Seizures & Epilepsy Flashcards
Terminology
Seizure:
epilepsy:
- neurolocalization?
- Seizure: A transient occurrence of signs due to abnormal excessive or synchronous neuronal activity in the thalamocortex
- Epilepsy: A condition of recurrent seizures due to a chronic brain disorder
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Neurolocalization: Thalamocortex
Seizure Stages
Prodrome: Period prior to seizure, with change in sensorium exhibited in behaviour; ~ hrs – days
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Aura: Initial motor / sensory signs (early ictus); ~ seconds
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Ictus: Seizure itself
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Post-ictus: Recovery period with transient abnormalities, e.g. mentation, menace, gait; ~ minutes – days
what is a cluster of seizures, vs status epilepticus?
- cluster >= 2 in 24h
- Status epilepticus: Continuous
Generalized Seizure
- origin
- localization?
- signs?
- Originates at some point within & rapidly engaging bilateral networks
- Location & lateralization not necessarily consistent
- Usually symmetric (may be asymmetric)
- Impaired consciousness
> Impaired awareness
Focal Seizure
- origin, localization
- Originate w/in networks limited to 1 hemisphere (unilateral)
- Ictal onset consistent between seizures
- Preferential propagation patterns may include other hemisphere
> focal to bilateral (“secondarily generalized”)
± impaired awareness
Generalized Seizures - descriptors
- Tonic-clonic
- Absence
- Myoclonic
- Clonic
- Tonic
- Atonic
Focal Seizures descriptors
- Sensory
- Altered consciousness
- Motor / autonomic signs
- Focal to bilateral tonic-clonic
Things Mistaken For Seizures
- Syncope: Transitory loss of consciousness, short, no pre-/post- ictus; cardiac vs respiratory
- Cataplexy/narcolepsy
- Neck Pain
- Vestibular dysfunction
- Metabolic encephalopathy
- Generalized tremor syndromes
- Exercise-induced weakness
- Compulsive disorders
- Stereotypy
- Feline estrus behaviours
- Myoclonus
Epilepsy Etiologies
- Idiopathic (Genetic)
- Structural (Metabolic)
- Unknown
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Intracranial vs Extracranial
Idiopathic Genetic Epilepsy
- origin?
- signs?
- who gets it?
- timing?
- tests
- prognosis
- Direct result of a known or presumed genetic defect
- Intracranial cause
- Generalized tonic-clonic seizures
- Dogs > > cats / horses
> australian and belgian shepherds - First seizure: 1-5 years of age
- Normal interictal neurologic exam & diagnostic tests (normal between seizures)
- Prognosis (efficacy of therapy) > breed related, Border Collies & Australian Shepherds worse
Progressive Myoclonic Epilepsy
- signs and progression?
- inheritance?
- Progressive, abnormal interictal NE
- Autosomal recessive genetic syndromes
Structural Epilepsy
- what is this?
- diagnostics?
- Signalment does not fit genetic epilepsy
> Breed, Age of seizure onset - Interictal abnormalities found on diagnostic tests, including NE
Structural Epilepsy
- extracranial toxic ddx
Lead
Organophosphates
Ethylene glycol
Chocolate
Xylitol
Structural Epilepsy Extracranial metabolic DDx
Hypoglycemia: iatrogenic, young/toy, insulinoma
Organ failure: hepatic/uremic encephalopathy Electrolyte abnormalities: Na+, H2O, K+, Ca2+ Hypoxemia
Hyperlipidemia
Hyperthermia
Structural Epilepsy Intracranial DDx
- vascular
- inflammatory/infectious
- truma
- anomaly
- Vascular: hypertension, hyper/hypoT4
- Inflammatory/Infectious: encephalitis: MUE, FIP, (bacterial, viral, fungal, protozoal, Rickettsial, larval migrans)
- Trauma: brain injury (old or new)
- Anomaly: hydrocephalus, cortical dysplasia (e.g., lissencephaly, porencephaly)
Structural Epilepsy Intracranial DDx
- neoplasia
- degenerative
- Neoplasia: Primary: meningioma, Secondary: HSA, LSA
- Degenerative: Mitochondrial encephalopathies / storage diseases / organic acidurias, thiamine deficiency (polioencephalomalacia)
Unknown Epilepsy
- etiology
- what is it?
- Truly idiopathic (but we all agree not to use this term… we already use the term ‘idiopathic’ for genetic…)
- Signalment does not fit genetic epilepsy
- No cause identified on diagnostic tests
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How? - Lesion is beyond the level of detection by current technology
- Genetic, just don’t know it yet
- Old injury (Birth? Previous encephalitis? Previous stroke?)
Cats - epilepsy etiology
- Idiopathic (genetic?) epilepsy: ~40%
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Not idiopathic if: - Status epilepticus
- > 7 years of age
- Abnormal interictal neurologic exam
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Hippocampal necrosis: ~11% - dont know if necrosis is cause or effect of seizures
- Orofacial signs & “absences”
- Acute cluster
epilepsy diagnostis - neuro exam: what does it tell us?
NAF:
- genetic (idiopathic) epilepsy
- (early neoplasia)
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Deficits:
- postictal
- drugs (therpapy)
- structural/metabolic epilepsy
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For thalamocortex:
- Mentation
- Menace response
- Nasal septum response
- Postural reactions
age of seizre patient - what origins might we suspect based on age?
<1y
* Congenital anomaly
* Hypoglycemia, PSS
* Infectious (distemper, FIP)
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1–5y
* Idiopathic (genetic) epilepsy
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>5y
* Neoplasia (primary»_space; secondary)
epilepsy diagnostics - minimum database
- CBC
- Serum biochem (5 tests of liver function)
- Glucose
- Albumin
- BUN
- Bilirubin
- Cholesterol
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- electrolytes - UA
Epilepsy diagnosis: Discretionary Database
- Thyroid panel: TT4, TSH, fT4
- Blood pressure (note machine, cuff, limb, recumbency, x3)
- Ocular exam
- Ammonia & pre/post-prandial BAs
- Fructosamine & glucose curve
- Glucose:insulin
- Toxicology
- Titres / PCR
- Met check: Thoracic rads + Abd US
Epilepsy Diagnosis: Advanced Database
- Only if previous tests are normal
- EEG: if not sure seizure
- MRI vs CT
- CSF analysis (“spinal tap”)
- Biopsy?
when to perform an MRI for seizure diagnostics
- Epileptic seizure onset < 6 m or > 6 y
- Abnormal interictal NE
- status epilepticus or cluster seizures
- presumptive IE but refractory to 1 ASD at highest tolerable dose
when might we require high-field MRI for seizure diagnotics
- Congenital/developmental: cortical dysplasia
- Infectious: distemper, rabies
- Metabolic: hepatic, thiamine
Idiopathic epilepsy diagnostic confidence criteria: (tiers)
- Tier I: normal minimum + discretionary database
- Tier II: normal BAs + advanced database
- Tier III: as above + ECG (ictal or interictal abnormalities)
When to start ASDs? why is it important?
- structural epilepsy (treat cause), prior brain pathology
- status epilepticus (>5 min) or >=3 seizures / 24h
- > =2 seizures / 6m
- prolonged, severe, unusual post-ictal periods
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Seizures beget seizures!
- seizures get entrenched in the brain by repetition > the more you control, the less they will seize in the future
Treatment: Client Education
- what are our goals?
- what else they need to know
- commitment, cost, monitoring
- Practical goals of therapy: not seizure eradication
> decreased frequency & severity - Expected adverse effects
- Commitment
> Lifestyle: Dosing requirements
> Cost: Drugs + routine monitoring bloodwork
> Organization: Seizure diary to monitor efficacy
seizure Treatment: Drug Choices
Phenobarbital
Potassium Bromide
Levetiracetam
Gabapentin/Pregabalin
Zonisamide
why not use diazepam for long-term seizure control?
Diazepam: too short-acting, tolerance builds up, emergency only
When to monitor [ASD]serum?
- @ steady-state after starting Tx or dose Δ
- Uncontrolled seizures despite apparently adequate dose
- @ signs of dose-related toxicity
- to check for pharmacokinetic change causing drift and compliance
Risks of seizure Tx? by type
- Type I: predictable, directly related to pharmacokinetics in dose-dependent fashion
- Type II: Idiosyncratic, potentially life-threatening
- Type III: Cumulative, potentially life-threatening
- Type IV: Delayed (carcinogenic/teratogenic), life-threatening
> these are not seen in any of our commonly used medications, but types 1-3 are
