Lecture 10: Vestibular Systems & Cerebellum Flashcards
(94 cards)
1
Q
Functions of the cerebellum are entirely _______ and it operates at a ____________ level
A
Motor; unconscious
**Controls balance, influences posture and muscle tone, and coordinates movements
2
Q
The laterally located hemispheres of the cerebellum are joined in the midline by the __________. The _____________ fissure separates the small anterior lobe from the larger posterior lobe. The ________________ fissure defines the flocculus and vermis, together they form the _________________ lobe
A
Vermis; deep primary fissure; posterolateral fissure; flocculonodular lobe
3
Q
What does the inferior cerebellar peduncle convey?
A
Afferents to the cerebellum from the SC and brainstem
4
Q
What do the juxtarestiform body (wall of the 4th ventricle) and the restiform body contain?
A
Juxtarestiform body = reciprocal fibers between the cerebellum and vestibular structures
Restiform body = fibers arising in SC or medulla
5
Q
What is the middle cerebellar peduncle composed of?
A
Afferents to the cerebellum from the contralateral pontine nuclei
6
Q
What does the superior cerebellar penduncle contain?
A
Predominately efferent fibers form cerebellar nuclei
- Distributed to diencephalon and brainstem
7
Q
What are the outputs/efferents of the cerebellum?
A
Deep cerebellar nuclei
8
Q
What are mossy fibers?
A
Cerebellar afferent axons that originate from cerebellar nuclei and other nuclei in the SC, medulla and pons
- branch profusely in granular layer and contact other cells at irregular intervals -> mossy fiber rosette
- Excitatory to granule cell and golgi cell dendrites
9
Q
What are climbing fibers of the cerebellar cortex?
A
Arise from inferior olicary nuclei -> olivaocerebellar fibers send collaterals to appropriate cerebellar nucleus, they terminate in molecular layer purkinje dendrites, each purkinje cell is innervated by a singe climbing fiber
10
Q
Explain multilayered (monoaminergic) fibers to the cerebellar cortex
A
Locus ceruleus, raphe nuclei and hypothalamus enter cerebellum via cerebellar peduncles and send collaterals to cerebellar nuclei. Axons branch diffusely and terminate in molecular and granular layers influencing all major cell types decreasing spontaneous discharge rates and altering responsiveness of purkinje cells
11
Q
What does the pontocerebellum comprise and what is its function?
A
Cerebellar hemisphere and dentate nuclei; muscle coordination and speed/force/trajectory of movements
12
Q
What does the vestibulocerebellum comprise and what is its function?
A
OLDEST! Flocculonodular lobe and fastigial nuclei; maintenance of balance and equilibrium
13
Q
What does the spinocerebellum comprise and what is its function?
A
Vermis and surrounding area with globose and emboliform nuclei; muscle tone and posture
14
Q
Explain the efferent output from the vestibulocerebellum
A
Cortical efferent fibers -> fastigial nucleus* -> vestibular nuclei -> reticular formation
**Portion of fastigial efferents are contralateral; LMN output is bilateral
15
Q
Explain the efferents for limb musculature of the spinocerebellum
A
Globose & emboliform nuclei* -> superior cerebellar peduncle -> red thalamus and nucleus
16
Q
Explain the efferents for axial musculature from the spinocerebellum
A
Vermal cortex & fastigial efferents* -> vestibular and reticular nuclei
17
Q
Explain the efferents from the pontocerebellum
A
Dentate nucleus -> contralateral red nucleus and ventral lateral nucleus of the thalamus via superior cerebellar peduncle -> VLN of thalamus to motor cortex
18
Q
What is the function of the medial longitudinal fasciculus?
A
Its the critical link between vestibular influences and horizontal gaze
**Eyes turn to side of stimulus
19
Q
Where do fibers of the medial longitudinal fasciculus decussate?
A
Lower pons
20
Q
What does the medial vestibulospinal tract influence?
A
The muscles of the neck, upper back and proximal upper limbs -> MVST is a key link in coordinating the positioning of the head relative to eye movements
**Head turns to side of stimulus
21
Q
What does the lateral vestibulospinal tract facilitate?
A
Positioning of the body relative to head position and gaze -> facilitates the extensor tone and reflexes of the antigravity axial and appendicular musculature
**Body turns to side of stimulus
22
Q
The vestibular nuclei have strong, bilateral projections into the reticular formation. How do these connections affect the somatic motor system?
A
They provide a mechanism for the visceral autonomic disturbances -> pallor, nausea, vertigo, vomiting, etc
23
Q
***The vestibular nerve has direct connections to which of the following? A. Dentate nucleus B. Flocculonodular lobe C. Paramedian pontine RF D. Abducens nerve
A
B. Flocculonodular lobe
24
Q
***The secondary connection from the vestibular nuclei controlling head position is which of the following? A. LVST B. MVST C. MLF D. Lateral reticulospinal tract
A
C. Medial longitudinal fasciculus
Eyes turn, head turns, body turns, vomit
25
What is a Doll’s eyes maneuver?
IN the unconscious pt WITHOUT cervical injury, side-to-side movement of the head should result in horizontal movement of the eyes in the opposite direction
26
What is a normal Doll’s eyes maneuver finding?
Head turns left with horizontal gaze to the right or vice versa
27
What doll’s eyes maneuver is indicative of left VI palsy?
Head turns right and right eye adducts (normal) but left eye stays neutral (should abduct) of vice versa
**lateral rectus paralysis
28
What doll’s eyes maneuver is indicative of right oculomotor palsy?
Head turns right and right eye stays neutral (should adduct) and left eye abducts (normal)
**Medial rectus paralysis
29
What dolls eyes maneuver is indicative of possible midbrain damage?
Head turns and no eye response -> neutral gaze
30
What is an oculocaloric test/how are the results interpreted?
In a conscious pt, cold water irrigation in external auditory meatus causes horizontal nystagmus to opposite side & warm water irrigation results in nystagmus to the same side
In an unconscious pt, injection of cold water results in horizontal gaze toward the same side of stimulus
**If the eyes dont respond to caloric testing, the pts brainstem reflexes are significantly impaired and there is increasing mortality
31
Explain the physiology behind the oculocaloric testing results of ice water being injected in the external auditory meatus of an unconscious pt
The injected water creates a convection current in the endolymph of the lateral semicircular duct, which is oriented in the horizontal plane at 30 degrees head flexion -> in pts with an intact brainstem, ice water testing causes the eyes to turn toward the stimulus and they show horizontal nystagmus to the non-stimulated ear
**nystagmus is named according to the fast component**
32
What is a normal finding of ice water caloric testing of right ear?
Right eye abducts and left eye adducts -> horizontal gaze to right
33
What ice water caloric testing finding of the right ear would be indicative of left III nerve palsy?
Right eye abducts and left eye has no response (should adduct)
34
What finding of ice water caloric testing of the right ear would be indicative of right VI nerve palsy?
Right eye has no response (should abduct) and left eye adducts (normal)
35
What finding of caloric ice water testing of the right ear woud be indicative of Left III and Right VI nerve palsies or possible midbrain damage (deep coma state)
No response in either eye (right eye should abduct and left eye should adduct)
36
***Analyze the following results of an oculocaloric test using ice water: irrigation of right ear resulted in no abduction of R eye and adduction of L eye. Irrigation in left ear resulted in no abduction of L eye and adduction of R eye. What do these findings indicate?
Bilateral abducens nerve palsy
37
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**After completing an oculocaloric test and concluding the pt has bilateral abducens nerve palsy, which of the following should you suspect?
A. Traumatic myelopathy
B. Increased intracranial pressure
C. Papiledema
D. Focal lesion
E. Poor prognosis
```
B. Increased intracranial pressure -> need to check for this because the abducens nerve is vulnerable to compression at the petrous portion of the temporal bone so this could be the cause of the palsy
38
Nystagmus is described according to the ________ component, which is directed ___________ the side of the lesion
Fast component; toward side of lesion
39
For vertigo, generally the dizziness is on the ____________ side as the lesion
Contralateral
**same as the slow component of the nystagmus
40
Postural impairment is assessed using the ___________ test. The normal function of the _______________ columns, ____________ system and ___________ is necessary to maintain balance while standing
Posterior columns (proprioception), vestibular system, and vision
41
How is a Romberg performed and how are the results interpreted?
Pt stands with feet together and closes eyes for one minute. -> if standing pt with his eyes closed sways or falls during test its positive and a type of sensory ataxia. Pt tends to fall toward the side of the lesion
42
If a pt is ataxic and the Romberg test is normal, what is this indicative of?
Cerebellar ataxia -> midline lesions of the cerebellum, especially the nodules cause truncal ataxia and postural imbalance
43
Unilateral lesions of the vestibular system cause signs and symptoms on the ____________ side of the lesion
Ipsilateral
44
Lesions of the MLF result in a characteristic disturbance of horizontal gaze referred to as _________________________
Internucear ophthalmoplegia (INO, syndrome of the MLF)
45
Pts with an internuclear ophthalmoplegia have an abnormal response to horizontal gaze in the direction of the ___________ side of the lesion
Contralateral
46
Do pts with internuclear ophthalmoplegia (INO) exhibit convergence on accommodation? Why or why not?
Yes bc the corticotectal fibers dont use the MLF pathway and MLF is where the lesion is that causes INO
47
How is an internuclear ophthalmoplegia (INO) named?
According to the side of oculomotor impairment. The MLF lesion is ipsilateral to the non-adducting eye
Ex. When attempting horizontal gaze to the left, the right eye doesn’t adduct and the left eye exhibits nystagmus then this is a right INO due to a lesion of the right MLF
48
**Interpret the results of a horizontal gaze test: horizontal gaze to the right is normal but gaze to the left shows no adduction of right eye and nystagmus of left eye. Name this condition
Right INO -> named for side of non-adducting eye
49
Name the condition: horizontal gaze to the left is normal. Faze to the right shows no adduction of the left eye and nystagmus of the right eye.
Left INO -> named for the side of the non-adducting eye
50
T/F: Accommodation does not use the MLF and is unaffected by INO
True! -> the corticotectal fibers directly descend from the frontal eye field to the oculomotor and edinger-Westphalia nuclei
51
The paramedian pontine reticular formation (PPRF) sends fibers to the ___________ nucleus of the same side for influencing the ipsilateral ________________ m. The PPRF also projects fibers thorugh the contralateral MLF to the contralateral ________________ nucleus that innervates the ________________ m.
Abducens nerve; ipsilateral lateral rectus; contralateral occulomotor n; medial rectus
52
What does a unilateral lesion of the paramedian pontine reticular formation result in?
Paresis or paralysis of horizontal gaze toward the same side of the lesion and a gaze preference away from the lesion -> this deficit is due to the destruction of fibers that course from the PPRF to the ipsilateral abducens nucleus and contralateral oculomotor nucleus
Ex. Lesion of Right PPRF results in pts inability to perform horizontal gaze to the right and their gaze preference is to the left
53
A unilateral lesion of the PPRF results in paresis or paralysis of horizontal gaze toward the ____________ side as the lesion and a gaze preference to the __________ side of the lesion
Paralysis of horizontal gaze toward side of lesion and gaze preference away from side of lesion
54
A lesion of the right PPRF results in paresis or paralysis of horizontal gaze to the _________ and gaze preference to the ________
Paralysis to the right and preference to the left
55
What is the big difference in symptoms between a lesion of the MLF (INO) and a lesion of the PPRF?
Lesion of the MLF has nystagmus associated with it
56
**A pts horizontal gaze to the left was normal. Horizontal gaze to the right showed no adduction of the left eye and horizontal nystagmus to the right eye. These findings indicate involvement of which of the following?
A. Paramedian pontine reticular formation
B. Medial longitudinal fasciculus
C. Abducens N
D. Occulomotor N
E. Optic N
B. MLF
**Lesions in PPRF arent associated with nystagmus
57
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**A pts horizontal gaze to the left was normal. Horizontal gaze to the right showed no adduction of the left eye and horizontal nystagmus to the right eye. These findings indicate a lesion on the:
A. Left
B. Right
C. Left PPRF
D. Unknown
```
A. Left
This is an INO and INO’s are named for the side of the non-adducting eye
58
**A pts horizontal gaze to the left was normal. Horizontal gaze to the right showed no adduction of the left eye and horizontal nystagmus to the right eye. What is this horizontal gaze finding called?
Left internuclear ophthalmoplegia (INO)
**This is a lesion of the MLF; named for the non-adducting eye**
59
***A neuro exam shows paralysis of horizontal gaze to the left and right. These findings indicate involvement of which of the following?
A. Abducens N
B. Medial longitudinal fasciculus
C. Oculomotor N
D. Paramedian pontine reticular formation
D. Paramedian pontine reticular formation
**No nystagmus involved so not an INO
60
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***A neuro exam shows paralysis of horizontal gaze to the left and right. These findings indicate a lesion on the:
A. Right
B. Left
C. Bilateral
D. Unknown
```
C. Bilateral
**This is a lesion of the PPRF (not MLF, no nystagmus)
61
What is the results of a bilateral lesion of the paramedian pontine reticular formation?
Paralysis of horizontal gaze to the right and left
62
All information entering the cerebellar cortex eventually converges upon the ___________ cells. The axons of these cells are the only efferents from the cerebellar cortex and most of them terminate in the deep cerebellar nuclei
Purkinje cells
63
Unilateral lesions of the cerebellum usually result in deficits on the __________ side of the lesion and midline lesions of the vermis often affect the ___________ musculature
Ipsilateral; axial
64
What are signs and symptoms of lesions of the cerebellum?
Ataxia (broad-based, staggering gait)
Dysmetria (cant touch fingertip to nose)
Dysdiadochokinesia (cant do rapid alternating movements)
Slurred or scanning speech
Rebound phenomenon (inability of opposing muscles to stop an action)
Hypotonia & hyporeflexia
Asthenia (weakness of limb or axial musculature)
Nystagmus
65
An intention tremor present with other signs and symptoms of a lesion to the cerebellum is indicative of lesions involving what 2 structures?
Superior cerebellar peduncle or dentate nucleus
66
What is the dentate nucleus mostly responsible for?
Planning and execution of fine movements
67
How does chronic ingestion of ethanol affect the cerebellum?
May cause cortical atrophy of the anterior lobe and in some cases of the posterior lobe (neocerebellum) and dentate nucleus
In later stages, pt presents with severe ataxia of LE and trunk and a relatively minor involvement of UE
- This disease may be seen in conjunction with conditions such as Korsakoff’s syndrome
68
What is Friedreich’s ataxia?
Autosomal recessive degenerative disease of adolescence and early adulthood involving a progressive neuronal necrosis and resultant demyelination of the proprioceptive neurons in the dorsal roots, post columns, medial lemniscus, and the spinocerebellar and corticospinal tracts
Also degeneration of purkinje cells, dentate nucleus and superior cerebellar peduncles
69
What is the corpus medullares?
Comprises the central core of white matter in the cerebellum
Composed of dense bundles of afferent and efferent fibers interconnecting the cerebellar peduncles, cerebellar nuclei and cerebellar cortex
70
Which of the 4 deep cerebellar nuclei is the most medial?
Fastigial nucleus
71
What deep cerebellar nuclei gives rise to the vast majority of efferents from the neocerebellum (post lobe)?
Dentate nucleus
72
The dentate nucleus s a large, convoluted cup-shaped nucleus that gives rise to the vast majority of the efferents from the neocerebellum. These efferents, along with those from the ____________ and ___________ deep cerebellar nuclei project to the ______________, ___________________, _________________ and _______________
globose and emboliform; red nucleus, ventral lateral nucleus of thalamus, brainstem of tegmentum and reticular formation
73
Where do most of the efferents in the superior cerebellar peduncle originate?
Dentate nucleus -> associated pathways are described collectively as dentato-
Ex. Dentato-rubral tract refers to fibers originating in the dentate, emboliform or lateral globose and terminating in the red nucleus
74
What type of information is conveyed by the dorsal spinocerebellar tract?
Unconscious, precise proprioceptive info from the lower 1/2 of the body and LE to the cerebellum
75
What type of information is conveyed by direct arcuate fibers/cuneocerebellar tract?
Unconscious, precise propriocetive info from the upper 1/2 of the body and UE
76
Where do the direct arcuate fibers (cuneocerebellar tract) originate and terminate?
Originate in the accessory cuneate nucleus and terminate in the vermis
77
Where does the dorsal spinocerebellar tract originate and terminate?
Originates in the nucleus dorsalis (C8-L1), courses thorugh the ipsilateral inferior cerebellar peduncle and terminates in the anterior vermis of the cerebellum
78
What type of information does the trigeminocerebellar tract convey?
General proprioceptive and exteroceptive info from the head
**This is one of 2 unconscious sensory tracts from the face
79
Where does the trigeminocerebellar tract originate and terminate?
A moderate number of fibers from the subnuclei rostralis and interpolaris of the descending nucleus of V project to the anterior vermis as the trigeminocerebellar fibers
80
Where do olivocerebellar fibers originate and terminate?
This is a large bundle of afferent fibers that originate in the inferior olivary nucleus (ION) and terminate as climbing fibers in the contralateral cerebellar hemisphere
81
What is the role of the inferior olivary nucleus (ION)?
Its an important processing and relay center for sensory info from the SC and motor info from the reticular formation and extrapyramidal system
The ION receives direct input from the central tegmental fasciculus and the spino-olivary tract
82
What tract is the critical link between the extrapyramidal system and the cerebellum?
Central tegmental fasciculus
**Extrapyramidal system is responsible for movements such as unconsciously swinging your hands while you walk or facial expressions while you talk
83
Where does the central tegmental fasciculus originate?
In the red nucleus, central (periqueductal) gray and the midbrain tegmentum.
- is in the center of the tegmental reticular formation and consists of ascending and descending fibers from the medial group (motor) of reticular nuclei
84
What fibers form all of the middle cerebellar peduncle?
Pontocerebellar fibers
- This massive bundle of fibers originates in the pontine nucleus which comprise the bulk of the pons
85
What type of information does the ventral spinocerebellar tract convey?
Unconscious, general proprioceptive info from lumbosacral levels to the cerebellum
86
Where does the ventral spinocerebellar tract originate and terminate?
Originates from scattered neurons in base of dorsal horn and intermediate gray -> decussates in ant white commissure and ascends in arterial funiculus -> passes thorugh superior cerebellar peduncle and terminates in ant vermis of cerebellum
87
What type of info does the trigeminocerebellar tract convey?
Unconscious, precise tactile and proprioceptive info from head to cerebellum
88
Where does the trigeminocerebellar tract originate and terminate?
Arises from main sensory nucleus of V and projects to anterior vermis of cerebellum via superior cerebellar peduncle
89
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***Cerebellar cortical influences converge on which of the following?
A. Deep cerebellar nuclei
B. Granule cells
C. Parallel fibers
D. Stellate cells
E. Purkinje cells
```
E. Purkinje cells
90
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***A unilateral lesion of the right cerebellar lobe would result in which of the following?
A. Bilateral cerebellar deficits
B. Contralateral cerebellar deficits
C. Ipsilateral cerebellar deficits
D. No neurological deficits
```
C. Ipsilateral cerebellar deficits
91
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***Olivocerebellar fibers have a strong influence on which of the following?
A. Cerebellar glomerulus
B. Deep cerebellar nuclei
C. Granule cells
D. Parallel fibers
E. Purkinje cells
```
E. Purkinje cells
92
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***Unconcious precise proprioceptive info from the UE is conveyed by which of the following?
A. Dorsal spinocerebellar
B. Central tegmental fasciculus
C. Ventral spinocerebellar tract
D. Cuneocerebellar tract
E. Trigeminocerebellar tract
```
D. Cuneocerebellar tract
93
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***The efferent fibers in the superior cerebellar peduncle project to which of the following?
A. Ventral posterior lateral nucleus
B. Ventral posterior medial nucleus
C. Ventral anterior nucleus
D. Intralaminar nuclei
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C. Ventral anterior nucleus
94
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***The cerebral cortex influences the cerebellum via which of the following?
A. Pontocerebellar fibers
B. Corticopontine fibers
C. Olivocerebellar fibers
D. Corticobulbar fibers
E. Central tegmental fasciculus
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B. Corticopontine fibers
