The document provides an overview of the anatomy and structures of the midbrain. It notes that the midbrain connects the pons and cerebellum to the forebrain, is about 0.8 inches long, and is traversed by the cerebral aqueduct filled with CSF. Key structures discussed include the crus cerebri, oculomotor nerve, superior and inferior colliculi, brachium, and trochlear nerve. The midbrain is divided into cerebral peduncles, tectum, and tegmentum. Transverse sections show structures like the substantia nigra, red nucleus, and tracts. Blood supply comes from the posterior cerebral, superior cerebellar, and basilar arteries.

1. Basic Anatomy
&
Applied aspects
By: Pulak Agrawal
Roll No.: 001

2. Midbrain:Midbrain: The midbrain develops from
mesencephalon. Cells within the midbrain
multiply continually and are compressed
to form cerebral aqueduct.
MidbrainMidbrain
 Connects the pons and cerebellum with the forebrain.
 It is about 0.8 inch in length
 The midbrain is traversed by a narrow channel called
cerebral aqueduct filled with CSF.

3.  AnteriorlyAnteriorly, it presents
two large bundles of
fibers, one on each
side of the midline,
called crus cerebricrus cerebri..
 The oculomotor nerveoculomotor nerve
emerges from the
medial aspect of the
crus of the same side
 The crus cerebri
bounds the
interpeduncular fossainterpeduncular fossa
on either side.
ANTERIOR SURFACEANTERIOR SURFACE

4. POSTERIOR SURFACEPOSTERIOR SURFACE
 PosteriorlyPosteriorly, the midbrain
presents four rounded
swellings called colliculi- Onecolliculi- One
SuperiorSuperior and inferiorinferior colliculi
on either side.
 Each colliculus is laterally
related to a ridge called
brachium.brachium.
o Superior and inferiorSuperior and inferior
brachiumbrachium arises from respective
colliculi
o Superior brachium connects the
superior colliculus to laterallateral
geniculate bodygeniculate body
o Inferior brachium connects the
inferior colluculus to medialmedial
geniculate bodygeniculate body
o In the midline below the inferior
colliculus, the trochlear nervetrochlear nerve
emerges which then winds round
the side of the midbrain to reach its
ventral aspectventral aspect

5. Lateral view

6. Structure of MidbrainStructure of Midbrain
 The midbrain comprises two lateral halves called-
Cerebral pedunclesCerebral peduncles; which is again divided into
1. anterior part- Crus cerebri
2. posterior part -Tegmentum
by a pigmented band of gray matter, substantia nigrasubstantia nigra
 The central narrow cavity is called the cerebral aqueduct or
aqueduct of Sylvius, which connects the 3rd
and 4th
ventricles.
 The tectum is the part of the midbrain posterior to the cerebral
aqueduct; it has four small surface swellings referred to previously;
these are two superior and two inferior colliculi.
 The tegmentum forms the floor of mid brain

7. TECTUM & TEGMENTUMTECTUM & TEGMENTUM

9. Transverse section at theTransverse section at the levellevel ofof
Superior ColliculiSuperior Colliculi
Superior colliculi
Substantia nigra
Oculomotor
nucleus
Red nucleus
Mesencephalic
nucleus of
trigeminal n.
Edgnger-westphal
nucleus

10. Tracts:Tracts:
MotorMotor
 Corticospinal
 Corticonuclear
 Temporopontin
e
 Frontopontine
 Medial
longitudinal
fasciculas
 Decussation of
rubrospinal tract
SensorySensory
 Trigeminal
 Spinal
 Medial

12. TransverseTransverse Section at the level ofSection at the level of
Inferior ColliculiInferior Colliculi
 Substantia
nigra
 Troclear
nucleus
 Mesencephal
ic nucleus of
trigeminal
nerve

13. Tracts:Tracts:
MotorMotor
 Corticospinal
 Corticonuclear
 Temporopontine
 Frontopontine
 Medial longitudinal
fasciculas
SensorySensory
 Lateral
 Trigeminal
 Spinal
 Medial lemnisci
 Decussation of
superior cerebellar
peduncles

14. Blood Supply:Blood Supply:
 Artery –Artery –
 posterior
cerebral artery
 superior
cerebellar artery
 basilar artery
 Veins –Veins –
Drained by
 basal or great
cerebral veins

19. Due to lesion of tegmentum of
midbrain.
1. External strabismus(lateral squint) & ptosis on same side – due to
involment of occulomoter nerve.
2. Tremor & twitching movement of opposite arm and leg – due to
involment of Red nucleus & superior cerebellar peduncle.

20.  Rubral tremor (Holme’s tremor):
A coarse, slow (4Hz) tremor, especially present in the
upper extremities, that is found at rest, postural and
intention.
Claude Syndrome:
Ipsi CN III, contra tremor, ataxia and incoordination
Parinaud’s Syndrome:
Due to lesion of superior colliculi as occurs when
this area becomes compressed by tumour of
pineal gland.
Weakness of upward gaze& vertical nystagmus

21. Refrences:
Snell's Clinical Neuroanatomy
IB Singh - Textbook of Human Neuroanatomy
internet