Color density spectral array of bilateral bispectral index system: Electroencephalographic correlate in comatose patients with nonconvulsive status epilepticus

PURPOSE to describe the characteristics of the color density spectral array (CDSA) of bilateral bispectral index (b-BIS) monitoring system in patients with comatose nonconvulsive status epilepticus (NCSE). We hypothesized that CDSA could be helpful for monitoring NCSE in critically subjects if continuous EEG (cEEG) is not available. METHODS we retrospectively analyzed comatose patients admitted to our neurological intensive care unit (NICU) from 2011 to 2014 with a diagnosis of definitive NCSE that underwent b-BIS monitoring for at least 24h to guide anesthetic sedation. Clinical, electroencephalography and neuroimaging findings were analyzed. Moreover, all parameters from the b-BIS data including the CDSA were reviewed during periods of NCSE (NCSE pattern) and profound sedation (sedation pattern). RESULTS 15 NCSE patients were included. The delay from the diagnosis of NCSE to the onset of b-BIS monitoring was 8 (0.5-31)h and total time of b-BIS monitoring 7.8±6.5 days. CDSA during NCSE pattern was characterized by continuous or intermittent red and dark red tones, spectral edge frequency (SEF) in the delta-theta range, with or without asymmetry and BIS number trend with significant variability. In contrast, CDSA during sedation revealed predominance of orange, yellow, green and occasionally blue tones, SEF in the alpha-beta range, absence of asymmetry and stability of BIS number. CONCLUSIONS b-BIS monitoring system and, in particular, CDSA used by nonexpert NICU personnel may be helpful to follow-up episodes of NCSE, to detect recurrences of nonconvulsive seizures (NCSzs), and to monitor profound anesthetic therapy in comatose patients when cEEG is not available.