Anatomy, Physiology and Neuropsychatric aspects of Cerebellum

1. Cerebellum
Dr. Cijo Alex

2.  The term cerebellum in latin means the little brain.

3. Contents
 Anatomy
 Physiology
 Neuropsychiatric aspects
 Clinical examination
 Role in specific conditions

4. Anatomy
 A part of the human brain that lies in the posterior
cranial fossa , inferior to occipital lobes.

5.  10% weight of entire brain.
 50% of neurons.
 Embryologically develops from metencephalon
which develops from rhombencephalon.

6. Anatomy contd…
External Structure.
 The external suface , called cerebellar cortex,is
composed of small folds termed foli seperated by
sulci.
 Consists of two lateral hemispheres interconnected
by a narrow portion called vermis.

8.  Divisions of cerebellum.

9.  The primary fissure seperates ant.lobe from postr
lobe.
 The postr.lateral fissure seperates postr.lobe from
floculonodular lobe.

10.  The cerebellum is connected to brainstem through
three cerebellar peduncles,superior,middle and
inferior, in which the afferent and efferent tracts are
present.

11.  Internal structure.
Consists of outer layer of gray matter and inner white
matter.
Cerebellar cortex is deeply folded into folia
producing a tree-like outline.
(Tree of Life)

12.  Layers of cerebellar cortex.
Consists of three layers , outer Molecular , middle
Purkinjee and inner Granular layer.
Inner white matter lies below the granular layer.

13. Internal structure
 Deep inside cerebellum,four nuclei are located
namely Fastigial , Globose ,Emboliform and Dentate
nuclei.

14. Anatomy contd…
Location of deep nuclei
Fastigeal  next to midline.
Globose &
Emboliform  slightly lateral.
Dentate  most lateral.

15.  Generally cerebellar cortex is associated with
processing inputs to cerebellum while the deep
nuclei are related to outputs.
 The phylogenetically old vermis and fastigial nucleus
is called “limbic cerebellum” and considered
separate from neo cerebellum of the cerebellar
hemispheres.

16. Physiology
 The cerebellum has been traditionally considered to
be solely with motor control.
 But recently many functional circuits have been
described which ascertains the role of cerebellum in
many other cognitive and affect functions.

17. Physiology contd…
 Cerebellum is now thought to have functional
connections with the functional circuits of brain like
Thalamocortical,Basal ganglia and Limbic system ,
though no clear evidence have been derived yet.
 Cerebellar inputs access areas of prefrontal cortex , with
a relay in thalamus.And these areas communicate
reciprocally creating closed loops or
channels.[cerebellothalamocortical system]
 Additional reciprocal connections link cerebellum with
hypothalamus and other areas of limbic sytem with a
relay in basilar part of pons.

18.  More recent studies in the last decade indicate that
cerebellum may also play an important role in
mediation of certain cognitive abilities through inputs
to portions of the thalamus that project to association
regions of cerebral cortex.
CEREBELLOTHALAMOCORTICAL SYSTEM
 Dorsolateral prefontal cortex receives inputs from
two ipsilateral thalamic nuclei,which receive inputs
from contralateral cerebellar dentate nucleus.

19. Physiology contd…
 Recent data suggest that lateralized cerebellar
damage is assosiated with predicted lateralised
cognitive phenomenon
ie,Right cerebellar damage with language
impairment and left with visuospatial impairment.
Damage to limbic cerebellum,notably the vermis may
produce defects in affect regulation , like irritability
and lability.

20.  Synaptic circuity within cerebellum.
As mentioned earlier ,cerebral cortex is associated
with afferents and inner cerebral nuclei with
efferents.
Afferents Mossy fibers and Climbing fibers.
Mossy fibers-Axons of neurons of pontine
nuclei,spinal cord and vestibular nuclei.(remember
functional classification of cerebellum)
Climbing fibers-Axons of neurons of inferior olive.

21.  Mossy Fibers
some branches form excitatory contact with granule
cells through glutamate
some branches excite local inhibitory interneurons
through glutamate.
some directly synapse with cerebellar nuclei.
Granule cells and local inhibitory interneurons inturn
report to purkinjee cells through glutamate and
GABA respectively and finally inhibit cerebellar
nuclei by GABA.

23.  Climbing fibers.
Some branches excite purkinjee cells through
Aspartate.
Some brances directly synapse to cerebellar nuclei.
Purkinjee cells inhibit the cerebellar nuclei through
GABA.
(Common pathway for mossy and climbing fibers)

24. Clinical examination for cerebellar
pathology
 Features of cerebellar lesions depends on the
location of lesion.

25. Clinical Examination
 Asynergy Lack of coordination among muscle groups.
May manifest as speech disorder/dysarthria.
 Ataxia Uncoordinated sequence of movements.
Truncal-cannot sit upright
Stance-Stands with legs apart& hands on wall
(Roomberg with eyes open)
Gait-unsteady wambling gait
(tandem walking)

26.  Astheniadecreased muscle tone
 Intention tremor involuntary rhythmical
movements.
(Finger nose test)
 Hypermetriarebound phenomenon.
 Pendular knee jerk
 Heel-shin test

27. Neuropsychiatric aspects of cerebellum
 Recent studies have proved that cerebellum is not
just a motor structure , but also modulates cognition
and affect.
 And so cerebellum is slowly assuming importance in
psychiatry also.
 Alcohol dependence is the single most important
cause of cerebellar damage followed by stroke and
neoplasm's.

28.  However the fact that most pathologies does not
affect cerebellum in isolation remains a hindrance in
the detailed evaluation of the role of cerebellum.For
example,cerebellar degenerations may include
cortical degeneration also.
 Also the phenomenon of crossed cerebellar
diaschisis-the reduction of blood flow to connected
neocortical areas after cerebellar damage means
study of isolated study of cerebral pathology is
difficult.

29. Neuropsychiatric aspects of cerebellum
contd….
Diseases that cause cerebellar damage.
 Thiamine deficiency
 Stroke
 Neoplasm's ,primaries and secondary's.
 Vit E deficiency
 Ethanol
 Phenytoin
 Lithium
 Trauma
 Radiation

30. Neuropsychiatric aspects of cerebellum
contd….
Clinical features of cerebellar damage.
 Motor features.
-Problems with balance and speech are often the
presenting complaint.
-Cerebellar gait– wide based and staggering , as if
drunk.
-Stairs are particularly difficult.
-Dysarthria--slurred speech, slowed and monotonic.

31. Neuropsychiatric aspects of cerebellum
contd…
 Cognitive features.
-Its been suggested that cognitive deficits follow
mostly after lesions of cerebellar hemisphere while
vermal lesions are prone to cause psychiatric
disturbances
-Procedural learning , executive functioning ,
language processing , visual – spatial orientation ,
sensory processing , timing and attention may be
affected.
-Within 10-15 years onset of cerebellar disease ,
about 20% of patients will meet DSM IV-TR criterion
for dementia

32. Neuropsychiatric aspects of cerebellum
contd….
 Psychiatric features.
-Much of studies have been conducted on patients
who had isolated posterior circulation strokes.
-35% of patients developed a major or minor
depression acutely.
-Personality changes like blunted affect and
disinhibition was seen in large infarcts.
-Nearly all forms of psychopathologies have been
identified in patients with cerebellar damage.
-The frequency of depression , mania , anxiety
syndromes and psychotic syndromes all are
elevated.

33. Role in specific conditions.
 Healthy subjects with reduced cerebellar volume.
Higher scores in scales for
Anxiety ,
Type A personality ,
Phobia ,
Hostility etc.

34. Role in specific conditions contd…
 Schizoprenia
Functional imaging studies have revealed abnormal
patterns of activation in the cerebellum, thalamus
and pre-frontal cortex,suggesting that dysfuntion of
this circuit [Cerebellothalamocortical system] might
be assosiated with the cognitive disturbances in
schizoprenia.
Reduced blood flow in PET scan have been also
noticed.
Demirtas et al (2010): stimulation of the vermis in 8
schizophrenic patients improvements in mood,
alertness, memory, attention, visual-spatial skills etc.

35. Role in specific conditions contd…
 Alcohol dependence.
Cerebellar degeneration might be as a result of
combination of ethanol , acetaldehyde and vitamin
deficiences.
Management requires total abstinence and vitamin
supplementation though complete recovery may not
possible.

36. Role in specific conditions contd…
 Premature and ELBW babies.
Neuro imaging studies have shown that cerebellum
is the part of brain that shows maximum growth in
postnatal period.It has also been shown that this
growth is influenced very much by environmental
factors.
Extreme LBW & prematurity can injure cerebellum
and lead to absence of major portions of cerebellum
leading to microcephaly and cognitive,language and
motor delays.

37.  Stroke
Patients with stroke lesions clinically and
radiologicaly limited to cerebellum may have deficits
in executive cognitive function,memory,language and
visuospatial function.

38. Role in specific conditions contd…
 ADHD
Neuroimaging studies have demonstarted smaller
cerebellar volumes in patients with ADHD.This was
mostly localised to vermis.
Greater impairment in task performance is assosited
with lower cerebellar activation.

39. Role in specific conditions contd….
 Reading disorders.
Brain imaging studies have revealed anatomical ,
metabolic and activation differences in cerebellum of
individuals with reading disorders, which is a specific type
of learning disorder.
Cerebellum is known to play a role in motor control and
thus in speech articulation.So cerebellar pathologies are
expected to cause deficiencies in phonation.
Additionally cerebellum plays a role in automatization of
activities like typing,driving and reading.

40. Role in specific conditions contd….
 Autism spectrum disorders
Cerebellar degenerative changes , especially
reduced purkinjee cells in vermis.
Some suggest that cerebellar malfuncion Loss of
modulatory control over frontal cortex  ASD

41. Role in specific conditions contd….
 Other conditions assosiated with reduced
cerebellar volume.
-Bipolar affective disorder.
-Anxiety.
-Post traumatic stress disorder.
-Antisocial personality disorder.

42. Cerebellar Cognitive Affective Syndrome
 Cerebellar cognitive affective syndrome (CCAS)
is a condition that follows lesions to the cerebellum.
This syndrome, described by Dr.Schmahmann et al
refers to deficits in the domains of cognition and
affect.
 Cognitive impairments:
 Executive dysfunctions e.g. in working memory and planning
 Visuo-spatial abnormalities e.g. in visual memory and visuo-spatial
organisation
 Linguistic dysfunction e.g. dysprosodia, agrammatism and anomia
 Affective impairments:
 anxiety, lethargy, depression, lack of empathy, ruminativeness,
perseveration, anhedonia and aggression

43. Thank You