Benign Pediatric Variants

Benign Pediatric Variants

John Giang, MD

Why it matters

Overreading normal variants is the most common route to a false diagnosis of epilepsy; wickets alone are the leading culprit. Variants have a preferred age, state and location, and none evolves, disturbs the background, or carries an after-going slow wave.

Key points

• Wicket waves. Arch-shaped temporal waves, 6–11 Hz, 60–200 µV, in brief non-evolving trains, mostly in drowsiness; no slow wave, no background disruption. Mu is the central look-alike and blocks with movement.
• RMTD. Flat-topped or notched 5–7 Hz mid-temporal runs, unilateral or bilateral independent, a few seconds to 15 s, constant frequency and amplitude, fading as drowsiness deepens; lack of evolution separates it from temporal seizures. Mostly adolescents and adults.
• POSTS. Surface-positive, sail-shaped occipital waves of N1–N2, bilateral but often asymmetric; positive polarity and sleep context rule out occipital spikes. Lambda waves are the awake twin during visual scanning. Appear from 3–5 yr, frequent 6–12 yr.
• Hypnagogic/hypnopompic hypersynchrony. High-voltage 3–5 Hz rhythmic delta-theta, diffuse or fronto-centro-parietal, at sleep onset or waking, sometimes with sharp components; peaks 2–4 yr, fades by adolescence. Monomorphic, no consistent spike, stops as sleep deepens.
• Benign sleep transients. Vertex waves: central, symmetric, phase-reversing, high-amplitude and spiky in children, often in trains in infancy. Spindles: 11–16 Hz parasagittal; asynchronous and long (10–15 s) in the first year, synchronous by 1–3 yr. K-complexes: high-amplitude biphasic, often followed by a spindle. Related: 14 and 6 Hz positive spikes (ages 12–20, 20–60% of normals), BETS (<50 µV, drowsiness only), 6 Hz phantom spike-wave.

Common pitfalls

• Judging morphology alone: polarity, state and location decide (POSTS positive; BETS and RMTD only in drowsiness).
• Calling hypersynchrony a spike-wave burst because a few waves look sharp.
• Expecting adult variants in toddlers (wickets, RMTD, 14 and 6) or child variants in teens (hypersynchrony, spiky vertex trains).
• Forgetting that variants vanish in deep sleep while true spikes are activated.
• Missing an isolated spike with a field and slow wave hidden inside a wicket run.