Brainstem B&B Flashcards
if you are looking at a cross-section of the brainstem and you do NOT see the 4th ventricles, which section are you looking at?
midbrain - cerebral aqueduct will be there instead (small circle)
remember CSF runs through cerebral aqueduct to 4th ventricle below
what anatomical structure can be used to orient yourself in the medulla of the brainstem (as opposed to midbrain or pons)?
inferior olivary nucleus - on the anterior lateral corners
only source of climbing fibers to the Purkinje cells in the cerebellum
what information does the medial lemniscus carry?
proprioception and vibration - connected to posterior columns of spinal cord
what is the function of the red nucleus in the midbrain?
fine tuning of movements
lesion —> tremor, ataxia
what is carried by the cerebral peduncle of the midbrain?
carries corticospinal and corticobulbar tracts - motor fibers
damage to this area —> UMN paralysis of face and lower extremities
what is the function of the medial longitudinal fasciculus (MLF) in the midbrain? where is it found?
small structure found in the middle, anterior to cerebral aqueduct
links oculomotor, trochlear, and abducent eye nerves
lesion —> problems with lateral gaze
Benedikt Syndrome
damage to the centrolateral region of the midbrain, lesioning:
1. CN3 —> oculomotor palsy
2. medial lemniscus —> contralateral loss of prop/vibr
3. red nucleus —> tremor, ataxia
what 3 structures are damaged in Benedikt Syndrome, and what associated symptoms does this cause?
damage to the centrolateral region of the midbrain, lesioning:
1. CN3 —> oculomotor palsy
2. medial lemniscus —> contralateral loss of prop/vibr
3. red nucleus —> tremor, ataxia
what region of the brainstem is affected when there is loss of CN3, the medial lemniscus, and the red nucleus?
midbrain - describing Benedikt Syndrome
damage to the centrolateral region of the midbrain, lesioning:
1. CN3 —> oculomotor palsy
2. medial lemniscus —> contralateral loss of prop/vibr
3. red nucleus —> tremor, ataxia
Pt presents with oculomotor palsy, contralateral loss of proprioception and vibration, and tremor + ataxia. Where is the lesion, and what is this syndrome called?
Benedikt syndrome: damage to the centrolateral region of the midbrain, lesioning:
1. CN3 —> oculomotor palsy
2. medial lemniscus —> contralateral loss of prop/vibr
3. red nucleus —> tremor, ataxia
Weber’s Syndrome
damage to anteriolateral portion of midbrain, lesion to:
1. CN3 —> oculomotor palsy
2. corticospinal tract —> contralateral hemiparesis
3. corticobulbar tract —> pseudobulbar palsy (UMN CN motor weakness - exaggerated gag reflex, tongue spasticity, spastic dysarthria)
what 3 structures are damaged in Weber’s Syndrome, and what associated symptoms does this cause?
damage to anteriolateral portion of midbrain, lesion to:
1. CN3 —> oculomotor palsy
2. corticospinal tract —> contralateral hemiparesis
3. corticobulbar tract —> pseudobulbar palsy (UMN CN motor weakness - exaggerated gag reflex, tongue spasticity, spastic dysarthria)
what region of the brainstem is damaged when there is loss of CN3, corticospinal tract, and corticobulbar tract?
Weber’s Syndrome: damage to anteriolateral portion of midbrain, lesion to:
1. CN3 —> oculomotor palsy
2. corticospinal tract —> contralateral hemiparesis
3. corticobulbar tract —> pseudobulbar palsy (UMN CN motor weakness - exaggerated gag reflex, tongue spasticity, spastic dysarthria)
Pt presents with oculomotor palsy, contralateral hemiparesis, and pseudobulbar palsy. Where is the lesion, and what is this syndrome called?
Weber’s syndrome: damage to anteriolateral portion of midbrain, lesion to:
1. CN3 —> oculomotor palsy
2. corticospinal tract —> contralateral hemiparesis
3. corticobulbar tract —> pseudobulbar palsy (UMN CN motor weakness - exaggerated gag reflex, tongue spasticity, spastic dysarthria)
Parinaud’s Syndrome
damage to posterior midbrain, lesion to superior colliculus and pretectal area
—> vertical gaze palsy + pseudo Argyll Robertson pupil
often from pinealoma/germinoma of pineal region - watch for cerebral aqueduct obstruction (non-communicating hydrocephalus)
what region of the brainstem is affected by Parinaud’s syndrome, and what symptoms does this cause?
damage to posterior midbrain, lesion to superior colliculus and pretectal area
—> vertical gaze palsy (rare - specific) + pseudo Argyll Robertson pupil
often from pinealoma/germinoma of pineal region - watch for cerebral aqueduct obstruction (non-communicating hydrocephalus)
what are the 2 cases in which you would observe an Argyll Robertson pupil in a patient?
pupil does not respond to light, but will constrict to follow finger to nose
most often associated with tertiary syphilis, but may also rarely see it with Parinaud’s Syndrome (damage to posterior midbrain - superior colliculi)
patient with vertical gaze palsy =
Parinaud’s Syndrome: damage to posterior midbrain, lesion to superior colliculus and pretectal area
—> vertical gaze palsy (rare, specific) + pseudo Argyll Robertson pupil
what is the usual cause of Parinaud’s Syndrome, and why is this clinically relevant?
damage to posterior midbrain, lesion to superior colliculus and pretectal area
—> vertical gaze palsy + pseudo Argyll Robertson pupil
often from pinealoma/germinoma of pineal region - watch for cerebral aqueduct obstruction (non-communicating hydrocephalus)
which 4 cranial nerves exit from the pons? what symptoms would accompany lesions of each?
- CN VIII (8), Vestibular nerve —> N/V, vertigo, nystagmus
- CN VII (7), Facial nerve —> facial droop, loss of corneal reflex
- CN VI (6), Abducens —> problem with lateral gaze
- CN V (5), spinal tract/nucleus of trigeminal —> loss of pain/temp in face
which nerve wraps around CN VI (abducens) and exits laterally from the pons?
CN VII, Facial nerve
what nerve provides pain and temperature sensation from the face? be specific
spinal tract and nucleus of the trigeminal nerve (CN V)
exits from the pons
what 3 structures located in the pons are needed for lateral gaze?
- MLF (medial longitudinal fasciculus)
- PPRF (paramedian pontine reticular formation)
- CN VI, abducens nerve
how will medial pontine syndromes present? (3)
damage to
1. corticospinal tract —> contralateral hemiparesis
2. CN VI (abducens) + MLF + PPRF —> lateral gaze palsy (can’t look towards affected side)
3. CN VII (facial) —> ipsilateral facial droop
how will lateral pontine syndromes present? (5)
damage to
1. CN VIII (Vestibulocochlear) —> nystagmus, vertigo, N/V + deafness
2. spinothalamic tract —> contralateral loss of pain/temp
3. spinal CN V (trigeminal) nucleus —> ipsilateral loss of facial pain/temp
4. sympathetic tract —> Horner’s syndrome
5. CN VII (facial) —> ipsilateral facial droop, loss of corneal reflex
what is the usual cause of a lateral pontine syndrome?
AICA (anterior inferior cerebellar artery) stroke
damage to
1. CN VIII (Vestibulocochlear) —> nystagmus, vertigo, N/V + deafness
2. spinothalamic tract —> contralateral loss of pain/temp
3. spinal CN V (trigeminal) nucleus —> ipsilateral loss of facial pain/temp
4. sympathetic tract —> Horner’s syndrome
5. CN VII (facial) —> ipsilateral facial droop, loss of corneal reflex
what is the function of the nucleus solitarius and dorsal motor nucleus X in the medulla?
receives autonomic sensory information and sends out efferents via vagus nerve (CN X)
what is the function of the nucleus ambiguous of the medulla?
shared motor nucleus of CN IX, X, XI
“ambiguous” because it cell bodies of all 3!
what is contained in the medullary pyramids?
corticospinal tracts
this is why loss of corticospinal tract is often referred to as “pyramidal dysfunction”
what is carried by the hypothalamospinal tract in the medulla?
sympathetic nerve fibers from the thalamus
lesion —> Horner’s syndrome
which cranial nerves are seen in a cross-section of the medulla? (4)
- CN V - spinal nucleus/tract of trigeminal
- CN VIII - vestibular
- CN X - vagus
- CN XII - hypoglossal
what symptoms are associated with medial medullary syndrome? (3)
- corticospinal tract —> contralateral hemiparesis
- medial lemniscus —> contralateral loss of prop/vibr
- CN XII (hypoglossal) —> flaccid paralysis tongue, deviating towards lesion (“licking the lesion”)
what type of stroke (location) would cause a medial medullary syndrome?
anterior spinal artery stroke
- corticospinal tract —> contralateral hemiparesis
- medial lemniscus —> contralateral loss of prop/vibr
- CN XII (hypoglossal) —> flaccid paralysis tongue, deviating towards lesion (“licking the lesion”)
Pt presents to the ED with muscle weakness and loss of sensation on their right side. The tongue is noted to deviate towards the left. Where is the stroke?
anterior spinal artery stroke —> medial medullary syndrome
- corticospinal tract —> contralateral hemiparesis
- medial lemniscus —> contralateral loss of prop/vibr
- CN XII (hypoglossal) —> flaccid paralysis tongue, deviating towards lesion (“licking the lesion”)
what symptoms are associated with lateral medullary syndrome, aka Wallenberg’s Syndrome? (5)
- CN VIII —> nystagmus, vertigo, N/V
- sympathetic tract —> ipsilateral Horner’s
- spinothalamic tract —> contralateral loss of pain/temp
- CN V spinal nucleus —> ipsilateral loss of facial pain/temp
- nucleus ambiguus (CN IX, X) —> hoarseness, dysphagia - helps differentiate from lateral pontine syndrome
Wallenberg Syndrome
aka lateral medullary syndrome
- CN VIII —> nystagmus, vertigo, N/V
- sympathetic tract —> ipsilateral Horner’s
- spinothalamic tract —> contralateral loss of pain/temp
- CN V spinal nucleus —> ipsilateral loss of facial pain/temp
- nucleus ambiguus (CN IX, X) —> hoarseness, dysphagia - helps differentiate from lateral pontine syndrome
how can lateral medullary syndrome be differentiated from lateral pontine syndrome?
lateral pontine: CN VIII, spinothalamic, CN V spinal nucleus, sympathetic tract, CN VII (facial droop)
lateral medullary syndrome: CN VIII, sympathetic tract, spinothalamic tract, CN V spinal nucleus, nucleus ambiguus (CN IX, X - hoarseness and dysphagia)
what is the usual cause of lateral medullary syndrome, aka Wallenberg’s Syndrome?
PICA (posterior inferior cerebellar artery) stroke
- CN VIII —> nystagmus, vertigo, N/V
- sympathetic tract —> ipsilateral Horner’s
- spinothalamic tract —> contralateral loss of pain/temp
- CN V spinal nucleus —> ipsilateral loss of facial pain/temp
- nucleus ambiguus (CN IX, X) —> hoarseness, dysphagia - helps differentiate from lateral pontine syndrome
Pt presents to ED with contralateral loss of sensation to the body, ipsilateral loss of sensation to the face, vertigo, and hoarseness. Where is the stroke?
PICA (posterior inferior cerebellar artery) stroke —> lateral medullary syndrome, aka Wallenberg’s syndrome
- CN VIII —> nystagmus, vertigo, N/V
- sympathetic tract —> ipsilateral Horner’s
- spinothalamic tract —> contralateral loss of pain/temp
- CN V spinal nucleus —> ipsilateral loss of facial pain/temp
- nucleus ambiguus (CN IX, X) —> hoarseness, dysphagia - helps differentiate from lateral pontine syndrome
what is the rule of 4’s for determining the location of brainstem vascular syndromes?
4 CNs in the medulla, pons, and above the pons
4 CNs divide into 12, and these are all found in the midline - CN III (3), IV (4), VI (4), and XII (12)
4 CNs do NOT divide into 12, and these are all lateral - CN V (5), VII (7), IX (9), and XI (11)
4 Midline columns start with M - Motor nucleus, Motor pathway, MLF, Medial lemniscus
4 lateral (Side) columns start with S - Sympathetic, Spinothalamic, Sensory, Spinocerebellar
which 4 cranial nerves are above the pons and can be used to localize a lesion to the brain stem using the rule of 4’s?
CN1 (olfactory) and CN2 (optic) - not in midbrain
occulomotor (CN3) —> eye turned out and down
trochlear (CN4) —> eye unable to look down when looking towards nose
which 4 cranial nerves are in the pons and can be used to localize a lesion to the brain stem using the rule of 4’s?
trigeminal (CN5) —> ipsilateral facial sensory loss … don’t use to localize to pons (long, stretches through pons and medulla), but use to localize to lateral tract
abducens (CN6) —> ipsilateral eye abduction (lateral) weakness
facial (CN7) —> ipsilateral facial weakness/ droop
auditory (CN8) —> ipsilateral deafness (don’t use vestibular symptoms, bc these can be from pons or medulla)
which 4 cranial nerves are in the medulla and can be used to localize a lesion to the brain stem using the rule of 4’s?
glossopharyngeal (CN9) —> ipsilateral pharyngeal sensory loss
vagus (CN10) —> ipsilateral palatal weakness
spinal accessory (CN11) —> ipsilateral shoulder weakness
hypoglossal (CN12) —> ipsilateral tongue weakness
what are the symptoms to look out for in a midline structure brainstem lesion, based off the rule of 4’s?
structures that are Midline:
Motor pathway (corticospinal) —> contralateral weakness
Medial lemniscus —> contralateral loss of prop/vibr
Medial longitudinal fasciculus —> ipsilateral intranuclear opthalmaplegia
Motor nucleus/nerve —> ipsilateral CN motor loss of those dividable by 12 (CN 3, 4, 6, 12)
what are the symptoms to look out for in a lateral structure brainstem lesion, based off the rule of 4’s?
structures that are on the Side:
Spinocerebellar pathway —> ipsilateral ataxia
Spinothalamic —> contralateral loss of pain/temp
Sensory nucleus of CN5 —> ipsilateral loss of facial pain/temp
Sympathetic pathway —> ipsilateral Horner’s syndrome
where is the lesion?
- weakness of left side
- no speech difficulty
- facial muscles move normally
- no opthalmoplegia
- tongue deviated towards the right
- loss of vibration on left side
[hint, use rule of 4’s!]
Midline tract lesion bc of loss of Movement pathway (corticospinal) and Medial lemniscus (vibr/prop)
hypoglossal (CN12) lesion (tongue) - must be right sided because tongue licks the lesion
… so lesion is in right medial medulla
This would be caused by stroke of anterior spinal artery
strokes of which arteries are responsible for lateral vs medial symptoms at the level of the midbrain, pons, and medulla?
midbrain: lateral & medial both supplied by posterior cerebral artery (PCA)
pons: lateral supplied by AICA (anterior inferior cerebral artery); medial supplied by basilar
medulla: lateral supplied by PICA (posterior inferior cerebral artery); medial supplied by ASA (anterior spinal artery)
if there is a facial nerve (CN VII) lesion, where is the stroke most likely?
CN VII is in the lateral pons - supplied by AICA (anterior inferior cerebral artery)
if there is an abducens nerve (CN VI) lesion, where is the stroke most likely?
CN VI is in medial pons - supplied by basilar artery
if there is an oculomotor nerve (CN III) lesion, where is the stroke most likely?
CN III is in medial midbrain - supplied by PCA (posterior cerebral artery)
[note PCA supplies both medial and lateral midbrain]
if there is a hypoglossal nerve (CN XII) lesion, where is the stroke most likely?
CN XII is in medial medulla - supplied by ASA (anterior spinal artery)
if there is an accessory nerve (CN XI) lesion, where is the stroke most likely?
CN XI is in lateral medulla - supplied by PICA (posterior inferior cerebral artery)
hemiplegia + CN III palsy =
Weber’s syndrome: stroke of branches of PCA (posterior cerebral artery)
Medial (Movement - corticospinal) midbrain (CNIII) lesion
where is the lesion?
- unable to complete left handed finger to nose test
- left eyelid droop, small pupil
- loss of pain/temp in right side
- hoarse voice
- loss of gag reflex in left throat
- palate raised on right side
- unable to complete left handed finger to nose test = left ataxia (spinocerebellar)
- left eyelid droop, small pupil = left CN V
- loss of pain/temp in right side = left Horner’s (sympathetic)
- hoarse voice = CN X
- loss of gag reflex in left throat = CN IX
- palate raised on right side = CN X
Sympathetic is on the Side, and CN IX, X are in medulla
… so lesion is in left lateral medulla, caused by stroke in left PICA = Wallenberg’s syndrome
where is the lesion?
- R deafness/tinnitus
- loss of R finger to nose
- R facial numbness
- no corneal reflex
- R facial spasms
- R deafness/tinnitus = CN VIII
- loss of R finger to nose = spinocerebellar
- R facial numbness = sensory
- no corneal reflex = CN V
- R facial spasms = CN VII
Spinocerebellar is on the Side, and hearing loss from CN VIII is in pons + CN VII is in pons
… so lesion is in right lateral pons = cerebellopontine angle syndrome, often caused by tumors (schwannomas)
which cranial nerves are found at the level of the midbrain, pons, and medulla, respectively?
midbrain: CN III, IV
pons: CN V, VI, VII, VIII
medulla: CN IX, X, XI, XII
what are the general functions carried out by the midbrain, pons, and medulla, respectively?
midbrain: projections to cortex (significant for movement and reward) + visual reflexes, motor control
pons: large pathway into cerebellum + related nuclei (balance, sound localization, eye movement, coordination)
medulla: regulation of physiological homeostasis (HR, respiration, vasomotor tone, gastric secretions) + related reflexes (vomiting, coughing, sneezing, swallowing, gagging)
what is the function of the rostral vs caudal part of the brainstem reticular formation?
reticular formation: net-like structure through entire core of brainstem, contains nuclei + projections to cortex controlling autonomic function/reflexes
rostral (reticular activating system) part (upper pons, midbrain) - controls alertness and consciousness
caudal part - controls cranial nerve and spinal motor and autonomic functions
lesions to the _____ of the brainstem lead to changes in consciousness, coma, delirium, lethargy, stupor, and/or obtundation
this area contains projections controlling attention, arousal, sleep, and wakefulness
reticular activating system (rostral part of brainstem reticular formation)
where/how does the placement of the medial lemniscus pathway shift?
shifts from medial to lateral climbing from caudal to rostral pons
Claude Syndrome affects what part of the brainstem? (specifically)
lesion to red nucleus in the midbrain —> contralateral tremor and ataxia
Benedikt Syndrome = _____ syndrome + _____ syndrome
explain
Benedikt Syndrome = Weber syndrome + Claude syndrome
Weber syndrome: lesion to CN III, corticospinal + corticobulbar tracts
Claude syndrome: lesion to Red nucleus
what are the 3 distinct processes of consciousness, and what brain structures control each of these?
Consciousness consists of three distinct processes:
1. Alertness – depends on Ascending Reticular Activating System
2. Attention – depends on monoamines, especially norepinephrine
3. Awareness – depends on cerebral cortex
locked-in syndrome is caused by a lesion in which part of the brainstem?
locked-in syndrome is caused by a pontine lesion, loss of:
—> corticospinal and corticobulbar
—> PPRF and CN VI (loss of horizontal eye movement)
vertical eye movements can be spared
