Authors :
Presenting Author: Sarah Otterson, MD, MS – University of New Mexico
Danny Rogers, MD, PhD – Interim Division Chief of Child Neurology, Neurology, University of New Mexico; Aaron Cardon, MD, MSc – Director of Pediatric Epilepsy in the Division of Child Neurology, Neurology, University of New Mexico
Rationale:
Dravet syndrome is a developmental and epileptic encephalopathy caused by SCN1A loss of function which can present with photoparoxysmal response (PPR) on EEG in up to half of patients. The prevalence of photosensitive seizures is less well defined; even so, interventions such as occlusive eye patching, sunglasses, and hats are often recommended by doctors or family support groups. Little has been published quantifying the effects of these interventions although subjectively some patients have shown benefit in retrospective case reports. In this study, we quantified myoclonic seizures using video EEG in a single patient with heterozygous exon 1 deletion in SCN1A while varying and measuring the amount of sunlight exposure. Patient was 22 months of age at the time of this study; prior EEG at nine months old showed no PPR. Before this study, parents observed that myoclonic seizures were photosensitive so they were intermittently patching one eye, minimizing indoor lights, and using sunglasses both indoors and outside. Our goal was to quantify the benefit of these environmental interventions.
Methods:
Video EEG was monitored while changing two variables: sunglasses ON or OFF and blinds OPEN or CLOSED. All artificial lights were turned off. EEG was reviewed via Nihon-Kohden software. We identified myoclonic seizures using both push button events, and similar electroclinical events found during visual review. Persyst was used to quantify spike frequency under each condition. Spikes were correlated with luminosity which was measured using an Arduino-based microcontroller and two photoresistors mounted as eyes on a plastic model which could wear sunglasses.
Results:
A total of 281 myoclonic seizures were captured over 6h and 11m of recording. These events were characterized by generalized bursts of spike and wave or polyspike and wave discharges lasting one to two seconds. Clinically, patient had subtle head jerks with occasional left arm jerks, time-locked to discharges on EEG. With blinds OPEN, we observed 2.82 seizures per minute (sz/min) with sunglasses OFF and 2.32 sz/min with sunglasses ON. With blinds CLOSED, we recorded 0.52 sz/min when the sunglasses were OFF, and 0.14 sz/min when the sunglasses were ON (Figure 1).
Luminosity measurements ranged from 530 lux when the sunglasses were OFF and the blinds OPEN, down to 2.4 lux with blinds CLOSED and sunglasses ON. Spikes were detected as frequently as 0.48 spikes per second and decreased as the light exposure decreased (Figure 2).
Conclusions:
In this single patient during a short (six hour) period, we demonstrated that decreasing sunlight exposure can reduce clinical seizure burden by up to 95%. Blind closure had a more dramatic effect than sunglasses with reduction by about 2.2 sz/min regardless of sunglasses use. Based on the luminosity measurements, seizure reduction was not directly proportional to light exposure because there was greater benefit with blinds CLOSED despite sunglasses providing comparable decrease in brightness.
Funding: None