(413) “The Secret Life of Pets” Triggered Low-Frequency Visual Reflex Epilepsy in A Child: A Novel Case

We present an interesting case of low-frequency visual reflex epilepsy at 27 months of age in a child with developmental delays

Methods:

4 y/o ex 32 wk male born an identical monozygotic twin with speech delay and autism spectrum disorder (ASD) was investigated at 27 months for seizures provoked by low-frequency external stimuli consisting of flashing lights and watching a specific clip from the movie "Secret Life of Pets." 

Results:

The patient demonstrated seizure provocation with visual stimuli at a frequency of 1 Hz. Seizures were triggered by flickering lights from opening/closing of car doors and while watching a clip from the movie “Secret Life of Pets” in which a cat opens and closes a refrigerator door. Video EEG captured reproducible seizure events provoked by the clip lasting ~15 seconds consisting of eyelid, facial and truncal myoclonus, repeated eye blinking, oral automatisms and clonic head movements unresponsive to vocal/tactile stimulation but no generalized convulsions. Ictal EEG consisted of bifrontal rhythmic 2-3 Hz delta with a diffuse spread greater on the left mixed with occipital sharps and theta slowing. The latency for the seizure was almost immediate and stopped upon cessation of the inciting stimulus with a quick return to baseline activity (Figure1a,b). EEG was otherwise normal with alpha background and no focal or generalized epileptiform spike-wave discharges interictally or at higher frequencies. Myoclonic eye blinking was precipitated at intermittent photic stimulation between 1-5 Hz (Figure2a,b). His identical twin also with ASD demonstrated myoclonic eye blinks to the same triggers. Extensive workup showed normal MRI brain, retinal exam, and karyotyping. SNP microarray showed interstitial duplication (gain) of ~721 kb in the long arm of chromosome 22 of unknown significance. Epilepsy panel found no pathogenic variants and no mutation was identified in CLN2/ Tripeptidyl peptidase 1, a treatable late infantile Neuronal ceroid lipofuscinosis. He is presently in seizure remission on a low dose of clobazam.

Conclusions:

Photosensitivity epilepsy is the most common form of reflex epilepsy with visual triggers that provoke seizures. They have a very peculiar phenomenology with triggers restricted to selective parameters like a defined frequency range of stimulus, a popular example being triggering of seizures with flashing red and blue fields at a frequency of 12.5 Hz in the pokemon series. In children with epilepsy, photoparoxysmal responses are seen at an increased incidence of 2-14% and even higher in patients with ASD. Photoparoxysmal response at low frequencies of 1-3 Hz are rare and necessitate additional metabolic workup including CLN2 disease. The spectrum of epilepsy in a child with neurodevelopmental disorders is highly complex, genetically heterogenous and appears to be a continuum of brain dysfunction. Further research is needed to understand the genetics of photosensitivity, epilepsy and ASD. Advances in technology should be applied to curb photosensitive exposure in digital and entertainment media.

Funding: Please list any funding that was received in support of this abstract.: Not applicable


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