like reading, calculating, touching, warm bathing, game playing, or noise.

"When I do a sudoku or a crossword puzzle and concentrate on a spot, while still scanning the horizontal and vertical options, my left hand freaks out," Ehrich said. "Freaks out means: a tremor begins. My hand cramps and moves without control. This will grow, unless I close my eyes. So my left hand is like the epicenter of a seizure."

Ehrich did have evidence of seizure on electroencephalography, which ceased as soon as he stopped trying to solve the puzzle, Feddersen and colleagues found.

To further assess what might be going on in his brain, the researchers conducted a CT while the patient did a sudoku puzzle, which showed hyperperfusion of the posterior cingulate gyrus.

A functional MRI also revealed maximal activation in the right central region on fMRI, as well as increases in somatosensory evoked potentials, which indicated a loss of U-fibers -- inhibitory fibers in the brain arranged in small loops under the brain cortex.

The findings imply that the hypoxia had probably caused some kind of diffuse, widespread damage that diminished inhibition and resulted in his symptoms, the researchers said.

"Due to the loss of U-fibers, inhibition is diminished and a 'physiological' activation results in a hyperexcitability," Feddersen told 麻豆传媒. "As this was exactly in the region were 3D visualisation takes part, the seizures were induced by 3D-imagination of sudoku puzzles."

Luckily, the cure was simple -- Ehrich stopped solving sudoku puzzles and has been seizure-free for more than 5 years, Feddersen said.

He told 麻豆传媒 this is the first and only case of sudoku-induced seizures in the medical literature, and the analysis helps provide a better understanding of what can happen when a patient sustains hypoxia.

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