Spike-wave index
Also written as: SWI — spike-wave index
A quantitative measure expressing the percentage of time that spike-wave discharges occupy during an EEG recording period.
Full Definition
The spike-wave index (SWI) is a quantitative EEG parameter that measures the proportion of time occupied by epileptiform discharges, typically expressed as a percentage. It is calculated by dividing the total duration of spike-wave activity by the total recording time. This index is particularly useful in assessing the burden of epileptiform activity in conditions like absence epilepsy or Lennox-Gastaut syndrome, where spike-wave discharges may be frequent or continuous. A higher spike-wave index often correlates with greater seizure severity and cognitive impairment. The measurement is valuable for monitoring treatment response and disease progression, especially in epileptic encephalopathies.
Usage
Usage note: Always express as a percentage and specify the recording conditions (awake, sleep, etc.).
In Context
- "The patient's spike-wave index decreased from 85% to 30% following initiation of valproate therapy." — EEG report
- "A high spike-wave index during sleep was associated with cognitive decline in this cohort." — Research paper