La revue Neuroscience & Biobehavioral Reviews propose un numéro spécial en Juin 2019 sur les symptômes régressifs dans les troubles du neurodéveloppement et génétiques.

Regression in neurodevelopmental and genetic disorders

1. Cosentino L, Vigli D, Franchi F, Laviola G, De Filippis B. Rett syndrome before regression : a time window of overlooked opportunities for diagnosis and intervention. Neuroscience & Biobehavioral Reviews ;2019 (2019/05/18/)

Rett syndrome (RTT) is a rare neurological disorder primarily affecting females, causing severe cognitive, social, motor and physiological impairments for which no cure currently exists. RTT clinical diagnosis is based on the peculiar progression of the disease, since patients show an apparently normal initial development with a subsequent sudden regression at around 2 years of age. Accumulating evidences are rising doubts regarding the absence of early impairments, hence questioning the concept of regression. We reviewed the published literature addressing the pre-symptomatic stage of the disease in both patients and animal models with a particular focus on behavioral, physiological and brain abnormalities. The emerging picture delineates subtle, but reliable impairments that precede the onset of overt symptoms whose bases are likely set up already during embryogenesis. Some of the outlined alterations appear transient, suggesting compensatory mechanisms to occur in the course of development. There is urgent need for more systematic developmental analyses able to detect early pathological markers to be used as diagnostic tools and precocious targets of time-specific interventions.

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2. Rankovic M, Zweckstetter M. Upregulated levels and pathological aggregation of abnormally phosphorylated Tau-protein in children with neurodevelopmental disorders. Neuroscience & Biobehavioral Reviews ;2019 (2019/03/01/) ;98:1-9.

The tubulin-associated unit (Tau) protein is an intrinsically disordered protein that plays a well-established role in promoting microtubule assembly and regulation of microtubule dynamics in neuronal axons at all stages of development. Identification of new interacting partners and different sub-cellular localizations of Tau in recent years led to the discovery of novel physiological functions in regulation of neuronal activity, neurogenesis, long-term depression, iron export and genomic integrity. In addition, Tau gene mutations, aberrant mRNA splicing and abnormal post-translational modifications, such as hyperphosphorylation, lead to formation of pathological, insoluble Tau aggregates that are a hallmark of neurodegenerative diseases, collectively known as tauopathies. Characterized by synaptic dysfunction, neuroinflammation/neuronal cell death and dementia, tauopathies are designated as a group of adult-onset neurodegenerative diseases. Recent studies summarized in this review document several neurological conditions and diseases in an early life stage with upregulated levels or even pathological aggregation of abnormally phosphorylated Tau protein. These findings suggest that Tau might play a previously underestimated role in neurodevelopmental disorders and regression in children.

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3. Boterberg S, Charman T, Marschik PB, Bölte S, Roeyers H. Regression in autism spectrum disorder : A critical overview of retrospective findings and recommendations for future research. Neuroscience & Biobehavioral Reviews ;2019 (2019/07/01/) ;102:24-55.

Historically, two onset patterns in autism spectrum disorder (ASD) were described : early onset of symptoms and regression in which one-third appear to show a loss of previously established skills in the second year of life. Since this phenomenon could represent a distinct ASD subtype and provide more insight into the etiology, diagnosis, and prognosis, many studies have compared these two groups. The present review discusses definitions, etiology, and methods used in research with a retrospective design and provides an overview of the results on early development and outcomes. However, retrospective research has not provided clear answers on regression as a distinct subtype of ASD and the historic division between early onset and regression does not seem to fit the empirical findings. Based on inconsistent results, future research on onset patterns in ASD needs to be more systematic on the definitions and methods used. Several recommendations to enhance the reliability of future retrospective results are discussed. The combination of a categorical and dimensional approach provides a new interesting framework.

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4. Sigafoos J, O’Reilly MF, Ledbetter-Cho K, Lim N, Lancioni GE, Marschik PB. Addressing sequelae of developmental regression associated with developmental disabilities : A systematic review of behavioral and educational intervention studies. Neuroscience & Biobehavioral Reviews ;2019 (2019/01/01/) ;96:56-71.

Developmental regression is characteristic of Rett syndrome and it also occurs in a number of other developmental disabilities. To assist clinicians in identifying promising therapeutic approaches, we identified 38 studies that sought to improve adaptive behavior functioning in cases where developmental regression had either already occurred or was likely to occur. Studies were summarized in terms of (a) participants, (b) intervention, (c) dependent variables, (d) outcomes, (e) study design, and (f) certainty of evidence. The available literature included 136 participants from preschoolers to adults. Most participants (n = 132) had Rett syndrome. Interventions targeted a range of dependent variables (e.g., challenging behavior, communication, motor, and play skills). Multi-component interventions derived from behavior analytic principles were the norm, suggesting the need for clinical expertise in the application of such principles. However, only 12 studies (with 44 participants) were rated as providing conclusive evidence of a positive intervention effect. Future research on the mechanisms underlying developmental regression might lead to new and more effective interventions.

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5. Müller M. Disturbed redox homeostasis and oxidative stress : Potential players in the developmental regression in Rett syndrome. Neuroscience & Biobehavioral Reviews ;2019 (2019/03/01/) ;98:154-163.

Rett syndrome (RTT) is a neurodevelopmental disorder affecting mostly girls. A seemingly normal initial development is followed by developmental stagnation and regression, leading to severe mental impairment with autistic features, motor dysfunction, irregular breathing and epilepsy. Currently, a cure does not exist. Due to the close association of RTT with mitochondrial alterations, cellular redox-impairment and oxidative stress, compounds stabilizing mitochondrial function, cellular redox-homeostasis, and oxidant detoxification are increasingly considered as treatment concepts. Indeed, antioxidants and free-radical scavengers ameliorate certain aspects of the complex and severe clinical presentation of RTT. To further evaluate these strategies, reliable biosensors are needed to quantify redox-conditions in brain and peripheral organs of mouse models or in patient-derived cells. Genetically-encoded redox-sensors meet these requirements. Expressed in transgenic mouse-models such as our unique Rett-redox indicator mice, they will report for any cell type desired the severity of oxidant stress throughout the various disease stages of RTT. Furthermore, these sensors will be crucial to evaluate in vitro and in vivo the outcome of mitochondria- and redox-balance targeted treatments.

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6. Tammimies K. Genetic mechanisms of regression in autism spectrum disorder. Neuroscience & Biobehavioral Reviews ;2019 (2019/07/01/) ;102:208-220.

Developmental regression occurs in approximately one-third of children with autism spectrum disorder (ASD). There is a strong genetic influence in ASD and hundreds of genes have been implicated. Theories suggest that regressive ASD is a neurobiological subtype with potentially different causes. This review examines the evidence of genetic influences in regression and provides a summary of its frequency among ASD-associated single-gene disorders. The few twin- and family studies reporting on the concordance of regressive ASD among twin pairs and siblings provide mixed results, and no conclusions of the variance explained by either genetic or environmental factors can be drawn. Among the 89 genes robustly associated with ASD, 16 have been connected to regression, of which seven showed rates of regression higher than 30% among the mutation carriers. The molecular functions of these genes highlight important roles of transcriptional and synapse regulation for regression. Overall, this review shows our limited understanding of factors influencing regressive ASD and calls for additional studies to answer the open questions.

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7. Camfield P, Camfield C. Regression in children with epilepsy. Neuroscience & Biobehavioral Reviews ;2019 (2019/01/01/) ;96:210-218.

Regression in children with epilepsy may involve loss of cognitive abilities, failure to progress or a slowing of developmental trajectory. A few seizures do not lead to regression. Large numbers of seizures may be associated with regression but the cause is an important cofounder. Individual spike discharges on EEG are associated with transient cognitive impairment and continuous spike discharges with regression. Regression may be global in continuous spike wave in slow sleep (CSWS) or specific (auditory agnosia) in Landau Kleffner syndrome. Regression is mild and transient in Rolandic Epilepsy or profound and permanent in West Syndrome. Epilepsy syndromes grouped under “epileptic encephalopathies” may lead to regression, although proof of this concept is not strong for many syndromes. The absence of cognitive assessment before epilepsy onset, the contribution of the cause and complications of treatment make for difficult methodological problems. The large majority of children with epilepsy do not have regression. There is need for more longitudinal studies of children with epileptic encephalopathies and other epilepsies associated with regression.

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8. Ozonoff S, Iosif A-M. Changing conceptualizations of regression : What prospective studies reveal about the onset of autism spectrum disorder. Neuroscience & Biobehavioral Reviews ;2019 (2019/05/01/) ;100:296-304.

Until the last decade, studies of the timing of early symptom emergence in autism spectrum disorder (ASD) relied upon retrospective methods. Recent investigations, however, are raising significant questions about the accuracy and validity of such data. Questions about when and how behavioral signs of autism emerge may be better answered through prospective studies, in which infants are enrolled near birth and followed longitudinally until the age at which ASD can be confidently diagnosed or ruled out. This review summarizes the results of recent studies that utilized prospective methods to study infants at high risk of developing ASD due to family history. Collectively, prospective studies demonstrate that the onset of ASD involves declines in the rates of key social and communication behaviors during the first years of life for most children. This corpus of literature suggests that regressive onset patterns occur much more frequently than previously recognized and may be the rule rather than the exception.

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9. Einspieler C, Marschik PB. Regression in Rett syndrome : Developmental pathways to its onset. Neuroscience & Biobehavioral Reviews ;2019 (2019/03/01/) ;98:320-332.

Rett syndrome (RTT) is an X-linked genetic disorder that occurs predominantly in females. The clinical picture associated with RTT is defined by core and supportive consensus criteria, with a period of behavioural regression being a conditio sine qua non. This review sheds light on atypical neurofunctions and potential behavioural biomarkers before the onset of regression. The main focus lies on (a) motor development, especially on purposeful hand movements and the occurrence of stereotypies ; and (b) speech-language and socio-communicative development. We outline potentially specific atypical behavioural patterns in these domains (e.g., vocalisations on inspiratory airstream) and different developmental traits of regression : (i) non-achievement of certain milestones : ‘regression’, here, might point to the fact that the lack of respective behavioural patterns appeared more and more worrisome with increasing age ; and (ii) developmental milestones were achieved and functions deteriorate or even get lost during regression. To conclude, we are not quite there yet, but seem to be on the right track towards defining new and reliable neurofunctional markers for early detection of RTT.

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10. Nielsen-Saines K. Perinatal HIV as an infectious cause of developmental regression. Neuroscience & Biobehavioral Reviews ;2019 (2019/07/01/) ;102:417-423.

Although many pathogens affect neurodevelopment, most do so by stalling or arresting developmental progress with damage to central nervous system (CNS) cells and circuits during fetal life, leaving lifelong sequelae after early neuronal infection. In utero infections with CNS repercussions generally result from direct infection of fetal neural cells, with varying degrees of CNS involvement depending on the stage of fetal development. Human Immunodeficiency Virus (HIV) is distinct from other conditions as it does not cause immediate repercussions to the CNS unless HIV perinatal infection is accompanied by other co-infections. Nevertheless, distinct from the other congenital infections which generally induce failure to attain developmental milestones, perinatal HIV infection causes developmental regression, with often indolent but progressive neurodevelopmental consequences. Loss of developmental milestones has long been recognized as an Acquired Immune Deficiency Syndrome defining condition, often with growth failure. HIV encephalopathy presents as developmental delay/loss of developmental milestones, with manifestations in motor, mental and expressive language functions. Perinatal HIV disease is herein reviewed, with focus on developmental outcomes, diagnosis and treatment.

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