Vestibulochochlear function/vestibular syndromes Flashcards
1
Q
Objectives (5)
A
- Recognize signs of vestibular dysfunction
- Recognize signs of cerebellar dysfunction
- List comp of Horner’s syndrome
- Differentiate peripheral from central vestibular lesions
- List differential diagnosis for central and peripheral vestibular disorders
2
Q
Vestibular fxn (4)
A
- Maintenance of posture and balance: head and body
- Fxns intimately with cerebellum
- Peripheral or central
- Neuroanatomic localization is critical to dx and px
3
Q
Vestibulocochlear neurons (4)
A
- Purely sensory n.
- Hair cells stereocilia that transform mechanical deformation into neural signals
- Transduction in organ of corti
- OoC houses hair cells for hearing
4
Q
Clinical eval precocial/altricial
A
Precocial 1. Chicken, sheep, cattle, horses 2. born with fully formed brains, functional hearing Altricial 1. Humans, monkeys, dogs, cats 2. Ear canals dogs/cats open ~ 2nd week 3. Complete maturation ~6-8 weeks
5
Q
Conductive deafness (5)
A
- Failure of conduction of sound waves from ear canal to inner ear
- Occlusion, cong/acquired
- Rupture of tympanic mem
- Fluid exudate, for bod, mass
- Age: presbucusis - ossicles
6
Q
Sensorial deafness (4)
A
- Alterations of neural structures of aud path
- Congenital - hair cells of OoC
- Acquired - inf, IC dz
- Baer test
7
Q
Congenital deafness
A
- Don’t breed uni or bilat affected (heriditary)
- White coat, blue eyes
- dalmations
8
Q
Vestibular Labyrinth and semicircular ducts:
Receptor: macula (3)
A
- Detect static or kinetic position
- Gravity and linear acceleration
- Otholitic membrane contains otoliths (statoconia)
* gravity one with stones
9
Q
Vestibular Labyrinth and semicircular ducts:
Receptor: Crista ampullaris (3)
A
- 3 in semicircular canal
- 90 degrees to each other
- Detect angular movements of the head
* this is the one with water
10
Q
CN VIII entry into skull (3)
A
- Axons enter cranial vault thru internal acoustic meatus at cerebellomedullary angel
- rostral medulla oblongata - Most axons synapse on CN VIII nuclei
- Few axons bypass CN VIII nuclei to enter the cerebellum
11
Q
Vestibular Nuclei (4)
A
- HUGE
- Four on each side of the brainstem: ventrolateral wall of 4th ventrical
- Axonal projections spinal cord: vestibulospinal tracts
- limb extensor tone (anti-gravity) - Axonal projections Rostrally: Medial Longitudinal Fasciculus (MLF)
- Ocular movements (CNN III/IV/VI)
- Head movements
12
Q
Vestibulospinal tracts (4)
A
- Lateral vestibulospinal tract - ipsilateral ventral funiculus
- Synapse on interneurons in spinal cord ventral gray
- mediate facilitation of extensor muscles and inhibition of flexor muscles
- IPSILATERAL SIDE
13
Q
Medial Longitudinal fasciculus (MLF)
A
- Rostral projections
- to nuclei of CN III, IV and VI
- responsible for oculocephalic reflex - Caudal projections
- medial vestibulospinal tract
- maintain body and limb position relative to head
14
Q
Extra ocular muscle innervation (3)
A
- CN III: oculomotor
- dorsal, medial and ventral recti mm. - CN IV: Trochlear n.
- dorsal oblique m.
- On opposite side - CN VI: Abducent n.
- Lateral rectus & retractor bulbi mm.
15
Q
Eye position: strabismus (5)
A
- abnormal
- ocular?
- Vestibular? - usually
- Congenital
- Mechanical
16
Q
Physiologic nystagmus (4)
A
- moves eye to hold images during head rotation or target motion
- Receptor: ear and CN VIII
- MLF connects VIII to III/IV/VI
- Bilateral, opposite effects on CN III, IV, VI
17
Q
Physiologic Nystagmus can test integrity of
A
Brainstem
-WORKS BILATERALLY
18
Q
Vomiting Center (2)
A
- In reticular formation of medulla (brainstem)
2. Receives afferent input from vestibular portion of vestibulocochlear nerve - motion sickness
19
Q
Cerebral projections (2)
A
- Synapses in thalamus (tells you you’re off balance)
2. Provides conscious awareness of body’s position in space
20
Q
Vestibular inputs are…
-ipsilateral/contralateral facilitation
A
- Bilateral and tonic
- If you excite one side
- Ipsilateral facilitation of extensors
- contralateral facilitation of flexors
21
Q
Fall/or pushed towards
A
affected side by the normal side
22
Q
Clinical signs (7)
A
- head tilt towrads
- circling, leaning, falling, rolling towards
- Unilateral or asymmetric ataxia towards
- Strabismus
- Nystagmus, FP away
- nausea
- +/- postural reaction deficits
23
Q
Pendular Nystagmus
A
weird siamese thing
24
Q
Peripheral lesions are in
A
Ear: Canal, bulla, CN VIII
25
Central lesions are in
1. Brainstem or cerebellum
2. Paradoxical
* Isolate clinical signs that involve only one
26
Vestibular lesion loc. (6)
| Peripheral CS
1. NO CP deficits
2. Normal mentation
3. Head tilt towards
4. Only deficits in CN VII or VIII
5. Strabismus
6. Nystagmus - any direction
- fast phase away (I think)
27
Vestibular lesion loc (6)
| Central CS
1. CP deficits
2. Dullness/stupor
3. Head tilt
4. Other CN deficits possible
5. Strabismus
6. Nystagmus
- any direction
- positional, vertical
- dysconjugate nystagmus - ALWAYS CENTRAL
28
Vestibular lesion loc (3)
| Pheripheral CS
1. Head tilt/ataxia, nystagmus
2. CN VII: facial n - innocent bystander
3. Horner's syndrome
29
Horner's syndrome (2)
1. Sympathetic dysfunction
| 2. Ptosis, enophthalmos, protruding nictitans
30
Peripheral vestibular dzs/TX
Idiopathic
Otitis media/interna
Neoplasia
Idiopathic
1. old dog (> 10yrs old, often large breed)
2. Severe head tilt and rapid nystagmus, non amb/gator rolling
3. anti-naus, anti-anx, IV fluids, +/- seds, Time, good px
Otitis media/interna
Otitis
1. Bacterial, polyp, PSOM (king charles thing)
2. long term Antibiotics (system), dermatologist, good px
Neoplasia
1. Ear canal AdenoCA
2. SCC
3. PX gaurded
31
Bilateral Peripheral Vestbular (5)
1. Lost BOTH left and right receptors
2. Loss of physiologic nystagmus
3. Symmetrical ataxia, truncal sway
4. Wide based and crouched
5. Usually bilateral otitis or polyps
32
Central vestibular about (5)
1. CN deficits other than CN VII & VIII
2. Mentation changes
- Ascending Reticular Activating System
3. Proprioceptive deficits
- these pathways don't go thru peripheral system
4. Paresis
- motor tracts transverse brainstem
5. Cerebellar and forebrain signs
33
```
Central vestibular (2)
Inflammatory
```
1. GME - likes caudal fossa
2. Variable prog
- response to tx
- immunosuppressive corticosteroids
- immune modulation (be careful of little things that may aspirate) CsA, Cytosar, CCNU, procarbazine, leflonumide
34
```
Central vestibular (3)
Otogenic intracranial infection
```
1. OMI penetrates cranial vault
2. Central vestibular signs
3. good prog with teatment
- sx: TECA/BO/VBO
- long-term antibiotics
- anti-Inflammatory corticosteroids
35
Central vestibular dz (7)
| Neoplasia
1. Not surgically accesible
2. RT
3. Meningioma
4. Choroid plexus tumors
- other glial tumors
5. CN VIII tumor
6. Cerebellar tumors pushing down
7. Skull tumors
36
Central Vestibular dz
| Vascular
1. Vascular-esp cerebellum
2. Rostral cerebellar artery
- supplies part of brainstem
- So, CP deficits
3. Good prognosis
- suportive care
- ID and treat underlying dz
37
Cerebellar syndrome
1. Cerebellum is inhibitory, modulatory
2. Defecits are spastic - hypermetria, ataxia, intention tremors
3. IPSILATERAL SIGNS
38
White shaker syndrome
1. Idiopathic tremors
2. Acquired action-related repetitive myoclonus
3. Idiopathic cerebellitis
4. Steroid responsive tremor syndrome
39
```
White shakes
Breed
CS
NE
CSF
```
```
Breed
1. young, often white, small breed dogs
-maltese, westie
CS
1. fine tremors in limbs, head, eyes
NE
1. normal
2. menace
3. Opsoclonus (weird eye rhythms
4. ataxia
5. hypermetria
CSF
1. Normal to mild lymphocytic pleocytosis
```
40
White shakers
DXs
Therapy
1. MRI, progression - hyperthermia...?!?!?!
2. Therapy: Corticosteroids, Diazepam, Beta blockers
3. Good prognosis, some relapse
41
Paradoxical vestibular syndrome (4)
1. LESION SAME SIDE AS CP DEFICITS
2. Head tilt away from lesion
3. Fast phase nystagmus may be towards
4. ALWAYS CENTRAL
42
Paradoxical vestibular syndrome
| DDX
1. Neoplasia
- choroid plexus tumor at the CPA
- meningioma
2. Inflammatory dz
3. Vascular event
