Nonconvulsive seizures (NCS) in children admitted to the Pediatric Intensive Care Unit (PICU) from Jan 2000 to Dec 2003 were analyzed in a study at The Hospital for Sick Children, Toronto, Ont, Canada. A NCS was defined as a deterioration of consciousness accompanied by at least one episode of electrographic seizure lasting longer than 10 s. Of 141 patients admitted with unexplained altered consciousness, no overt seizure, and EEG recording within 24 h, 23 (16.3%) had NCS. Male to female ratio was 1.9:1. The mean age was 40.1 mo (range: 1 mo to 18 y); infants <1 mo were excluded. No preexisting disease was present in 10 (43%); 8 (35%) had a history of seizures, 2 (9%) congenital heart disease, and 3 (13%) other underlying disease. None had nonconvulsive status epilepticus. The etiology of NCS was an acute structural brain lesion in 11 (48%); cerebral infarction in 6, subdural hematoma in 3, cerebral hemorrhage in 1, and AV malformation in 1. Other etiologies included meningitis in 3 (13%), seizure disorder in 3 (13%), sepsis in 2 and pneumonia in 2. EEG showed right-sided epileptiform discharges in 9 (39.2%), most commonly temporal; the EEG pattern was S/W in 9 (39.1%). The mean duration of EEG discharge was 159 s (range: 10 s to 11 min). MRI or CT was abnormal in 18 (78.2%), most commonly cerebral infarction in 6 (26.1%), followed by diffuse edema in 5 (21.7%). Brain imaging and EEG were concordant in localization in 10 (55.6%). All seizures responded to treatment with IV phenobarbital or phenytoin. 
COMMENT. Of children admitted to the PICU with altered state of consciousness, 16% have NCS. A higher prevalence (33%) reported in a previous study is explained by the inclusion of neonates and PLEDs. In contrast to adults who often have preexisting epilepsy and traumatic brain injury as precursors of NCS, children have no preexisting disease in 43% of cases, cerebral infarction as the most common NCS etiology, and a predominance of right hemisphere localization. An early EEG is indicated in children with deterioration of consciousness of uncertain origin.
Nonconvulsive status epilepticus is described in 19 pediatric patients admitted to the Epilepsy Center, Columbia University, NY, June 2000 - Dec 2003. Five developed NCSE following convulsive SE and 12 followed brief convulsions. Acute hypoxic-ischemic injury was the most frequent etiology (in 5 (26%)). Six had associated periodic lateralized epileptiform discharges (PLEDs), and 1 had generalized periodic epileptiform discharges (GPEDs), both associated with worse outcome. Five (26%) died of the underlying acute medical illness. Prolonged EEG monitoring may be warranted after brief convulsive seizures to exclude NCSE.