Extreme delta brush: a unique EEG pattern in adults with anti-NMDA receptor encephalitis

Abstract

Objectives: To determine continuous EEG (cEEG) patterns that may be unique to anti-NMDA receptor (NMDAR) encephalitis in a series of adult patients with this disorder.

Methods: We evaluated the clinical and EEG data of 23 hospitalized adult patients with anti-NMDAR encephalitis who underwent cEEG monitoring between January 2005 and February 2011 at 2 large academic medical centers.

Results: Twenty-three patients with anti-NMDAR encephalitis underwent a median of 7 (range 1-123) days of cEEG monitoring. The median length of hospitalization was 44 (range 2-200) days. Personality or behavioral changes (100%), movement disorders (82.6%), and seizures (78.3%) were the most common symptoms. Seven of 23 patients (30.4%) had a unique electrographic pattern, which we named "extreme delta brush" because of its resemblance to waveforms seen in premature infants. The presence of extreme delta brush was associated with a more prolonged hospitalization (mean 128.3 ± 47.5 vs 43.2 ± 39.0 days, p = 0.008) and increased days of cEEG monitoring (mean 27.6 ± 42.3 vs 6.2 ± 5.6 days, p = 0.012). The modified Rankin Scale score showed a trend toward worse scores in patients with the extreme delta brush pattern (mean 4.0 ± 0.8 vs 3.1 ± 1.1, p = 0.089).

Conclusions: Extreme delta brush is a novel EEG finding seen in many patients with anti-NMDAR encephalitis. The presence of this pattern is associated with a more prolonged illness. Although the specificity of this pattern is unclear, its presence should raise consideration of this syndrome.

Figure 1. Continuous EEG recording in a 23-year-old woman with anti-NMDA receptor encephalitis, seizures, and coma

(A) The initial EEG tracing demonstrates generalized rhythmic and semirhythmic delta frequency activity at 1 Hz with superimposed, frontally predominant bursts of rhythmic beta frequency activity. High pass filter 0.5 Hz; low pass filter 70 Hz; notch filter off. (B) Time-frequency analysis of the EEG tracing. A compressed spectral density array over 30 seconds of recording demonstrates increased low-frequency power with rhythmic bursts of 18−32 Hz power, which is characteristic of the extreme delta brush pattern.

Figure 2. Continuous EEG recording in a 19-year-old man with anti-NMDA receptor encephalitis associated with dyskinesias, seizures, and coma

The initial EEG demonstrates generalized rhythmic delta frequency activity at 2–2.5 Hz with superimposed rhythmic beta frequency activity.

Figure 3. Continuous EEG from the patient in figure 2, 7 months after initiation of aggressive immunotherapy, including rituximab, cyclophosphamide, IV methylprednisolone, and IV immunoglobulin

The extreme delta brush pattern has resolved, and background EEG activity has largely normalized.