anatomy of midbrain and pons
TRANSCRIPT
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Midbrain and Pons
To MBBS 2nd year
26-02-2017
By Dr. Laxman Khanal
Assistant professor, Department of anatomy
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Identify the cranial nerves.
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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
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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.
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External feature of midbrain and pons- anterior view
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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
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Pons:
• Pontine branches• AICA• Sup cerebellar artery
Midbrain:
• Posterior cerebral artery• Superior cerebellar artery
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Which sections are important?
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Facial colliculus
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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?
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Descending tract in brainstemCorticospinal fibersCorticonuclear fibersCorticopontocerebellar fibers
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Ascending tract- #MSTLDC/Medial lemniscusSpinal lemniscusTrigeminal lemniscusLateral lemniscus
Spinal lemniscus1. Anterior spinothalamic tract2. Lateral spinothalamic tract3. Spinotectal tract
Medial longitudinal fasciculus
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@ Trigeminal nerve@ Facial colliculus
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66
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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
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TS – lower pons
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TS – upper pons
Cranial nerve nucleiMain sensory nucleus of Vth nerveMotor nucleus of Vth nerveNo inferior cerebellar peduncle
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Millard-Gubler syndrome: #P67Ventral pontine syndrome
• Ipsilateral medial squint• Ipsilateral facial palsy• Contralateral hemiplegia
Most common tumor of brainstemAstrocytoma of pons
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Midbrian cross section
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S1. Tectum 2. Cerebral peduncleTegmentumCrus cerebri
Interpeduncular fossa
Parkinson’s disease
Substantia nigra
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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
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Blockage of cerebral aqueduct
Weber syndrome1. Crus cerebri2. Oculomotor nerve# COW
Benedict syndrome1. Red nucleus2. ML3. Oculomotor nerve