Download - Anatomy of Midbrain and pons
Midbrain and Pons
To MBBS 2nd year
26-02-2017
By Dr. Laxman Khanal
Assistant professor, Department of anatomy
Identify the cranial nerves.
Identify this swelling in pons.
Q. Trigeminal nerve has its nuclei in which part of brain stem?a.Midbrainb.Ponsc. Medulla oblongatad.All of the above
Objectives
• To review the anatomy of the upper brainstem
• To develop a three-dimensional picture of the interior of the midbrainand pons.
• To know the positions of cranial nerve nuclei and the paths of variousascending and descending nerve tracts.
• To assess the signs and symptoms presented by a patient and identifythe exact location of a structural lesion.
External feature of midbrain and pons- anterior view
External feature- posterior view
Visible part: Tectum1. Corpora quadrigemina2. 4th CN
Visible part: Tegmental part1. Forms upper part of floor of 4th
ventricle2. Median sulcus3. Medial eminence (facial colliculus)4. Sulcus limitans
Pons:
• Pontine branches• AICA• Sup cerebellar artery
Midbrain:
• Posterior cerebral artery• Superior cerebellar artery
Which sections are important?
Facial colliculus
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?
Descending tract in brainstemCorticospinal fibersCorticonuclear fibersCorticopontocerebellar fibers
Ascending tract- #MSTLDC/Medial lemniscusSpinal lemniscusTrigeminal lemniscusLateral lemniscus
Spinal lemniscus1. Anterior spinothalamic tract2. Lateral spinothalamic tract3. Spinotectal tract
Medial longitudinal fasciculus
@ Trigeminal nerve@ Facial colliculus
66
7
Trapezoid body
MLF
Tegmentum
Basal part
Pontine nuclei
Transverse pontine fibers(pontocerebellar fibers)
Corticospinal and corticonuclear fibers
Superior and inferior cerebellar peduncle
MSTLMedial LSpinal LTrigeminal LLateral L
7
FC
TS – lower pons
TS – upper pons
Cranial nerve nucleiMain sensory nucleus of Vth nerveMotor nucleus of Vth nerveNo inferior cerebellar peduncle
Millard-Gubler syndrome: #P67Ventral pontine syndrome
• Ipsilateral medial squint• Ipsilateral facial palsy• Contralateral hemiplegia
Most common tumor of brainstemAstrocytoma of pons
Midbrian cross section
S1. Tectum 2. Cerebral peduncleTegmentumCrus cerebri
Interpeduncular fossa
Parkinson’s disease
Substantia nigra
Crus cerebri (motor zone)• Contains descending fibers1. Up to pons- FP+TP2. Up to motor nuclei of CNs- CN3. Up to spinal cord- CS
FP
TPCSCN
Pontine nucleus
Crossing of rubrospinal tract
Mesencephalic nucleus
MLF
MSTL MST
Crossing of sup cerebellar peduncle
To cerebellum
S
Blockage of cerebral aqueduct
Weber syndrome1. Crus cerebri2. Oculomotor nerve# COW
Benedict syndrome1. Red nucleus2. ML3. Oculomotor nerve