Cerebellar cognitive affective syndrome

CCAS also called Schmahmann's syndrome is a condition that follows from lesions (damage) to the cerebellum of the brain. It refers to a constellation of deficits in the cognitive domains of executive function, spatial cognition, language, and affect resulting from damage to the cerebellum. Impairments of executive function include problems with planning, set-shifting, abstract reasoning, verbal fluency, and working memory, and there is often perseveration, distractibility and inattention. Language problems include dysprosodia, agrammatism and mild anomia. Deficits in spatial cognition produce visual–spatial disorganization and impaired visual–spatial memory. Personality changes manifest as blunting of affect or disinhibited and inappropriate behavior. These cognitive impairments result in an overall lowering of intellectual function. CCAS challenges the traditional view of the cerebellum being responsible solely for regulation of motor functions. It is now thought that the cerebellum is responsible for monitoring both motor and nonmotor functions. The nonmotor deficits described in CCAS are believed to be caused by dysfunction in cerebellar connections to the cerebral cortex and limbic system.

Affective components

Cognitive components

Deficits in

Schizophrenia: Schmahmann’s dysmetria of thought hypothesis has been applied to these psychiatric disorders. In schizophrenia, it has been suggested that there is dysfunction of the cortical-thalamo-cerebellar circuit, which leads to problems with emotional behaviors and cognition. Supporting this idea are postmortem studies that have shown smaller anterior portions of the vermis and reduced density of the Purkinje cells in the vermis in schizophrenia. There are several pieces of evidence that support the hypothesis that symptoms of some psychiatric disorders are the result of cerebellar dysfunction. One study found that people with schizophrenia had smaller inferior vermis and less cerebellar hemispheric asymmetry than control adults.
Depression
Bipolar disorder
ADHD: It has also been found that individuals with ADHD have smaller posterior inferior lobes than a control group. Other studies have suggested that the size of the vermis is correlated with the severity of ADHD. A study of people with dyslexia showed lower activation via positron emission tomography (PET) in the cerebellum during a motor task relative to a control group. It may be possible to further understand the pathology of these psychiatric disorders by studying CCAS.
Developmental dyslexia
Down syndrome, and Fragile X syndrome.

Cerebellar agenesis, Dysplasia and hypoplasia, Cerebellar stroke, Tumor, Trauma
Cerebellitis
Neurodegenerative diseases such as progressive supranuclear palsy and multiple system atrophy.
Developmental lesions
Overall, patients with damage to either the posterior lobe of the cerebellum or with bilateral lesions had the greatest severity of symptoms, whereas patients with lesions in the anterior lobe had less severe symptoms.

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