Neuro: Lecture 7 - Brainstem Flashcards
What are the 3 longitudinal divisions of the brainstem?
Basilar - front
Tegmentum - middle
Tectum - back
The tectum is only found in the….
Midbrain
Tectum
posterior
reflexive movements
*only in midbrain
tegmentum
Middle
sensory
reticular formation
adjusts the general level of activity throughout the nervous system
Basilar
Anterior
motor
What is the basis pedunculi?
Basilar portion of midbrain
-anterior
-motor
substantia nigra
one of the nuclei in the basal ganglia circuit
What is the midbrain tegmentum?
Middle
sensory
what is the pedunculopontine nucleus?
it is part of the basal ganglia circuit and regulates muscle tone
what does the medial longitudinal fasiculus do?
it controls coordination of the L/R eye movements
what does the periaqueductal gray do?
it surrounds the cerebral aqueduct
nociceptive inhibition
coordinates reactions to pain, threats, and emotion
What is the midbrain tectum
Posterior
relfexive movements
What does the superior colliculus do?
motor and sensory info to orient head and eyes
What does the inferior colliculus do?
relays info from cochlear nerve to superior colliculus and thalamus
The pretectal area of the midbrain does what?
mediates eye reflexes
What is the red nucleus?
a sphere of gray ma tter that is part of a cognitive- motor circuit involving the cerebral cortex motor areas, inferior olive, cerebellum, and red nucleus
What cranial nerve nuclei are found in the midbrain tegmentum
3 and 4
what is the only cranial nerve that exits posteriorly?
CN IV
what forms the wall of the 4th ventricle?
pons
what forms the posterior wall of the 4th ventricle?
cerebellum
What 2 tracts synapse in the pons? Most of the tracts do not
corticopontine tract
corticobrainstem tract
corticopontine tract course
Synapse on pontine nuclei -> pontocerebellar fibers -> middle cerebellar peduncle -> synapse in contralateral cerebellar hemisphere
corticobrainstem tract course
synapses with trigeminal motor nucleus and facial nucleus
What kind of fibers are in the superior cerebellar peduncle?
Sensory fibers (from cerebellum)
what does the superior cerebellar peduncle do?
it connects the midbrain with the cerebellum, transmitting primarily efferent (SENSORY FIBERS, NOT MOTOR) info from the cerebellum
What can you find in the basilar portion of the pons?
Descending tracts- corticospinal, corticobrainstem, corticopontine
Pontine nuclei
Pontocerebellar axons
What can be found in the tegmentum of the Pons?
Sensory Tracts
Reticular Formation
Autonomic pathways
CN V1,6,7,8 nuclei
What cranial nerve nuclei exits between the pyramid and inferior olive?
CN 12
What cranial nerves exit from the lateral groove lateral to the inferior olive?
CN IX, X
Where are most of the CN nuclei located in the upper medulla?
In the dorsal part from medial to lateral
solitary nucleus
taste from CN 7 and 9 afferents
autonomic afferents from CNs 9 and 10
spinal trigeminal nucleus
processes pain and temperature information from the ipsilateral face.
inferior olivary nuclei
receives input from most motor areas of the brain and spinal cord.
important for motor learning and
timing and control of ongoing movement
where are the spinal trigeminal nucleus and nucleus ambiguous located?
lateral upper medulla
What is the nucleus ambiguus for?
Motor output to swallowing/vocalization muscles
(Which would be CN 9, 10, 12)
Where is the nuclei of CN VIII located?
the medullopontine structure
The medulla sends many fibers (spinocerebellar, olivocerebellar,
vestibulocerebellar, and reticulocerebellar) to the cerebellum via the
inferior cerebellar peduncle
What is the only tract that enters the medulla from the cerebellum
(The rest enter medulla -> inferior cerebellar peduncle -> cerebellum)
Cerebellovestibular tract
what tract cross at the inferior border of the medulla?
lateral corticospinal tract
The DCML crosses in the inferior medulla ________ to the crossing of the corticospinal tract
Posterior
what are the branches of the vertebral artery?
anterior spinal artery
posterior inferior cerebellar artery
The anterior inferior cerebellar artery supplies the _____ whereas the Posterior inferior cerebellar artery supplies the _______
Pons
Medulla
what are the branches of the basilar artery?
anterior inferior cerebellar artery
superior cerebellar artery
is the middle cerebral artery part of the circle of willis?
NO
What arteries supply the midbrain?
posterior cerebral artery
midbrain branches of basilar artery
what arteries supply the pons?
Basilar
AICA
arteries supply the medulla?
anterior spinal artery
PICA
what are the sensory (ascending) tracts?
dorsal column/medial lemniscus, spinothalamic, spinocerebellar, trigeminal lemniscus
what are the motor (descending) tracts?
corticospinal, cortiobulbar, corticopontine, corticoreticular
What are the 4 brain stem tracts?
Rubrospinal Vestibulospinal Reticulospinal Tectospinal
What are the general brain stem functions
Modulates conciousness
Regulates vital signs
Conveys signal from cortex to spinal cord
What are the 4 cardinal signs of brain stem dysfunction? 4 Ds
Dysphagia, Dysarthria, diplopia, dysmetria
what centers of the brainstem regulate vital functions?
medullary and pontine centers
Damage to brain stem could cause….
Heart to stop beating
BP to fluctuate
Breathing to stop
Disorders of conciousness are due to damage of_______
Reticular activating formation/ reticular formation
People in vegetative or minimally concious states have loss of tissue in subcoritcal/thalamic/brainstem regions
Single cranial nerve/nuclei lesions result in _____________ signs
ipsilateral
lesions of lateral corticospinal and dorsal column tracts in the brainstem usually cause ____________ signs. Why?
contralateral
tracts cross the midline in the inferior medulla
Anteriormedial midbrain syndrome (webers) is caused by….
Blockage of PCA or Basilar artery
What are the primary structures affected by Anteromedial midbrain syndrome (webers)
Corticospinal tract- contralateral motor paralysis (cut above)
Occulomotor nerve nucleus- Ipsilateral loss of eye movements. Paralysis of eyelid, dilated pupil
Red Nucleus- loss of motor coordination, ataxia, CONTRALATERAL, inappropriate laughing and crying. Lability
What does CN3 palsy look like?
Eye deviated down and out
ptosis
Lateral inferior pontine syndrome is due to occlusion of the….
Anterior inferior cerebellar artery
What are the clinical manifestations of lateral inferior pontine syndrome
What artery?
Cochlear nucleus- ipsilateral hearing loss
Vestibular nucleus affected- dysequilibrium, nausea, vomiting
Impaired descending sympathetic- ipsilateral Horner’s syndrome
Trigeminal nerve- ipsilateral pain and temp loss of face
Salivatory nucleus- decreased tears and salivation
Spinothalamic tract- contralateral pain and temperature sensation to body
Facial nerve- ipsilateral loss of facial muscles
Remember, Trigeminal, Facial, And Vestibulocochlear nerve are all on the pons and the pons is supplied blood by AICA
Damage to what nerve causes Bell’s palsy
How will Bell’s palsy differ from a facial weakness after stroke
Facial nerve
Stroke is usually only lower facial weakness
(Upperface muscle preserved due to dual innervation of the upper face)
How will Bell’s palsy differ from a facial weakness after stroke
Bells Palsy: facial nerve LMNL - ipsilateral weakness of upper and lower face
stroke: UMNL - contralateral lower face weakness
What is Horner’s syndrome?
Miosis- pupil constricted
Ptosis- drooping eye lid
Anhidrosis- drying of skin in the area
Damage to sympathetic nerves
Locked in syndrome is due to damage of the….
Basiliar artery impacting the ventral pons bilaterally
What are the primary structures involved in locked in syndrome-
B corticospinal tracts- paralysis below the head
B corticobulbar tracts- paralysis of facial muscles
B abducens tracts- unable to move eyes to side
Note: most of the time cranial nerve 3 is preserved but sometimes its impacted
What are spared in locked-in syndrome?
Reticular activating formation/ reticular formation
Vertical gaze centers are spared.
Middle medullary syndrome is caused by a blockage in the ….
Anterior spinal artery
anterior spinal artery runs down the middle of the medulla
What is the 2nd most common place to have a stroke in the brainstem?
AICA
What are the primary structures affected by medial medullary syndrome
hypoglossal nerve- ipsilateral tongue protrusion
DCML- contralateral loss of DCML senses
Lateral corticospinal- contralateral hemiparesis
Remember the hypoglossal nerve comes off of the medial medulla!
What is the most common brainstem stroke, and what artery causes it?
Lateral medullary syndrome (wallenberg)
Due to blockage of PICA
What structures are affected due to Wallenberg syndrome (lateral medullary syndrome)
Vagus nerve/Solitary nucleus- elevated HR
Vestibular nucleus- balance
Vagus nerve nucleus- altered vitals
Trigeminal Nerve
Inferior cerebellar peduncle - ataxia/coordination ipsilateral
Salivatory nucleus - unable to salivate or make tears
Spinothalamic tract- contralateral
Descending sympathetic- ipsilateral Horner syndrome
Nucleus ambiguus (9 10) and 12 cranial nerve. Tongue/ larynx/pharynx affected. Lack of gag reflex
The reticular formation is in the _______ of the pons
tegmentum
