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.

Oculomotor Function in Individuals With Rett Syndrome.

BACKGROUND: Individuals with Rett syndrome (RTT) are notoriously reliant on the use of eye gaze as a primary means of communication. Underlying an ability to communicate successfully via eye gaze is a complex matrix of requirements, with an intact oculomotor system being just one element. To date, the underlying neural and motor pathways associated with eye gaze are relatively under-researched in RTT. PURPOSE: This study was undertaken to plug this gap in knowledge and to further the understanding of RTT in one specific area of development and function, namely oculomotor function. MATERIAL AND METHODS: The eye movements of 18 girls and young women with RTT were assessed by electronystagmography (ENG). This tested their horizontal saccadic and smooth pursuit eye movements as well as optokinetic nystagmus and vestibulo-ocular reflex. Their results were compared with normative data collected from 16 typically developing children and teenagers. RESULTS: Overall, the individuals with RTT demonstrated a range of eye movements on a par with their typically developing peers. However, there were a number of difficulties in executing the ENG testing with the RTT cohort which made quantitative analysis tricky, such as reduced motivation and attention to test materials and low-quality electrode signals. CONCLUSIONS: This study suggests that individuals with RTT have an intact oculomotor system. However, modifications should be made to the ENG assessment procedure to combat problems in testing and add strength to the results. Further investigation into these testing difficulties is warranted in order to inform such modifications.