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Abnormalities of alpha rhythm, photic response, and mu rhythm

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(Figure 4-1 to 4-25 and 4-28)

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Figure 4-1.

Posterior Slow Wave of Youth. EEG of an 11-year old girl with a new onset of insomnia, weight loss, and depression shows occipital slow theta and delta slow waves (arrows) mixed with and briefly interrupting the alpha rhythm on both sides.

Posterior slow waves of youth (youth waves or polyphasic waves) are physiologic theta or delta waves accompanied by the alpha rhythm and creating spike-wave-like phenomenon. They are most commonly seen in children aged 8–14 years but are uncommon in children under 2 years. They have a 15% incidence in persons aged 16–20 years but are rare in adults after age 21 years. They are typically seen both unilaterally and bilaterally in a single recording. They are always accompanied by the alpha rhythm, and are attenuated with eye opening, disappear with the alpha rhythm during drowsiness and light sleep, and may be accentuated by hyperventilation.13

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Figure 4-2.

Posterior Slow Wave of Youth. EEG of a 10-year old boy with recurrent syncope shows occipital slow waves (arrows) mixed with and briefly interrupting the alpha rhythm on the right side.

Posterior slow waves of youth (youth waves or polyphasic waves) are physiologic theta or delta waves accompanied by the alpha rhythm and creating spike-wave-like phenomenon. They are most commonly seen in children aged 8–14 years but are uncommon in children under 2 years. They have a 15% incidence in persons aged 16–20 years but are rare in adults after age 21 years. They are typically seen both unilaterally and bilaterally in a single recording. They are always accompanied by the alpha rhythm, and are attenuated with eye opening, disappear with the alpha rhythm during drowsiness and light sleep, and may be accentuated by hyperventilation.13

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Figure 4-3.

Posterior Slow Wave of Youth; Attenuated with Eye Opening. EEG of a 10-year-old boy with syncope showing occipital slow theta and delta waves (arrows) mixed with and briefly interrupting the alpha rhythm in both occipital regions but maximally expressed in the left hemisphere. This is so-called “posterior slow waves of youth” that are physiologic findings seen commonly in children aged 8–14 years. They are always accompanied by the alpha rhythm, and are attenuated with eye opening (open arrow), and disappear with the alpha rhythm during drowsiness and light sleep.13

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Figure 4-4.

Posterior Slow Wave of Youth; Activated with Eye Closure. (Same EEG as in Figure 4-3) Alpha rhythm and posterior slow waves of youth are activated by eye closure.

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