Slow alpha variant: A normal <scp>EEG</scp> pattern

Slow alpha variant is a rare normal EEG pattern, a subharmonic of the alpha rhythm. Typically, it has half that of the patient's alpha rhythm frequency—usually 4–6 Hz.1, 2 It is mostly seen in adults, and its characteristics resemble those of the alpha rhythm concerning location (posterior head regions), state (relaxed wakefulness), morphology (sinusoidal or, at times, with a notched appearance), and reactivity to eye opening/closure.1, 2 Correctly identifying this normal variant helps avoid misinterpreting this pattern as abnormal—namely posterior irregular or regular slowing. In this multimedia teaching material, we present the EEG of a 51-year-old right-handed male with a history of HIV infection and epilepsy of unknown type featuring unprovoked convulsions since the age of 48 years. He underwent a routine EEG, which was normal. Further, it showed a distinct intermittent pattern in the posterior head regions with a subharmonic relationship to the patient's alpha rhythm (aka posterior dominant rhythm) consistent with slow alpha variant (Figures 1 and 2). Kaley J. Marcinski Nascimento: drafting of the manuscript for content, including medical writing for content; major role in the acquisition of data; study concept or design; analysis or interpretation of data. Sándor Beniczky: revision of the manuscript for content, including medical writing for content; major role in the acquisition of data; study concept or design; analysis or interpretation of data. Fábio A. Nascimento: revision of the manuscript for content, including medical writing for content; major role in the acquisition of data; study concept or design; analysis or interpretation of data. No targeted funding reported. This work has not been previously presented. Data S1. Data S2. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Slow alpha variant is a/an: 2. In which location do you typically find slow alpha variant: 3. On EEG a patient has an alpha rhythm frequency (aka posterior dominant rhythm) of 12 Hz. If a slow alpha variant is present, which of the following is its most likely frequency? Answers may be found in the supporting information.