Describe in detail the implications of cerebellum in psychiatric disorders?

DNB - PSYCHIATRY , PHY MED AND REHAB

MD - PSYCHIATRY , PHY MED AND REHAB

FINAL EXAM

Q 1 DESCRIBE IN DETAIL THE IMPLICATIONS OF CEREBELLUM IN PSYCHIATRIC DISORDERS ?

A 1 INTRODUCTION

1 Cerebellum exerts a regulatory effect that enhance and supplement other brain functions throughout direct and indirect circuits

2 It not only has role in movement , gait , posture and balance but also exerts equally important role in cognition , emotion processing and behaviour

ROLE OF CEREBELLUM

1 Cerebellum is connected with motor pathways , cortical association areas involved with superior menta functions

2 It recieves input from spinal cord , vestibular nuclei , spinal relay nucleus of brain stem ( inferior olive and pontine )

A ) Afferents from spinal cord and brain stem enters via inferior cerebellar peduncle whereas from cerebrum thru middle cerebellar peduncle - these all are related to proprioception , motor , gait and posture processing

B ) Out of this afferent pathways - corticopontocerebellar is the most important of all - it connects contralaterally in a somatic way

Others are - olivocerebellar tract and vestibulocerebellar tract

B ) Efferent are of three types

1 fibers that originate in cerebellar vermis projecting to fastigial nucleus and then to pons and reticular formation

2 fibers that originate in intermediate zone of cerebellum and then to red nucleus and thalamus

3 fibers that originate in lateral zone of cerebellum and then to dentate nucleus and thalamus

3 Cerebellar nuclei projects to caudal ventrolateral contralateral thalamic nuclei and then to frontal motor cortex and moreover it also connects with limbic cortex

4 More recently it is also linked with clock function - primary function is to mediate and encode temporal information independent of motor cortex

CEREBELLUM AND PSYCHIATRIC DISORDERS

1 SCHIZOPHRENIA-

A ) is severe and highly heritable disorder that has been linked to multiple genes and neurodevelopmental factors

B ) Is associated with global impairments in cognition with altered executive functions ( action planning , inhibition , cognitive flexibility , monitoring , abstract reasoning ) , memory difficulties , attention difficulties and language deficits

C ) There is evidence that it has altered corticocerebellar connectivity and there is disruption of cortico thalamo cerebellar cortical circuit leading to abnormal cognitive functioning

D ) Moreover there is smaller total cerebellar volume , smaller vermis volume , reduction of hemisphere and tract hypoactivity ( fronto - thalamus )

E ) Patients usually have decreased blood flow in cerebellum and there is more affection laterally

2 BIPOLAR DISORDERS

A ) is a chronic and generally life long condition and is characterised by unusual shifts in mood state , energy level and behaviour

B ) In this condition there is atrophy of cerebellum and there is greater risk in over 50 yr old

C ) Vermis ( V 2 ) portion is more affected as there is greater shrinkage of volume followed by V 3 - posterior inferior cerebellar abnormalities are more common

D ) Patients also with this condition has lower blood supply and increased glucose metabolism

3 UNIPOLAR DEPRESSION

A ) is a mood disturbance characterised by psychic , physical , cognitive , physiological and behavioural alterations

B ) In this there is increased activation of cerebellar hemispheres specifically in the anterior cerebellar vermis

C ) Also there is reduced cerebellar blood flow and reduced cerebellar volume

4 ANXIETY DISORDERS

In this there is hyperarousal of cerebellum leading to smaller cerebellar volume

There is increased activity in the cerebellar vermis

5 NEURODEGENERATIVE DISORDERS

A ) In this there is reduction in cerebellar volume

B )in alzheimer disease there is deposition of neurofibrillary tangles in cerebellum and also there is loss of granule cells

C ) Microscopically also there is decrease in climbing fibers in vermis , flocculus and cerebellar hemispheres

6 ATTENTION DEFICIT HYPERACTIVE DISORDERS

A ) there is decrease in cerebellar volume