Seizures & Epilepsy Flashcards
Seizure
Definition
Transient event that includes symptoms and/or signs of abnormal excessive hypersynchronous activity in the brain.
A seizure is a symptom and one must search for underlying cause, acute or chronic
Epilepsy
Definition
A disease of the brain defined by any of the following conditions:
≥ Two unprovoked (or reflex) seizures occurring > 24 h apart
OR
One unprovoked (or reflex) seizure and a 60% likelihoood of a recurrent sz
Provoked Seizures
Seizures can be provoked by many causes including:
- Acute head trauma
- CNS infection
- Hypoxia/Ischemia
-
Acute metabolic causes
- Hypo/Hypernatremia
- Hypomagnesemia
- Uremia
- Hepatic failure
-
Toxins
- Drugs (tricyclics, neuroleptics, etc.)
- Alcohol withdrawal
- Recreational drug
Epilepsy
Etiologies
Causes of epilepsy include the following:
- Genetic
-
Structural processes
- Past parenchymal injury
- Tumors
- Cortical malformations
- Vascular malformations
- Cerebrovascular disease
- Hippocampal sclerosis
- Unknown
Seizures and Epilepsy
Pathophysiology
- Glutamate ⇒ major excitatory neurotransmitter
- GABA ⇒ major inhibitory neurotransmitter in the brain.
- Seizures result from an imbalance between excitation and inhibition, with either too little inhibition or too much excitation
- Epilepsy is caused by the bursting behavior of an epileptic neuronal aggregate
- Abnormal neurons display prolonged depolarization with repetitive sodium dependent action potentials which is called a paroxysmal depolarization shift.
- At the time of a seizure, this discharge spreads into the neighboring areas with propagation to the other areas of the brain
Seizure Triggers
Causes of decreased threshold to have a seizure:
- Stress, emotion
- Sleep/sleep deprivation
- Fever/illness
- Medications, metabolic disturbance
- Hyperventilation (absence seizures)
-
Reflex seizures – 4-7% prevalence in epilepsy
- Visual stimuli: strobe lights, visual patterns
- Musicogenic: specific songs, genres of music, tones
- Reading, eating, calculating
Epilepsy
Epidemiology
- Cumulative epilepsy incidence: 4.4% (~1 in 23 people) by age 85
- Adults: ~75% epilepsy with focal seizures
- Children: ~55% epilepsy with focal seizures
- Mortality long-term is twice that of general population overall
- Up to 1%/year for patients with uncontrolled seizures
Epilepsy
Morbidity
Morbidity is significant and can be due to all of the following:
- Traumatic injuries
- Underemployment
- Antiepileptic drug side effects
- Cognitive dysfunction
- Neuropsychiatric comorbidities higher prevalence over non-epilepsy population:
- ADHD, depression, anxiety, sleep disorders, migraine
Simple
Partial Seizures
Partial: seizures starting in one area of the brain
Simple (no loss of consciousness or memory)
- Sensory: visual, olfactory, gustatory, vertiginous
- Motor: focal motor without march, focal motor with march (Jacksonian), postural
- Sensory-Motor
-
Psychic (abnormal thoughts or perceptions): Dysphasic, dysmnesic, cognitive, illusions, structured hallucination
- Dysmnesic = inability to learn simple new skills in spite of an ability to perform complex skills learnt before the onset of the disorder
- Autonomic (heat, nausea, flushing, etc.): epigastric sensation, pallor, sweating, flushing, piloerection, pupillary dilation
Complex
Partial Seizures
Partial: seizures starting in one area of the brain
Complex: consciousness or memory impaired
- With or without aura (warning)
- With or without automatisms
Secondarily Generalized Seizures
- Begins focally, with or without focal neurological symptoms
- Becomes generalized
- Variable symmetry, intensity, and duration of tonic (stiffening) and clonic (jerking) phases
- Typical duration 1-3 minutes
- Postictal confusion, somnolence, with or without transient focal deficit
Generalized Seizures
Seizures starting in both sides of the brain at the same time
- Absence
- Myoclonic
- Clonic
- Tonic
- Tonic-Clonic
- Atonic
Unclassifiable Seizures
- Complex Partial Seizures
- Impaired consciousness
- Clinical manifestations vary with site of origin and degree of spread
- Presence and nature of aura
- Automatisms
- Other motor activity
- Duration typically < 2 minutes
Epileptic Myoclonus
- Brief, shock-like jerk of a muscle or group of muscles, usually < 50 ms
- Differentiate from benign, nonepileptic myoclonus (e.g., while falling asleep)
- EEG: Generalized 4-6 Hz polyspike-wave discharges
Typical Absence Seizures
- Brief staring spells (“petit mal”) with impairment of awareness
- 3-20 seconds
- Sudden-onset and sudden-resolution
- Often provoked by hyperventilation
- Onset typically between 4-14 years of age
- Often resolve by 18 years of age
- Normal development and intelligence
- EEG: Generalized 3 Hz spike-wave discharges
Atypical Absence Seizures
- Brief staring spells with variably reduced responsiveness
- 5-30 seconds
- Gradual (seconds) onset and resolution
- Generally not provoked by hyperventilation
- Onset typically after 6 years of age
- Often in children with global cognitive impairment
- EEG: Generalized slow spike-wave complexes (<2.5 Hz)
- Patients often also have Atonic and Tonic seizures
Tonic Seizures and Atonic Seizures
-
Tonic seizures
- Symmetric, tonic muscle contraction of extremities with tonic flexion of waist and neck
- Duration: 2-20 seconds
- EEG – Sudden attenuation with generalized, low-voltage fast activity (most common) or generalized polyspike-wave
-
Atonic seizures
- Sudden loss of postural tone
- When severe often results in falls
- When milder produces head nods or jaw drops
- Consciousness usually impaired
- Duration: usually seconds, rarely more than 1 minute
- EEG – sudden diffuse attenuation or generalized polyspike-wave
2017 ILAE Classification of Seizures