Effects of sedation on auditory brainstem response in Rett syndrome

Atypical brain responses to 40-Hz click trains in girls with Rett syndrome: Auditory steady-state response and sustained wave

AIM

The current study aimed to infer neurophysiological mechanisms of auditory processing in children with Rett syndrome (RTT)-rare neurodevelopmental disorders caused by MECP2 mutations. We examined two brain responses elicited by 40-Hz click trains: auditory steady-state response (ASSR), which reflects fine temporal analysis of auditory input, and sustained wave (SW), which is associated with integral processing of the auditory signal.

METHODS

We recorded electroencephalogram findings in 43 patients with RTT (aged 2.92-17.1 years) and 43 typically developing children of the same age during 40-Hz click train auditory stimulation, which lasted for 500 ms and was presented with interstimulus intervals of 500 to 800 ms. Mixed-model ancova with age as a covariate was used to compare amplitude of ASSR and SW between groups, taking into account the temporal dynamics and topography of the responses.

RESULTS

Amplitude of SW was atypically small in children with RTT starting from early childhood, with the difference from typically developing children decreasing with age. ASSR showed a different pattern of developmental changes: the between-group difference was negligible in early childhood but increased with age as ASSR increased in the typically developing group, but not in those with RTT. Moreover, ASSR was associated with expressive speech development in patients, so that children who could use words had more pronounced ASSR.

CONCLUSION

ASSR and SW show promise as noninvasive electrophysiological biomarkers of auditory processing that have clinical relevance and can shed light onto the link between genetic impairment and the RTT phenotype.

Evoked Potentials and EEG Analysis in Rett Syndrome and Related Developmental Encephalopathies: Towards a Biomarker for Translational Research

Rett syndrome is a debilitating neurodevelopmental disorder for which no disease-modifying treatment is available. Fortunately, advances in our understanding of the genetics and pathophysiology of Rett syndrome has led to the development of promising new therapeutics for the condition. Several of these therapeutics are currently being tested in clinical trials with others likely to progress to clinical trials in the coming years. The failure of recent clinical trials for Rett syndrome and other neurodevelopmental disorders has highlighted the need for electrophysiological or other objective biological markers of treatment response to support the success of clinical trials moving forward. The purpose of this review is to describe the existing studies of electroencephalography (EEG) and evoked potentials (EPs) in Rett syndrome and discuss the open questions that must be addressed before the field can adopt these measures as surrogate endpoints in clinical trials. In addition to summarizing the human work on Rett syndrome, we also describe relevant studies with animal models and the limited research that has been carried out on Rett-related disorders, particularly methyl-CpG binding protein 2 (MECP2) duplication syndrome, CDKL5 deficiency disorder, and FOXG1 disorder.

Sensory evoked potentials in patients with Rett syndrome through the lens of animal studies: Systematic review

OBJECTIVE

Systematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations).

METHODS

Pubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards.

RESULTS

ERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients.

CONCLUSIONS

While there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms.

SIGNIFICANCE

The review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.

Safety and effectiveness of chloral hydrate in outpatient paediatric sedation for objective hearing tests

OBJECTIVES

Chloral hydrate is a sedative that has been used for many years in clinical practice and, under proper conditions, gives a deep and long enough sleep to allow performance of objective hearing tests in young children. The reluctance to use this substance stems from side effects reported over time that can vary, depending on dose, procedure settings and immediate life supporting intervention when needed. Our study adds to those that have appeared in recent years, showing that chloral hydrate is an effective and safe substance when is used in proper conditions.

METHODS

The study included 322 children who needed sedation for objective hearing tests, from April 2014 to March 2018. Parents were instructed to bring the child tired and fasted for at least 2 h before sedation. The sedative was administered by trained staff in the hospital, and the child was monitored until awaking.

RESULTS

In our study group, over half of the children were in the age 1-4 years group, and only 15% were older than 4 years. The dose of chloral hydrate ranged between 50 and 83 mg/kg body weight, with an average of 75 mg. Successful sedation occurred in 94.1% of children; 0.9% of children awoke during testing and required supplemental sedation or rescheduling of the testing. The most common side effects were vomiting, agitation, prolonged sleep, and failure to fall asleep.

CONCLUSIONS

Comparing the side effects of chloral hydrate in our study with those from other studies, ours were similar to those described in the literature. In our study chloral hydrate was effective and had only limited adverse effects. The use of chloral hydrate under hospital conditions with proper monitoring could be a practical and safe solution for outpatients or those with short-term hospitalisation.

Pre-treatment with Melamil Tripto® induces sleep in children undergoing Auditory Brain Response (ABR) testing

OBJECTIVES

Previous studies have shown that tryptophan and vitamin B6 used in conjunction with melatonin induce sleep more effectively than melatonin alone. This study aims at evaluating the efficacy of different dosages and timings of administration of a solution containing melatonin, tryptophan, and vitamin B6 for inducing sleep in children undergoing ABR testing.

METHODS

294 children scheduled for Auditory Brain Response (ABR) evaluation were administered a solution containing melatonin, tryptophan, and vitamin B6 to induce sleep before the exam. Two different administration timings (pre-treatment and single shot treatment) and three dosages (0.5 ml in pre-treatment, 1.5 ml in pre-treatment, and 3 ml in single shot) were tested. The following parameters were evaluated: time needed for the subject to fall asleep before ABR testing, subject sl'eep features during ABR testing (quality, stability, duration), recorded ABR quality (including presence of abnormalities in amplitude and latency), subject waking up modality, and time needed for the subject to wake up at the end of the ABR exam.

RESULTS

Quality of ABR signals was similar across treatments, and subjects responded in a similar manner in terms of time needed to wake-up and wake-up modality. However, pretreatment with the 1.5 ml dose induced sleep faster than the two other dosages, and the length of the induced sleep was longer than that induced by pre-treatment with 0.5 ml. In general, the pre-treatment with 1.5 ml led to a shorter ABR exam, because reduces the time for inducing sleep, allows a long sleeping phase with a good quality, without variation in the wakening up times.

CONCLUSIONS

Melamil Tripto^® is an alternative to sedative drugs for inducing sleep in pediatric subjects undergoing ABR testing. A pre-medication with 1.5 ml of MT 1 week before ABR testing further improves the strength of the solution.

Visual Evoked Potentials in Rett Syndrome

Investigators from the Boston Children's Hospital recorded pattern-reversal visual evoked potentials (VEPs) in Mecp2 heterozygous female mice and in 34 girls with Rett syndrome (RTT).

The auditory brainstem response: latencies obtained in children while under general anesthesia

BACKGROUND

The auditory brainstem response (ABR) test is frequently employed to estimate hearing sensitivity and assess the integrity of the ascending auditory system. In persons who cannot participate in conventional tests of hearing, a short-acting general anesthetic is used, recordings are obtained, and the results are compared with normative data. However, several factors (e.g., anesthesia, temperature changes) can contribute to delayed absolute and interpeak latencies, making it difficult to evaluate the integrity of the person's auditory brainstem function.

PURPOSE

In this study, we investigated the latencies of ABR responses in children who received general anesthesia.

RESEARCH DESIGN

Between subject.

STUDY SAMPLE

Twelve children between the ages of 29 and 52 mo, most of whom exhibited a developmental delay but normal peripheral auditory function, comprised the anesthesia group. Twelve participants between the ages of 13 and 26 yr with normal hearing thresholds comprised the control group.

DATA COLLECTION AND ANALYSIS

ABRs from a single ear from children, recorded under general anesthesia, were retrospectively analyzed and compared to those obtained from a control group with no anesthesia. ABRs were generated using 80 dB nHL rarefaction click stimuli. T-tests, corrected for alpha slippage, were employed to examine latency differences between groups.

RESULTS

There were significant delays in latencies for children evaluated under general anesthesia compared to the control group. Delays were observed for wave V and the interpeak intervals I-III, III-V, and I-V.

CONCLUSIONS

Our data suggest that caution is needed in interpreting neural function from ABR data recorded while a child is under general anesthesia.