Seizure Disorders (Week 5--Stern) Flashcards
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
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
How is neuronal dysfunction reflected?
Intrinsic electrical rhythms across cerebral tissue change
The EEG represents post-synaptic potentials within pyramidal layers of neocortex
Epilepsy
Seizure occurrence and presence of an enduring, intrinsic predisposition to seizures
Includes more than 40 different syndromes
Are all seizures signs of epilepsy?
No, a seizure can be extrinsically provoked and not be a sign of epilepsy
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
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%
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
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
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
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
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)
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
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
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
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
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
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
Treatment for MTLE
Anti-seizure medications usually not effective for full seizure control but surgical removal of abnormal tissue is effective
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
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
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
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”)
