Autism and Cerebellar Mutism: A Review of the Neuroanatomical Findings

Miktat Kaya

doi:10.4172/2165-7890.1000105

Abstract

Autistic Spectrum Disorder (ASD) is behaviorally defined syndrome characterized by atypical social interaction, disordered verbal and non-verbal communication, restricted areas of interest and limited imaginative play. The prevalence of ASD is considered to be approximately 4 to 5 per 1000, but numbers differ according to criteria used for diagnosis [1]. Individuals with ASD have three core features; 1. Impairments of reciprocal social interactions, 2. Abnormal development and use of language and 3. Repetitive and ritualized behaviors and a narrow range of interests. In addition to the core features of autism, there are common co-morbid neurological disorders. The prevalence of mental retardation in the autism spectrum is approximately 30%. Epilepsy prevalence associated with autism varies from 5% to 44%. Anxiety and mood disorders are also very common in autism. There is heterogeneity in the onset of autism. Although some children have signs of development delays between 0-18 months of life, up to 40% of children with ASD initially demonstrate the near-normal development until 18-24 months. As Brunelle et al. says: All the results are converging toward the description of anatomical and functional anomalies in the regions of the so-called “social brain” [2]. Several brain regions such as frontal lobe, the superior temporal cortex, the parietal cortex, and amygdala have been implicated in social behavior. But the recent developments make us think more about the role of cerebellum in ASD. This review presents an overview of the neuroanatomical abnormalities that occur within ASD. We discuss the findings that have advanced our understanding of cerebellar organization in ASD.

Highlights

Since the view of Autistic Spectrum Disorder (ASD) has changed greatly, the hypothesis of an organic etiology has gradually become more important
One of the most prominent theories of the neuropathology of ASD is that the brain undergoes an abnormal development time course that appears to include a period of early overgrowth followed by deceleration in age-related growth in some individuals with ASD
The abnormal brain enlargement observed in children with ASD is mainly in white matter, not gray matter [4]

Summary

Introduction

Since the view of ASD has changed greatly, the hypothesis of an organic etiology has gradually become more important. When we consider cerebellum as the common source of the pathology in ASD and Cerebellar Mutism (CM), it could be said that three major neuropathologic findings have been described: (1) curtailed development of neurons in the forebrain limbic system (anterior cingulate gyrus, hippocampus, subiculum, etorhinal cortex, and mamillary body (2) decreased number of Purkinje cells in the cerebellum (3) age-related differences in cell size and neuronal number in the cerebellar and the inferior olivary nuclei, suggesting an evolving process and disturbance in the synaptic relationships of these structures. Brain development is comprised of several stages, including proliferation and migration of neurons, creation of dendritic arbors and synaptic connections, and eventually dendritic pruning and programmed cell death. Related to many functions of the brain, cerebellum has to be investigated much more

Neuroanatomical Findings in Autism

The number of neurons

The extent of neuronal dentritic growth and number of synapses

The number and size of glial cells

Conclusions