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EEG in Status Epilepticus

Paul A. Garcia, M.D.

For discussion today

• Recognizing Seizures

• Recognizing Status

• Assessing Treatment

…hard to define, but "I know it when I see it "

Potter Stewart on pornography

Inter-observer Agreement

• Experienced: Kappa= 0.5

• Inexperienced: Kappa= 0.29

• Agreement also dependent upon pattern

Ronner HE et al, Seizure. in press

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Seizure pattern examples

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Less agreement

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Recognizing Status

• Clinical

• EEG

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Status Epilepticus: Definition

• Traditionally, >30 minutes continuous

• Current practice

– Tonic-Clonic seizures rarely greater than 2 minutes

– CPS rarely longer than 10 mins

When is EEG needed?

Clinical seizures don’t stop with initial treatment s

Clinical seizures stop but patient doesn’t improve as expected

Clinical seizures stop and there is no expectation of clinical improvement

Pharmacological paralysis

Baseline encephalopathy

Clinical information not diagnostic

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EEG patterns of status epilepticus

• Most clear when the patterns approach what we recognize as “ictal” based on experience with discrete seizures

• Some EEG patterns are common to seizures, normal physiological function and encephalopathy

• EEG patterns in rodent status

Discrete seizures

Merging seizures

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Continuous Discharges

FP1-C3FP1-C3

C3-O1C3-O1

FP1-T3FP1-T3

T3-O1T3-O1

FP2-C4FP2-C4

C4-O2C4-O2

FP2-T4FP2-T4

T4-O2T4-O2

CommentComment

TimeTime 0:01:01:080:01:01:08 0:01:01:100:01:01:10 0:01:01:120:01:01:12 0:01:01:140:01:01:14 0:01:01:160:01:01:16

FP1-C3

C3-O1

FP1-T3

T3-O1

FP2-C4

C4-O2

FP2-T4

T4-O2

Comment

Time 0:01:01:08 0:01:01:10 0:01:01:12 0:01:01:14 0:01:01:16

Continuous discharges with periods of attenuation Periodic discharges

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PLEDs

• Non-specific pattern suggesting focal injury superimposed on diffuse dysfunction

• Ictal EEG pattern with focal seizures

• EEG pattern following seizures

Status?

Approach to assessing PEDs

• Clinical context

• Benzodiazepine trial

– EEG response

– Clinical response

• The company that they keep

• Observation over time

Diagnosing “occult” status

• 18-34% with unexplained encephalopathy have seizures

• ~10% with unexplained encephalopathy have non-convulsive status epilepticus

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Risk factors for occult seizures

• Convulsive seizures

• Remote history of seizures/epilepsy

• Periodic discharges

Treating Refractory Status Epilepticus: EEG titration of anesthesia

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Monitoring status epilepticus

• Continuous EEG

• Experienced ICU staff

• With the exception of HIE, outcomes are unpredictable—some do well after prolonged anesthesia

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EEG in Status Epilepticus: Conclusions

Attention to common ictal EEG patterns will lead to recognition of status epilepticus in most cases

EEG is needed to guide treatment if initial medications fail to control status

• EEG is important to exclude ongoing seizures if clinical information doesn’t do so

• EEG is needed to diagnose “occult” status in patients with otherwise unexplained mental status changes

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