L57 EEG and Epilepsy Flashcards
Define EEG
surface recording of the electrical activity of nerve cells of the brain
*summation of EPSPs and IPSPs
what are EEGs used to assess?
- brain damage
- epilepsy
- brain death
- sleep stages
what are the types of EEG electrodes?
surface electrodes on scalp
intracranial
strip or grid electrodes
*nasopharyngeal electrodes, foramen ovale electrodes, subdural and depth electrodes (use only when the info from routine scalp is inconsistent), sphenoidal electrodes
what system does EEG electrode placement use?
international 10/20 system - the electrodes are placed with a distance from each other of 10% or 20% of the head circumference
19 electrodes + reference electrode (farthest away from brain) + ground electrode
what are the electrodes connected to and what does that do?
electrocencephalograph (a differential amplifier - 1 amplifier for 2 electrodes)
it amplifies the brain activity and records it on a strip of paper or stores it electronically
what is the amplitude of the EEG when measured on the scalp?
100 microvolts
brain wave activity can be either ____ or ____
rhythmic or arrrhythmic
*or both!
brain wave activity varies in..?
polarity
shape
frequency
what does brain wave activity amplitude range from?
20-60 microvolts
name the 4 main types of normal brain waves?
- beta
- alpha
- theta
- delta
describe beta-activity
low amplitude
high frequency
< 12 Hz
present over frontal regions of awake person
describe alpha-activity
8-12 Hz
present over posterior (occipital) regions
background frequency of awake person with eyes closed
describe theta-activity
4-7 Hz
found in drowsy adult persons + children
detected in hypnagogic states (trances, hypnosis, light sleep and just before falling asleep)
describe delta-activity
< 4 Hz
seen in certain encephalopathies and in deep sleep in normal adults
what do EEGs of a normal awake person consist of?
alpha activity + some low amplitude beta activity
*notice clear differences between L and R and frontal and occipital
what EEG pattern is common in infants?
delta-activity
what EEG pattern is common in young child?
theta and delta activity
what EEG pattern is common in middle age adults?
alpha and beta activity
what EEG pattern is common in older adults?
low amplitude alpha activity + scattered theta and delta waves
the slower the waves, the more ____ the abnormality
severe
- EEGs are expected to be symmetrical
- asymmetrical EEG = indication of some kind of a lesion in the brain (bleeding, infarction, tumor etc.)
What EEG abnormalities indicate epileptiform activity
sharp waves, spikes, spike + waves complexes
What are indications for EEG
- seizure disorders- locate focus + type of seizure
- eval of transient spells - TIA, residual ischemic neurological deficit (RIND), completed infarction vs. syncope, hysterical episodes
- intracranial disease process (tumor, access)
- diffuse disturbances of cranial function = metabolic disorder, encephalitis, degen process like v.Creutzfeldt-Jakob disease, sleep disorders
- coma
- brain death (ceased activity), isoelectric EEG
define epilepsy
chronic condition of repetitive seizures
- most common ever neurological disease with 6.5% prevalence
- in all ages, races, social classes
- if a person has a seizure one time, its not epilepsy
- everyone has an individual seizure threshold and might experience a seizure under certain circumstances
what are ways seizures start?
- neuronal damage (genetic, traumatic, metabolic)
- astroglial damage (weak K+ buffering and/or glutamate uptake)
- excessive excitiation (more glutamate released, high ext. of K+)
- less inhibition (loss of GABAergic interneurons)
how do seizures stop?
- membrane shunting of postsynaptic neuronal currents
- astroglial K+ biffering and/or glutamate uptake
- reduced excitation - less glutamate release or glutamate receptors
- inhibition - more GABAergic neuron activity
- decrease in energy (ATP) - acidosis, block of gap junctions
what are examples of epileptic potentials?
- spikes
- sharp waves
- hypsarrhythmia
- sharp and slow waves
- spikes and waves
- polyspikes and waves
what are the causes of epilepsy?
- primary seizures
- secondary seizures - intracranial or extracranial / focal or generalized
what is a primary seizure?
idiopathic, cryptogenetic
thought to result from constitutional or genetic disposition
threshold for seizures lower than normal
what is secondary seizure?
acquired (aka symptomatic, partial, focal)
results from known pathologic lesion or disease process
includes focal vs. generalized and intracranial vs. extracranial
what are intracranial causes?
-primary - genetic, biochem predisposition
-secondary
tumor
vascular (infarction, hemorrhage)
ateriovenous malformation
trauma (penetrating wound, depressed fracture)
infection (abcess, encephalitis)
congenital and hereditary disease (tuberous sclerosis)
what are extra cranial causes
metabolic-electrolytes, biochem, inborn errors of metabolism anoxia hypoglycemia drugs drug withdrawal alcohol withdrawal
describe partial focal seizures
originate of a small group of neurons = seizure focus
can be simple or complex
describe simple focal seizure
motor, sensory, autonomic, psychological symptoms
no alteration of consciousness
describe complex focus seizures
alteration of consciousness
secondarily generalized
define aura
symptoms preceding the onset of partial seizures, abnormal sensations (fear, rising feeling in abs, specific odor) originating from the seizure focus
describe primary generalized seizures
no aura, no focal symptoms, both hemispheres involved
convulsive or non-convulsive
what are the types of primary generalized seizures
- absence typical/atypical - nonconvulsive generalized seizures - absence seizure (petit mal) of children
- myoclonic
- clonic
- tonic
- tonic-clonic
- atonic
describe the tonic-clonic (grand mal) seizure
tonic phase (30s) - begins abruptly often with a grunt or cry due to tonic contraction of the diaphragm and thorax = forced expiration. Pt may fall to ground, may lose urine, may bite his tongue, become cyanotic
Clonic phase - jerking of extremities
postictal phase - pt may be sleepy, disorientated, may complain about headache and muscle soreness
what constitutes the minimal criteria for the dx of epilepsy?
recurrent seizures
what are positive symptoms
sensory - seeing light flashes, feeling of fear, hearing noises or people talking
motor- jerking of arm, leg or face
what are negative symptoms
sensory - slowing of normal brain function, depression of consciousness
motor - Todd paralysis
what is Todd paralysis
transcient paralysis (30 m to 36 h) hemiparesis seizure speech problems vision problems
describe status epilepticus
no recovery, interictal, period between seizures
medical emergency
-metabolic derangements - hypoxia, hypotension, hypoglycemia, acidemia = brain damage!
systemic complications - cardiac arrhythmias, pulmonary edema, hyperthermia, rhabdomyolysis (rapid breakdown, lysis of skeletal muscle due to injury of muscle tissue)
what are the tx options of epilepsy?
drugs that block excitation
drugs that enhance inhibition
name and describe the drugs that block excitation
phenytoin, carbamazepine, lamotriginum
reduce the flow of Na and Ca ions into the neurons and increase the level of the NT GABA and suppress the release of NT glutamate = less excitability
name and describe the drugs that enhance inhibition
GABAergic benzodiazepeines, barbs
potentiate inhibitory GABAa receptors and inhibit excitatory AMPA receptors
what is the MOA of levetiracetam
decrease the voltage-operated delayed rectifier K current without effect on Na and A-type K currents = reduced repetitive action potential generation
reduction of N-type and P=Qtype Ca currents = decreased NT release
binds to a synaptic vesicle protein, SV2A, which is believed to impede conduction across synapses
what are tx options for drug-resistance epilepsy
surgery
invasive vagus nerve stimulation
transcutaneous vagus nerve stimulation
