Neonatal Med.  2020 Nov;27(4):202-206. 10.5385/nm.2020.27.4.202.

KCNQ2 Encephalopathy Showing a Distinct Ictal Amplitude-Integrated Electroencephalographic Pattern

• Kwak N
• Lee YJ
• Kim D
• Hwang SK
• Kwon S
• Lee EJ

• KMID: 2510827
• DOI: http://doi.org/10.5385/nm.2020.27.4.202

Abstract

KCNQ2 mutations induce a neonatal-onset epileptic encephalopathy of widely varying severity, ranging from benign familial neonatal epilepsy to severe refractory epileptic encephalopathy. Refractory seizures with KCNQ2 mutations have a positive response to sodium-channel blockers. Recently, a distinctive ictal pattern has been reported during amplitude-integrated electroencephalographic (aEEG) monitoring in infants with KCNQ2 encephalopathy. Herein, we describe a case of KCNQ2 encephalopathy with this distinctive ictal aEEG pattern, which was confirmed using conventional electroencephalography (EEG). A 3-day-old female infant presented with neonatal seizures accompanied by cyanosis and desaturation. Her seizure semiology was tonic and focal clonic. Her ictal aEEG demonstrated a sudden rise in amplitude followed by a suppressed background pattern. This pattern was also confirmed on conventional EEG. Her seizures were refractory despite the administration of multiple conventional antiepileptic drugs. Finally, c.794C>T; p. (Ala265Val) mutation was observed in the KCNQ2 gene on genetic testing, and she was diagnosed with KCNQ2 encephalopathy. Identifying this distinctive ictal pattern on aEEG monitoring facilitates the early detection of KCNQ2 encephalopathy and timely targeted treatment in patients with refractory seizures.

Keyword

KCNQ2; Mutation; Infant; Seizures; Epilepsy; Electroencephalography

Figure

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  Figure 1. Brain magnetic resonance imaging of the patient with KCNQ2 encephalopathy. (A) T2-weighted imaging and (B) susceptibility-weighted imaging at day 2 of life showing cystic germinal matrix hemorrhage at the left caudothalamic groove.

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  Figure 2. Seizure pattern of the patient with KCNQ2 encephalopathy on amplitude-integrated electroencephalography (aEEG). The upper panel displays the aEEG and the lower panel displays the corresponding electroencephalography (EEG) at that point indicated by the vertical red line. The aEEG shows two ictal discharges (box), a brief rise in amplitude in the upper and lower margins followed by suppression of the background pattern. The initial phase of the ictal discharges (red line in A) shows runs of spike and wave discharges on raw EEG (B). The later phase of the ictal discharges (red line in C) shows diffuse background suppression on raw EEG (D).

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  Figure 3. Seizure pattern of the patient with KCNQ2 encephalopathy on electroencephalography (EEG). (A) Interictal EEG, (B) ictal EEG shows that the fast activities began mainly from the right frontal area (circle, seizure onset), evolving to generalized spikes and waves (C) that were followed by generalized diffuse background attenuation. (D, E) Postictal EEG showing a burst suppression pattern.

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  Figure 4. Sanger sequencing confirms KCNQ2 mutation [c.794C>T; p. (Ala265Val)] (arrow).

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