Neurorestorative effects of cerebellar transcranial direct current stimulation on social prediction of adolescents and young adults with congenital cerebellar malformations

BACKGROUND

Converging evidence points to impairments of the predictive function exerted by the cerebellum as one of the causes of the social cognition deficits observed in patients with cerebellar disorders.

OBJECTIVE

We tested the neurorestorative effects of cerebellar transcranial direct current stimulation (ctDCS) on the use of contextual expectations to interpret actions occurring in ambiguous sensory sceneries in a sample of adolescents and young adults with congenital, non-progressive cerebellar malformation (CM).

METHODS

We administered an action prediction task in which, in an implicit-learning phase, the probability of co-occurrence between actions and contextual elements was manipulated to form either strongly or moderately informative expectations. Subsequently, in a testing phase, we probed the use of these contextual expectations for predicting ambiguous (i.e., temporally occluded) actions. In a sham-controlled, within-subject design, participants received anodic or sham ctDCS during the task.

RESULTS

Anodic ctDCS, compared to sham, improved patients' ability to use contextual expectations to predict the unfolding of actions embedded in moderately, but not strongly, informative contexts.

CONCLUSIONS

These findings corroborate the role of the cerebellum in using previously learned contextual associations to predict social events and document the efficacy of ctDCS to boost social prediction in patients with congenital cerebellar malformation. The study encourages the further exploration of ctDCS as a neurorestorative tool for the neurorehabilitation of social cognition abilities in neurological, neuropsychiatric, and neurodevelopmental disorders featured by macro- or micro-structural alterations of the cerebellum.

Unilateral cerebellar hypoplasia in a 9-year-old child with chronic granulomatous disease: A case report

Unilateral cerebellar hypoplasia is a rare neurological condition that affects the development of the cerebellum, causing symptoms like poor coordination, balance issues, tremors, and speech problems. Unilateral cerebellar hypoplasia can occur as an isolated finding or as part of a larger neurological disorder or hereditary disease. There have been rare recorded instances where patients with chronic granulomatosis disease have been found to have neurological symptoms, such as brain abscesses or persistent inflammation, even though that CGD primarily affects the immune system and causes recurrent infections. A 9-year-old male with a known diagnosis of CGD presented to our neurology outpatient department with complaints of frequent falls and speech abnormalities. His parents described suspicious seizure-like movements and poor scholarly performance. Neurologic examination showed ataxic gait, slurred speech, and right-sided plantar extensor reflex. Initial laboratory findings were normal. MRI revealed marked reduced volume of the left cerebellar hemisphere with intact vermis and asymmetry of the posterior fossa. The residual left cerebellar hemisphere showed a normal folia and gray-white matter differentiation pattern. CSF filled the space created by the left hypoplastic cerebellum. A diagnosis of unilateral cerebellar hypoplasia was made. There is no known direct association between chronic granulomatous disease and unilateral cerebellar hypoplasia. However, more research is required to discover whether there is any connection between them. Although it is possible for a child to have CGD and UCH, managing such cases requires a multidisciplinary approach involving neurologists, immunologists, and other specialists to provide appropriate care and treatment.

[Rhombencephalosynapsis : a rare cerebellar malformation not to miss]

Rhombencephalosynapsis (RS) is a rare cerebellar malformation characterized by the association of partial or total vermis agenesis and fusion of the cerebellar hemispheres. This malformation is often associated with supratentorial cerebral abnormalities and more rarely with extra-cranial abnormalities. The severity of the clinical manifestations and the prognosis of RS depend on the findings of the posterior fossa and the associated anomalies. This clinical case presents an isolated complete RS, documented by antenatal ultrasound, fetal and postnatal/mortem magnetic resonance imaging (MRI) and pathological examination. A RS should be suspected on antenatal morphological ultrasound in case of reduction in size of the posterior fossa and in the absence of vermis. Fetal MRI is the imaging modality of choice to confirm the diagnosis. In the event of medical termination of pregnancy, the autopsy is rarely accepted by the parents, limiting postnatal investigations. This is why postnatal/postmortem MRI can prove to be an alternative to confirm and better document this rare pathology. Finally, multidisciplinary collaboration is essential to make the diagnosis and to ensure the best care.

Joubert Syndrome with Orofacial Digital Features

Joubert syndrome (JS) is an autosomal recessive inherited disorder characterized by hypotonia, cerebellar vermis hypoplasia, ocular abnormalities (e.g., pigmentary retinopathy, oculomotor apraxia, and nystagmus), renal cysts, and hepatic fibrosis. Respiratory abnormalities, as apnea and hyperpnea, may be present, as well as mental retardation. Since the clinical findings of JS are quite heterogeneous, determination of radiological findings is essential.

What cerebellar malformations tell us about cerebellar development

Structural birth defects of the cerebellum, or cerebellar malformations, in humans, have long been recognized. However, until recently there has been little progress in elucidating their developmental pathogenesis. Innovations in brain imaging and human genetic technologies over the last 2 decades have led to better classifications of these disorders and identification of several causative genes. In contrast, cerebellar malformations in model organisms, particularly mice, have been the focus of intense study for more than 70 years. As a result, many of the molecular, genetic and cellular programs that drive formation of the cerebellum have been delineated in mice. In this review, we overview the basic epochs and key molecular regulators of the developmental programs that build the structure of the mouse cerebellum. This mouse-centric approach has been a useful to interpret the developmental pathogenesis of human cerebellar malformations. However, it is becoming apparent that we actually know very little regarding the specifics of human cerebellar development beyond what is inferred from mice. A better understanding of human cerebellar development will not only facilitate improved diagnosis of human cerebellar malformations, but also lead to the development of treatment paradigms for these important neurodevelopmental disorders.

[Dandy-Walker malformation]

The Dandy-Walker malformation is the most frequent cerebral malformation. It is defined by hypoplasia and upward rotation of the vermis cerebelli, a cystic enlargement of the fourth ventricle and in total an enlarged posterior fossa with cranially shifted position of the lateral sinus, tentorium and torcula herophili. This malformation was first described by Dandy and Blackfan in 1914 then supplemented again by Taggart and Walker in 1942. The current description as Dandy-Walker malformation was introduced in 1954 by Bender. In addition to these classical findings, the Dandy-Walker malformation is characterized by other abnormalities and malformations of the central nervous system (CNS) including agenesis of the corpus callosum, heterotopia, occipital meningocele, visual deficits and epilepsy. Neurogenetic and imaging examinations have led to a better understanding of this malformation.

Joubert syndrome: neuroimaging findings in 110 patients in correlation with cognitive function and genetic cause

BACKGROUND

Joubert syndrome is a clinically and genetically heterogeneous ciliopathy. Neuroimaging findings have not been systematically evaluated in a large cohort of patients with Joubert syndrome in correlation with molecular genetic cause and cognitive function.

METHODS

Brain MRI of 110 patients with Joubert syndrome was included in this study. A comprehensive evaluation of brain MRI studies for infratentorial and supratentorial morphological abnormalities was performed. Genetic cause was identified by whole-exome sequencing, and cognitive functions were assessed with age-appropriate neurocognitive tests in a subset of patients.

RESULTS

The cerebellar hemispheres were enlarged in 18% of the patients, mimicking macrocerebellum. The posterior fossa was enlarged in 42% of the patients, resembling Dandy-Walker malformation. Abnormalities of the brainstem, such as protuberance at the ventral contour of the midbrain, were present in 66% of the patients. Abnormalities of the supratentorial brain were present in approximately one-third of the patients, most commonly malrotation of the hippocampi. Mild ventriculomegaly, which typically did not require shunting, was present in 23% of the patients. No correlation between neuroimaging findings and molecular genetic cause was apparent. A novel predictor of outcome was identified; the more severe the degree of vermis hypoplasia, the worse the neurodevelopmental outcome was.

CONCLUSIONS

The spectrum of neuroimaging findings in Joubert syndrome is wide. Neuroimaging does not predict the genetic cause, but may predict the neurodevelopmental outcome. A high degree of vermis hypoplasia correlates with worse neurodevelopmental outcome. This finding is important for prognostic counselling in Joubert syndrome.

Cerebellar Malformation: Deficits in early neural tube identity found in CHARGE syndrome

Long predicted from studies of model vertebrates, the first human example of abnormal patterning of the early neural tube leading to underdevelopment of the cerebellum has been demonstrated.