ANATOMY OF INTERNAL FEATURES OF MIDBRAIN, SUPERIOR COLLICULI, RED NUCLEUS, OCULOMOTOR NERVE NUCLEAR COMPLEX, EDINGER WESTPHAL NUCLEUS, DORSAL TEGMENTAL DECUSSATION OF MEYNERT ,LAMNISCUS

1. MID BRAIN :PART 2
( Anatomy of internal features of Midbrain at
the level of superior colliculi)
Dr Pooja Dhabhai
(Assistant Professor Anatomy
R.N.T. Medical College, Udaipur)

2. • Cut section of midbrain
,central grey matter
along with cerebral
aqueduct
• Substantia nigra, this
feature remain
common at both the
levels
• Crus cerebri remain
same at both the levels

3. TRANSVERSE SECTION OF MIDBRAIN AT
LEVEL OF SUPERIOR COLLICULI

4. Oculomotor nerve nuclear complex
• This section is at the level of superior colliculus
• Nuclei closely related with central grey matter
• There will be presence of Oculomotor nerve
nuclear complex , there are verious subdivisions,
each individual right and left side divided into
subdivisions .
• subdivision of oculomotor nerve complex are
1. Inferolateral nuclei: will supply fibers to inferior
rectus muscle
2. Ventromedial nucleus: it will supply fibres to
medial rectus muscle
3. Intermediate nucleus: it will supply fibres to
inferior oblique muscle
4. Caudal central nucleus: it will supply fibres to
levator palpebri superioris muscle
5. Median raphe nucleus: will supply the fibers to
superior rectus muscle
So here only two extraocular muscles are left
beyond oculomotor nucleus those are
Lateral rectus muscle supplied by abducent
nerve, superior oblique muscle supplied by
trochlear nerve
Oculomotor nerve complex will supply the
somatic efferent functional componant
(therefore they will supply these extraocular
muscles which are derived from somite)

5. Edinger westphal nucleus
Exactly cranial to oculomotor
nerve nucleus complex is
presence of
 Edinger westphal nucleus:
• it is a parasympathetic
component of oculomotor
nerve nuclear complex only
• but it will carry general visceral
efferent functional component
• it will supply parasympathetic
secretomotor fibers through
ciliary ganglion which will help
in constriction of pupil (it will
supply sphinctor pupile muscle),
it will supply one more muscle
called ciliaris muscle( it will do
accomodation for the near
vision)
 Mesencephalic nucleus

6. Red nucleus( main component of this
section)
 Red nucleus : present dorsal
to medial part of substantia
nigra
• In freshly cut sections it will
appear pink in colour because
of abundance of iron pigment
• It will be extending from the
level of superior colliculi till
almost the subthalamic nucleus
• This is a main component of
identification of midbrain at the
level of superior colliculus
• This Red nucleus will have
Ventral tegmental decussation
of forel: rubro spinal tract

7. Connections of Red Nucleus
Afferent:
1. cerebelorubral fibres( contralateral
half of cerebellum)(dentate
,emboliform ,globose)
A. emboliform ,globose connected to
Magnocelular portion of red
nucleus(older portion)
B. Dentate fibers connected to
parvocelular portion of red
nucleus(newer portion)
2. Cerebral hemisphere (ipsilateral)
Efferent: ( outgoing channel)
1. Rubrospinal tract
2. Rubrobulbar tract will supply efferent
fibers from red nucleus to motor nu
of trigeminal nerve and facial nerve
3. Rubroreticular tract
4. Rubrolivary tract

8. Dorsal tegmental decussation of meynert
Dorsal tegmental
decussation of meynert
(tectospinal
tract):efferent fibres
coming from superior
colliculi give crossing
and form this
decussation

9. Lamniscus (only three)
• Medial lamniscus
• Trigeminal lamniscus
• Spinal lamniscus
• These lamnisci are commen
with that of cross section at
the level of inferior colliculus
Lateral lamniscus is auditory
pathway ,it will submerged
with inferior colliculus so there
is no lateral lamniscus at this
level
 pretectal nucleus: present
anterolateral to superior
colliculi ,will directly supply
fibers to edinger westphal
nucelus (concerned with
pupillary light reflex)

10. Superior colliculi: ovoid mass present at the tectum
connections
• Afferent: fibers coming from
• Retinotectal: from Retina
• Corticotectal fibres: visual area 17,18,19
• Spinotectal fibres : will carry sensations in form
of cutaneous receptors (cutaneous sensations
from spinal cord to superior colliculus)
• Ipsilateral inferior colliculi: auditory impulses
are coordinated with visual impulses
• Efferent
Tectospinal tract ,
Tectobulbar: superior colliculi will send the fibres to
cranial nerve nuclei 3,4,6 nerves which is
required for the movement of head and neck,
movement of eye towards the source of sound
These two tracts are involved in
1. movement of eyes and h& n towards auditory
stimuli
2. movement of eyes and h& n towards cutaneous
stimulation
3. tight closure of eyelids when exposed to bright
light
4. scanning movements of the
objects(whenever your eyes are scanning the
objects which are moving to and frow) this
movement controlled by tectospinal as well
as tectobulbar tract
5. Moving the head and neck towards the

11. TRANSVERSE SECTION OF MIDBRAIN
AT LEVEL OF SUPERIOR COLLICULI

12. Clinical Anatomy at the level of
midbrain

13. WEBER’S SYNDROME
1. There may be Occlution of
oculomotor nerve
because of this there will
be Unilateral paralysis of
a)levator palpabre
superioris: therewill be
unilateral ptosis( drooping)
of eye lid
b)loss of sphinctor pupillae
and ciliaris muscle: pupil
will remain dilated and fix
c)Lateral sqint/lateral
statismus (lateral rectus is
normal)
2. Involvement of Pyramidal
tract: upper motor neuron
type of paralysis in opposite
side of body

14. BENEDIKT’S SYNDROME
• Lesion of red
nucleus:functions of red
nucleus also will lost
• Medial lamniscus is
involved : consious
muscle joint sensation
along with
touch,pressure,lost(contr
alateral half)
• Oculomotor nerve lesion
:symptoms of webers
syndrome
• Superior cerebellar
peduncle

15. PARINAUD’S SYNDROME
• Compression of
the tectum
region(by penial
gland)in the
area of superior
colliculi: it will
produce
upward gaze
syndrome

16. PARINAUD’S SYNDROME

17. A QUICK REVISION

22. TRANSVERSE SECTION OF MIDBRAIN
AT LEVEL OF SUPERIOR COLLICULI

26. THANK YOU