Distinguishing vertex waves from vertex spikes

Various features define vertex waves. Since spikes may only appear in sleep, distinguishing these from spikes at the vertex requires considerable care. Their morphologies may be indistinguishable. Similarly, vertex waves may be followed by slow waves. Consider the following example:

The following represents the same page as above, but on the bipolar montage.

While vertex waves may be asymmetric, the presence of a dipole, best seen on the referential montage, distinguishes spikes at the vertex from vertex waves. On the referential montage, the electro-negative discharges appear at CZ-C4, while synchronously electropositive at C3. These, therefore, do not represent vertex waves.

Sometimes spikes only appear during sleep, but in this patient, they can also be seen during wakefulness, with a similar dipole.