Rett syndrome

Behavioral video analysis supports Rett syndrome research

Tuesday, 25 November, 2014

Rett syndrome (RTT) is a severe progressive neurodevelopmental disorder. It affects girls almost exclusively and is characterized by normal early growth and development followed by a slowing of development, loss of purposeful use of the hands, distinctive hand movements, slowed brain and head growth, problems with walking, seizures, and intellectual disability (Rett Syndrome Fact Sheet, 2014). In the study discussed in this blog post, the researchers indicated that normal cooing and babbling were absent in the first two years of life. They also observed finger movements and found that they occurred sporadically with limited variability. Let us zoom in on this original article published in the Journal of Developmental and Physical Disabilities.

Early onset stage

Recently, Christa Einspieler, Peter Marschik, and colleagues investigated subtle RTT symptoms in early childhood development. They focused on this particular stage because it is the one most often overlooked in the diagnosis of RTT; symptoms of the disorder are often vague, and parents and doctors may not notice the subtle slowing of development at first.

Twin study

Einspieler et al. analyzed videotapes of a pair of twin girls with RTT in order to compare behaviors. By studying previously recorded video material, they were able to describe the motor and communicative development of the two girls with RTT. The recordings were made at a time when the parents were not aware that their daughters had RTT; the disorder was diagnosed at 24 months for both girls.

Behavioral coding

Behaviors were coded using The Observer XT software, version 11. Motor behavior during the first 3 months of life was evaluated by means of the Prechtl assessment of general movements (see Einspieler and Prechtl 2005; Einspieler et al. 2004 for details about the Prechtl assessment).
Einspieler and colleagues took careful note of all behaviors that deviated from the normal standard, including movements that were “normal” but not displayed at the usual age, such as sideways rolling and the girls’ reaction to their names being called. Also observed were the “abnormal” behaviors like frozen smiles without eye contact. The twins overall displayed a positive mood and smiled frequently, but their smiles were sometimes interspersed with frozen, bizarre movements during which eye contact was avoided.
The researchers also analyzed the age-specific quality of gross and fine motor behaviors as well as the quality and rate of occurrence of age-specific vocalizations. Fixed vocal signals like crying and laughing were noted if abnormal.

Rett symptoms are present in early childhood

According to the researchers, this study provides more evidence supporting the idea that both subtle and obvious neurodevelopmental abnormalities might be observable in some RTT children before the more apparent signs of regression start to show. Abnormalities can be evident in the motor, speech-language and communicative domains; close monitoring of children’s early psychomotor behaviors can be revealing of certain developmental disorders.

The importance of detailed analysis

The first two years of life have previously been viewed as asymptomatic for children with RTT. Retrospectively, and only through the careful analysis of videotapes taken as early as 1 week after birth, Einspieler et al. were able to identify the subtle indicators of RTT which became more and more prominent in the motor as well as speech-language-communicative domains. The results of this study should aid in the argument for early screening and clinical assessment in children with possible developmental abnormalities.

The Observer XT

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References

  • Einspieler, C.; Marschik, P.B.; Domingues, W.; Talisa, V.B.; Bartl-Pokorny, K.D.; Wolin, T.; Sigafoos, J. (2014). Monozygotic twins with Rett syndrome: phenotyping the first two years of life. Journal of Developmental and Physical Disabilities, 26, 171-182.
  • Rett Syndrome Fact Sheet, 2014, http://www.ninds.nih.gov/disorders/rett/detail_rett.htm
  • Einspieler, C., & Prechtl, H. F. (2005). Prechtl’s assessment of general movements: a diagnostic tool for the functional assessment of the young nervous system. Mental Retardation and Developmental Disabilities Research Reviews, 11, 61–67.
  • Einspieler, C., Prechtl, H. F. R., Bos, A. F., Ferrari, F., & Cioni, G. (2004). Prechtl’s method on the qualitative assessment of general movements in preterm, term and young infants. London: Mac Keith Press. Distributed by Cambridge University Press.