Abstracts

Rationale: Midline spikes are defined as epileptiform activity arising from the midsagittal region of the brain. Isolated midline spikes are uncommon. Earlier studies have shown that midline spikes are more common in children and highly associated with seizures. Both generalized and focal seizures have been described. These studies have been limited to small cohorts of children with epilepsy, and few have examined isolated midline discharges. Some studies have found midline spikes associated with benign epilepsy, especially in young children during sleep (Capovilla). We attempted to better define the electro-clinical findings in patients with midline spikes by evaluating clinical features and follow up EEG’s in comparison to age and sex matched control patients who had EEGs for various indications. Methods: All EEGs at BC Children’s Hospital are entered in a database, which includes EEG interpretation and clinical data obtained by an EEG technologist . The database was queried for midline spikes between 1992 and 2014. Patients less than 2 months of age, in a coma state and with ictal midline spikes were excluded. Midline spikes were defined as epileptiform discharges localized to Cz, Pz and/or Fz. Patients with epileptiform discharges at other sites or patient’s whose midline spikes had a broad field or side bias were exlcuded. Patients with a follow-up EEG within 12-24 months were included. If several EEG’s were done in this time, data from the EEG’s was combined. A 10% sample of each group was interpreted blindly by at least 2 of the investigators to verify the EEG interpretation. An age and matched control group were randomly selected from the database. Clinical data, including seizure types and frequency, medications and development were obtained from the database and retrospective chart review. Outcome was evaluated by looking at development, neurologic exam, seizure frequency and number of medications at follow-up. The midline spike group was compared to the control group to determine if there were any significant differences. Results: From a total of 30,760 patients referred for an EEG from 1992 to 2014, we identified 123 patients who met our inclusion criteria. No significant difference between the midline and control groups was noted in terms of seizure types, etiology,and neuro-imaging (all P value >0.05).  Patients with midline spikes had a greater frequency of seizures than the controls. 31% were seizure free, 35% had less than one seizure per month and 34% had frequent seizures (more than monthly). In the control group, 51% were seizure free, 29% had less than one seizure per month, and 18% had frequent seizures (more than monthly) (P=0.005). Seizures were focal or generalized. More children had development delay in the midline group compared to the control group (43% vs 29%, Odds ratio 1.8 95%CI [1.1, 3.2], P=0.03). Children without seizures in the midline group also had a higher risk of development delay compared to the control group (40% vs 17%, odds ratio 3.16, 95%CI [1.1, 8.8], P=0.03).  Conclusions: The results of the present study allow further delineation of electroclinical features of midline spikes. This is the largest reported group of isolated midline spikes. The study confirms that isolated midline spikes are rare in the pediatric population. Patients with midline spikes can have focal or generalized epilepsy. In our study, all patients had follow-up EEG’s, which may have excluded some of the benign or non-epileptic cases. The patients with midline spikes had a higher risk of developmental delay, whether they had seizures or not. Patients with midline spikes also had a higher frequency of seizures, suggesting they have frequent seizures that may be difficult to manage.  Funding: None