A 14-year-old girl presented to the epilepsy monitoring unit for diagnostic evaluation of recurrent episodic abdominal pain. During the admission, multiple typical episodes lacked ictal correlate, and she was diagnosed with nonepileptic events. However, her long-term EEG recording revealed several transient findings in wakefulness and sleep exemplifying normal developmental variants in the awake (Figure 1) and asleep (Figure 2) EEG. Posterior slow waves of youth, 14 and 6 Hz positive spikes, and alpha squeak are rare before 2 years, and only alpha squeak persists after adolescence.1,2 Lambda waves and positive occipital sharp transients of sleep do not occur younger than 1 year and are more common in later childhood through adulthood.1,2 Rhythmic midtemporal theta of drowsiness occurs from adolescence through adulthood.2 We show examples of these variants in 3 separate montages, highlighting the montage(s) in which each is best appreciated.1,2 Proper recognition of these age-appropriate normal EEG variants is key to avoid overinterpretation and misdiagnosis.2
(A) Alpha squeak (red box) is a fast posterior dominant rhythm evident during eye blinks. (B) Lambda waves (red arrows) are positive occipital sharp waves present during visual scanning of high-contrast environments. (C) Posterior slow waves of youth (red boxes) are delta waves embedded within the posterior dominant rhythm.
(A) 14 and 6 Hz positive spikes (red box) are 1–2 second bursts of spiky, arciform waveforms. (B) Rhythmic midtemporal theta of drowsiness (red box), or psychomotor variant, consists of nonevolving runs of prominent theta activity. (C) Positive occipital sharp transients of sleep (red arrows) are morphologically similar to lambda waves.
Author Contributions
L. Basovic: drafting/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. K. Walsh: analysis or interpretation of data; additional contributions: designing and crafting figures. C.J. Chu: drafting/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.
Study Funding
No targeted funding reported.
Disclosure
The authors report no relevant disclosures. Go to Neurology.org/N for full disclosures.
Footnotes
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Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
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Submitted and externally peer reviewed. The handling editor was Resident and Fellow Deputy Editor Ariel Lyons-Warren, MD, PhD.
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Teaching slides links.lww.com/WNL/C994
- Received January 23, 2023.
- Accepted in final form May 11, 2023.
- © 2023 American Academy of Neurology
