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Kho et al. studied a patient in whom drawing, but not writing, selectively triggered seizures with a right frontal onset. Their findings in the patients with reflex epilepsy support current models in the neurocognition of drawing.
see page 723
Figuring out drawing-induced epilepsy
Commentary by Bruce L. Miller, MD
The article by Kho et al. is a major contribution to the rich and fascinating literature on the reflex epilepsies. Clinically, the triggers may be remarkably specific; seizures can be induced by viewing round objects, viewing specific video games or cartoons (including Pokemon),1 listening to specific songs or nursery rhymes, playing mah jong or planning to move in chess, touching hot water, or brushing ones teeth. Similarly, experiencing specific emotions or movements can trigger seizures. Genetic forms of epilepsy can cause certain types of reflex epilepsy, but focal lesions also can be a trigger.
In this report a young fashion design student experienced arm twitches followed by loss of consciousness induced by drawing. Spike and wave activity in the right frontotemporal region could be precipitated by copying a complex figure, drawing a figure from memory, or even when he imagined himself in the activity of drawing. In contrast, drawing simple repeating figures, picturing complex visual scenes, calculating, writing, or reading did not induce seizure activity.
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The mechanisms underlying reflex epilepsies remain uncertain. The simplistic notion is that those brain regions sub-serving specific functions that are also triggers for the seizure are hyperexcitable. While this may be an accurate description—and pharmacologic manipulations that decrease excitation (by interfering with glutamate neurotransmission) or increase inhibition (by increasing GABA neurotransmission2,3) suggest that this is plausible—it falls far short of explaining exactly how the normal physical structure or chemical connections of the brain are deranged. Further, it is unclear to what extent genetic models, in which these studies are performed—such as photic-induced seizures in the baboon, Papio papio—are analogous to reflex seizures in humans, even those induced by photic stimulation, a fairly common occurrence among the reflex epilepsies.
This case offers interesting insights into the cognitive processes involved with drawing, a relatively understudied topic. The dissociation between writing and drawing emphasizes the presence of anatomically distinctive cognitive modules in the dominant and nondominant hemispheres. Inducing a system in the nondominant hemisphere involved with various components of creating a picture was enough to trigger a right frontoparietal seizure focus. In contrast, activating the dominant hemisphere with tasks like writing or calculating did not. This case helps to stimulate new work to determine the mechanisms associated with reflex epilepsy while challenging cognitive neurologists to think about the anatomic systems involved with the creation of a drawing.
see page 723
References
-aminobutyric acid uptake inhibitor, tiagabine, is anticonvulsant in two animal models of reflex epilepsy. Eur J Pharmacol 1995;273:259–265.[Medline]Related Article
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