Unilateral rhythmic hand tapping in Rett syndrome: is this stereotypy?

Movement disorders in patients with Rett syndrome: A systematic review of evidence and associated clinical considerations

AIM

This systematic review identified and thematically appraised clinical evidence of movement disorders in patients with Rett syndrome (RTT).

METHOD

Using PRISMA criteria, six electronic databases were searched from inception to April 2021. A thematic analysis was then undertaken on the extracted data to identify potential themes.

RESULTS

Following the thematic analysis, six themes emerged: (i) clinical features of abnormal movement behaviors; (ii) mutational profile and its impact on movement disorders; (iii) symptoms and stressors that impact on movement disorders; (iv) possible underlying neurobiological mechanisms; (v) quality of life and movement disorders; and (vi) treatment of movement disorders. Current guidelines for managing movement disorders in general were then reviewed to provide possible treatment recommendations for RTT.

CONCLUSION

Our study offers an enriched data set for clinical investigations and treatment of fine and gross motor issues in RTT. A detailed understanding of genotype-phenotype relationships of movement disorders allows for more robust genetic counseling for families but can also assist healthcare professionals in terms of monitoring disease progression in RTT. The synthesis also showed that environmental enrichment would be beneficial for improving some aspects of movement disorders. The cerebellum, basal ganglia, alongside dysregulation of the cortico-basal ganglia-thalamo-cortical loop, are likely anatomical targets. A review of treatments for movement disorders also helped to provide recommendations for treating and managing movement disorders in patients with RTT.

An electromyographic assessment pilot study on the reliability of the forearm muscles during multi-planar maximum voluntary contraction grip and wrist articulation in young males

BACKGROUND

Electromyographic systems are widely used in scientific and clinical practice. The reproducibility and reliability of these measures are crucial when conducting scientific research and collecting experimental data.

Reviewing Evidence for the Relationship of EEG Abnormalities and RTT Phenotype Paralleled by Insights from Animal Studies

Rett syndrome (RTT) is a rare neurodevelopmental disorder that is usually caused by mutations of the MECP2 gene. Patients with RTT suffer from severe deficits in motor, perceptual and cognitive domains. Electroencephalogram (EEG) has provided useful information to clinicians and scientists, from the very first descriptions of RTT, and yet no reliable neurophysiological biomarkers related to the pathophysiology of the disorder or symptom severity have been identified to date. To identify consistently observed and potentially informative EEG characteristics of RTT pathophysiology, and ascertain areas most worthy of further systematic investigation, here we review the literature for EEG abnormalities reported in patients with RTT and in its disease models. While pointing to some promising potential EEG biomarkers of RTT, our review identify areas of need to realize the potential of EEG including (1) quantitative investigation of promising clinical-EEG observations in RTT, e.g., shift of mu rhythm frequency and EEG during sleep; (2) closer alignment of approaches between patients with RTT and its animal models to strengthen the translational significance of the work (e.g., EEG measurements and behavioral states); (3) establishment of large-scale consortium research, to provide adequate Ns to investigate age and genotype effects.

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.

Hand stereotypies: Lessons from the Rett Syndrome Natural History Study

OBJECTIVE

To characterize hand stereotypies (HS) in a large cohort of participants with Rett syndrome (RTT).

METHODS

Data from 1,123 girls and women enrolled in the RTT Natural History Study were gathered. Standard tests for continuous and categorical variables were used at baseline. For longitudinal data, we used repeated-measures linear and logistic regression models and nonparametric tests.

RESULTS

HS were reported in 922 participants with classic RTT (100%), 73 with atypical severe RTT (97.3%), 74 with atypical mild RTT (96.1%), and 17 females with MECP2 mutations without RTT (34.7%). Individuals with RTT who had classic presentation or severe MECP2 mutations had higher frequency and earlier onset of HS. Heterogeneity of HS types was confirmed, but variety decreased over time. At baseline, almost half of the participants with RTT had hand mouthing, which like clapping/tapping, decreased over time. These 2 HS types were more frequently reported than wringing/washing. Increased HS severity (prevalence and frequency) was associated with worsened measures of hand function. Number and type of HS were not related to hand function. Overall clinical severity was worse with decreased hand function but only weakly related to any HS characteristic. While hand function decreased over time, prevalence and frequency of HS remained relatively unchanged and high.

CONCLUSIONS

Nearly all individuals with RTT have severe and multiple types of HS, with mouthing and clapping/tapping decreasing over time. Interaction between HS frequency and hand function is complex. Understanding the natural history of HS in RTT could assist in clinical care and evaluation of new interventions.

Tapping-lips aggravated interictal bilateral discharges in EEG in the patients with Rett syndrome: a case report

Background

Rett syndrome (RTT) is a severe neurodevelopmental disorder mainly affecting females. One of the main clinical manifestations is hand stereotypies, which is presumed to based on dysfunction rather than on structural impairment. Reflex interictal discharge precipitated by tapping-lips in electroencephalogram (EEG) is a rare phenomenon among RTT.

Case presentation

We firstly reported a case of RTT concerning interictal reflex discharge precipitated by tapping- lips. The child, female, 5 years old, presented with a significant regression in motor development and language skills. She almost always tapped the lips with the right hand and stopped only when was interrupted. Her EEG results displayed extensive low amplitude fast wave could be elicited by lightly and slowly- rhythm tapping lips and multifocal bilateral discharges could be precipitated by relatively stronger and quicker rhythm action. It was when the movement stopped that corresponding discharges immediately disappeared. Besides, the reflex discharges were not precipitated by tapping- lips using observer’s hand at the certain tempo and intensity. The hand stereotypies did not respond to antiepileptic drugs.

Conclusions

Tapping- lips may be a somatosensory stimulation to precipitate interictal discharges in RTT, which may provide another idea to enrich the insight on hand stereotypies of RTT.