Correct answer: B. 14 and 6 Hz positive bursts

Previously called 14 and 6 Hz positive spikes, 14 and 6 Hz positive bursts is a benign variant characterized by 14 and 6 Hz bursts of arciform, surface-positive spikes found maximally in the posterior temporal regions (2). Because of their comb-like morphology, they are also called ctenoids (ktenois is comb in Greek). Both frequencies may occur independently, unilaterally, asynchronous, or bilaterally asymmetric as seen here maximally at P8/O2. Typically, the benign variant appears in bursts of 0.5-2 seconds, although the patient in this case had prolonged runs lasting minutes. The intracranial source of 14 and 6 Hz positive bursts has not been fully elucidated. Stereo-EEG studies have shown correlation to the ipsilateral hippocampus (1). The study demonstrated both frequencies to coincide with an atypical hippocampal waveform. This correlation emphasizes the benign nature of this variant. All answer choices are benign variants; they are non-evolving, and predominantly emerge in light sleep. Wickets (A) are also arciform with 6-11 Hz brief runs but are surface-negative. 6 Hz phantom spike and slow wave (C), as the name suggests, refers to low amplitude spikes followed by more prominent higher amplitude slow wave component. Of the two subtypes, FOLD (Female, Occipital location, Low amplitude Drowsiness) as compared to WHAM (Wake, High amplitude, Anterior location, Male) is more benign with a lower prevalence in epilepsy patients. RMTD (D) is characterized by rhythmic 4-7 Hz theta maximal in the mid temporal regions but are surface-negative.

Correct answer: A. Temporal lobe epilepsy

14 and 6 Hz positive bursts were previously thought to be associated with psychiatric conditions and epilepsy. There remains uncertainty of its clinical significance. There is increased incidence in childhood peaking in adolescence and decreasing with advanced age (D). In all age groups, this pattern had higher incidence in patients with metabolic encephalopathies including hepatic encephalopathy as in this patient. Other studies have shown association with normal brain activity and no significant clinical difference between patients without this variant. (1)