Spikes and Sharp Waves

Spikes are transients, clearly distinguishable from background activity, with pointed peak and a duration of approximately 20–70 ms, whereas sharp waves are the same as spikes, but with a duration of 70–200 ms.

Bifrontal spikes

• An epileptiform transient clearly distinguished from the background activity, although amplitude varies. A pointed peak at a conventional time scale and duration of 70-200 ms, usually with a steeper ascending phase when compared to the descending phase. Main component is generally negative relative to other areas, and may be followed by slow wave of the same polarity.
• The term should be restricted to epileptiform discharges, and does not apply to: (a) distinctive physiological events such as vertex sharp transients, lambda waves and positive occipital sharp transients of sleep, (b) sharp transients poorly distinguished from background activity (without or with a slow wave for example six Hz spike-and-slow-wave).
• Sharp waves should be differentiated from spikes, i.e. transients having similar characteristics but shorter duration.