Sharp Slow Waves in the EEG

ABSTRACT

There exists a paucity of data in the EEG literature on characteristics of “atypical” interictal epileptiform discharges (IEDs), including sharp slow waves (SSWs). This article aims to address the clinical, neurophysiological, and neuropathological significance of SSW.

The EEGs of 920 patients at a tertiary-care facility were prospectively reviewed over a period of one year. Thirty-six patients had SSWs in their EEG. Of these, 6 patients were excluded because of inadequate clinical data. The clinical and neuroimaging data of the remaining 30 patients were then retrospectively collected and reviewed, and the findings were correlated.

The data revealed that SSWs were rare and age-related EEG events occurring primarily in the first two decades of life. All patients with SSWs had documented epilepsy, presenting clinically with partial or generalized epilepsy. It is notable that one-third of the patients with SSWs had chronic or static central nervous system (CNS) pathology, particularly congenital CNS anomalies.

Though more than one mechanism may be involved in the pathogenesis of SSWs, this research indicates that the most compelling theory is a deeply seated cortical generator giving rise to this EEG pattern. The presence of SSWs should alert clinicians to the presence of partial or generalized epilepsy or an underlying chronic or static CNS pathology, in particular congenital CNS anomalies, underscoring the significance of brain magnetic resonance imaging in the work-up of this population.

KEY WORDS:

• EEG
• IED variant
• interictal epileptiform discharges (IEDs)
• sharp slow waves (SSWs)
• sharp waves

ACKNOWLEDGMENTS

This study was conducted at and sponsored by King Khaled Hospital, Kingdom of Saudi Arabia. The study was not funded. Dr. Janati proffered the idea, critiqued the paper, helped with the analysis of the data, and helped revise the manuscript. Dr. ALGhasab prepared the manuscript. Drs. Alshammari, ALGhassab, and AL-Aslami interpreted and collected the data.

The authors thank Michael K. Janati (for editing the paper), Jeffrey F. Ricablanca, Thamer Saleh Seif, Zenaida M. Hipolito, Fahad Saad ALGhassab, and Haithm F. Alsheal.