well describes the external and internal anatomy of upper brain stem. slide also explain some lesion disorders of pons and midbrain.

1. Midbrain and Pons
To MBBS 2nd year
26-02-2017
By Dr. Laxman Khanal
Assistant professor, Department of anatomy

2. Identify the cranial nerves.

3. Identify this
swelling in
pons.
Q. Trigeminal nerve has its nuclei in which
part of brain stem?
a.Midbrain
b.Pons
c. Medulla oblongata
d.All of the above

4. Objectives
• To review the anatomy of the upper brainstem
• To develop a three-dimensional picture of the interior of the midbrain
and pons.
• To know the positions of cranial nerve nuclei and the paths of various
ascending and descending nerve tracts.
• To assess the signs and symptoms presented by a patient and identify
the exact location of a structural lesion.

5. External feature of midbrain and pons- anterior view

6. External feature- posterior view
Visible part: Tectum
1. Corpora quadrigemina
2. 4th CN
Visible part: Tegmental part
1. Forms upper part of floor of 4th
ventricle
2. Median sulcus
3. Medial eminence (facial colliculus)
4. Sulcus limitans

7. Pons:
• Pontine branches
• AICA
• Sup cerebellar artery
Midbrain:
• Posterior cerebral artery
• Superior cerebellar artery

8. Which sections are important?

9. Facial colliculus

10. How to study the cross section
• Different level of cross sections should be differentiated by-
1. What is the CSF filled cavity ?
2. What are the cranial nerve nuclei?
3. What are the ascending tracts ?
4. What are the descending tracts?

11. Descending tract in brainstem
Corticospinal fibers
Corticonuclear fibers
Corticopontocerebellar fibers

12. Ascending tract- #MSTL
DC/Medial lemniscus
Spinal lemniscus
Trigeminal lemniscus
Lateral lemniscus
Spinal lemniscus
1. Anterior spinothalamic tract
2. Lateral spinothalamic tract
3. Spinotectal tract
Medial longitudinal
fasciculus

13. @ Trigeminal nerve
@ Facial colliculus

14. 66
7
Trapezoid body
MLF
Tegmentum
Basal part
Pontine nuclei
Transverse pontine fibers
(pontocerebellar fibers)
Corticospinal and corticonuclear fibers
Superior and inferior
cerebellar peduncle
MSTL
Medial L
Spinal L
Trigeminal L
Lateral L
7
FC

15. TS – lower pons

16. TS – upper pons
Cranial nerve nuclei
Main sensory nucleus of Vth nerve
Motor nucleus of Vth nerve
No inferior cerebellar peduncle

17. Millard-Gubler syndrome: #P67
Ventral pontine syndrome
• Ipsilateral medial squint
• Ipsilateral facial palsy
• Contralateral hemiplegia
Most common tumor of brainstem
Astrocytoma of pons

18. Midbrian cross section

19. S1. Tectum
2. Cerebral peduncle
Tegmentum
Crus cerebri
Interpeduncular fossa
Parkinson’s disease
Substantia nigra

21. Crus cerebri (motor zone)
• Contains descending fibers
1. Up to pons- FP+TP
2. Up to motor nuclei of CNs- CN
3. Up to spinal cord- CS
FP
TP
CS
CN
Pontine nucleus
Crossing of rubrospinal tract
Mesencephalic
nucleus
MLF
MSTL MST
Crossing of sup cerebellar peduncle
To cerebellum
S

24. Blockage of
cerebral aqueduct
Weber syndrome
1. Crus cerebri
2. Oculomotor nerve
# COW
Benedict syndrome
1. Red nucleus
2. ML
3. Oculomotor nerve