Table 1 KCNQ2 mutations and main features of the patients
Mutation | Seizure onset (days) | Initial seizure type | Seizure evolution | First EEG | Development (age at evaluation) | |
|---|---|---|---|---|---|---|
Patient 1 | c.C860A p.T287N | 1 | Clonic and tonic. Multiple seizures daily. | 2 weeks: seizure offset. | Suppression-burst. | Poor eye contact, poor head control (9 months). Normal HC. |
Patient 2 | c.G523T p.V175L | 15 | Myoclonic jerks. No erratic myoclonus. | 0-3 months: myoclonic jerks. | Discontinuous. | Deceased at 17 months. |
Bursts of polyspikes generalized or in the in central regions. | No eye contact, no head control. HC : 41cm. | |||||
3–6 months: reflex audiogenic seizures. | ||||||
6–12 months: epileptic spasms. | ||||||
>12 months: myoclonic jerks. | ||||||
Patient 3 | c.C926T p.A309V | 3 | Tonic, pallor, Multiple seizures daily. | 0-24 months: multiple daily focal seizures. 2–5 years: 1 seizure/week. 7 years: epilepsy offset. | Suppression-burst. | Poor eye contact. Global hypotonia, unable to sit (2 years) |
Patient 4 | c.C821T p.T274M | 2 | Tonic and hypotonic. Epileptic spasms. | 2 months: seizure free. Erratic intermittent myoclonus. | Suppression-burst. | Poor eye contact, no head control, global hypotonia (14 years). Normal HC. |
Right temporal, asymptomatic seizures. | ||||||
Patient 5 | c.G715C p.G239R | 2 | Tonic and tonic-clonic, cyanosis. | 2-6 weeks: Tonic and tonic-clonic seizures in clusters. 2 m: seizure stop | Poor activity. Prolonged periods of flatness of the traces. Generalized spikes predominating on the left hemisphere. Then suppression-burst. | Good eye contact. Sitting, hand use (10 months). Walking (22 months). |
No speech (4 y) Normal HC | ||||||
Patient 6 | c.C881T p.A294V | 2 | Left and right clonic jerks, facial cyanosis. | 3 months: Seizure offset. | Suppression-burst. | Poor head control, unable to sit, no voluntary movement, no language (2 years). |
Patient 7 | c.C881T p.A294V | 1 | Isolated access of cyanosis. Then recurrent hypertonic posture. | 7 months: epileptic spasms. | Suppression-burst. | Eye contact. Strabismus. |
No sit, no speech (11 y). | ||||||
Multiple focal seizures: tonic contractions of one or several limbs, cyanosis. | ||||||
2–9 years: seizure-free. | ||||||
> 9 years: monthly GTC seizures. | ||||||
Patient 8 | c.T911C p.F304S | 1 | Tonic asymmetric. | 2 months: multifocal seizures. 4 months: rhythmic jerks. 3 years: tonic seizures, cyanosis. 3-11y: Persistence of tonic seizures, cyanosis. | Bursts of multifocal spikes and periods of poorness of the activity. | Unable to sit, poor use of hands. No language. Feeding difficulties (gastrostomy, 11 years) |
Patient 9 | c.G566T p.G189V | 3 | Tonic. | 0-6 months: multiple focal seizures. 6–24 months: epileptic spasms. Seizure free since then. | Suppression-burst. | Poor eye contact. Global hypotonia, unable to sit (10 years) |
Patient 10 | c.G793A p.A265T | 1 | Tonic and/or clonic, Multiple seizures daily. | >4 months: myoclonic jerks | Burst of asynchronous spikes and sharp waves. Periods of discontinuity with flatness of the traces without classical suppression burst. | Poor eye contact. Global hypotonia, poor head control, pyramidal signs (6 months) |
Patient 11 | c.A886C p.T296P | 1 | Tonic, cyanosis, Multiple seizures daily. | 0-19 days: multiple seizures. 6-18 m: no seizure. 18 m- 11y: several episodes of CTGC or PS with secondary generalization. | Left or right spikes on a moderately abnormal background. | Walking (18 months). Poor language, autistic features (11 years) |
Patient 12 | c.2318dupG p.C774Lfs*91 | 4 | Partial motor seizure with asymmetric tonic extension of one limb. Bilateral clonic seizures. Apnea. | 1 month: seizure free. | Suppression-burst. | Slight peripheral hypertonia (3 months). Good outcome, walking (18 months), normal language (5 years) |
Patient 13 | c.G471A p.W157X | 4 | Hemi corporeal, left or right. | 0-11 months: partial clonic seizures. Then seizure offset. | Poor, discontinuous. | Independent walking (4 y). No language (6.5 y). Normal HC 52.5 cm |
Patient 14 | c.G868A p.G290S | 1 | Tonic. | Many motor seizures during the neonatal period. 2 m: Seizure stop. AED withdrawn at 4 years. | Asymmetrical suppression-burst with multifocal slow waves, left frontal and right occipital spikes. Periods of generalized flattening. | Sitting (3 y) hand stereotypies. Unable to walk/stand, stereotypies, pyramidal signs. Poor language. Normal HC (16 y). |
Patient 15 | c.C881T p.A294V | 8 | Myoclonic jerks, Multiple seizures daily. | 0-3 months: myoclonic jerks. 3 months: seizure offset. Therapy stopped at 6 months. | Suppression burst. | Sit (2 y). No walking, 2–3 words. Understands simple orders. Strabismus, nystagmus (3 y) |
Patient 16 | c.997C>T. p.R333W | 2 | Bilateral tonic clonic And right clonic | 0-3 y: active epilepsy, motor seizures 3-10 y: seizure free 10-20 y: monthly focal seizures | Slow waves with asynchronous bilateral spikes and intermittent flattening | First steps (18 m). Few words (3 y) Able to read but cannot write, limited communication skills, marked bradypsychia, hand stereotypies (26 y) |