Answer:

Lambda waves (LW)¹ are surface positive occipital “sharp waves” rarely confused with epileptiform discharges.  LW may be elicited on EEG if scanning eye movements of complex visual stimuli are encountered in a well-lighted environment.  LW are usually < 50 uV, 200-300 msec duration, and recurrent in series time-locked to saccadic eye movements.  LW are similar to POSTS in morphology, polarity, and location but are occur in wakefulness and as an evoked response while POSTS appear spontaneously and during physiologic sleep. An age relationship was suggested with LW greater in the 3-12 age range with prevalence that decreases over the lifecycle. LW are felt to be associated with occulomotor visual-integration. Our patient had migraine with aura and clinically suspected syncope.  ASA accompanied by slightly higher doses of naldolol used for her hypertension yielded rare “visuals”.  While TV may have triggered LW² to appear on ambulatory EEG it was unable to be recovered to provide validation.   

References

1. Gastaut H.  Un signe electroencephalographique peu connu: les pointes occipitals survenant pendant l’overture des yeux. Rev Neurol (Paris), 1951;84:640-643.
2. Watching TV: A previously unrecognized powerful trigger of lambda waves. J Clin Neurophysiol 2011;28:400-403.