9. The colliculi
Large nuclei of gray matter, lying beneath the
corresponding surface elevation.
Superior colliculi
• Larger and darker
• Connected to Lateral Geniculate
Body (LGB)
• Control reflex movements of the
eyes, head and neck in response to
visual stimuli
Inferior colliculi
• Connected to Medial Geniculate
Body (MGB)
• Control reflex movements of the
head, neck, and trunk in response to
auditory stimuli
Cruciform
sulcus
10. Lateral viewSuperior and inferior
Brachia ascending in
anterolateral direction
Geniculate Bodies
• Small, oval swellings
projecting from the
thalamus.
• Consists axons of the
optic tract/ auditory.
Lateral geniculate body
Medial geniculate body
Inferior
brachium &
colliculus
Superior
brachium &
colliculus
13. Internal structureCerebral aqueduct
•lined by ependyma
& surrounded by the
central gray matter
Tectum
•Colliculi
Cerebral peduncle
•Tegmentum
•Crus cerebri
•Substantia Nigra
•Interpeduncular
fossa
14. Transverse Sections
Cavity, Nuclei, Tracts (motor/sensory)
Superior Colliculus Inferior Colliculus
Sup Colliculus
M.N nucleus
CN: 5
Occulomot
or Nerve &
Nucleus
Red
Nucle
us
Red
Nucle
us
Sub NSub N
Crus
Cerebri
Crus
Cerebri
TP
FP
C Spinal
C Bulb
Leg
Head
Arm
MLF
R S T
Trigeminal
Spinal &
Medial
Leminisci
Inf Colliculus
Trochlear
Nerve &
Nucleus
Lateral,
Trigeminal
Spinal &
Medial
Leminisci
Sup. C.P
IPF
15. The Red Nucleus
Reddish, Rounded mass
of gray matter in
tegmentum
– Vascularity
– An iron-containing
pigment in cytoplasm
of many neurons.
Afferent fibers
Cerebral cortex, Cerebellum,
thalamus, SN & spinal cord.
Efferent fibers
Spinal cord, Reticular formation
& thalamus
18. Anatomical considerations
• Narrow stalk.
• Ascends out of the posterior cranial fossa through
the relatively small rigid opening in the tentorium
cerebelli.
• Two important cranial nerve nuclei.
• Reflex centers (the colliculi)
• the red nucleus and substantia nigra, [influencing
motor function]
• Ascending and descending tracts
19. Oculomotor nucleus
• Ipsilateral paralysis of the extra ocular muscles
• Parasympathetic nucleus --- dilated pupil with absent light reflex.
Trochlear nucleus
• Contralateral paralysis of the sup oblique.
Blockage of the Cerebral Aqueduct
• Tumor
20. Vascular lesions
Weber’s syndrome
Contralateral hemiplegia of the limbs, face & tongue
---crus cerebri
Ipsilateral deficits in eye motor activity -- oculomotor
nerve
Benedikt syndrome
Contralateral hemi anesthesia---Medial lemniscus
Involuntary movements of contralateral limbs----
Red nucleus
22. Gross Anatomy
• “Bridge“ connecting both
cerebellar hemispheres
• 1 inch (2.5 cm) long
Anterior Surface
• Convex from side to side
• Many transverse fibers
converging on each side ---the
middle cerebellar peduncle.
• The basilar groove
Anterolateral Surface
• CN 5,6,7,8
23. Posterior surface
• Hidden, triangular
• Forms Upper half of the
floor of the 4th ventricle
• Limited laterally by the
superior cerebellar
peduncles
• Median sulcus.
• Medial eminence (Lateral
elongated elevation,
bounded laterally by the
sulcus limitans
• Facial colliculus
– Expanded inferior end
of the medial eminence
(root of CN: 7
• Substantia ferruginea
– Bluish grey floor of the
superior part of the
sulcus limitans
• Area vestibuli
– Lateral to the sulcus
limitans
– underlying vestibular
nuclei
24. Transverse Section at level of
Fascial Colliculus
Transverse Section at level of
Trigeminal Nuclei
Fourth
Ventricle
Sup. Med velum
Motor & Sensory
nuclei CN:V
Pontine Nuclei
Trapezoid
body
Transverse pontine
Corticospinal, corticonuclear fibers
MLF RF
Spinal, Lateral,
Medial Leminisci
Sup. Cerebellar Peduncle
Mid. Cerebellar
Peduncle
Sup. Med velum
4thVent
Pontine
nuclei
Facial, abducent
Nuclei & nerves
Med Vestibular N
CN:V Nucleus
& Spinal tract
MLF
Cerebellar peduncles
25. Clinical significance
• Sensory and motor nuclei of 5th, 6th, 7th & 8th cranial
nerve.
• Respiratory nuclei:
– Apneustic & pneumotaxic centers work w/ the medulla to
maintain respiratory rhythm
• Cerebellar peduncles to/from the cerebellum
• Ascending, descending, and transverse tracts that
interconnect other portions of the CNS
29. Gross Appearance
Spino-medullary junction
• Foramen magnum (at the origin
of roots of the 1st cervical spinal
nerve)
• Lower part closed around central
canal
• Upper open part related to lower part
of 4th ventricle
• Connects the pons
superiorly with the spinal
cord inferiorly.
• Conical shape, its broad
extremity directed
superiorly
• 3cm X 2cm at its widest part
30. Ventral
Aspect
CN XII
IX,XI
X
• Olives
• Posterolateral to the pyramids
• oval elevations (inferior olivary nuclei)
• Inferior cerebellar peduncles
• Posterior to olives
• Connect the medulla to the cerebellum.
• Anterior median fissure
• Pyramids
• Corticospinal fibers originating in
precentral gyrus
• Taper inferiorly (decussation)
31. Posterior Surface
• Superior half forms the lower part of
the floor of the fourth ventricle.
• Inferior half
– Posterior median sulcus.
• Gracile tubercle---- gracile nucleus.
• Cuneate tubercle---cuneate nucleus.
32. Internal Structure
1. Level of the olives
– across the inferior part of
the fourth ventricle
2. Level of decussation of
lemnisci
– The great sensory
decussation.
3. Level of decussation of
pyramids
– The Great motor
decussation
33. Level of the Olives
Inf. Medullary Valum
Vestibulo-cochlear
Nuclear Complex
Medial, Inf. V
Ant, Post. Ch
Olivary Nuclear
Complex
Dorsal acc, Inf, Medial acc
Hypoglossal Nucleus
& Nerve
PyramidsArcuate nuclei
Ant. Median Fissure
Olive
Medial Leminiscus
Tectospinal tract
Lat. Spinothalamic tract
Ant. Spinocerebellar Tract
N. Ambiguus
Spinal N & Tract
of CN:VRet formation
N. Tractus Solitarius
Dorsal Vagal
Nucleus & Nerve
MLF
4th V
ICP ICP
34. Nucleus
Ambiguus
Large motor neurons,
situated deep within
the reticular
formation.
The emerging nerve
fibers join the CN IX, X
and cranial part of CN
XI and are distributed
to voluntary skeletal
muscle.
35. Level of Decussation of Lemnisci
Nucleus Gracilis & Cuneatus
Fasciculus Gracilis
& Cuneatus
Spinal Nucleus
& Tact CN:V
Spinal Root CN:XI
Inferior Olivary
Nucleus
Hypoglossal
Nucleus & Nerve
PyramidsDecussation Medial Leminisci
(b/w pyramids & central GM)
Post. Spinocerebellar tract
Lat. Spinothalamic tract
Ant. Spinocerebellar tract
Medial
Longitudinal
Fasciculus
Central Canal
36. Level of Decussation of Pyramids
Nucleus Gracilis &
Cuneatus
Fasciculus Gracilis &
Cuneatus
Spinal Nucleus &
Tact CN:V
Spinal Root CN:XI
MLF
Acc. Olivary Nucleus
Pyramid
Central Canal
Post. Spinocerebellar Tract
Lat. Spinothalamic Tract
Ant. Spinocerebellar Tract
Lat. Corticospinal tract
with Decussation of
Pyramids
37. Clinical significance
• Nuclei of CN: 9, 10, 11 , 12
• Ascending & Descending tracts
• Respiratory centers
• Herniation
– d.t increased I/C pressure
– Headache, neck stiffness, paralysis
of last four CN
– Arnold-Chiari malformation
(congenital)
38. Medial
Medullary
Syndrome
(Anterior Spinal
Artery)
inferior alternating hemiplegia
1. Contralateral hemiplegia ---- pyramids or the corticospinal fibers
2. Contralateral loss of position sense, vibratory sense and discriminative touch----
medial leminiscus
3. Ipsilateral deviation and paralysis of the tongue---- hypoglossal nucleus or nerve
