cerebellum its function and releveance in psychiatry

CEREBELLUM-ITS FUNCTION AND RELEVANCE IN PSYCHIATRY

The cerebellum, which lies just dorsal to the pons and medulla, consists of two highly convoluted lateral cerebellar hemispheres and a narrow medial portion, the vermis. It is connected to the brain by three pairs of dense fiber bundles called the peduncles.

CEREBELLAR STRUCTURE

CEREBELLAR CIRCUITCerebellum receives inputs from the spinal cord and from many regions of both the cortical and subcortical brain. In this way, the cerebellum receives extensive information from somesthetic, vestibular, visual, and auditory sensory systems, as well as from motor and nonmotor areas of the cerebral cortex.

Disorders of the Cerebellum and Its Connections

Cerebellum seems to work as an ”internal clock”, which comes into play during the control of movement, as well as during perceptual processing.

CEREBELLUM FUNCTIONS• For many years, functions related only to

movement, gait, posture, and balance were attributed to the cerebellum.

• Cerebellum promotes the synchrony and accuracy of movement required for purposeful motor activity.

• However, some studies have suggested a possible involvement of the cerebellum in cognition, emotion processing and behaviour. Rev Bras Psiquiatr. 2008;30(3):281-9

Disorders of the Cerebellum and Its Connections

SIGNS AND SYMPTOMS OF CEREBELLAR DAMAGE

• Loss of muscle tone • Incoordination of volitional movement, with

abnormalities in the rate, range, and force of movement, so that there is irregular acceleration and deceleration of the movement resulting in an intention tremor

• Minor muscle weakness, fatigability, and impairment of associated movements problems maintaining equilibrium.

Psychiatry (Edgemont) 2010;7(9):38–43

BALANCE• Lesions that involve the superior cerebellar

peduncle, which ascends to the thalamus, or the dentate nucleus, which indirectly projects to the premotor cortex, cause the most severe and enduring cerebellar symptoms.

• However, lesions of the cerebellar vermis, which is in the midline, cause more severe disturbances of equilibrium and gait.

HYPOTONIA • Hypotonia can be tested by tapping the wrists of

the outstretched arms. • The affected limb will be displaced through a

wider range than normal, due to the hypotonic muscles reduced ability to fixate the arms.

• Pendularity in the knee-jerk reflex due to defective tonic contraction of the quadriceps

CEREBELLUM AND PSYCHIATRIC DISORDERS

• Although the cerebellum has an important role in gait and motor function, the importance of the cerebellum to psychiatric disorders has recently been the subject of focus and debate.

• There is increasing evidence that the cerebellum is not only connected with motor pathways but also with other cortical and association areas involved in superior mental functions, suggesting the involvement of the cerebellum in cognition in the pathophysiology of psychiatric disorders.

Rev Bras Psiquiatr. 2008;30(3):281-9

AUTISM SPECTRUM DISORDERS

• Autism is associated with repetitive and stereotypic movement, impaired communication, and profound difficulties with social reciprocity.

• Patients with autism have been found to have a reduction of Purkinje cell density in the cerebellar cortex.

• Patients with autism also have cytoplasmic inclusions in their Purkinje cells, a reduction in the number of cells, and ectopic grey matter in the deep cerebellar nuclei, as well as an intense neuroinflammatory process extending to the cerebellar white matter. Psychiatry (Edgemont) 2010;7(9):38–43

SCHIZOPHRENIA• Alteration in cortico-cerebellar activity• Cerebellar atrophy• Patients with schizophrenia have decreased blood flow in

the cerebellum leads to diverse functional systems of the brain, including memory, attention, social cognition, and emotion.

• Soft neurological signs suggestive of cerebellar dysfunction, such as subtle ataxia, difficulties in coordination, dysdiadochokinesia, intentional tremor, dysmetria of the ocular saccadic movements are frequent in patients with schizophrenia


SCHIZOPHRENIA • Additionally, emergence of positive symptomatology

(especially delusions), as well as cognitive deficits and negative symptomatology, including flattened affect, thought disorder, avolition, social isolation, and poor speech, have frequently been reported in individuals with cerebellar lesions.

• Thus Converging evidence from neuroimaging and cognitive studies suggests cerebellar abnormalities in schizophrenia, leads to some of the positive, negative, and cognitive symptoms present in this disease.


BIPOLAR DISORDER• Cerebellar atrophy & reduction in blood flow• Yates et al. found a greater rate of cerebellar atrophy in

patients with bipolar disorder who were over 50 years old, but not in younger bipolar patients compared with healthy volunteers.

• Alcohol abuse may contribute to abnormal cerebellar anatomy in bipolar patients

• posterior-inferior cerebellar vermal abnormalities are present in patients with multiple-episode bipolar disorder


DEPRESSION • Cerebellar atrophy• Cognitive deficits in depressed patients were

related to lower cerebellar cortex activity.• Impairment in emotion expression might be,

part, due to a disruption in the functional connection between the cerebellum and frontal lobe.


ANXIETY DISORDERS• Cerebellum might play a role in anxiety

manifestations like posttraumatic stress disorder (PTSD) and generalized anxiety disorder (GAD).

• The cerebellum seems to be reduced in its volume but more activated in some tasks in patients with anxiety disorders.


NEURODEGENERATIVE DISORDERS• Cerebellar volume seems to be reduced in patients with

dementia.• In Alzheimer’s disease (AD), cerebral structures interconnected

with cerebellum are affected by neurofibrillary tangles and neuronal loss in later stages of the disease. Additionally, although cerebellum is virtually free of neurofibrillary pathology, the magnitude of cerebellar atrophy strongly correlates with duration and stage of illness.

• In most of the of studies, cerebellum atrophy is evident only in late stages of disease


CEREBELLAR-COGNITIVE AFFECTIVE

SYNDROME (CCAS)

cerebellum its function and releveance in psychiatry

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