Abstracts

Rationale: Midline (Cz-Pz) interictal spikes have been described with generalized and partial epilepsies in children. Most studies have been limited to small numbers, and have not agreed upon a common etiology for isolated midline discharges. The aim of this study is to describe the clinical characteristics and neuroimaging findings in children with isolated Cz-Pz discharges, in an attempt to define the electro-clinical syndrome of midline spikes. Methods: Retrospective review of medical records was conducted on all patients with isolated midline spikes identified in the EEG database at CHB from 2005 to 2009. Records were reviewed for presence of seizures, seizure types, other neurological diagnoses, and neuroimaging findings. EEG studies including follow up EEG data was also reviewed for precise location of the spikes over the scalp. EEG source analysis was also conducted on randomly sampled cases. Results: Of the 68 patients identified, 40 (59%) had a history of seizures, while 28 (41%) did not have seizures. Among the group of children with seizures, complex partial seizures were the most common type (65%). In 25% of these patients, follow-up EEG showed the presence of new epileptiform discharges in other scalp regions including central, parietal and temporal sites. Neuroimaging studies showed focal findings in 60% of cases. In children with generalized seizures (35%), atonic/tonic seizures were the most common subtype (6/13) followed by complex febrile seizures (3/13). In the group of children without epilepsy, other conditions included developmental delay (41%), pervasive developmental disorder (18%), ADHD (10%), and syncope (18%). Follow-up EEG studies in this group showed either disappearance (31%) or persistence (47%) of midline discharges, and also the presence of new discharges at other sites (22%). EEG source analysis for a quarter of the randomly sampled cases showed the onset of the midline discharges was right parietal (37%), left parietal (25%), right occipital (25%), right frontal (13%) from a superficial source. Conclusions: Midline spikes are seen not only in children with partial and generalized epilepsies, but also incidentally in children with diverse behavioral problems without having a seizure disorder. New discharges often appear on follow up at other sites, while they may disappear with time in children without epilepsy.