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Neuroscience > L57 EEG and Epilepsy > Flashcards

L57 EEG and Epilepsy Flashcards

1
Q

Define EEG

A

surface recording of the electrical activity of nerve cells of the brain

*summation of EPSPs and IPSPs

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2
Q

what are EEGs used to assess?

A
  • brain damage
  • epilepsy
  • brain death
  • sleep stages
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3
Q

what are the types of EEG electrodes?

A

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

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4
Q

what system does EEG electrode placement use?

A

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

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5
Q

what are the electrodes connected to and what does that do?

A

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

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6
Q

what is the amplitude of the EEG when measured on the scalp?

A

100 microvolts

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7
Q

brain wave activity can be either ____ or ____

A

rhythmic or arrrhythmic

*or both!

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8
Q

brain wave activity varies in..?

A

polarity
shape
frequency

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9
Q

what does brain wave activity amplitude range from?

A

20-60 microvolts

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10
Q

name the 4 main types of normal brain waves?

A
  • beta
  • alpha
  • theta
  • delta
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11
Q

describe beta-activity

A

low amplitude
high frequency
< 12 Hz
present over frontal regions of awake person

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12
Q

describe alpha-activity

A

8-12 Hz
present over posterior (occipital) regions
background frequency of awake person with eyes closed

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13
Q

describe theta-activity

A

4-7 Hz
found in drowsy adult persons + children
detected in hypnagogic states (trances, hypnosis, light sleep and just before falling asleep)

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14
Q

describe delta-activity

A

< 4 Hz

seen in certain encephalopathies and in deep sleep in normal adults

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15
Q

what do EEGs of a normal awake person consist of?

A

alpha activity + some low amplitude beta activity

*notice clear differences between L and R and frontal and occipital

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16
Q

what EEG pattern is common in infants?

A

delta-activity

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17
Q

what EEG pattern is common in young child?

A

theta and delta activity

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18
Q

what EEG pattern is common in middle age adults?

A

alpha and beta activity

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19
Q

what EEG pattern is common in older adults?

A

low amplitude alpha activity + scattered theta and delta waves

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20
Q

the slower the waves, the more ____ the abnormality

A

severe

  • EEGs are expected to be symmetrical
  • asymmetrical EEG = indication of some kind of a lesion in the brain (bleeding, infarction, tumor etc.)
21
Q

What EEG abnormalities indicate epileptiform activity

A

sharp waves, spikes, spike + waves complexes

22
Q

What are indications for EEG

A
  • 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
23
Q

define epilepsy

A

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
24
Q

what are ways seizures start?

A
  • 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)
25
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
26
what are examples of epileptic potentials?
- spikes - sharp waves - hypsarrhythmia - sharp and slow waves - spikes and waves - polyspikes and waves
27
what are the causes of epilepsy?
- primary seizures | - secondary seizures - intracranial or extracranial / focal or generalized
28
what is a primary seizure?
idiopathic, cryptogenetic thought to result from constitutional or genetic disposition threshold for seizures lower than normal
29
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
30
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)
31
what are extra cranial causes
``` metabolic-electrolytes, biochem, inborn errors of metabolism anoxia hypoglycemia drugs drug withdrawal alcohol withdrawal ```
32
describe partial focal seizures
originate of a small group of neurons = seizure focus | can be simple or complex
33
describe simple focal seizure
motor, sensory, autonomic, psychological symptoms | no alteration of consciousness
34
describe complex focus seizures
alteration of consciousness | secondarily generalized
35
define aura
symptoms preceding the onset of partial seizures, abnormal sensations (fear, rising feeling in abs, specific odor) originating from the seizure focus
36
describe primary generalized seizures
no aura, no focal symptoms, both hemispheres involved | convulsive or non-convulsive
37
what are the types of primary generalized seizures
1. absence typical/atypical - nonconvulsive generalized seizures - absence seizure (petit mal) of children 2. myoclonic 3. clonic 4. tonic 5. tonic-clonic 6. atonic
38
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
39
what constitutes the minimal criteria for the dx of epilepsy?
recurrent seizures
40
what are positive symptoms
sensory - seeing light flashes, feeling of fear, hearing noises or people talking motor- jerking of arm, leg or face
41
what are negative symptoms
sensory - slowing of normal brain function, depression of consciousness motor - Todd paralysis
42
what is Todd paralysis
``` transcient paralysis (30 m to 36 h) hemiparesis seizure speech problems vision problems ```
43
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)
44
what are the tx options of epilepsy?
drugs that block excitation | drugs that enhance inhibition
45
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
46
name and describe the drugs that enhance inhibition
GABAergic benzodiazepeines, barbs potentiate inhibitory GABAa receptors and inhibit excitatory AMPA receptors
47
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
48
what are tx options for drug-resistance epilepsy
surgery invasive vagus nerve stimulation transcutaneous vagus nerve stimulation

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