Significance of interictal occipital epileptiform discharges in children.

Objective: Interictal occipital epileptiform abnormalities have not been well characterized. The objective of this pilot study was to assess their significance in children.

Methods: A search was performed on the EEG database for the keywords "occipital", "spike", "sharp wave" and "epileptiform". Patients were divided into two groups based on the absence of all (group 1) or presence of any (group 2) of the following criteria: mental retardation, cerebral palsy, neurological deficits, abnormal MRI and/or intractable epilepsy. Special attention was given to the spike/sharp wave amplitude/duration and background slowing.

Results: A total of 44 children (eight months to 15 years) were studied. Groups 1 and 2 were each composed of 22 children. Background slowing was more frequent in group 2 (10/22, 45%) compared to group 1 (1/22, 4.5%; p = 0.002). In group 2, 8/22 (36%) had spikes or sharp waves with amplitudes below 50 microV or above 150 microV with a positive predictive value of 89%, and a negative predictive value of 39%. Only 1/22 (4.5%) in group 1 had epileptiform activity outside of the 50-150 microV range.

Conclusions: The presence of very high or low-amplitude occipital epileptiform abnormalities or background slowing may be indicative of encephalopathy.