Cerebellar Cognitive Affective Syndrome

Executive function deficits include problems with working memory, as tested with reverse digit span; mental flexibility is tested using tasks of set shifting; and perseveration is demonstrated using bedside tests of mental control. Patients may have concrete thinking, poor problem-solving strategies, and impaired ability to multitask, with trouble planning, sequencing, and organizing their activities.

Mental representation of visual spatial relationships can be impaired. Visuospatial disintegration is apparent when attempting to copy or recall visual images. Identification of multiple features within a complex diagram (simultanagnosia) is difficult.

Expressive language can be abnormal, characterized by long response latency, brief responses, reluctance to engage in conversation, and word-finding difficulties. Verbal fluency is decreased affecting phonemic (letter) more than semantic (category) naming. Mutism occurs postoperatively for vermis tumors, particularly in children but also in adults subsequent to cerebellitis, infarction, and hemorrhage. Speech may have abnormal syntax, resulting in agrammatism. Degraded control of volume, pitch, and tone can produce high-pitched, hypophonic speech.

Short-term memory impairments include difficulty learning and spontaneously recalling new information, reflecting deficient strategies for organizing verbal or visual-spatial material for encoding, and difficulty locating information in memory stores. Successful recall is aided by a structured approach to the task, using clues and other prompts. Conditional associative learning is degraded, as shown in studies of classic conditioning in cerebellar patients (as well as in animals). Mental arithmetic is impaired. Ideational apraxia and hemi-inattention have been reported.

The affective component of the CCAS occurs when lesions involve the limbic cerebellum in the vermis and fastigial nucleus. Patients exhibit difficulty modulating behavior and personality style, have flattened affect or disinhibition manifesting as overfamiliarity, and flamboyant or impulsive actions. Behavior may be regressive and childlike, sometimes with obsessive-compulsive traits. Patients can be irritable, with labile affect and poor attentional and behavioral modulation. Acquired panic disorder is described in this setting as well.

Early evidence indicates that there are five domains of behavioral dysregulation caused by cerebellar damage. These are impairments of attentional control, emotional control, autism spectrum disorders, psychosis spectrum disorders, and difficulties with the social skill set. Within each of these domains, there are hypometric/diminished behaviors and hypermetric/exaggerated behaviors, consistent with the dysmetria of thought theory of the cerebellar role in nervous system function.

The intellectual and emotional impairments from damage to the cognitive and limbic posterior lobe of the cerebellum may be more disabling than motor deficits, and when the anterior lobe is spared, these occur in the absence of the motor syndrome. Recognizing the nonmotor manifestations of cerebellar lesions can lead to earlier diagnosis of cerebellar damage and facilitate treatment of cognitive emotional consequences of disrupted cerebellar modulation of higher function. The nature of these deficits provides new avenues for conceptualizing mental illnesses, including autism, schizophrenia, bipolar disorder, attention deficit disorder, and dyslexia. Appreciating the role of the cerebellum beyond motor control therefore has implications for understanding and improving neuropsychiatric disorders. This represents a radical departure from our previous understanding of the functions of the “little brain” and is an area of active investigation in neuroscience. The neural substrates that support this nonmotor cerebellar role are discussed in Plate 8-13.

Only gold members can continue reading. Log In or Register to continue