Abstracts

Subclinical Rhythmic Epileptiform Discharge of Adults (SREDA) is a non-ictal electrographic variant most frequently characterised as a 5-7 Hz rhythm of abrupt onset and termination and located maximally in the temporoparietoocipital regions. It differs from an ictal pattern in a lack of evolution in frequency, distribution and morphology, and in the subjects[apos] lack of clinical change during the duration of the discharge.(1) SREDA has most often been described in adults in the 4th to the 9th decades, but Najarajan et al have described this pattern in 2 young girls.(2,3) We report its occurrence in a young man whose SREDA had characteristics described as rare in adults. In the pediatric division of our institution, approximately 2200-2500 routine EEGs and 150-200 prolonged video-EEG studies are performed each year. Since 2001, only one case of SREDA in a pediatric patient was seen in our institution. Case Report: The patient initially presented at the age of 14 for staring spells. His neurologic examination and IQ were normal. An intial routine and video EEG were interpreted as showing non-convulsive status, despite his ability to interact during the discharges. He was placed on valproate with no clinical change. A second video EEG 3 years later showed bursts of 5-6 Hz discharges occaisionally slowing to 1-2 Hz which were consistently maximal in the frontal regions and at the vertex, bilaterally synchronous in onset, and persisting in light sleep. The bursts lasted up to 5 minutes in duration and ended abruptly with re-emergence a normal background, and comprised [gt]50% of the record during the 3 days of monitoring. The SREDA persisted unchanged during activation procedures, eye opening and closing, and repetition of syllables such as [quot]lilt[quot]. During the bursts, he repeatedly demonstrated his ability to follow commands, answer questions, play video games, and complete neuropsychologic testing. SREDA is rare EEG pattern occurring in approximately 1/2500 adult recordings and documented in patients with such non-epileptiform complaints as headaches, dizziness, and depression, as well as seizures. Atypical SREDA variants charcterised as frontally predominant, or occurring as delta frequencies, or having a waxing and waning pattern have also been described, comparable to what we saw in our patient. (2) While our experience at our institution confirms that of Nagarajan et all that SREDA is not seen exclusively in adults, it also suggests that SREDA is more rare in pediatric patients.
1. Westmoreland B. and Klass D. A Distinctive Rhythmic EEG Discharge of Adults. Electroencephalography and Clinical Neurophysiology, 1981, 51:186-191.
2. Westmoreland B. and Klass D. Unusual variants of subclinical rhythmic electrographic discharge of adults (SREDA). Electroencephalography and Clinical Neurophysiology, 1991, 102:1-4.
3. Nagarajan L. et al Subclinical Rhythmic EEG Discharge of Adults: SREDA in Two Children. Pediatric Neurology, 2001; 24:313-316.