Seizures Flashcards
An epileptic seizure is caused by
Excessive excitation of neutrons in the cerebral cortex.
Alterations in the neural environment can decrease the threshold of activation sufficient to result in a seizure.
Neuron environment can be altered due to
Genetically determined factors, inflammation, oedema, pressure from SOLs
Focal seizures
abnormal activity in an isolated region
- usually lateralised CSs - contralateral to seizure focus
- can secondarily generalise
Generalised seizures cause
Abnormal neuronal activity in both hemispheres = loss of consciousness, bilaterally symmetrical muscle activity, recumbency ± jaw movements & autonomic signs.
Most common type of seizures
generalised
Cluster of seizures =
2+ in <24h
Status epilepticus =
Seizure which is not self limiting.
Lasts >5mins or 2+ without complete recovery in between lasting >30mins
Phases of seizure activity
- prodrome - abnormal behaviour hrs/days prior
- aura - initial focal sensory signs - secs/mins prior
- Agitation. Hide away or may seek their owner. - ictus - seizure
- Post ictal signs - hrs/days after. Disorientation, ataxia, proprioceptive deficits, blindness, pacing, polyphagia, aggression.
Causes of seizures can be
Intra-cranial or extra-cranial
Extra-cranial seizures
response of the ordinary brain to insults from inside the body (metabolic) or outside (toxins) - altered composition of blood flowing through the brain triggers a seizure
Intra-cranial seizures
Structural brain lesion or a functional disorder e.g. idiopathic epilepsy.
Ddx intra-cranial lesions
Haemorrhage or infarction Meningitis/meningoencephalitis Trauma (at time or 3-6mo later) malformation, hydrocephalus Neoplasia - e.g. glioma, meningioma Lysosomal storage dz
Only definitive test that an event is a seizure
EEG during episode
Hx to help determine if the event is a seizure
- Post-ictal behaviour changes?
- Muscle tone - generally increased in seizures and ‘floppy’ in syncope
- Autonomic signs?
- Can the animal be distracted during the episode?
Potential cause of seizures esp. in older cats
hypertension
Indications for advanced imaging
<6mo or >6yrs
cluster seizures or status epileptics
intra-ictal deficits consistent with a forebrain lesion
refractory to drug tx despite adequate serum levels
Stages of idiopathic epilepsy dx.
Stage I:
▪ 2+ unprovoked seizures >24hrs apart
▪ Onset 6mo-6yrs
▪ Normal inter-ictal physical & neurological exam
▪ No abnormalities on haematology, biochemistry, urinalysis
Stage II: stage I + unremarkable bile acid stim, brain MRI & CSF analysis
Stage III: I, II + consistent EEG abnormalities.
Goals for epileptic management
Overall QOL most important
Reasonable aim = 1 short, self limiting seizure every 3mo.
Guidelines for starting anti-epileptic drug therapy (5 points)
▪ 2+ seizures in 6mo
▪ Increasing fr./severity
▪ Cluster seizures or status epilepticus
▪ An underlying progressive disease causing them
▪ Severe post-ictal signs e.g. aggression or blindness.
Anti-epileptic drug options
Phenobarbitone - licensed mono therapy
Potassium Bromise (NOT cats) - refractory to phenobarbitone tx
Imepitonin
Levetriacetam - may be useful if routine cluster seizures
Diazepam - rectal formula for owners to give at home for a seizure >2-3mins
Phenobarbitone
Licensed monotherapy for idiopathic epilepsy
Potassium bromide
Licenced for use in dogs with idiopathic epilepsy refractory to phenobarb tx
Can induce vomiting, pancreatitis & aggression.
Imepitoin
Licenced monotherapy in dogs with idiopathic epilepsy.
Don’t use if hx of cluster seizures or status epilepticus - poor efficacy.
Levetriacetam
May be useful in dogs routinely showing cluster seizures. Used immediately following 1st seizure.
Aim - reducing number + severity of further seizures in the cluster
Diazepam
Rectal formula can be dispensed for the owner to give at home with a seizure lasting more than 2-3mins.
