The cerebellum and cognition.

A central aspect of the cerebellar cognitive affective syndrome is the dysregulation of affect that occurs when lesions involve the ‘limbic cerebellum’ (vermis and fastigial nucleus). In this case series we describe neuropsychiatric disturbances in adults and children with congenital lesions including cerebellar agenesis, dysplasia, and hypoplasia, and acquired conditions including cerebellar stroke, tumor, cerebellitis, trauma, and neurodegenerative disorders. The behaviors that we witnessed and that were described by patients and families included distractibility and hyperactivity, impulsiveness, disinhibition, anxiety, ritualistic and stereotypical behaviors, illogical thought and lack of empathy, as well as aggression and irritability. Ruminative and obsessive behaviors, dysphoria and depression, tactile defensiveness and sensory overload, apathy, childlike behavior, and inability to appreciate social boundaries and assign ulterior motives were also evident. We grouped these disparate neurobehavioral profiles into five major domains, characterized broadly as disorders of attentional control, emotional control, and social skill set as well as autism spectrum disorders, and psychosis spectrum disorders. Drawing on our dysmetria of thought hypothesis, we conceptualized the symptom complexes within each putative domain as reflecting either exaggeration (overshoot, hypermetria) or diminution (hypotonia, or hypometria) of responses to the internal or external environment. Some patients fluctuated between these two states. We consider the implications of these neurobehavioral observations for the care of patients with ataxia, discuss the broader role of the cerebellum in the pathogenesis of these neuropsychiatric symptoms, and revisit the possibility of using cerebellar stimulation to treat psychiatric disorders by enhancing cerebellar modulation of cognition and emotion.

The neuropsychiatry of the cerebellum - insights from the clinic.

Pediatric low-grade gliomas encompass a heterogeneous set of tumors of different histologies. Cerebellar pilocytic astrocytomas occur most frequently followed by supratentorial diffuse fibrillary astrocytomas. Recent research has implicated activation of the RAS/RAF/MEK pathway in tumorigenesis of these tumors. Surgery is the mainstay of therapy. Overall survival rates for patients whose tumors are completely resected are 90% or greater, 10 years from diagnosis. Conversely, most optic pathway/hypothalamic, deep midline, and brain stem gliomas have minimal potential for resection; these tumors can be difficult to treat and deserve special attention. Combination chemotherapy is currently recommended as front-line adjuvant treatment for progressive or recurrent tumors. Second-line radiotherapy can also improve overall survival but is associated with more frequent and significant neurocognitive, endocrine, and other long-term toxicities.

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Pediatric Low-Grade Gliomas

Sporadically advocated over the last two centuries, a cerebellar role in cognition and affect has been rigorously established in the past few decades. In the clinical domain, such progress is epitomized by the “cerebellar cognitive affective syndrome” (“CCAS”) or “Schmahmann syndrome.” Introduced in the late 1990s, CCAS reflects a constellation of cerebellar-induced sequelae, comprising deficits in executive function, visuospatial cognition, emotion–affect, and language, over and above speech. The CCAS thus offers excellent grounds to investigate the functional topography of the cerebellum, and, ultimately, illustrate the precise mechanisms by which the cerebellum modulates cognition and affect. The primary objective of this task force paper is thus to stimulate further research in this area. After providing an up-to-date overview of the fundamental findings on cerebellar neurocognition, the paper substantiates the concept of CCAS with recent evidence from different scientific angles, promotes awareness of the CCAS as a clinical entity, and examines our current insight into the therapeutic options available. The paper finally identifies topics of divergence and outstanding questions for further research.

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The Cerebellar Cognitive Affective/Schmahmann Syndrome: a Task Force Paper

The authors performed a systematic review and meta-analysis of studies evaluating the affective component of the cerebellar cognitive affective syndrome. Depressive and anxiety symptoms and personality changes were more frequent in patients with spinocerebellar ataxia. Patients with cerebellar lesions were more likely to have depression, deficits in the ability to experience emotions, and behavioral difficulties. A meta-analysis revealed modestly higher scores on the Hamilton Depression Rating Scale (HAM-D) among patients with cerebellar disease. This review highlights the need for cohort studies using noncerebellar comparison groups, more sensitive measures, and appropriate-sized populations with isolated cerebellar lesions to thoroughly assess the affective component of the cerebellar cognitive affective syndrome.

https://neuro.psychiatryonline.org/doi/pdf/10.1176/jnp.2009.21.3.245

Evaluating the Affective Component of the Cerebellar Cognitive Affective Syndrome

Nineteen children were acutely dysphoric, inattentive, irritable, and sometimes mute following midline posterior fossa neoplasm resection and arteriovenous malformation hemorrhage. These symptoms represent an acute manifestation of the cerebellar cognitive affective syndrome. The authors aimed to describe the acute psychiatric changes in mood and behavior in children with posterior fossa lesions and to evaluate the relationship of posterior fossa syndrome to cerebellar cognitive affective syndrome.

Linda Woodall

Papers

Case Series: Acute Mood Symptoms Associated With Posterior Fossa Lesions in Children