Challenges in evaluating the oculomotor function in individuals with Rett syndrome using electronystagmography

Background: Rett syndrome (RTT) is a neurological disorder characterized by a broad spectrum of symptoms. Communication is a major area of difficulty. Use of eye tracking technology offers a potentially effective method of communication when underpinned by intact oculomotor function. In this study, oculomotor function was assessed using electronystagmography (ENG). However, challenges were encountered when examining individuals with RTT. Purpose: To improve oculomotor examination in individuals with RTT by evaluating the challenges encountered during ENG examination. Material and methods: Oculomotor function was examined in 17 girls and young women with RTT and 16 typically developing (TD) individuals using ENG. Observational analysis of both performance and results indicated that challenges in examination were mainly related to quality of attention and quality of signals. Subsequently these outcome values were explored quantitatively according to percentage looking time for attention and drift for signal quality. Results: A significantly reduced level of attention and suboptimal electrode signals were evident in the RTT group when compared with the TD group for all tests except torsion swing. Conclusion: The challenges in testing confirm that regular oculomotor examination should be adjusted to meet the needs of individuals with RTT. It is hypothesized that the RTT group's higher quality of attention on the torsion swing can be explained by the more forceful vestibular rather than visual-ocular stimulus operating in this test. Suggested adaptations include reducing the number of electrodes, changing the picture stimuli and bringing them closer, performing observational assessments rather than ENG, and using virtual reality goggles. (C) 2018 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.