What is burst suppression in seizure treatment?

Burst Suppression in Seizure Treatment

Burst suppression is an EEG pattern characterized by more than 50% of the recording consisting of periods of very low voltage activity (<10 µV) alternating with high-amplitude bursts, representing profound brain inactivation that serves both as a therapeutic endpoint in refractory status epilepticus and as a prognostic marker after cardiac arrest. 1

Definition and EEG Characteristics

• Burst suppression consists of alternating periods: suppression phases (near-flat EEG with voltage <10 µV) interrupted by bursts of high-voltage electrical activity 1
• The pattern is considered present when suppressions occupy >50% of the EEG recording time 1
• This pattern indicates severe brain dysfunction and occurs during deep anesthesia, hypothermia, severe encephalopathy, or medically-induced coma 2

Clinical Context: Two Distinct Uses

1. Therapeutic Goal in Refractory Status Epilepticus

• Burst suppression is intentionally induced with anesthetic agents (pentobarbital, propofol, midazolam) as the treatment endpoint for refractory status epilepticus 3
• Achieving a "flat" EEG (deeper suppression) predicts better seizure control than burst-suppression alone: 17 of 20 patients (85%) with flat EEG achieved persistent seizure control versus only 6 of 12 patients (50%) with burst-suppression pattern 3
• The spectral composition within bursts predicts treatment success: bursts containing predominantly delta power (91.59%) indicate successful seizure termination, while bursts with faster frequencies (theta, alpha, beta) suggest ongoing seizure activity merely interrupted by anesthesia 4
• Isolated epileptiform discharges during burst suppression do not predict outcome, but recurrence of electrographic status after anesthetic taper predicts clinical relapse 3

2. Prognostic Marker After Cardiac Arrest

• Timing is critical for interpretation: burst suppression within the first 24-48 hours after return of spontaneous circulation (ROSC) may be compatible with neurological recovery 1, 5
• Persistent burst suppression at ≥72 hours from ROSC consistently predicts poor neurological outcome with 91.7-100% specificity 1
• Burst suppression should never be used alone for prognostication—international guidelines strongly recommend multimodal assessment combining EEG with somatosensory evoked potentials, clinical examination, and neuroimaging 1

Important Clinical Nuances

Spatial Heterogeneity

• Burst suppression is not always a global phenomenon: bursts can be substantially asynchronous across different cortical regions, and burst suppression may occur in limited cortical areas while other regions show continuous activity 2
• Unihemispheric burst suppression suggests an epileptic mechanism rather than metabolic suppression, particularly when associated with structural lesions or focal seizures 6

Pattern Variations

• Specific burst suppression patterns carry different prognostic weight: identical bursts or burst suppression associated with status epilepticus have very high specificity for poor outcome 1
• Heterogeneous burst suppression at 6-120 hours after ROSC predicts poor outcome with 90.7-100% specificity 1

Critical Pitfalls to Avoid

• Do not interpret burst suppression during therapeutic hypothermia or within 24 hours of cardiac arrest as definitively poor prognosis—it may be transient and reversible 1
• Ensure adequate EEG recording quality: electrical interference and artifacts can mimic or obscure burst suppression patterns, leading to false interpretations 1
• In refractory status epilepticus, do not assume burst suppression equals seizure control—analyze the spectral content of bursts, as persistence of fast frequencies indicates ongoing seizure activity 4
• Never use burst suppression as the sole criterion for withdrawal of life-sustaining treatment—this creates self-fulfilling prophecy and requires multimodal assessment 1
• Recognize that sedation must be cleared before prognostic interpretation in post-cardiac arrest patients 1

Monitoring Approach

• Continuous EEG monitoring is superior to intermittent recordings for detecting evolution of burst suppression patterns and identifying breakthrough seizures 5, 7
• Monitor for at least 24 hours initially, as seizure patterns may emerge days after presentation 7
• In therapeutic burst suppression for status epilepticus, titrate anesthetics to achieve maximal suppression (flat EEG) rather than settling for burst-suppression pattern alone 3