1. PONS & MID-BRAIN STRUCTURE/BLOOD SUPPLY/CRANIAL NERVES ATTACHMENTS
Lecture….by Prof. Ansari
Saturday, April 22, 2017
(for MBBS SEMESTER IV students only)

2. The learning outcomes
Draw the internal structure of pons and midbrain.
Identify the cranial nerves attachments to pons and midbrain.
Mention other nuclei present at these levels.
Describe the blood supply of pons, midbrain & correlate the clinical situation with the Cerebrovascular accident.
Identify the cross sections of pons and midbrain the - grey matter and white matter.

3. A case of pontine hemorrhage
A 50 year-old male was admitted to the emergency room because of sudden weakness on his right leg and arm.
An elevated arterial blood pressure (200/130 mmHg) was disclosed but his general physical exam was otherwise unremarkable.
Neurological examination revealed a complete right-sided hemiparesis. Consciousness was not impaired and there were no cerebellar signs or cranial nerves dysfunction.
There were no signs of ipsi-lateral or contralateral VII nerve palsy but a supra- nuclear facial palsy was present.
A mild dysarthria was recorded and the patient referred no dizziness, tinnitus or dysphagia. Previous medical history indicated untreated elevated blood pressure for the last 5 years.
A computed tomographic (CT) scan showed a hematoma located in the left pontine tegmentum.

4. PONS It is a part of brain stem.
It lies between midbrain and medulla oblongata.
It has a basilar part/ ventral part, and a dorsal part which forms the floor of IV ventricle.
Three cranial nerves are related to pons, trigeminal nerve is attached to the pons on ventral part.
Abducent nerve is related at the lower border of pons and pyramid.
Occulomotor nerve arises at the upper border of pons, in the interpeduncular fossa.

6. CRANIAL
NERVES
ATTACHED
AT THE BASE
OF BRAIN

7. CROSS SECTION OF PONS

8. A cross section of mid-pons
A. Superior vestibular nucleus
B. Main Sensory nucleus of Trigeminal
C. Motor nucleus of Trigeminal
D. Lateral vestibular nucleus
E. Pontine Nuclei
F. Dorsal Longitudinal Faciculus
G. Superior Medullary Velum
H. Fourth Ventricle
I. Medial Longitudinal Faciculus
J. Middle Cerebellar Peduncle (MCP)
K. Pontocerebellar fiber of MCP
L. Dorsal Nucleus of Vagus (motor)
M. Trigeminal Nerve Fibers (root)
N. Pontocerebellar fibers
O. Medial Lemniscus (Located medially to
the Anterolateral system and Lateral Lemniscus.)
P. Pyramidal Tract and Corticopontine Tract
Q. Fibers of the Trigeminal Nerve
R. Olivary cerebellar fibers
S. Trapezoid Body (Auditory Decussation)

9. IV
VENTRICLE
TEGMENTUM PART
BASILAR PART

12. Nuclei of cranial nerves in pons
Facial nerve nuclei, motor / sensory/autonomic.
Trigeminal nuclei, motor/ main sensory/spinal/ mesencephalic.
Abducent nucleus / purely motor.
Nuclei pontis.

13. Floor of IV ventricle

14. White fibers at pons Corticopontine fibers Corticospinal fibers
Corticopontocerebellar fibers
Corticonuclear fibers
Trapezoid body

15. OVERVIEW OF PONS

16. Mesencephalon It is at the cranial end of pons.
It has a dorsal portion called as tectum.
The ventral portion is called as cerebral peduncle.
The space between the two cerebral peduncle is the interpeduncular fossa.

17. A 69-year-old Moroccan man, with a medical history of untreated hypertension, developed suddenly diplopia, a droop of both upper eyelids with the inability to open his eyes. The symptoms were constant and did not fluctuate during the day
He denied any weakness, numbness or change in mental status. Initial physical examination found bilateral ptosis with a limitation in adduction, elevation and depression of both eyes which was more marked on the right side. Both pupils were in miosis. The remaining neurological examination was strictly unremarkable. His blood pressure was 220/120mmHg on admission. Initial blood tests showed a normal full blood count, normal urea, electrolytes and C-reactive protein. Computed tomography (CT) of the brain revealed a spontaneously high-density lesion of the midbrain consistent with a midbrain hematoma.
The oculomotor function gradually and completely improved over eight months of follow-up.

18. Structures in the interpeduncular fossa
1.Optic nerve
2.Optic chiasma
3.Optic tract
4.Tuber cinereum
5.Mammillary bodies
6.Ant.perforated substance.
7.Olfactory tract
8.Pons
9=Uncus

19. A cross section of midbrain at inferior colliculus
A. Midline of Tectum
B. Cerebral Aqueduct
C. Inferior Colliculus
D. Inferior Brachium and Lateral Lemniscus
E. Anterolateral system
F. Medial Lemniscus
G. Substantia Nigra
H. Cerebral Peduncle
I. Corticobulbar Tract
J. Frontopontine Fibers
K. Corticospinal Tract
L. Pontine Nuclei
M. Interpeduncle Fossa
N. Decussation of Superior Cerebellar Peduncle
O. Trochlear Nucleus
P. Periaqueductal Gray Matter
Q. Medial Longitudinal Faciculus
R. Reticular Formation
S. Parieto-occopitotemporal Pontine Fibers

20. Cross section of midbrain
Inferior colliculus
Substantia
nigra
Superior
Cerebellar
Peduncle
decussation
PAG
Cerebral peduncle

21. Superior colliculus
Oculomotor fibers

22. Cross section of midbrain at the level of superior colliculus
A. Cerebral Aqueduct
B. Red Nucleus
C. Interpeduncle Fossa
D. Oculomotor Nucleus
E. Superior Colliculus
F. Tectum
G. Lateral Lemniscus
H. Thalamus (Medial Genculata Nucleus)
I. Substantia Nigra
(pars compacta)
J. Substantia Nigra
(pars reticularis)
K. Oculomotor Fibers
L. Periaqueductal Gray Matter
M. Anterolateral System
N. Medial Lemniscus
O. Parieto-occopitotemporal Pontine Fibers
P. Corticospinal Tract
Q. Corticobulbar Tract
R. Frontopontine Fibers

23. Various nuclei at midbrain
Oculomotor nucleus
Trochlear nucleus
Mesencephalic nucleus
Red nucleus
Substantia nigra
Edinger-Westphal nucleus

24. White matter at mesencephalon
Superior cerebellar peduncles decussations
Medial lemniscus/lateral lemniscus/trigeminal lemniscus/spinal lemniscus
Crus cerebri

25. Blood supply of pons &midbrain
Cortical branches and central branches arise from basilar artery and circle of Willis.
Pontine hemorrhage leads to bursting head ache, pinpoint pupil, and hyperthermia.
Injury to the Corticospinal fibers leads to hemiplegia.

26. CIRCLE OF WILLIS

27. Red nucleus and substantia nigra
They are concerned with the extrapyramidal tract.
Injury to these nuclei will result in tremors, Parkinsonism, and nystagmus.
These symptoms can be corrected by supplementing the neurotransmitter dopamine.

28. Periaqueductal gray

29. Electrical stimulation of the PAG results in immediate and profound analgesia
Stimulation of the dorsal and lateral aspects of the PAG (in the rat) can provoke defensive responses characterized by freezing immobility, running, jumping, tachycardia, and increase in blood pressure.
Stimulation of the caudal ventrolateral PAG can result in an immobile, relaxed posture known as quiescence.
It also plays a role in female copulatory behavior.

30. Periaqueductal gray
CEREBRAL
AQUEDUCT
RED NUCLEUS

31. References
%20l%20central%20nervous%20system-brain.htm
htm
mnemonics.html

32. A 62-year old male has sustained several injuries from a car accident
A 62-year old male has sustained several injuries from a car accident. Upon administering a neurological examination, you suspect that the patient has damage to the right caudal medulla. Why do you think this?
A. The patient's right eye exhibits hypertropia and he complains of diplopia,
B. The patient's tongue deviates towards to right when you asked him to stick it out and his uvula deviates towards the left when you ask him to say, "aahhh".
C. The patient has a loss of taste on the right anterior 2/3rds of his tongue
D. The patient exhibits anosmia (inability to smell)
E. The patient complains of excruciating pain on the right side of his face