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Y4 SA - Neurology > The vestibular system and hearing > Flashcards

The vestibular system and hearing Flashcards

1
Q

What are the functions of the vestibular system?

A
  • Maintain balance!
  • Maintain normal orientation relative to gravitational field
  • Maintain position of the eyes, neck, trunk and limbs relative to position and movement of the head at all times
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2
Q

Describe the peripheral vestibular system

A
  • Outside the brain
  • Receptors in the inner ear and vestibulocochlear nerve (CN8)
  • 3 ducts oriented at right angles to each other – rotation of head makes endolymph flow within one or more ducts
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3
Q

Describe the central vestibular system

A

Brainstem - 4 nuclei that receive information from nerves and pass on message to rest of brain and spinal cord
Cerebellum - Inhibits vestibular nuclei and keeps them under control

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4
Q

When vestibular disease is bilateral what is the most common cause?

A

Bilateral middle ear disease

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5
Q

What are the clinical signs of vestibular disease?

A
  • Ipsilateral head tilt (Towards the lesion )
  • If affects both sides, rather than the head tilt, you get a head sway…
  • Ataxia and wide-base stance
  • Leaning and falling
  • Less commonly tight circling
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6
Q

Describe a paradoxical head tilt, sometimes seen in vestibular disease?

A
  • Flocculonodular lobe or caudal cerebellar peduncle
  • Head tilt contralateral to lesion + some signs of cerebellar disease e.g. hypermetria
  • Head tilt is always towards the lesions unless it’s a cerebellar lesion
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7
Q

Describe the nystagmus seen in vestibular disease

A
  • Lesion on side of the slower phase…
  • Vertical suggest central lesion
  • Pendular nystagmus – same speed on both sides – due to a dysfunction in the visual pathways (more common in oriental cat breeds)
  • May be positional
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8
Q

What is positional strabismus?

A

If you lift the head up, on the abnormal side the eye will sink down

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9
Q

Describe the signs of central vestibular disease

A
  • Paresis possible
  • Proprioceptive deficits possible
  • Mentation may be affected
  • CNV-XII may be affected
  • Vertical, horizontal or rotational nystagmus
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10
Q

Describe the signs of peripheral vestibular disease

A

No paresis
No proprioceptive deficits
Alert mentation
CNVII may be affected
Horners possible
Horizontal or rotational nystagmus

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11
Q

Where is Horners sydrome most commonly localised?

A

Middle ear

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12
Q

List some causes of central vestibular disease

A
  • Head trauma
  • Metronidazole
  • Brain malformation
  • Hypothyroidism
  • Brain tumour
  • Thiamine deficiency
  • Cerebrovascular disease
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13
Q

List some causes of peripheral vestibular disease

A

Otitis media/internal
Trauma to middle/inner ear
Congenital vestibular disease
Hypothyroidism
Idiopathic vestibular disease
Middle ear neoplasia

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14
Q

What is cerebrovascular disease?

A

Abnormality caused by disruption of blood supply

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15
Q

What occurs as a clinical manifestation of cerebrovascular disease?

A

Stroke or Cerebrovascular Accident

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16
Q

What are the consequences of a stroke/ Cerebrovascular Accident?

A

Ischaemia - arterial or venous obstruction
Haemorrhagic - rupture of blood vessels

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17
Q

What are the clinical signs of cerebrovascular disease?

A

Clinical signs vary but acute and non- progressive; signs of central vestibular disease

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18
Q

How is cerebrovascular disease diagnosed?

A

MRI:
- Well-defined, sharply demarcated lesions with minimal to no mass effect
- Limited to the vascular territory of a main cerebral or perforating artery

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19
Q

List the common concurrent diseases seen with cerebrovascular disease?

A
  • Chronic kidney disease
  • Hypertension
  • Hyperadrenocorticism
  • Protein losing enteropathy
  • Neoplasia
  • Cardiac disease
  • Angiostrongylus vasorum
  • Diabetes mellitus, hypothyroidism
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20
Q

How is cerebrovascular disease treated?

A

Treatment – supportive or if underlying disease
Prognosis fair to good: 1/2 - 2/3 good outcome
Concurrent medical conditions:
- Shorter survival times
- More likely to have recurrence of strokes

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21
Q

MUO stands for?

A

Meningoencephalomyelitis of unknown origin

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22
Q

What is meningoencephalomyelitis of unknown origin?

A

Immune mediated brain diseases
Common in dogs
GME – Granulomatous ME
NME – Necrotising ME
NLE – Necrotising leukoencephalitis
Meningo (meninges) - encephalo (brain) – myelitis (spinal cord)

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23
Q

Which patients most commonly present with granulomatous meningoencephalomyelitis?

A

Young adults (3-8y), toy and terrier breeds

24
Q

What are the clinical signs of granulomatous meningoencephalomyelitis?

A
  • Often caudal fossa (vestibular and cerebellar) but anywhere
  • Can effect spinal cord (+/- brain)
  • May just cause acute blindness
25
How is granulomatous meningoencephalomyelitis diagnosed?
MRI: Multiple ill-defined hyperintensities on T2WI and FLAIR CSF analysis: Usually mononuclear pleocytsos
26
Which patients most commonly present with necrotising meningoencephalomyelitis?
Pug, Chihuahua, Yorkie, Maltese, Pekingese, Shih- Tzu, WHWT, Boston terrier, Miniature pinscher, French Bulldog…
27
What are the clinical signs of necrotising meningoencephalomyelitis?
Worse prognosis, areas of necrosis mostly in cerebral cortex often coalesce to form large areas of cavitation - Seizures, blindness, altered behaviour, circling, depression
28
How is meningoencephalomyelitis of unknown origin treated?
Immunosuppression: Corticosteroids High mortality Lifelong medication
29
What is a negative prognostic indicator for meningoencephalomyelitis of unknown origin?
Seizures and signs of raised ICP on MRI
30
What is a positive prognostic indicator for meningoencephalomyelitis of unknown origin?
Younger age and early diagnosis (within 7 days)
31
Are cats more likely to have immune mediated or inflammatory brain disease?
Inflammatory
32
What are the causes of CNS involvement in cats with FIP?
Lesions result from immune- complex-mediated vasculitis
33
List the neurological signs seen in cats with FIP
- Insidious signs, progressive, can be focal, diffuse or multifocal - More commonly localise to the cerebellomedullary region (tetraparesis, ataxia, nystagmus and loss of balance) - Occasionally only progressive spinal cord disease - Sometimes also behavioural changes, seizures +/- iritis, anterior uveitis, chorioretinitis
34
Why are neurological signs linked to FIP hard to diagnose?
Dry form of FIP
35
How is FIP diagnosed?
- Clinical signs: +/- ocular changes lymphopenia, neutrophilia, non-regenerative anaemia - Increased serum α-1-acid glycoprotein (AGP) - Very high serum titres of FCoV Ab - Albumin to globulin ratio <0.8g/dL - CSF (variable): usually high protein and pleocytosis (mononuclear or mixed)
36
How does FIP appear on MRI?
Periventricular contrast enhancement, ventricular dilation and hydrocephalus
37
How are neurological signs linked to hypothyroidism treated?
Reversible with supplementation of levothyroxine
38
Describe metronidazole toxicity
Uncommon; signs of CVS, seizures, tremors, rigidity Usually when doses ≥60mg/kg/day but lower doses have been reported
39
How does thiamine deficiency lead to CNS signs?
- Low amount in food; overcooked food cats - Fed with all-fish diet - Essential for complete oxidation of Glucose in Krebs cycle - Tissues dependent on glucose for energy (brain, heart) more affected - Anorexia, lethargy - Vestibular signs - Seizures - Reduced VOR, mydriasis with reduced PLR
40
What is the most common primary brain tumour?
Caudal fossa meningiomas
41
Which structures pass by the middle ear?
CN VII CN VIII Sympathetic supply to eye
42
What are the clinical signs of otitis media/interna?
Facial paralysis Peripheral vestibular signs Horner syndrome Pain opening the mouth
43
List the primary factors causing otitis media/interna
Hypersensitivity - atopic dermatitis, adverse cutaneous food reaction Keratinisation defects
44
List the predisposing factors for otitis media/interna
Conformation: hairy, narrow, pendulous Over cleaning Swimming/persistently wet
45
List the perpetuating factors for otitis media/interna
Progressive pathological change Infections
46
What is the most common cause of peripheral vestibular disease in dogs?
Idiopathic vestibular disease
47
How does Idiopathic vestibular disease present?
No central signs such as proprioceptive deficits, vertical nystagmus, multiple CNs affected, etc Acute onset of peripheral signs: - Rolling, falling, vomiting, ataxia - Head tilt - Nystagmus (horizontal or rotatory) - Commonly happens simultaneously with facial paralysis
48
How is Idiopathic vestibular disease diagnosed/treated?
Unknown aetiology; spontaneous recovery without any treatment Diagnosis of exclusion
49
How are patients with idiopathic vestibular disease monitored/managed?
No specific treatment, just symptomatic as required In general, patients may be nauseous: Ondansetron, Maropitant Stimulation is important - Do not keep quiet all the time - Take out slowly but ensure gets up often for short periods of time - Teaches the vestibular system all over again what is normal
50
What is the most common cause of facial paralysis/paresis?
Idiopathic
51
What are the clinical signs of facial nerve paralysis/paresis?
Drooping of face (on the same side), widening of palpebral fissure Food saliva may drop from side of mouth Absence/reduction palpebral reflex (can’t blink)
52
How is deafness classified?
- Age of onset congenital late onset - Location of the defect: Peripheral or Central - Underlying cause: inherited acquired - Sensorineural (from cochlea to brain) or conductive (failure to conduct sound from outer to inner ear)
53
Name the most common type of deafness
Congenital sensorineural deafness (from cochlea to brain)
54
Which dogs and cats most commonly present with Congenital sensorineural deafness
Dog and cat breeds with white pigmentation and blue eye colour
55
Describe acquired deafness
Can be partial or complete - Chronic otitis interna and/or media (SN + C) - Ototoxicity (SN) - Noise trauma (SN) - Presbycusis (old age, SN) - Anaesthesia associated deafness (SN)
56
Name two hearing tests
Brainstem auditory evoked responses Otoacoustic emissions

Y4 SA - Neurology (7 decks)

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