The Rhombencephalon or Hind brain.ppt

These are slides describing the hindbrain and it's related nerve tracts

1. THE RHOMBENCEPHALON
OR HIND BRAIN
Components
•Medulla oblongata
•Pons
•Cerebellum

2. •Medulla oblongata and Pons are part of the
brain stem
•Brain Stem (BS) is part of the brain connecting
the cerebrum and diencephalon with the
spinal cord.
•The BS extends from just above the aperture
in the tentorium cerebelli to C1 vertebra
below the foramen magnum
Introduction

3. Cont...
•The BS consists of fibres and cells.
•Most of the fibres ascend or descend
longitudinallly as in the spinal cord.
•Cells aggregate into nuclei

4. Cont...
•Nuclei of three groups in the BS;
1.Nuclei of the third to twelfth cranial nerves.
2.Reticular formation
3.Other nuclei ; colliculi, the red nucleus,
substantianigra, pontinenuclei and Olivary
nucleus.
•Some of its cells form “vital centres” Cardiac,
respiratory, vasomotor.

5. External appearance

6. MEDULLA OBLONGATA
Content outline
•Introduction
•External appearance
•Internal structure
•Blood supply
•Clinical correlates

7. Introduction
•Part of brainstem btn the pons and spinal
cord.
•Extends thru the foramen magnum to the
level of the atlas.
•Above the foramen magnum it is embraced
dorsally by the cerebellar hemispheres.
•The lower end is the “closed part” of the
medulla and the upper part is the “open part”

8. External appearance of the brain stem

9. Cont..
•Ventrally, medulla contains a deep groove
with bold convexity on either side, the
pyramid.
•Due to contained corticospinal fibres.
•Lateral to the pyramid is another convexity the
olive, due to underlying inferior olivary
nucleus.

10. Cont..
•Lateral to the olive, the lateral surface of the
medulla is formed by the inferior cerebellar
peduncle.
•6
th
, 7
th
and 8
th
C.N emerge btn the pons and
medulla.
•The rootlets of the 9
th
, 10
th
, and cranial part of
the 11
th
emerge lateral to the olive.
•Those of the 12
th
rootlets btn the pyramid and
the olive.

11. Cont..
•Dorsally, the lower part of the floor of the 4
th
ventricle forms the upper part of the medulla.
•At the lower corner of the diamond shaped
floor the hypoglossal trigone is adjacent to the
midline, with the vagal trigone lateral to it.
•Higher up and at the lateral corners of the
diamond is the vestibular area and medullary
striae.

12. Cont...
•In the lower or closed part of the medulla, the
4th ventricle has become narrowed to tiny
central canal.
•External dorsal surface shows small
elevations, the gracile and cuneate tubercles,
the former being medial to the latter.

13. Internal appearance
•This is studied at different levels
1.Decussation of pyramids
2.Decussation of lemnisci
3.Level of the olive and inferior cerebellar
peduncles
4.Just inferior to pons

14. Levels 1 and 2

15. Level Cavity Nuclei Motor Tracts Sensory Tracts
Decussationof
pyramids
Central canalNucleus gracilis,
nucleus cuneatus,
spinal nucleus of
cranial nerve V,
accessory nucleus
Decussation of
corticospinal tracts,
pyramids
Spinal tract of
cranial nerve V,
posterior
spinocerebellar
tract, lateral
spinothalamic tract,
anterior
spinocerebellar
tract
Decussation of
medial lemnisci
Central canalNucleus gracilis,
nucleus cuneatus,
spinal nucleus of
cranial nerve V,
accessory nucleus,
hypoglossal
nucleus
Pyramids Decussationof
medial lemnisci,
fasciculus gracilis,
fasciculus cuneatus,
spinal tract of
cranial nerve V,
posterior
spinocerebellar
tract, lateral
spinothalamictract,
anterior
spinocerebellar
tract

16. Olives, inferior
cerebellar
peduncle
Fourth ventricleInferior olivary
nucleus, spinal
nucleus of cranial
nerve V, vestibular
nucleus,
glossopharyngeal
nucleus, vagal
nucleus,
hypoglossal
nucleus, nucleus
ambiguus, nucleus
of tractus
solitarius
Pyramids Medial
longitudinal
fasciculus,
tectospinal tract,
medial lemniscus,
spinal tract of
cranial nerve V,
lateral
spinothalamic
tract, anterior
spinocerebellar
tract
Just inferior to ponsFourth ventricleLateral vestibular
nucleus, cochlear
nuclei
No major changes
in distribution of
gray and white
matter

17. Levels 3 and 4

18. Blood supply
•Branches of the vertebral and basilar arteries.
•Laterally and dorsally by the posterior inferior
cerebellar artery

19. Clinical applications
•The MO not only contains many cranial nerve
nuclei that are concerned with vital functions
(e.g., regulation of heart rate and respiration),
•Contains ascending and descending tracts
connecting the spinal cord to the higher
centers of the nervous system. These tracts
may become involved in demyelinating
diseases, neoplasms, and vascular disorders
•These are affected when there are lesions in
the MO.

20. Contd
•Medulary coning: Raised Pressure in the
Posterior Cranial Fossa may lead to herniation
of the tonsils of the cerebellum and the
medulla oblongata—tends to be pushed
toward the area of least resistance i.e.
through the foramen magnum. This will
produce the symptoms of headache, neck
stiffness, and paralysis of the
glossopharyngeal, vagus, accessory, and
hypoglossal nerves owing to traction.

21. Contd
•In these circumstances, it is extremely
dangerous to perform a lumbar puncture
because the sudden withdrawal of
cerebrospinal fluid may precipitate further
herniation of the brain through the foramen
magnum and a sudden failure of vital
functions, resulting from pressure and
ischemia of the cranial nerve nuclei present in
the medulla oblongata

22. •Arnold-Chiari Phenomenon/malformation is a
congenital anomaly in which there is a
herniation of the tonsils of the cerebellum and
the medulla oblongata through the foramen
magnum into the vertebral canal

23. Lateral Medullary Syndrome of Wallenberg:
•May be vascular
•Signs and symptoms:
–dysphagia and dysarthria due to paralysis of the ipsilateral palatal and
laryngeal muscles (innervated by the nucleus ambiguus);
–analgesia and thermoanesthesia on the ipsilateral side of the face
(nucleus and spinal tract of the trigeminal nerve);
–vertigo, nausea, vomiting, and nystagmus (vestibular nuclei);
–ipsilateral Horner syndrome (descending sympathetic fibers);
–ipsilateral cerebellar signs—gait and limb ataxia (cerebellum or
inferior cerebellar peduncle); and contralateral loss of sensations of
pain and temperature (spinal lemniscus—spinothalamic tract).

24. Medial Medullary Syndrome:
•The medial part of the medulla oblongata is supplied
by the vertebral artery.
•Thrombosis of the medullary branch produces the
following signs and symptoms:
–contralateral hemiparesis (pyramidal tract),
–contralateral impaired sensations of position and
movement and tactile discrimination (medial lemniscus),
and
–ipsilateral paralysis of tongue muscles with deviation to
the paralyzed side when the tongue is protruded
(hypoglossal nerve).

25. Content outline
•External appearance
•Internal structure
•Blood supply
•Clinical correlates
PONS

28. Introduction
1inch long, a bridge btnmedulla oblongata and the
midbrain
Anterior is convex wthfibresforming the middle cerebellar
peduncle
Basilar groove that lodges the basilar artery
Anterolateral-trigeminal nerve
In the groove btnthe ponsand medullar,frommedial to
lateral emerges the CN VI, VII & VIII.

31. •Posterior surface hidden from view by the
cerebellum
•Forms upper half of the floor of the 4
th
ventricle
•Central canal of the midbrain(aqueduct)
opens out at the upper border of the pons
into the cavity of the pons

32. •Dorsal to the aqueduct lies the tectum(the
four colliculi).
•Ventral lies ascending tructs(tegmentum),and
ore ventral the descending tracts(crus
cerebri).
•Dorsal wall of the pons consist of the roof of
the 4
th
ventricle covered wth a sheet of white
matter called the superior medullary vellum.
Internal structures of Pons

33. Medial lemniscus-rotates as it passes from the
medulla to the pons
Facial nucleus lies posterior to the medial
lemniscus,itsfibreswinds around the nucleus of
the abducentnerve producing the facial colliculus
Medial longitudinal fascicullusis beneath the
floor of the 4
th
ventricle-connects the vestibular
and coclearnuclei wththe nuclei controlling the
extraocularmuscles(CN III, IV, VI).
Transverse section through the caudal
part of the pons

36. Medial vestibular nuclei is lateral to the abducent
nerve
Superior vestibular nuclei & posterior and
anterior coclearnuclei are also found at this
level.
Spinal nucleus of the trigeminal nerve-lies
anteromedialto the inferior cerebellar peduncle
Trapezoid body is made up of fibresfrom the
cochlea nucleus and the nucleus of the trapezoid
body

37. At the basilar part of the pons-pontinenuclei
Cortical pontinefibresterminate in the pontine
nuclei.axonsof these cells give rise to the
transverse fibresof the pons,whichcross the
midline and intersect corticospinaland
corticonucleartracts
These fibresenter the middle cerebellar
peduncle and are distributed to the cerebellar
hemisphere.ths connections forms the main
pathway linking the cerebral cortex to the
cerebellum

38. •Similar to the caudal part plus the motor and
principal sensory nuclei of the trigeminal
•Motor nucleus of the trigeminal is beneath
the lateral side of the 4
th
ventrical-fibres goes
anterior and exit
•Principal sensory of the trigeminal is situated
on the lateral side of the motor
nucleus,continous wth the nucleus of the
spinal tracts
Transverse section through the cranial
part of the pons

40. •Superior cerebellar peduncle is posteral
lateral to the motor nucleus of trigeminal
•Trapezoidand the medial lemniscus are at the
same positions

41. •Blood supply
-pontine branches of the basilar artery,with
contributions from superior cerebellar artery
and anterior inferior cerebellar vessels
-veins drain to the inferior petrosal sinus and the
basilar plexus

42. •Also in form of syndromes
•Tumours
-ipsilateral cranial nerve paralysis and contralateral
hemiparesis e.g
•weakness of muscles of the face(facial nerve
nucleus),
•nystagmus(vestibular nucleus)
•hearing loss(cochlea),
•quadriparesis,contralateral hemiparesis(corticospinal
fibres)
Clinical colerrates

43. •Pontine haemorrhage
-basilar artey,anterial,inferior and superior
cerebellar arteries-unilateral haemorrhage
may results into ipsilateral facial
paralysis,contralateral paralysis of
limbs(corticospinal fibres).

45. THE CEREBELLUM

46. Outline:
•Introduction
•General features
•Anatomy
i. Structure
ii. Blood Supply
•Cortex
•Deep nuclei
•Cerebellar mechanisms
•Cerebellar afferents
•Cerebellar efferents
•Clinical applications

47. Introduction
•Important role in motor control.
•also involved in some cognitive fxns(attention,
language), and probably in some emotional fxns
(regulating fear and pleasure responses).
•movement-related functions most clearly
understood.
•*does not initiate movement, but contributes to
coordination, precision, and accurate timing.

48. Contd
‘’The essential function of the cerebellum is to
coordinate, by synergistic action, all reflex and
voluntary muscular activity. Thus, it graduates
and harmonizes muscle tone and maintains
normal body posture. It permits voluntary
movements, such as walking, to take place
smoothly with precision and economy of
effort” Snell (2010).

49. Intro cont..
•receives input from sensory systems and from
other parts of the brain and spinal cord, and
integrates these inputs to fine tune motor
activity.
•Hence damage does not cause paralysis, but
instead produces disorders in fine movement,
equilibrium, posture, and motor learning.

50. General features:
•situated in posterior cranial fossa
•covered superiorly by tentorium cerebelli.
•largest part of hindbrain (rhombencephalon)
•lies posterior to 4th ventricle, pons, and
medulla
•ovoid in shape and constricted in its median
part.
•consists of 2 hemispheres joined by vermis.

51. •connected to brainstem by 3 symmetrical
bundles of nerve fibers calledcerebellar
peduncles:supr.(to midbrain), middle(to
pons), and infr.(to medulla).
•*Most input to cerebellum is thru middle and
infrpeduncles & most output via superior
peduncle.
•3 lobes: the anterior, middle (aka posterior),
and flocculonodular.

53. •separated by primary& uvulonodular
fissures.
•external surface displays large no. of narrow
folds (folia),oriented transversely.
•*cerebellum is connected to ipsilateral body
fxns. There4, whenever it connects to portions
of the brain that have crossed fxns (e.g.
cerebral cortex), the connection must cross.

55. Anatomy
Structure:
•consists of
-an outer covering of gray matter, the cortex
-the underlyingwhite matter, the medulla
•4 paired deep cerebellar nucleiare located
within the white matter , above the 4th
ventricle. (B’se they lie in roof of ventricle,
sometimes referred to as roof nuclei.)

56. •These nuclei are, from lateral to medial
dentate, emboliform globose, fastigial."Don't
Eat Greasy Food",
•*B’se of relation to 4
th
ventricle, mass lesions
or swelling of the cerebellum (eg, b’se of
edema after an infarct) can cause obstructive
hydrocephalus.

58. Blood supply
superior cerebellar
artery(SCA),
anterior inferior
cerebellar
artery(AICA), and
posterior inferior
cerebellar
artery(PICA).

59. Cortex:
•Cortex arranged into folds called folia.
•A sagittal section thru the cerebellum divides
the folia at right angles, giving the cut surface
a branched appearance, called the arbor vitae
(“tree of life”). See fig. prev. page
•divided into 3 layers: (1) an external molecular
layer; (2) a middle Purkinje cell layer; and (3)
an internal granular layer.

62. •Molecular Layer contains 2 types of neurons: the
outer stellatecell and the inner basket cell.
•receive excitatory inputs from the parallel fibers
(extensions of granular cells into the molecular
layer) and project back to Purkinje cells, which
they inhibit.
•Purkinje Cell Layer contains purkinjecells.
•Their dendrites pass into the molecular layer &
synapse with dendrites of basket and stellate
cells.

63. •Their axons project to the deep cerebellar
nuclei, esp. the dentate, & form inhibitory
synapses.
•A few Purkinje cell axons pass directly to the
vestibular nuclei of the brainstem
•The purkinjecell is the only cell type that has
an axon that leaves the cortexand this cell
provides the primary output from the
cerebellarcortex.

64. •Granular Layer is packed with small granule
cells which have synaptic contact with mossy
fiber input.
•The axon of each granule cell passes into the
molecular layer, where it forms excitatory
synapses with Purkinje cell dendrites.
•Also scattered throughout the granular layer
are Golgi cells.

65. CerebellarCortical Mechanisms
•The climbing & the mossy fibers constitute
the two main lines of input to the cortex and
are excitatory to the Purkinje cells.
•The climbing fibers are the terminal fibers of
the olivocerebellartracts.
•They ascend thru the granular layer of the
cortex and terminate in the molecular layer
•Each synapses with dendrites of 1 to 10
Purkinje neurons.

66. •The mossy fibers are the terminal fibers of all
other cerebellar afferent tracts.
•They have multiple branches and exert a much
more diffuse excitatory effect.
•A single mossy fiber may stimulate thousands
of Purkinje cells thru the granule cells .
•The stellate, basket, and Golgi cells serve as
inhibitory interneurons.

67. •They limit the area of cortex excited & also
influence the degree of Purkinje cell excitation
produced by the climbing and mossy fiber
input.
•By this means, fluctuating inhibitory impulses
are transmitted by the Purkinje cells to the
intracerebellarnuclei, which, in turn, modify
muscular activity through the motor control
areas of the brainstem and cerebral cortex.

68. •Thus, the Purkinje cells form the center of a
functional unit of the cerebellarcortex.
•the excitatory climbing and mossy afferent fibers
use glutamate (GABA) as the transmitteron the
dendrites of the Purkinje cells.
•Other afferent fibers entering the cortex liberate
norepinephrineand serotonin that modify the
action of the glutamate on the Purkinje cells.

71. Deep CerebellarNuclei
•Four pairs of masses of grey matter
embedded in white matter
•dentate, emboliformglobose, fastigial.
•Neurons in these nuclei project out of the
cerebellum and thus represent the major
efferent pathway from the cerebellum.
•Cells in the nuclei receive inhibitory input
(gamma-aminobutyricacid [GABA]-ergic) from
Purkinje cells.

72. •while excitatory inputs are from outside the
cerebellum (pontine, inferior olivary, and raphe
nuclei, reticular formation, locus ceruleus).
•Inputs giving rise to climbing and mossy fibers
also project excitatory collaterals to the deep
cerebellarnuclei.
•Cells in the nuclei fire tonicallyat rates reflecting
the balance between the opposing excitatory and
inhibitory inputs that converge on them.

73. •Efferent information from the deep cerebellar
nuclei leaves the cerebellum to be distributed
to the remainder of the brain and spinal cord.

74. Cerebellar Afferent Fibers
•a) From cerebral cortex: The cerebral cortex
sends information to the cerebellum by 3
pathways;
(1)corticopontocerebellar,
(2)cerebro-olivocerebellar, &
(3)cerebroreticulocerebellarpathway.
b) From spinal cord: The spinal cord sends
information to the cerebellum from
somatosensoryreceptors by 3 pathways:

75. (1) the anterior spinocerebellartract,
(2) the posterior spinocerebellartract, and
(3) the cuneocerebellartract.
c) From the Vestibular Nerve
d) Other Afferent Fibers (from red nucleus &
tectum)

77. Corticopontocerebellar Pathway
•fibers arise from nerve cells in frontal, parietal,
temporal, and occipital lobes of the cerebral
cortex
•descend thru the corona radiataand internal
capsule and terminate on the pontinenuclei.
•The pontinenuclei give rise to the transverse
fibers of the pons,
•these cross the midline and enter the opposite
cerebellarhemisphere as the middle cerebellar
peduncle

78. Cerebro-olivocerebellarPathway
•fibers arise from nerve cells in the frontal,
parietal, temporal, and occipital cerebral
cortex
•descend thru corona radiataand internal
capsule to terminate bilaterally on the inferior
olivarynuclei.
•inferior olivarynuclei give rise to fibers that
cross the midline and enter the opposite
cerebellarhemisphere thru the inferior
cerebellarpeduncle. These fibers terminate as
the climbing fibers in the cerebellarcortex.

79. CerebroreticulocerebellarPathway
•fibers arise from nerve cells from many areas of
the cerebral cortex, particularly the sensorimotor
areas.
•descend to terminate in the reticular formation
on the same side and on the opposite side in the
ponsand medulla.
•The cells in the reticular formation give rise to the
reticulocerebellarfibers that enter the cerebellar
hemisphere on the same side through the
inferior and middle cerebellarpeduncles.

80. •This connection between the cerebrum and
the cerebellum is important in the control of
voluntary movement. Information regarding
the initiation of movement in the cerebral
cortex is probably transmitted to the
cerebellum so that the movement can be
monitored and appropriate adjustments in the
muscle activity can be made.

81. Anterior SpinocerebellarTract
•axons entering the spinal cord from the posterior
root ganglionterminate by synapsingwith the
neurons in the nucleusdorsalis(Clarke's column)
at the base of the posterior gray column.
•Most of the axons of these neurons cross to the
opposite side and ascend as the anterior
spinocerebellartractin the contralateralwhite
column;
•some of the axons ascend as the anterior
spinocerebellartract in the lateral white column
of the same side.

82. •The fibers enter the cerebellum thru the
superior cerebellar peduncle and terminate as
mossy fibers in the cerebellar cortex.
•Collateral branches that end in the deep
cerebellar nuclei are also given off.
•It is believed that those fibers that cross over
to the opposite side in the spinal cord cross
back within the cerebellum.

84. •The anterior spinocerebellar tract is found at
all segments of the spinal cord,
•its fibers convey muscle joint information from
the muscle spindles, tendon organs, and joint
receptors of the upper and lower limbs.
•It is also believed that the cerebellum receives
information from the skin and superficial
fascia by this tract.

85. Posterior SpinocerebellarTract
•axons entering the spinal cord from the posterior
root ganglion enter the posterior gray column
•They terminate by synapsingon the neurons at
the base of the posterior gray column known
collectively as the nucleus dorsalis(Clarke's
column).
•The axons of these neurons enter the
posterolateralpart of the lateral white column on
the same side and ascend as the posterior
spinocerebellartract to the medulla oblongata.

86. •Here, the tract enters the cerebellum through
the inferior cerebellarpeduncle and terminates
as mossy fibers in the cerebellarcortex.
•Collateral branches that end in the deep
cerebellarnuclei are also given off.
•The posterior spinocerebellartract receives
muscle joint information from the muscle
spindles, tendon organs, and joint receptors of
the trunk and lower limbs.

87. CuneocerebellarTract
•fibers originate in the nucleus cuneatusof the
medulla oblongata
•enter the cerebellarhemisphere on the same side
thru the inferior cerebellarpeduncle.
•The fibers terminate as mossy fibers in the
cerebellarcortex.
•Collateral branches that end in the deep
cerebellarnuclei are also given off.
•This tract receives muscle joint information from
the muscle spindles, tendon organs, and joint
receptors of the upper limb and upper part of the
thorax.

88. CerebellarAfferent Fibers From the
Vestibular Nerve
•The vestibular nerve receives information
from the inner ear concerning motion from
the semicircular canals and position relative to
gravity from the utricle and saccule.
•The vestibular nerve sends many afferent
fibers directly to the cerebellum through the
inferior cerebellar peduncle on the same side.

89. •Other vestibular afferent fibers pass first to
the vestibular nuclei in the brainstem, where
they synapse and are relayed to the
cerebellum thru the inferior cerebellar
peduncle on the same side.
•All the afferent fibers from the inner ear
terminate as mossy fibers in the
flocculonodular lobe of the cerebellum.

91. CerebellarEfferent Fibers
•The entire output of the cerebellarcortex is thru
the axons of the Purkinje cells.
•Most of the axons of the Purkinje cells end by
synapsingon the neurons of the deep nuclei.
•The axons of the neurons that form the cerebellar
nuclei constitute the efferent outflow from the
cerebellum.
•A few Purkinje cell axons pass directly out of the
cerebellum to the lateral vestibular nucleus.
•Cerebellum efferentsconnect with the red
nucleus, thalamus, vestibular complex, and
reticular formation.

93. Globose-Emboliform-RubralPathway
•Axons of neurons in the globose and
emboliform nuclei travel thru the superior
cerebellar peduncle and cross the midline to
the opposite side in the decussation of the
superior cerebellar peduncles.
•The fibers end by synapsing with cells of the
contralateral red nucleus, which give rise to
axons of the rubrospinal tract.

94. •Thus, this pathway crosses twice, once in the
decussation of the superior cerebellar
peduncle and again in the rubrospinal tract
close to its origin.
•By this means, the globose and emboliform
nuclei influence motor activity on the same
side of the body.

95. DentothalamicPathway
•Axons of neurons in the dentate nucleus travel
thru superior cerebellarpeduncle and cross
midline to the opposite side in the decussationof
the superior cerebellarpeduncle .
•The fibers end by synapsingwith cells in the
contralateralventrolateralnucleus of the
thalamus.
•The axons of the thalamic neurons ascend thru
the internal capsule and corona radiataand
terminate in the primary motor area of the
cerebral cortex.

96. •By this pathway, the dentate nucleus can
influence motor activity by acting on the motor
neurons of the opposite cerebral cortex;
•impulses from the motor cortex are transmitted
to spinal segmental levels through the
corticospinaltract.
•Remember that most of the fibers of the
corticospinaltract cross to the opposite side in
the decussationof the pyramids or later at the
spinal segmental levels.

97. •Thus, the dentate nucleus is able to
coordinate muscle activity on the same side of
the body.
FastigialVestibular Pathway.
•The axons of neurons in the fastigialnucleus
travel thru the inferior cerebellarpeduncle
and end on the neurons of the lateral
vestibular nucleus on both sides.

98. •Remember that some Purkinje cell axons
project directly to the lateral vestibular
nucleus.
•The neurons of the lateral vestibular nucleus
form the vestibulospinal tract.
•The fastigial nucleus exerts a facilitatory
influence mainly on the ipsilateral extensor
muscle tone.

99. FastigialReticular Pathway
•The axons of neurons in the fastigial nucleus
travel thru the inferior cerebellar peduncle
and end by synapsing with neurons of the
reticular formation.
•Axons of these neurons influence spinal
segmental motor activity thru the
reticulospinal tract.

101. Clinical applications
•Each cerebellar hemisphere is connected by
nervous pathways principally with the same
side of the body;
•thus, a lesion in one cerebellar hemisphere
gives rise to signs and symptoms that are
limited to the same side of the body; talk of
ipsilateral.

102. Signs and Symptoms of Cerebellar Disease
•The following symptoms and signs are
characteristic of cerebellar dysfunction.
Hypotonia
•The muscles lose resilience to palpation. There
is diminished resistance to passive movements
of joints. Shaking the limb produces excessive
movements at the terminal joints. The
condition is attributable to loss of cerebellar
influence on the simple stretch reflex.

103. Postural Changes and Alteration of Gait
•The head is often rotated and flexed, and the
shoulder on the side of the lesion is lower
than on the normal side. The patient assumes
a wide base when he or she stands and is
often stiff legged to compensate for loss of
muscle tone. When the individual walks, he or
she lurches and staggers toward the affected
side.

104. Disturbances of Voluntary Movement (Ataxia)
•The muscles contract irregularly and weakly.
Tremor occurs when fine movements, such as
buttoning clothes, writing, and shaving, are
attempted. When the patient is asked to
touch the tip of the nose with the index finger,
the movements are not properly coordinated,
and the finger either passes the nose (past-
pointing) or hits the nose. A similar test can be
performed on the lower limbs by asking the
patient to place the heel of one foot on the
shin of the opposite leg.

105. Dysdiadochokinesia
•is the inability to perform alternating
movements regularly and rapidly. Ask the
patient to pronate and supinate the forearms
rapidly. On the side of the cerebellar lesion,
the movements are slow, jerky, and
incomplete.

106. Disturbances of Reflexes
•Movement produced by tendon reflexes tends
to continue for a longer period of time than
normal. The pendular knee jerk, for example,
occurs following tapping of the patellar
tendon. In cerebellar disease, because of loss
of influence on the stretch reflexes, the
movement continues as a series of flexion and
extension movements at the knee joint; that
is, the leg moves like a pendulum.

107. Nystagmus
•An ataxia of the ocular muscles, is a
rhythmical oscillation of the eyes. This
rhythmic oscillation of the eyes may be of the
same rate in both directions (pendular
nystagmus) or quicker in one direction than in
the other (jerk nystagmus). The movement of
nystagmus may be confined to one plane and
may be horizontal or vertical, or it may be in
many planes when it is referred to as rotatory
nystagmus.

108. Essential reference
Snell, Richard S (2010) Clinical Neuroanatomy,
7th Edition, Lippincott Williams & Wilkins