Cerebellar cognitive-affective syndrome, also called Schmahmann syndrome, is a condition resulting from lesions of the cerebellum. It refers to a group of disorders in the cognitive domains of executive function, spatial perception, language and other effects of cerebellar damage. Executive function disorders include problems with planning, task switching, abstract thinking, verbal fluency and working memory, and are often accompanied by perseveration, distractibility and inattention. Language problems include dysarthria, agrammatic aphasia and mild nomenclature aphasia. Spatial perception disorders result in poor visuospatial organization and poor visuospatial memory. Personality changes are manifested by emotional blunting or inappropriate behavior. These cognitive impairments result in an overall decline in intellectual function. This syndrome challenges the traditional view that the cerebellum is solely involved in the regulation of motor functions. The cerebellum is now thought to be responsible for the regulation of a wide range of motor and nonmotor functions. The non-motor disturbances seen in CCAS are also thought to result from dysfunctional connections between the cerebellum and the cerebral cortex and limbic system. CCAS has been diagnosed in both children and adults. The precise manifestations of the disease vary from individual to individual, likely reflecting the precise location of the cerebellar damage. Researchers have subsequently expanded on the affective component of the syndrome, i.e., the neuropsychiatric manifestations. They have reported numerous cases in which patients with single cerebellar damage exhibit vagueness, hyperactivity, impulsivity, disinhibition, anxiety, stereotyped and ritualistic behaviors, irrational thinking, lack of empathy, aggression, irritability, obsessive and ruminative behaviors, dysphoria and depression, tactile defensiveness and sensory overload, apathy, infantile behavior, and an inability to understand social boundaries and identify hidden motives. CCAS can be identified by a pattern of disturbances that includes executive function, visuospatial perception, language performance, and changes in emotions and personality. The low number of diagnosed cases may reflect a lack of awareness of the syndrome in the medical and scientific community. The nature and diversity of symptoms are also challenging. Levels of depression, anxiety, emotional dysregulation, and dysregulation of emotions vary from patient to patient. Symptoms of cerebellar-cognitive-affective syndrome are often quite severe after acute injury in adults and children, but tend to decrease over time. This supports the view that the cerebellum plays a role in regulating cognitive processes. There are a number of psychiatric disorders that have been linked to cerebellar dysfunction and that are similar to the symptoms of CCAS. Cerebellar lesions have been suggested to play a role in some features of psychiatric disorders, such as schizophrenia, depression, bipolar disorder, attention deficit hyperactivity disorder, developmental dyslexia, Down syndrome, and fragile X syndrome. Schmahmann's dysmetropia hypothesis has been applied to these psychiatric disorders. In schizophrenia, dysfunction of the corticocortico-thalamo-cerebellar circuit has been suggested, which in turn causes problems with emotional behaviors and emotional cognition. Postmortem studies have supported this idea, showing smaller anterior portions of the cerebellar vermis and lower Purkinje cell density in cerebellar vermis in patients with schizophrenia. There is also ample evidence to support the hypothesis that symptoms of some psychiatric disorders are due to cerebellar dysfunction. One study found that people with schizophrenia had smaller inferior cerebellar vermis and decreased asymmetry between the cerebellar hemispheres compared with controls. People with ADHD were also found to have smaller posterior inferior lobes compared with controls. Other studies have reported a correlation between cerebellar vermis size and ADHD severity. A PET study of people with dyslexia showed reduced cerebellar activity during motor tasks compared with controls. The pathogenesis of these psychiatric disorders may be better understood by studying CCAS. The symptoms of CCAS vary depending on the many possible causes, but all cases present with a cluster of central symptoms regardless of the cause. Causes of CCAS include cerebellar agenesis, dysplasia, or hypoplasia, stroke, tumors, cerebellar inflammation, trauma, and neurodegenerative diseases. CCAS can also be seen in children with prenatal, early postnatal, or developmental lesions. In these cases, the cerebellum is affected by lesions that cause cognitive and emotional deficits. The severity of CCAS varies depending on the location and extent of the lesion. In the original report describing the syndrome, patients with bilateral hemispheric infarction, pancerebellar disease, or large unilateral posterior inferior cerebellar artery infarction had greater cognitive impairment than patients with small right PICA infarction, small right anterior internal cerebellar artery infarction, or superior cerebellar artery territory. In general, patients with posterior cerebellar damage or bilateral lesions have the most severe symptoms, while patients with frontal lobe lesions have less severe symptoms. In children, patients with astrocytoma have performed better on neuropsychological tests than their peers with medulloblastoma. When diagnosing a patient with CCAS, medical professionals must remember that there are many different causes of the syndrome. Current treatments for CCAS focus on relieving symptoms. One treatment used is cognitive behavioral therapy, which involves making the patient aware of his or her cognitive problems. For example, many patients with CCAS have difficulty multitasking. With CBT, the patient must recognize this problem and focus on one task at a time. This technique is also used to relieve some motor symptoms. In a case study of a patient with CCAS resulting from a stroke, the patient showed improvements in mental function and attention with reality orientation therapy and attention training. Reality orientation therapy consists of repeated exposure to past event cues, such as images. Attention training consists of visual and auditory tasks that improve attention. The patient had difficulty applying these skills to “real life” situations. His family's help at home played a significant role in restoring his ability to perform activities of daily living. The family motivated the patient to perform basic tasks and set a regular schedule for him to follow. Transcranial magnetic stimulation has been suggested as a potential treatment option for cerebellar psychopathology. One study used TMS on the cerebellar vermis of a population of patients with schizophrenia. After stimulation, patients showed increased happiness, alertness, and energy, along with decreased sadness. Neuropsychological testing after stimulation showed improved working memory, attention, and visuospatial skills. Exercises to relieve motor symptoms are another treatment for CCAS. These exercises have also been shown to be helpful in treating cognitive symptoms. Medications used to relieve disorders caused by traumatic brain injury in adults have been suggested as a treatment option for CCAS. Bromocriptine, a direct D2 agonist, has been shown to help with executive function and spatial learning abilities. Methylphenidate, in turn, helps with attention and inhibition disorders. Neither of these medications have yet been tested in CCAS patients. It is also possible that some CCAS symptoms improve over time without formal treatment. In the original report of the syndrome, four patients with the syndrome were re-examined one to nine months after their initial neuropsychological evaluation. Three of them showed improvement in their symptoms without any formal treatment, with executive function being the only deviation from the norm. The symptoms worsened over time in the last patient. This patient experienced cerebellar atrophy and deterioration in visuospatial abilities, conceptual formation, and verbal memory. None of the above treatments has been tested in a large enough sample to determine their effect on patients with CCAS. Further research is needed on CCAS treatments.