Brainstem
description
Transcript of Brainstem
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Brainstem
David A. Morton, Ph.D.Jan 10th, 2013
Midbrain and Pons
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Objectives• Explain how spinal nerves differ from cranial nerves• Name all the cranial nerves and know their components and functions• Identify and locate the CN’s associated with the medulla, pons and midbrain• Recognize the major internal and external landmarks on the dorsal and ventral
surface of the brain stem, so that you can determine if a gross or stained cross section is medulla, pons or midbrain.
• Identify on a typical cross section all the brain stem nuclei containing motor neurons that end on striated muscle.
• List the cranial nerves that contain parasympathetic fibers, the location of their nuclei, and their function
• Explain why cranial nerves are so important in localizing lesions.• Name reflexes that test these nerves and brain stem levels.• Relate branches of the vertebrobasilar blood supply to the medulla and pons
explaining the deficits that would occur with vascular occlusion.
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Directional terms with Brain
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CN I – Olfactory nerve
Cranial nerve overview
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CN II – Optic nerve
Cranial nerve overview
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CN III – Oculomotor nerve
Cranial nerve overview
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CN IV – Trochlear nerve
Cranial nerve overview
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CN V – Trigeminal nerve
Cranial nerve overview
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CN VI – Abducens nerve
Cranial nerve overview
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CN VII – Facial nerve
Cranial nerve overview
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CN VIII – Vestibulocochlear nerve
Cranial nerve overview
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CN IX – Glossopharyngeal nerve
Cranial nerve overview
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CN X – Vagus nerve
Cranial nerve overview
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CN XI – Spinal accessory nerve
Cranial nerve overview
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CN XII – Hypoglossal nerve
Cranial nerve overview
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Brainstem
• Midbrain
• Pons
• Medulla
Brain Overview
Medulla
Pons
Midbrain
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Diencephalon
• Thalamus
• Hypothalamus
• Pineal gland
Brain Overview
PHTh
Th
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• Corpus callosum
• Lateral ventricle
• 3rd ventricle
• Cerebral aqueduct
• 4th ventricle
Brain Overview
4
Corpus callosum
3
LV
aq
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Spinal Cord and Spinal Nerve Review
Alar
Basal
Sulcus limitans
Spinal cord
Som S
VS
VM
SM
Spinal nerve anatomy
• Dorsal root
• Somatic sensory neurons
• Visceral sensory neurons
• Ventral root
• Visceral motor neurons
• Somatic motor neurons
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Internal anatomy of brainstem
Alar
Basal
Sulcus limitans
Spinal cord
Som S
VS
VM
SM
Alar
Basal
Sulcus limitans
Medulla
Som S
VSVM
SMBM
The fate of the alar and basal laminae
• Why are brain stem sensory nuclei lateral
to motor nuclei in brainstem?
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External anatomy:
• Quadrigeminal plate
• Superior colliculus
• Inferior colliculus
• Cerebral peduncles
• CN IV
Midbrain (mesencephalon)
SC
CPIC
IV
Dorsal view of brainstem
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External anatomy:
• Quadrigeminal plate
• Superior colliculus
• Inferior colliculus
• Cerebral peduncles
• CN III (arrows)
Midbrain (mesencephalon)
Rostral midbrain
Caudal midbrain
SC
IC
CP
CP
Dorsal view of midbrain
CP
Ventral
Ventral
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Cranial nerve nuclei
• Rostral midbrain
• Oculomotor nucleus
• Edinger-Westphal nucleus
• Caudal midbrain
• Trochlear nucleus
Oculomotor nucleus
Edinger-Westphal nucleus
Trochlear nucleus
Midbrain
MotorSensory
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Internal anatomy
• Tectum
• Tegmentum
• Central gray matter
• Red nucleus
• Substantia nigra
• Cerebral peduncles
Midbrain (Rostral)
Subs
tantia n
igra
Cere
bral
pedu
ncle
Aq
Tectum
Tegmentum
Rn
Rostral midbrain
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Internal anatomy
• Oculomotor nucleus
• Edinger-Westphal nucleus
Midbrain (Rostral)
Subs
tantia n
igra
Cere
bral
pedu
ncle
Aq
Rostral midbrain
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Internal anatomy
• Trochlear nucleus
Midbrain (Caudal)
Caudal midbrain
Horizontal section
Red nucleus
Substantia nigra
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Functional significance of midbrain:
• Visual and auditory reflexes
• Coordinates eye movements
• Pupillary reflex
• Consciousness and arousal (RAS)
Midbrain
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Arterial supply. Branches off the:
• Posterior cerebral artery
• Basilar artery
Midbrain
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Pupi
llary
and
Acc
omm
odati
on R
eflex
es
CN II
Bilateral contraction of sphincter pupillae and
ciliary muscles
CN III
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External anatomy:
• Basilar pons (pons proper)
• Middle cerebellar peduncle (MC)
• Basilar artery
• 4th ventricle
• CNN V, VI, VII, VIII
Pons
MC
V
VI VIIVIII
Pons
4th vent.
Horizontal section
MC
4th
4th
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Cranial nerve nuclei
• Rostral Pons
• Trigeminal nucleus
• Caudal Pons
• Abducens nucleus
• Facial nucleus
• Sup salivatory nucleus
Trigeminal nucleus
Facial nucleus
Abducens nucleus
Pons
MotorSensory
Sup salivatory nucleus
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4th Ventricle
Motor nucleus of V
TegmentumR.F.
Pons Proper
Axons of the sensory part of V
Axons of the motorpart of V
Pons (Rostral/Mid)
Internal anatomy
• Trigeminal motor nucleus
• Functional significance
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Pons (caudal)
Facial nucleus
• Branchial motor nucleus
• Innervate muscles of face
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Pons (caudal)
Superior salivatory nucleus
• Visceral motor (Para)
• Origin of preganglionic
parasympathetic neurons
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Pons (caudal)
Abducens nucleus
• Origin of Abducens n. (CN VI)
• Homolog to ventral horn
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Pons (caudal)
Internal anatomy
• Facial nucleus
• Superior salivatory nucleus
• Abducens nucleus
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Corneal reflex
Spinal trigem. Nucleus & Tract
• Consensual reflex
• Sensory: CN V-1 to spinal trigeminal nucleus
• Motor: Facial nucleus out to the temporal branch of CN VII
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Corneal ReflexSemilunar ganglion
of CN V
CN V-1
L R
Spinal trigeminal nucleus
Touch the cornea
Blink(Orbicularis occuli muscle)
Facial motor nucleus
Temporal branch of CN VII
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Pons
Arterial supply. Branches off the:
• Basilar artery
• Median and Circumferential
branches
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Match the following reflexes with their associated brainstem level:
a. corneal reflex testing?
b. Gag reflex testing?
c. pupillary light reflex testing?
I II III
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Match the following reflexes with their associated brainstem level:
a. corneal reflex testing?
b. Gag reflex testing?
c. pupillary light reflex testing?
I
II
III
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You have a patient who cannot look to the right with the right eye or smile or wrinkle
the right side of their face. Characterize the lesion as to level, side, structure(s) involved.
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You have a patient who cannot look to the right with the right eye or smile or wrinkle
the right side of their face. Characterize the lesion as to level, side, structure(s) involved.
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What reflex would be abnormal in a patient with a lesion that included the circled area?
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What reflex would be abnormal in a patient with a lesion that included the circled area?
Abducens nucleus
Facial nucleus
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