Fisch EEG Primer Chapter 17

Question 1

What are the patterns of localized epileptiform activity?

Answer 1

consists of single or multiple focal spikes (often electronegative) and slow waves often in combination with slow waves

Question 2

What is the appearance of most interictal epileptiform abnromality?

Answer 2

usually brief in duration (less than 1 second) and almost always exceeds the amplitude of surrounding background

Question 3

What is the appearance of localized icatal epilepiform activity?

Answer 3

repetetive, rythmic waveforms that vary in form, frequency, and topography throghout the seizure
NOTE: subtle changes of EEG need to be correlated with clinical manifestations. Occasionally opposite pattern with subclinical seizures.

Question 4

What are the clinical correlates of localized epileptiform activity?

Answer 4

Symptoms vary depending on the location of the focal discharges

Question 5

What is the typical cause of focal epileptiform activity?

Answer 5

partial damage in a circumscribed coritcal area - other cases unknown cause; injuries, tumors, stroke, degenerative conditions, developmental, metabolic, infectious

Question 6

What is the proposed mechanism of focal epileptiform activity?

Answer 6

paroxysymal depolarizing shifts of membrane potential by pacemaker neurons (epileptic neurons) - shifts limited by time and space

Question 7

How can one distinguish between interictal waveforms and other sharp transients: (6)

Answer 7

1) epileptiform usually asymmetric wave (first have shorter duration than second half)
2) epileptiform usually followed by a slow wave
3) epileptiform often have multiple phases
4) epileptiform does not ONLY have abrupt increase of sharply contoured waveforms
5) epileptiform often interrupts background beyond duration of spike wave
6) epileptiform should be detected at remote electrodes

Question 8

What are the three ways that ictal and interictal waves differ?

Answer 8

1) wave shape - interictal usually spike/wave followed by slow wave, intermittent // ictal isually rythmic with changing countours, frequency, and amplitude
2) distribution - interictal limited (minimum surface area 6cm2 but most 10-20cm2)
3) duration - interictal usually more brief unless associated with behavioral change

Question 9

Senile and presenile dementia are know to cause what type of focal EEG abnormalities?

Answer 9

sharp transients in the same distribution as the intermittent left temporal slow waves which are characteristically seen in older persons - seizures slightly more frequent

Question 10

Jakob-Creutzfeldt disease is know to cause what type of focal EEG abnormalities?

Answer 10

periodic sharp wave complexes. many time located in the left or right parieto-occipital area before becoming more generalized. - associated with myoclonic twitching

Question 11

Tuberous sclerosis is associated with what type of focal EEG abnormalities?

Answer 11

single or multiple spike and wave, possibly generalized asynchrous slowing; infants often display hypsarrythmia

Question 12

Sturge Weber Syndrome is know to cause what type of focal EEG abnormalities?

Answer 12

epileptiform 50% of cases with local reductions in amplitude

Question 13

Porencephaly, microgyria, pachygyria, agyria, holoprosencephaly, and hydrocephaly is know to cause what type of focal EEG abnormalities?

Answer 13

all can cause spikes but more characteristically cause focal slowing

Question 14

Bilateral optic neuritis in children is know to cause what type of focal EEG abnormalities?

Answer 14

may lead to occipital spikes unassociated with seizures

Question 15

Acute metabolic encephalopathy is know to cause what type of focal EEG abnormalities?

Answer 15

generalized bisyncrhonous and asynchronous slow waves

Question 16

Cerebral lipidoses are know to cause what type of focal EEG abnormalities?

Answer 16

focal or multifocal spikes (e.g. ceroid lipofuscinosis aka Bielschowsky-Jansky is associated with high amplitude occipital spikes in response to slow photic stimulation

Question 17

Acute strokes are know to cause what type of focal EEG abnormalities?

Answer 17

focal slowing and epileptiform discharges - PLEDs occurred in approximately 1-2% of individuals with non-hemorrhagic infarcts

Question 18

Basilar artery migraine is know to cause what type of focal EEG abnormalities?

Answer 18

posterior epileotpform activity or slow waves during or between attacks

Question 19

Old strokes are know to cause what type of focal EEG abnormalities?

Answer 19

focal epileptiform activity moths or years after stroke - more likely in thos who showed epileptiform activity acutely

Question 20

Chronic subdural hematoma is know to cause what type of focal EEG abnormalities?

Answer 20

rarely cause activity in area of slowing or decreased amplitude - usually develop in area after surgical evacuation of hematoma

Question 21

AVM is know to cause what type of focal EEG abnormalities?

Answer 21

focal epileptiform discharges due to free iron deposited in surrounding tissues

Question 22

early post-traumatic seizures are know to cause what type of focal EEG abnormalities?

Answer 22

focal spikes and sharp waves - similar recordings may be seen after brain surgery

Question 23

late posttraumatic seizures are know to cause what type of focal EEG abnormalities?

Answer 23

particularly with penetrating injuries, focal epileptiform discharges

Question 24

Supratentorial brain tumor are know to cause what type of focal EEG abnormalities?

Answer 24

most likely to produce focal epileptiform zone in slow growing area (oligodendroglioma/angioma > astrocytoma/meningioma > glioblastomas/metastases — epileptiform activity is USUALLY localized to site of tumor, but can appear bilaterally

Question 25

Meningitis and encephalitis are know to cause what type of focal EEG abnormalities?

Answer 25

focal spikes only rarely in adults; neonates are likely to react focally to widespread cerebral insult (e.g. syphilis, meningitis, cmv)

Question 26

thrombophlebitis of the cerebral venous sinus system is know to cause what type of focal EEG abnormalities?

Answer 26

focal or unilateral spikes in addition to decreased amplitude and slow waves

Question 27

What is an infectious cause of the syndrome of hemiconvulsions, hemiplegia, and epilepsy (HHE syndrome) in children?

Answer 27

Septic phlebitis of the lateral cavernous sinus - characterized by longlasting repetetive seizures of unilateral onset

Question 28

Herpes simplex encephalitis is know to cause what type of focal EEG abnormalities?

Answer 28

periodic sharp waves in the temporal regions

Question 29

Subacute sclerosing panencephalitis is know to cause what type of focal EEG abnormalities?

Answer 29

high amplitude periodic sharp waves complexes which begin locally

Question 30

Psychiatric disease is know to cause what type of focal EEG abnormalities?

Answer 30

focal temporal spikes, focal cerebral lesions must be searched