# Clinical, Cognitive and Behavioural Assessment in Children with Cerebellar Disorder
## 3 Developmental Cerebellar Cognitive-Affective Syndrome
### Neurodevolmental Disorders  
As previously mentioned, cerebellum abnormalities are associated to various types of neurodevelopmental disorders, the most studied being ASD, ADHD and for some extent, developmental dyslexia [22; 49; 50; 51; 52].  
Autoptic studies of patients with ASD have revealed a marked reduction in density of cerebellar Purkinje cells, particularly in the lateral hemispheres [52] and in the vermis [53]. Moreover, studies have reported altered connectivity between the cerebellum and cortical regions in ASD [54], and correlation between cerebellar gray matter volume and social impairment in ASD [49; 55].  
The important role of the cerebellum and in particular the postero-lateral portions of the hemispheres, in ASD-related behaviors, has been confirmed by a study combining neuroimaging and neuromodulation in humans and mice. Neuromodulation of the right Crus I in typical humans resulted in altered functional connectivity with the inferior parietal lobule, the same circuit presenting atypical connectivity in ASD children. Atypical structural connectivity in the same connection between Right Crus I-inferior parietal lobule was also evident in the Purkinje neuron of the ASD mouse model. Additionally, chemogenetically mediated inhibition of Right Crus I Purkinje Neuron activity in mice was sufficient to generate ASD-related social, repetitive, and restricted behaviors, while stimulation of Crus I rescued social impairment in the ASD mouse model [56].  
Dysfunctions of the cerebellum, particularly of the cerebellar vermis, has been accepted as a potential etiological component of ADHD [32; 50]. Earlier structural neuroimaging studies with children and adults with ADHD described reduced cerebellar volumes even after correction for total cerebral volume [57; 58]. Similarly to ADHD patients, smaller cerebellar volume and reduced GM have been observed in preterm children with impulsive symptomatology [59].  
Additionally, abnormal cerebellar connectivity patterns have been described in ADHD children and adults. In adult patients, the cerebellum exhibits reduced connectivity with the prefrontal cortex [60], while altered resting-state connectivity in the cerebellum have been found in ADHD children [61]. [PERSON] et al. [62] investigated striatal connectivity in an extensive sample of adolescents with a diagnosis of ADHD as well as in their healthy relatives. Hyperactivity, impulsivity and inattention were related to greater connectivity of the posterior putamen with the cerebellum and occipital cortex.  
In particular, dysregulation of prefrontal and cerebellar activity seems to be differently involved in neurofunctional subtypes of ADHD models: the inability to engage the cerebellum as well as prefrontal and parietal cortices during response inhibition tasks was found in adolescents with executive deficits, while patients with emotional and motivational deficits over-engaged the amygdala and ventral striatum during rewarded tasks with no change in prefrontal-cerebellar network [63].  
The cerebellar deficit hypothesis of dyslexia posits that dysfunction of the cerebellum is the underlying cause of reading difficulties observed in this common learning disability [33]. According to the cerebellar hypothesis, the research group of [PERSON] and [PERSON] have argued that abnormal cerebellar function impacts not only articulatory and phonological awareness skills, but also skills outside of language that are associated with the cerebellum and reported to be affected in dyslexia, including balance, automaticity, habituation to eye-blink conditioning, and timing skills [51].  
However, neuroscience experiments showed limited support to the cerebellar deficit hypothesis of dyslexia [64; 65], suggesting that cerebellar dysfunction is not the sole cause of dyslexia, but in some dyslexics it is part of the distributed network of regions that fail to develop and/or fail to wire together properly [66].