Vertex Sharp Wave Transients

EEG Sample Credit: The Learning EEG (learningeeg.com)

Vertex Sharp Wave Transients (V Waves)

V waves can be recognized in infants at as early as 2 months of age. Low-voltage theta with POSTS, low-voltage V waves, and drifting horizontal eye movements with decreased muscle artifact denote N1 sleep. V waves first appear as a sign of late drowsiness in N1 sleep with a lower amplitude and are less sharply contoured as compared to that seen in N2. V waves should be easily distinguishable from the background.  

They are bilateral phase reversing discharges over the central regions maximal at CZ and the central derivations. V waves usually have a maximal amplitude (on referential montages) and reverse phase (on bipolar montages) at the CZ electrode.  The spread may involve the neighboring central (C3, C4) and sometimes frontal electrodes. 

V waves are diphasic, sharply contoured, surface-negative waves followed by a small positive phase lasting 70-200ms, with highly variable amplitude that are generally symmetrical and synchronous These waves appear singly in adults or in serial repetitive runs especially in young children and may be quite sharp or high amplitude. In adults, the amplitude is usually 100 to 150μV, and in children up to 250μV. Although they are scary looking they are normal and rarely considered epileptiform. A V wave is primarily a spontaneous phenomenon but they can be elicited by a light arousal stimulus.