Brief potentially ictal rhythmic discharges in critically ill adults

Brief potentially ictal rhythmic discharges, termed B(I)RDs, have been described mainly in neonates, and their significance in adults remains unclear.

To describe the incidence of B(I)RDs in critically ill patients and investigate their association with seizures and outcome.

We reviewed the records of prospectively identified patients with B(I)RDs and patients serving as controls matched for age (±5 years) and primary diagnosis.

The prevalence of seizures during continuous electroencephalography and functional outcome, as measured by the Glasgow Outcome Scale, were determined.

We identified B(I)RDs in 20 patients (2%). The pattern most often consisted of very brief (1-3 seconds) runs of sharply contoured theta activity without obvious evolution. All patients with B(I)RDs had cerebral injury, and in cases with a single focal lesion (11 [55%]), B(I)RDs were localized in the same region in all but 2 cases (18%). Patients with B(I)RDs were more likely to have seizures during continuous electroencephalography than were patients without B(I)RDs (15 of 20 [75%] vs 10 of 40 [25%]; P < .001), and 9 patients with B(I)RDs (60%) had only subclinical seizures. Brief potentially ictal rhythmic discharges were identified before seizures in all but 1 case (93%) and ceased in all 12 cases (80%) in which seizures were controlled. Patients with B(I)RDs tended to have a worse outcome than controls (16 [80%] vs 25 [63%]); however, this finding was not statistically significant.

Brief potentially ictal rhythmic discharges in critically ill patients are associated with a high prevalence (75%) of electrographic seizures and might serve as an early predictor of seizures during subsequent monitoring. A larger prospective study is needed to better understand their clinical and prognostic significance.