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Y4 SA - Neurology > Seizures in small animals > Flashcards

Seizures in small animals Flashcards

1
Q

What is a seizure?

A

A transient occurrence of convulsions of focal motor, autonomic or behavioural signs due to abnormal excessive or synchronous epileptic neuronal activity in the brain

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2
Q

Where are seizures localised to?

A

Forebrain

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3
Q

What other clinical signs can be seen with forebrain lesions

A

Behaviour change
Compulsive circling or pacing
Head turn on same side as the lesion
Loss of vision on opposite side as the lesion
Postural reaction deficits on opposite side

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4
Q

Name an excitatory and inhibitory neurotransmitter

A

Glutamate – EXCITATORY
GABA - INHIBITORY

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5
Q

Describe the pathogenesis of seizures

A

Imbalance in excitation and inhibition
- Either excessive excitation OR decreased inhibition
- Neurons become hypersynchonised -> Seizure

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6
Q

Name and describe the 4 stages of a seizure

A

1 = prodrome - any predictive or preceding events
(2 = Aura - initial manifestation of a seizure – from human medicine)
3 = Ictal - seizure event – involuntary muscle tone or movement +/- abnormal sensations or behaviour
4 = Post-ictal - minutes to days. Can have unusual behaviour or neurological deficits e.g. aggressive, blindness

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7
Q

Describe the main features of the ictal event

A

Usually around 60-90 seconds
Peracute in onset
Characteristics are the same for each event
Occurs most commonly at sleep or rest
Autonomic signs are common

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8
Q

Name the 2 major phenotypic categories of icteral seizures

A

Generalised
Focal

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9
Q

What are generalised seizures?

A

Involvement of both cerebral hemispheres simultaneously
CONSIOUSNESS IMPAIRED

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10
Q

What are the phases of generalised seizures?

A

May have one or several of the following phases:
1. Tonic – clonic
- Extend all 4 limbs
- Extend neck
- Dramatic posture
2. Tonic
3. Clonic
4. Myoclonic - Brief, involuntary shock like
5. Atonic - Complete lack of muscle tone – flop

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11
Q

What is a focal seizure?

A

Initial activation of ONE part of region in the forebrain
Clinical signs remain unilateral

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12
Q

Name the 3 forms of focal seizures

A

Motor
Autonomic
Behavioural

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13
Q

What are audiogenic reflex seizures?

A

Cats
Late onset (median 15 years)
Reflex seizure - seizure that is objectively and consistently precipitated by environmental or internal stimuli e.g. sounds

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14
Q

List the DDx for seizures

A

Narcolepsy/ cataplexy
Neuromuscular collapse
Syncope
Paroxysmal dyskinesia
Painful episodes
Metabolic disease
Vestibular disease
Idiopathic head tremor syndrome

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15
Q

What are the causes of reactive seizures?

A
  • Seizure occurring as a natural response from the normal brain to a transient disturbance in function
  • Concurrent neurological signs usually present
  • Metabolic or the result of intoxication
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16
Q

What are the causes of idiopathic epilepsy?

A

Genetic or presumed genetic in origin
No inter-ictal neurological signs

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17
Q

What are the causes of structural epilepsy?

A
  • Epileptic seizures which are provoked by intracranial or cerebral pathology
  • Concurrent neurological signs usually present
  • E.g. inflammatory, neoplastic, traumatic
18
Q

How is idiopathic epilepsy diagnosed?

A

Diagnosis of exclusion
Dogs between 6 months and 6 years
Normal neurological examination between seizures

19
Q

When is MRI indicated for dogs with idiopathic epilepsy?

A
  • Age of onset <6 months or >6 years
  • Inter-ictal neurological abnormalities consistent with intracranial neurolocalisation
  • Status epilepticus or cluster seizure
  • Previous presumptive diagnosis of IE and drug- resistance with a single ASD titrated to the highest tolerable dose
20
Q

When is treatment indicated for epilepsy?

A
  • Structural or metabolic epilepsy
  • Status epilepticus or cluster seizures
  • An inter-ictal period of 6 months or less
  • Post-ictal signs are severe or last longer than 24 hours
  • The seizure frequency and/or duration is increasing and/or seizure severity is deteriorating over 3 interictal periods
  • The 1st seizure is within 1 month of a traumatic event e.g. RTA
21
Q

Why is anti-seizure medication not given unless 100% necessary?

A

Adverse effects

22
Q

How is epilepsy treated?

A
  • Epilepsy cannot be cured with medication, but drugs are used to symptomatically suppress epileptic seizures
  • 3 licenced maintenance treatments in dogs
  • No drugs licenced in cats
23
Q

What are the main considerations regarding epilepsy treatment?

A

General health of the patient
Owner’s lifestyle
Financial limitations
Owner compliance with the therapeutic regimen

24
Q

Name the 3 licensed epileptic drugs for dogs

A

Phenobarbital
Bromide
Imepitoin

25
Q

Describe the mechanism of action of phenobarbital

A

Augments the inhibitory effect of GABA - prolonging the chloride channel opening at GABAA receptor

26
Q

Describe the monitoring needed for phenobarbital use

A
  • 2 weeks after any dose change (inc. haematology, biochemistry)
  • 3 months (inc. haematology, biochemistry)
  • 6 months (inc. biochemistry)
27
Q

List the side effects of phenobarbital

A
  • Sedation, ataxia
  • Polyuria, polydipsia, polyphagia
  • Hepatotoxicity
  • Haematological abnormalities (neutropaenia, anaemia, thrombocytopaenia)
  • Pseudolymphoma
28
Q

When is phenobarbital contraindicated?

A

Contraindicated in dogs with hepatic dysfunction - increased risk of hepatic injury

29
Q

How is bromide administered to patients?

A

Usually administered as either potassium (KBr) or sodium (NaBr) salts

30
Q

When is bromide not licensed?

A

As a monotherapy

31
Q

Describe the MOA of bromide

A

Competes with Cl- transport across nerve cell membranes and inhibits Na+ transport - membrane hyperpolarisation which raises the seizure threshold

32
Q

Describe the considerations when using bromide in patients

A
  • CONSISTENT DIET
  • Monitoring: 12 weeks (inc. haematology and biochemistry)
33
Q

What are the side effects of bromide?

A

Sedation
Ataxia and paresis
Bromism (serum concentration >30mmol/L) = toxicity

34
Q

When is imepitoin not licensed?

A

Not licenced for use in cluster seizures or structural epilepsy

35
Q

When is imepitoin licensed?

A

As a monotherapy

36
Q

Describe the MOA of imepitoin

A

Low affinity partial agonist for the benzodiazepine binding site of the GABAA receptor

37
Q

Describe the metabolism of imepitoin

A

Metabolised by the liver
Excreted by faecal route

38
Q

Which anti-epileptic drug doesn’t require monitoring?

A

Imepitoin

39
Q

Which anti-epileptic drug can be used off-license in cats?

A

Phenobarbital

40
Q

Name 2 off-license antiseizure medications

A

Levetiracetam
Zonisamide

41
Q

Name the antiseizure medication of choice for patients with liver disease

A

Levetiracetam

Y4 SA - Neurology (7 decks)

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