In an EEG displayed at 30mm/sec, a high voltage transient lasting 2mm is categorized as what?

The categorization of a high voltage transient lasting 2mm on an EEG displayed at a speed of 30mm/sec is classified as a spike. In EEG terminology, a spike is defined as a waveform that is characterized by its sudden onset, typically lasting less than 70 milliseconds, with an amplitude that is significantly higher than the surrounding background activity.

When viewed on the paper at a speed of 30mm/sec, a 2mm transient indicates it lasts approximately 66.67 milliseconds (since 2mm at 30mm/sec corresponds to 2/30 seconds). This fits well within the definition of a spike. The high voltage aspect also contributes to its classification as such since spikes are usually associated with a notable increase in voltage compared to the baseline EEG.

In contrast, theta and alpha waves have distinct frequency bands and characteristics that do not match a high voltage transient, nor do they have the quick onset and resolution associated with a spike. A sharp wave would also involve a different morphology, typically appearing more rounded and has a duration longer than spikes. The criteria for spikes emphasize their brief duration and high amplitude, clearly aligning with the scenario provided in the question.