Seizure Disorders (Week 5--Stern) Flashcards Preview

Block 5: Neuroscience > Seizure Disorders (Week 5--Stern) > Flashcards

Flashcards in Seizure Disorders (Week 5--Stern) Deck (23):
1


Seizure

An event

Clinical manifestation of abnormal and excessive excitation and synchronization of cerebral neurons

Manifestations vary and depend on localization

Produce alteration in cognition through transient dysfunction within a population of cerebral neurons

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When does a seizure produce loss of consciousness


When the neuron population is large and bilateral

When the RAS is impaired (by brainstem compression)

When both cerebral hemispheres are dysfunctional

Note: hemispheric dysfunction that is not diffuse and bilateral may alter consciousness without complete loss of consciousness

3


How is neuronal dysfunction reflected?


Intrinsic electrical rhythms across cerebral tissue change

The EEG represents post-synaptic potentials within pyramidal layers of neocortex

4


Epilepsy


Seizure occurrence and presence of an enduring, intrinsic predisposition to seizures

Includes more than 40 different syndromes

5


Are all seizures signs of epilepsy?


No, a seizure can be extrinsically provoked and not be a sign of epilepsy

6


How common is epilepsy?


Third most common chronic neurologic disorder

10% lifetime risk

Only 0.5-0.8% prevalence in developed countries

Affects all ages but max risk when younger than 2 and older than 65

7


Causes of epilepsy


6% of children of parent with epilepsy (genetic causes)

26% mental retardation

22% stroke

10% Alzheimer's disease

However, no apparent cause at time of diagnosis in 70%

8


Consciousness


Doesn't have precise definition

Is not all or nothing

Is not a focal process

Relies on integrity of reticular activating system (RAS) that originates in brainstem and projects superiorly, uses thalamus as intermediate then gets to cerebral hemispheres to stimulate them

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Altered mental status


Consciousness: apparent lack of cognitive activity; typically abnormal postural tone

Alertness: somnolence; non-somnolence

Awareness: may be focal deficit; may be subtle

Interactive ability: needs direct evaluation; may need detailed evaluation

10


Types of seizures


Generalized: tonic-clonic, tonic, clonic, atonic, absence, myoclonic

Partial: simple partial, complex partial, secondary generalized

Focal: motor, sensory, autonomic, dyscognitive, evolving into bilateral convulsive

Note: partial = focal

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Causes of epilepsy


Diverse--anything that could damage gray matter

Abnormalities of neuron channels could produce only seizures and nothing else

Cause of acute, symptomatic seizure produces fixed injury and leads to epilepsy with seizures that are similar to initial provoked episode

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2 types of seizure


Partial seizure (focal seizure): begins with one region and may spread; simple partial seizure (no impairment of consciousness or memory), complex partial seizure (alteration in consciousness), secondarily generalized seizure (partial that has become generalized across hemispheres and presents as whole body convulsion)

Generalized seizure: generalized at onset and caused by abnormality in bilateral cerebral rhythms modulated by thalamus; generalized tonic-clonic, etc; absence seizure (have loss of consciousness but no changes in postural tone or convulsions)

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Simple partial seizures/auras


No impairment of mentation

Hallucinations: gustatory, olfactory, visual, auditory, somatosensory, vestibular

Cognitive changes: language, memory (deja vu, jamais vu), fear

Autonomic changes: eipgastric rising sensation, chill, fear-associated

Involuntary motor activity: rhythmic jerks, somatotopic progression

Any experience that the brain may produce: synesthesias

14


Complex partial seizures


Altered mental status (dyscognitive) but not necessarily loss of consciousness

May or may not follw aura

No major change in postural tone

Often repetitive oral or manual automatisms

Sometimes wandering behavior or verbal repetitions

Amnesia during seizure and peri-ictal period

Duration usually less than 2 minutes

Followed by confusion, fatigue, headache, focal neurologic deficit

15


EEG of a complex partial seizure


Note: ictal means event and is used when describing seizure or migraine

Progression of focal seizures include evolution of ictal rhythm

EEG pattern evolves in distribution across scalp, amplitude, rhythmicity and frequency

16


Generalized tonic-clonic seizures


Can be either secondary generalized (partial/focal seizure) or generalized seizure and you can't tell without more information!

Obvious loss of consciousness

May or may not follow warning/aura

May or may not follow complex partial seizure

Forced gaze deviation

Generalized increased tone followed by generalized rhythmic jerks

Duration usually less than 3 minutes

Often oral or bodily injury and/or urinary incontinence

Followed by confusion, amnesia, weakness, headache, myalgias and sometimes focal neurological deficit

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Evaluation for seizures

History: focal onset and full manifestation, prior seizures or similar episodes, risk factors and triggers

Neurological examination for focal cortical deficit

Routine blood laboratory screening tests

Consideration of tox screen

Brain imaging (MRI, CT)

EEG

Common conditions that may mimic seizures such as syncope

18


Mesial temporal lobe epilepsy (MTLE)


Anterior, medial temporal lobe

History: cerebral insult before age 5, complex febrile convulsion, family hx epilepsy or febrile convulsion

Seizures: onset mid to late childhood recognized years later, auras sometimes in isolation (limbic function manifestations), complex partial seizures (bland or manual automatisms), secondarily generalized seizures are infrequent

Cognitive deficits (memory loss)

Remission after initial treatment lasts years

Seizures become intractable in adulthood

Interictal behavioral disturbances (depression)

Underlying pathology usually hippocampal sclerosis or malformation of anterior temporal lobe

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Treatment for MTLE


Anti-seizure medications usually not effective for full seizure control but surgical removal of abnormal tissue is effective

20

Characteristic diagnostic test results in MTLE


EEG: focal temporal interictal epileptiform discharges

MRI: atrophy and signal abnormality in hippocampus

Neuropsychological testing: unilateral memory deficit

Normal physical exam

21


First aid for seizure


Protect from hazards: location, circumstance, clothing, jewelry, eyeglasses etc

Monitor seizure duration

If generalized convulsion, turn on side with head inclined down to keep airway clear after seizure

Transfer to hospital if: first seizure, multiple seizures or status epilepticus, injury, diabetes, pregnancy

Do not put object in mouth or restrain

22


Idiopathic vs. cryptogenic vs. remote symptomatic seizures


Idiopathic = primary, essential, no outside cause

Cryptogenic = there IS a cause, there is a focus, we just don't know what the pathology is yet

Remote symptomatic

23


What might you see during the post-ictal period (after the seizure)?


Focal deficit in the area that the seizure occurred

For example, patient had seizure in dominant hemisphere so in post-ictal period had language deficits (couldn't remember the word "seizure")

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