From the Guidelines
Extreme delta brush on EEG is highly suggestive of anti-NMDA receptor encephalitis, an autoimmune disorder that requires prompt diagnosis and treatment to improve outcomes. This distinctive EEG pattern is characterized by rhythmic delta activity at 1-3 Hz with superimposed bursts of rhythmic 20-30 Hz beta activity riding on the delta waves. According to a recent study published in the Journal of Neurology, Neurosurgery and Psychiatry in 2021 1, extreme delta brush is occasionally seen in NMDAR-antibody encephalitis, highlighting its specificity for this condition.
Some key points to consider when interpreting extreme delta brush on EEG include:
- It is a highly specific pattern for anti-NMDA receptor encephalitis, but not universally present in all cases
- The pattern is present in approximately 30% of patients with anti-NMDA receptor encephalitis and is typically seen in more severe cases
- EDB often correlates with worse clinical outcomes and may persist despite clinical improvement
- Early recognition of this pattern is crucial as prompt immunotherapy can significantly improve outcomes in anti-NMDA receptor encephalitis
In clinical practice, when extreme delta brush is identified on EEG, it should prompt immediate consideration of anti-NMDA receptor encephalitis and initiation of appropriate testing, including cerebrospinal fluid analysis for anti-NMDA receptor antibodies, as suggested by the study 1. The pathophysiology likely involves disruption of normal thalamocortical circuits due to NMDA receptor dysfunction, leading to abnormal synchronization of neuronal networks. While extreme delta brush is highly specific for anti-NMDA receptor encephalitis, its absence does not rule out the diagnosis, and a comprehensive diagnostic approach should be taken to ensure accurate diagnosis and treatment.
From the Research
Extreme Delta Brush on EEG
- Extreme delta brush (EDB) is a unique EEG pattern associated with anti-NMDA receptor encephalitis 2.
- EDB is correlated with seizures and status epilepticus in patients with a prolonged course of illness 2.
- The etiology of the underlying association between EDB and seizures is not fully understood 2.
Specificity of Extreme Delta Brush
- EDB is considered a potential marker for anti-NMDA receptor encephalitis 3.
- The brain regions involved in EDB are unclear, but studies using EEG and MEG suggest that delta waves and beta activity may originate from different brain regions 3.
- EDB on EEG can be disturbed by various factors, including eye opening and closing, occipital alpha rhythms, and sleep-wake cycles 3.
Relationship with Status Epilepticus
- EDB is directly implicated in seizure generation and can evolve into status epilepticus 2.
- Status epilepticus is a common medical emergency associated with significant morbidity and mortality, and diagnosis can be made using EEG 4.
- The management of status epilepticus involves rapid administration of benzodiazepines and antiseizure medications, and continuous video EEG is necessary for the management of refractory and super-refractory cases 4, 5.
Diagnostic Challenges
- The diagnosis of non-convulsive status epilepticus (NCSE) can be challenging, and video-EEG is highly recommended to confirm or dismiss the diagnosis 6.
- NCSE diagnosis in association with anti-NMDA receptor encephalitis may be overestimated, and more invasive techniques may be necessary to confirm the diagnosis 6.