part iii the use of eeg epilepsy periodic patterns other
TRANSCRIPT
PART III
THE USE OF EEG
EpilepsyPeriodic patterns
Other
1. Epilepsy
1. Yield after single seizure 50% (at best)• higher if done sooner• increases up to 80% with 4th EEG
2. Epileptic abnormalities seen in approx. 0.5% of normals
• 2-14% with migraine, prior trauma, etc…• 5-8% children• 35% siblings of epileptics
3. Poor predictive value
AAN practice parameter Neurology 2007; 69: 1996
4. EEG most useful to classify the epileptic syndrome
International classification of epilepsies
• Localization – idiopathice.g. benign rolandic
• Localization – symptomatic/cryptogenic
e.g. TLE
• Generalized – idiopathice.g. JME
• Generalized – symptomatic/cryptogenic
e.g. Lennox-Gastaut
• Age of onset
• Seizure Type(s)
• Family History
• Exam/Imaging
• EEG
Epilepsia 2001; 42:796.
Epilepsy cont…
King et al. Lancet 1998; 352: 1007
• Syndrome diagnosed clinically in 47%• With EEG, 77%
• EEG within 24hr, 51% vs. 34%
• Initial EEG 43%, after SD-EEG 61%
Epilepsy cont…
• Therefore…use the EEG to classify the epileptic syndrome, not to diagnose seizures
• e.g. TLE vs. JME
2. Periodic Patterns
Stereotypical sharp complexes repeating at a constant time interval for most or all of the
recording.
Periodic
Stereotypical
Sharp
Repeating
Constant time interval
Most of the recording
Rhythmic
• Rhythm = “the regular, measured flow of sound…or action”
• Rhythmic activity can be brief, and is continuous
Hirsch et al. J Clin Neurophysiol 2005
Periodic Patterns cont…
• UNILATERAL
PLEDs, Status
• BILATERAL
• Short latency (<4 sec)
Triphasic waves, periodic complexes (of CJD)
BiPLEDs, Status
• Long latency (>4 sec)
Burst-suppression, SSPE
Alternatively…
• PLEDs
• BiPLEDs
• GPEDs• Status, periodic complexes (CJD), SSPE, burst-
suppression etc…• triphasic waves??
PLEDs
• Considered to be an interictal epileptic pattern (but strongly assoc. with seizures)
• BiPLEDs occur independently over both hemispheres
PLEDs
Same patient (change timescale)
Periodic Complexes of CJD
• Can be biphasic, triphasic etc…
• Can be unilateral initially
• Not seen in nvCJD, FFI, only 10% other genetic CJD, rarely with v/v @ codon 129
• Distinguish from triphasic waves based on clinical context
• Distinguish from PLEDs or status by reaction to stimuli, disappearance with sleep
Periodic complexes in CJD (from Ebersole and Pedley)
Periodic complexes in CJD (poor example)
Triphasic waves
• Toxic-metabolic encephalopathy
• Typical of (but not specific for) hepatic encephalopathy
Triphasic waves (Fisch and Spehlmann)
Triphasic waves
Burst-suppression
Burst-suppression
SSPE
from Ebersole & Pedley)
Status
Chong J Clin Neurophysiol 2005 adapted from Young Neurology 1996
Status
NCSE post-arrest
3. Other
• Coma• Brain death• EEG not indicated in headache*
• Can consider in certain situations (pregnancy
• EEG not useful in syncope• 2003-2007 JGH 517 EEG’s for syncope, LOC, or
fall• 57 abnormal (0 epileptic, 6 potentially epileptic)• Only 5 changed management
*Neurology 1995;45:1263 Neurology 2002;59:490**Arch Int Med 1990;150:2027
PART IV
SLIDESHOW
3 Hz spike and wave with hyper
Focal interictal epileptic activity (right anterior temporal)
Cont… next page
Generalized interictal epileptic activity
Burst-suppression
Cont…next page
Focal seizure (glioma)
PLEDS
(Focal) non-convulsive status
Hypsarrythmia with infantile spasm
BECRS
Burst-suppression post-arrest
Triphasic waves
Periodic complexes in CJD (from Fisch and Spehlmann)
Focal slowing and epileptic activity, patient with sepsis
Independent seizures 37 week HIE Ebersole and Pedley
Cz-C3
Sp1-Sp2
Cz-C4
EOG
Fp1-F7
T5-O1
Fp2-F8
T6-O2
Asystole secondary to a seizure
Cont…next page
PLEDS I year post TBI
REVIEW
TAKE-HOME MESSAGE
1. To read an EEG:
-orient yourself
-have an approach
-describe what you see
TAKE-HOME MESSAGE
2. The EEG is prone to artifact. Findings such as epileptic activity or focal slowing are often a judgement call, and can be seen in normal people. Therefore, the EEG is not absolute.
TAKE-HOME MESSAGE
3. The EEG is not good at diagnosing or “ruling-out” seizures. It is far more useful for correctly classifying the epileptic syndrome.
TAKE-HOME MESSAGE
4. Exam questions will not be subtle (No artifacts, no subtle focal slowing)
REFERENCES
Drury I, Beydoun A. Pitfalls of EEG interpretation in epilepsy. Neurol Clin 1993; 11: 857-81.
Noachtar S et al. A glossary of terms… Electroencephalogr Clin Neurophysiol Suppl 1999; 52: 21-41.
Engel J. A proposed diagnostic scheme for people with epileptic seizures and with Epilepsy: Report of the ILAE Task Force on classification and terminology. Epilepsia 2001; 42: 796-803.
Sundaram et al. EEG in epilepsy: current perspectives. Can J Neurol Sci 1999; 26: 255-62.
Young GB. Metabolic and inflammatory cererbral diseases: electrophysiological aspects. Can J Neurol Sci 1998; 25: S16-S20.
Blume WT. Clinical and basic neurophysiology of generalised epilepsies. Can J Neurol Sci 2002; 29: 6-18.