Introduction: “Subclinical Spikes” (SCS) are electrographic spikes without known or observable clinical seizure manifestations, and may be associated with neuropsychological, behavioral and academic impairments. [Mintz et al. 2009]

Methods: Retrospective review and analysis of patients without known epilepsy with unexpected SCS found on digital dense array electroencephalography (dEEG).

Results: 27 subjects (20 male, 7 female) ranging in age from three to 13 years (mean 7.5 years) with diagnoses of ADHD, learning disorders and/or behavioral issues who had unexpected SCS on dEEG were identified. Baseline spike burden was determined from a 41-minute routine awake/drowsy dEEG recording, ranging from 0.07 spikes/minute (spm) to 18.53 spm. Nine patients had frontal spikes, 16 central-temporal and two occipital. 12 subjects had magnetic resonance imaging (MRI), all unremarkable except two: venous angioma and temporal arachnoid cyst. 19 subjects (70%) had baseline neuropsychological (NP) assessments, all with significant abnormalities, including cognitive deficits in working memory, attention and processing speed. 10 subjects (37%) were treated with antiepileptic drugs (AED), all associated with significant spike suppression. Five (50%) had a repeat NP assessment after a one-year interval, all with significant NP improvements.

Conclusion/Discussion: Unexpected SCS can be found in patients presenting with cognitive and neurobehavioral disorders not related to epilepsy, and may be associated with impairments of neurological and NP functioning. AEDs can result in improvements in clinical and NP surrogate markers in some patients, associated with concomitant spike suppression, suggesting the concept of “Epilepsy Spectrum Disorders”. Further longitudinal studies are needed to define these associations.