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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
Q

How is granulomatous meningoencephalomyelitis diagnosed?

A

MRI: Multiple ill-defined hyperintensities on T2WI and FLAIR
CSF analysis: Usually mononuclear pleocytsos

26
Q

Which patients most commonly present with necrotising meningoencephalomyelitis?

A

Pug, Chihuahua, Yorkie, Maltese, Pekingese, Shih- Tzu, WHWT, Boston terrier, Miniature pinscher, French Bulldog…

27
Q

What are the clinical signs of necrotising meningoencephalomyelitis?

A

Worse prognosis, areas of necrosis mostly in cerebral cortex often coalesce to form large areas of cavitation
- Seizures, blindness, altered behaviour, circling, depression

28
Q

How is meningoencephalomyelitis of unknown origin treated?

A

Immunosuppression: Corticosteroids
High mortality
Lifelong medication

29
Q

What is a negative prognostic indicator for meningoencephalomyelitis of unknown origin?

A

Seizures and signs of raised ICP on MRI

30
Q

What is a positive prognostic indicator for meningoencephalomyelitis of unknown origin?

A

Younger age and early diagnosis (within 7 days)

31
Q

Are cats more likely to have immune mediated or inflammatory brain disease?

A

Inflammatory

32
Q

What are the causes of CNS involvement in cats with FIP?

A

Lesions result from immune- complex-mediated vasculitis

33
Q

List the neurological signs seen in cats with FIP

A
  • 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
Q

Why are neurological signs linked to FIP hard to diagnose?

A

Dry form of FIP

35
Q

How is FIP diagnosed?

A
  • 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
Q

How does FIP appear on MRI?

A

Periventricular contrast enhancement, ventricular dilation and hydrocephalus

37
Q

How are neurological signs linked to hypothyroidism treated?

A

Reversible with supplementation of levothyroxine

38
Q

Describe metronidazole toxicity

A

Uncommon; signs of CVS, seizures, tremors, rigidity
Usually when doses ≥60mg/kg/day but lower doses have been reported

39
Q

How does thiamine deficiency lead to CNS signs?

A
  • 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
Q

What is the most common primary brain tumour?

A

Caudal fossa meningiomas

41
Q

Which structures pass by the middle ear?

A

CN VII
CN VIII
Sympathetic supply to eye

42
Q

What are the clinical signs of otitis media/interna?

A

Facial paralysis
Peripheral vestibular signs
Horner syndrome
Pain opening the mouth

43
Q

List the primary factors causing otitis media/interna

A

Hypersensitivity - atopic dermatitis, adverse cutaneous food reaction
Keratinisation defects

44
Q

List the predisposing factors for otitis media/interna

A

Conformation: hairy, narrow, pendulous
Over cleaning
Swimming/persistently wet

45
Q

List the perpetuating factors for otitis media/interna

A

Progressive pathological change
Infections

46
Q

What is the most common cause of peripheral vestibular disease in dogs?

A

Idiopathic vestibular disease

47
Q

How does Idiopathic vestibular disease present?

A

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
Q

How is Idiopathic vestibular disease diagnosed/treated?

A

Unknown aetiology; spontaneous recovery without any treatment
Diagnosis of exclusion

49
Q

How are patients with idiopathic vestibular disease monitored/managed?

A

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
Q

What is the most common cause of facial paralysis/paresis?

A

Idiopathic

51
Q

What are the clinical signs of facial nerve paralysis/paresis?

A

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
Q

How is deafness classified?

A
  • 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
Q

Name the most common type of deafness

A

Congenital sensorineural deafness (from cochlea to brain)

54
Q

Which dogs and cats most commonly present with Congenital sensorineural deafness

A

Dog and cat breeds with white pigmentation and blue eye colour

55
Q

Describe acquired deafness

A

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
Q

Name two hearing tests

A

Brainstem auditory evoked responses
Otoacoustic emissions

Y4 SA - Neurology (7 decks)

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