Bispectral index (BIS) monitoring of acute encephalitis with refractory, repetitive partial seizures (AERRPS)

Abstract

Diagnosis of ictal discharges during epileptic activity should be based on raw electroencephalography (EEG). The apparatus necessary for such a diagnosis would typically require time to properly set up and operate. The bispectral index (BIS), an EEG-derived parameter that is easy to establish and easy to use, has been shown to correlate with numerous EEG conditions and may represent a useful tool. Acute encephalitis with refractory, repetitive, partial seizures (AERRPS) is an epileptic syndrome first described by Sakuma in Japan in 2001. We assessed the utility of using BIS monitoring as a diagnostic tool and as a monitor of anticonvulsive therapy in a 14-year-old patient admitted to the intensive care unit with AERRPS. After BIS monitor montage, BIS, electromyography (EMG) and raw EEG data were continuously recorded. Epileptic seizures lasting 1-2 min were repeated every 3-4 min. Using paired t-test analysis, mean +/- SD BIS and EMG peak values at the start of epileptic seizures (94.5+/-3.6, 55.8+/-2.5 dB) were significantly higher than values measured at the end of seizures (55.1+/-12.5, 34.5+/-2.8 dB), respectively. Real-time EEG revealed bursts of epileptiform discharges replaced by slow d and q waves with ictal remissions. During induced pharmacologic barbiturate/diazepam coma, BIS decreased to near isoelectricity (11.9+/-2.5) with a steady increase in suppression ratio (65.5+/-9.7). The characteristic BIS profile of repetitive 1-2 min high EEG/EMG activity could serve as an indicator of a global increase in cerebral activity with seizures. Our report suggests that BIS, an easy-to-use device, might be helpful in monitoring clinical trends after EEG confirmation of diagnosis as well as in successfully depicting the efficacy of therapy.