Genotype-Phenotype Correlations and Functional Outcomes in Pediatric Patients with <i>KCNQ2</i>-Related Epilepsy: A Multicenter Observational Study in Korea

Eon Ah Kim; Mi-Sun Yum; Seungbok Lee; Jae So Cho; Jeehun Lee; Byung Chan Lim

doi:10.26815/acn.2024.00787

Ann Child Neurol > Volume 33(2); 2025 > Article

Kim, Yum, Lee, Cho, Lee, and Lim: Genotype-Phenotype Correlations and Functional Outcomes in Pediatric Patients with KCNQ2-Related Epilepsy: A Multicenter Observational Study in Korea

Original article

Annals of Child Neurology 2025;33(2):48-55.

Published online: March 21, 2025

DOI: https://doi.org/10.26815/acn.2024.00787

Genotype-Phenotype Correlations and Functional Outcomes in Pediatric Patients with KCNQ2-Related Epilepsy: A Multicenter Observational Study in Korea

Eon Ah Kim, MD¹

, Mi-Sun Yum, MD¹

, Seungbok Lee, MD^2,³, Jae So Cho, MD⁴, Jeehun Lee, MD⁵, Byung Chan Lim, MD²

¹Department of Pediatrics, Asan Medical Center Children’s Hospital, University of Ulsan College of Medicine, Seoul, Korea

²Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Korea

³Department of Genomic Medicine, Seoul National University Hospital, Seoul, Korea

⁴Department of Pediatrics, Seoul National University Bundang Hospital, Seongnam, Korea

⁵Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine Seoul, Korea

Corresponding author: Mi-Sun Yum, MD Department of Pediatrics, Asan Medical Center Children’s Hospital, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea
Tel: +82-2-3010-3386, Fax: +82-2-2045-4054 E-mail: misun.yum@gmail.com

Received November 27, 2024 Revised January 15, 2025 Accepted January 16, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

Potassium voltage-gated channel subfamily Q member 2 (KCNQ2)-related epilepsy, caused by mutations in the KCNQ2 gene, encompasses a spectrum of epileptic phenotypes, ranging from self-limited epilepsy to severe developmental and epileptic encephalopathy (DEE). Although the mutational background of these disorders has been characterized, predicting outcomes based solely on genetic variants remains challenging.

Methods

This multicenter observational study investigated the clinical features, genotype-phenotype correlations, and comorbidities in pediatric patients with KCNQ2-related epilepsy in Korea. Conducted across three tertiary hospitals, the study enrolled 20 pediatric patients with genetically confirmed KCNQ2-related epilepsy. Data were collected from medical records, including demographic information, age at seizure onset, types of seizures, comorbidities, and treatment history.

Results

Of the 20 patients enrolled, nine had self-limited epilepsy, while 11 had DEE. Missense mutations were more prevalent in the DEE group, whereas truncation mutations were associated with milder forms of epilepsy. Although 75% of cases achieved effective seizure control, 55% of patients exhibited comorbidities such as intellectual disability and neuropsychiatric disorders. Genotype-phenotype correlations revealed variability in clinical outcomes, with specific mutations in similar regions resulting in different phenotypes.

Conclusion

This study highlights the complexity of KCNQ2-related epilepsy, demonstrating that genotype-phenotype correlations are not straightforward and may be influenced by genetic modifiers, environmental factors, or dominant negative effects. While seizure control often improves, neurodevelopmental challenges may persist, underscoring the need for therapeutic approaches that address both seizure management and developmental support. Further research into the relevant non-genetic factors is essential to enhance the understanding and treatment of KCNQ2-related epilepsy.

Keywords: KCNQ2 potassium channel; Epilepsy; Brain diseases; Genotype

Introduction

Potassium voltage-gated channel subfamily Q member 2 (KCNQ2)-related epilepsy comprises a spectrum of neonatal or infantile onset epileptic phenotypes that vary from self-limited epilepsy to developmental and epileptic encephalopathy (DEE) [1]. These conditions are caused by mutations in the KCNQ2 gene, which encodes a subunit of the voltage-gated potassium channel that regulates neuronal excitability [2]. The estimated incidence of KCNQ2-related epilepsy ranges from 2.93 to 3.59 per 100,000 live births [3], with seizures typically beginning within the first few days to weeks of life [4].

KCNQ2-related epilepsy exhibits a wide spectrum of clinical phenotypes [5]. Beyond the commonly observed self-limited neonatal epilepsy (SeLNE) and KCNQ2-DEE, there are less common manifestations. These include self-limited neonatal-infantile epilepsy, self-limited infantile epilepsy (SeLIE), neonatal encephalopathy with non-epileptic myoclonus, infantile or childhood-onset DEE, isolated intellectual disability without epilepsy, and myokymia [4]. The spectrum of KCNQ2-related neurodevelopmental disorders ranges from normal cognitive function to severe impairments in motor skills, behavior, and social interaction [6]. This variability carries significant long-term consequences. Adults with KCNQ2 encephalopathy often exhibit a high prevalence of intellectual disability and neuropsychiatric disorders. This occurs despite a reduction or cessation in seizure frequency during adulthood, although there remains a risk of seizure recurrence later in life [1,7,8].

Patients with DEE experience medication-resistant seizures and often develop severe intellectual and motor disabilities. Even when these patients achieve seizure freedom through antiseizure medication (ASM), their long-term outcomes remain generally poor. In contrast, patients with self-limited epilepsy usually respond well to ASMs and experience favorable outcomes [9]. Missense variants in KCNQ2 are frequently linked to more severe forms of DEE, whereas truncating mutations are typically associated with milder phenotypes, such as self-limited epilepsy [10]. However, the relationship between genotype and phenotype is not straightforward [11], suggesting that other genetic modifiers or environmental factors might also play a role in determining clinical outcomes [12]. This complexity underscores the importance of further research to elucidate the mechanisms driving these disorders.

This study investigated the phenotype of KCNQ2-related epilepsy among a pediatric cohort in Korea, specifically examining the relationship between genotype and phenotype and the associated comorbidities. By analyzing clinical data, genetic variants, and long-term functional outcomes comprehensively, the study sought to enhance understanding of KCNQ2-related epilepsy and its effects on neurodevelopment, as well as to investigate how comorbidities might influence patient prognosis.

Materials and Methods

This multicenter, observational study was conducted at three tertiary hospitals in Korea, starting in November 2023. It included patients who experienced seizures and had confirmed KCNQ2 mutations identified through genetic testing. All participants had a follow-up period of at least 6 months, which allowed for the assessment of comorbidities and their Functional Status Scale (FSS). The study evaluated the clinical features, genetic findings, and functional status of each patient using established scales. Additionally, data were collected on patient medical histories, types of seizures, electroencephalography (EEG) findings, and comorbid conditions. This study was approved by Institutional Review Board of Asan Medical Center (approval number:2023-0695), and informed consent was waived by the board.

1. Patient population and data collection

Patient data were gathered from medical records, including demographic details, age at seizure onset, types of seizures, comorbidities, and treatment history. Patients were categorized into two groups according to their type of epilepsy: the self-limited epilepsy group and the DEE group. The self-limited epilepsy group comprised patients diagnosed with self-limited familial neonatal epilepsy (SeLFNE), self-limited familial neonatal-infantile epilepsy (SeLFNIE), SeLNE, and SeLIE. Within the DEE group, patients were further divided based on the timing of seizure onset into neonatal-onset and non-neonatal onset subgroups.

2. Genetic analysis

Genetic analysis was conducted to identify pathogenic variants in the KCNQ2 gene. Both whole-exome sequencing and targeted gene panel testing were employed to detect relevant mutations. Variants were verified using Sanger sequencing, and family members were tested as needed. For each patient, the genetic location, type of mutation (e.g., missense, nonsense, frameshift), and any previously reported associated phenotypes were documented. This data was subsequently utilized to explore genotype-phenotype correlations within the patient cohort.

3. EEG and imaging studies

All patients underwent at least one EEG, during which the findings were assessed for background activity and the presence of epileptiform discharges (EDs). Background activity was classified as normal, slow, or burst suppression, while EDs were categorized based on the number of regions involved as focal, multifocal, or generalized. Brain magnetic resonance imaging scans were also performed to evaluate structural abnormalities, with findings categorized as either normal or abnormal.

4. Outcomes

After receiving an epilepsy diagnosis, all patients were treated with at least one ASM. To identify effective ASMs for the self-limited epilepsy and DEE groups, responsive ASMs were defined as those that reduced seizure frequency by 50% or more.

Functional outcomes were evaluated using the FSS, a validated instrument that assesses six domains of pediatric functioning: mental status, sensory function, communication, motor function, feeding, and respiratory status [13]. Each domain is rated on a scale from normal (1 point) to very severe dysfunction (5 points), with the total score ranging from 6 (normal) to 30 (severe dysfunction). The FSS was administered during the most recent follow-up appointment to assess the current functional status of each patient.

Results

1. Patient demographics

This study collected data from three tertiary hospitals in South Korea, enrolling 20 patients, 45% of whom were male. The average age at first seizure onset was 484 days, ranging from 1 day to 12 years, with a mean follow-up period of 4 years and 1 month (range, 6 months to 12 years). The ages at seizure onset were categorized into three groups: neonates, infants, and children. Of the 20 patients, 13 (65%) were neonates, three (16%) were infants, and four (21%) were children. The study cohort included nine patients with self-limited epilepsy, comprising four without a confirmed family history and five with a confirmed family history. Among those with a confirmed family history, four experienced their first seizure during the neonatal period, and one during infancy. Additionally, 11 patients were diagnosed with DEE; five were classified in the neonatal seizure onset group, and six in the non-neonatal seizure onset group (Table 1).

2. Genetic information

All 20 enrolled patients exhibited unique genetic variants, with the exception of one sibling pair (patients 8 and 9) and another unrelated pair (patients 19 and 20), as detailed in Table 2 [10,14-27]. A comparison between the self-limited epilepsy group and the DEE group showed variations in both the location and type of mutations. In the self-limited epilepsy cases, the majority of variants (6/9, 67%) were located in the C-terminal region (Fig. 1). Nonsense mutations were the most prevalent type (4/9, 44%), followed by missense and frameshift mutations. Among the 11 patients with DEE, mutations were also primarily found in the C-terminal region (5/11, 45%). However, missense mutations were notably more common, representing 90% (9/11) of the cases (Fig. 2). Table 2 provides a comparison of the phenotypes associated with KCNQ2 mutations reported in previous studies and those observed in this patient cohort.

3. Clinical phenotypes

In the self-limited epilepsy group, which included nine patients, the first seizure occurred between days 3 and 7 of life in four patients, and on day 124 in another patient. Additionally, five patients in this group had a family history of seizures, suggesting a possible hereditary component in this subgroup. In contrast, the DEE group, which consisted of 11 patients with more complex presentations, experienced an average seizure onset at 825 days.

EEG was performed for all patients at their initial presentation. In both groups, 80% (16/20) of the initial EEG backgrounds appeared normal. Among the remaining four patients, only one from the self-limited group exhibited a burst suppression pattern. In the DEE group, two patients showed burst suppression patterns, and one displayed slow background activities. However, EDs were observed in 75% (15/20) of the patients. These discharges were classified as focal (localized to one region), multifocal (spanning multiple regions), or generalized. Specifically, focal, multifocal, and generalized discharges were observed in eight, five, and two patients, respectively. The self-limited epilepsy group demonstrated significantly better seizure control than the DEE group, with all patients remaining seizure-free for over 1 year. Overall, 75% of the cohort (15/20) maintained a seizure-free status for more than 1 year (Table 3).

4. Outcomes

In the self-limited epilepsy group, sodium channel blockers were effective in four out of nine cases (44.4%), with phenytoin (DPH) and carbamazepine proving effective in three and one patient, respectively. For those with neonatal-onset epilepsy within this group, phenobarbital was effective in two patients. Additionally, levetiracetam (LEV), clobazam, and valproic acid each demonstrated efficacy in one patient. In the DEE group, sodium channel blockers were effective in four out of 11 cases (36%), with DPH effective in two patients, oxcarbazepine in one patient, and lamotrigine in one patient. Other medications, including vigabatrin, LEV, and perampanel, were effective in two, one, and one patient, respectively. To further evaluate patient outcomes, the FSS was employed to assess and compare functional status across both groups. Among the 20 patients, the average FSS was 7.6 (Table 4). Eleven patients were assigned a score of six, indicating no functional impairment. All nine patients in the self-limited epilepsy group achieved this score, confirming normal functional status across the group. In contrast, the DEE group exhibited an average FSS of 8.82, indicating mild dysfunction, with individual scores ranging from 6 to 15. Mild dysfunction in this group was often associated with impairments in communication and motor functioning, due to intellectual disability or autism spectrum disorder (ASD), while mental status and respiratory functioning remained normal in most cases. In the self-limited epilepsy group, no comorbidities were observed. However, in the DEE group, six out of 11 patients had intellectual disability or developmental disability, two had ASD, and two exhibited both intellectual disability and movement disorders. In one case, the patient is still an infant, and no comorbidities have been identified to date.

Discussion

The findings of this study provide valuable insights into the genotype-phenotype correlation in KCNQ2-related epilepsy, highlighting distinct differences in genetic variants, clinical outcomes, and treatment responses between self-limited epilepsy and DEE. Consistent with prior research, missense mutations were predominantly associated with the DEE group, especially when located in the C-terminal region of the KCNQ2 gene. This region is commonly linked to more severe developmental impairments and treatment-resistant epilepsy, suggesting that missense mutations may significantly alter protein function, thus contributing to the severe neurological and developmental profiles observed in DEE. Conversely, truncating mutations, including nonsense and frameshift mutations, were more common in the self-limited epilepsy group. Interestingly, certain cases in this study highlighted the complexity of these genotype-phenotype correlations. For example, patient 15 exhibited a DEE phenotype, despite carrying a genetic variant previously associated with self-limited epilepsy. This observation illustrates that the genotype-phenotype correlations in KCNQ2-related epilepsy are not entirely predictable. It also suggests that additional genetic modifiers, epigenetic influences, or environmental factors may also influence the clinical variability in this disorder [28]. Regarding clinical outcomes, comorbidities were predominantly observed in the DEE group, whereas the self-limited epilepsy group had notably fewer associated conditions, indicating a more favorable neurodevelopmental outcome. These findings are consistent with results from previous studies. Functional outcomes, as assessed by the FSS, also reflected this distinction: the self-limited epilepsy group consistently demonstrated normal function, while those in the DEE group exhibited mild impairments, particularly in the communication and motor domains, likely influenced by comorbid intellectual disability or ASD. Sodium channel blockers demonstrated relatively higher efficacy in KCNQ2-related epilepsy by reducing hyperexcitability caused by the functional loss of potassium channels. In this study, they were used in a significant proportion of cases, with potentially responsive ASMs observed in 40% (8/20) of the total cohort. Specifically, in the self-limited epilepsy group, sodium channel blockers were effective in 44.4% (4/9) of patients, while in the DEE group, they were effective in 33.3% (4/11) of patients. However, the DEE group showed less effectiveness in seizure control, with seizures persisting in four out of 11 patients. Nevertheless, considering the intractability of DEE, sodium channel blockers can still be considered a first-choice treatment for seizure control in cases of KCNQ2 epilepsy.

This study has several limitations that warrant consideration. First, the small sample size and the focus on a single ethnic cohort limit the generalizability of the findings to other populations. Second, as this was a multicenter retrospective study that relied on data collected from each hospital, it faced challenges in obtaining detailed information on ASM usage and seizure types, highlighting inherent limitations in data collection. Third, although KCNQ2-related epilepsy typically presents within the first few days to weeks after birth, this study included patients with relatively older ages of seizure onset, introducing variability in phenotype analysis. Future studies should aim to address these limitations by including a larger, more ethnically diverse population and collecting comprehensive data on ASM usage, seizure types, and seizure onset patterns. Additionally, exploring potential differences in seizure onset age based on specific genetic variants could further clarify the genotype-phenotype correlation. By overcoming these challenges, future research could enhance our understanding of KCNQ2-related epilepsy and support the development of tailored therapeutic strategies to optimize patient outcomes.

In conclusion, KCNQ2-related epilepsy exhibits complexities that challenge the assumption that mutation type alone determines the clinical course. This underscores the importance of gaining a broader understanding of additional factors that may influence KCNQ2-related phenotypes. Furthermore, research should focus on identifying potential genetic modifiers or environmental factors that could account for the variability in KCNQ2 phenotypes, thus supporting tailored treatment planning. This study highlights the intricate relationship between genotype and phenotype in KCNQ2-related epilepsy, emphasizing the necessity for a personalized approach that adapts therapeutic strategies to individual phenotypes. Such an approach is aimed at optimizing neurodevelopmental outcomes and enhancing the quality of life for patients with KCNQ2-related epilepsy.

Conflicts of interest

Jae So Cho is a managing editor and Jeehun Lee is an editorial board member of the journal, but they were not involved in the peer reviewer selection, evaluation, or decision process of this article. No other potential conflicts of interest relevant to this article were reported.

Author contribution

Conceptualization: MSY, SL, JSC, and BCL. Data curation: EAK, MSY, SL, JSC, JL, and BCL. Funding acquisition: BCL. Visualization: EAK. Writing - original draft: EAK and MSY. Writing - review & editing: EAK and MSY.

Acknowledgments

This study was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (RS-2023-00265923).

Fig. 1.

Distribution of identified mutations within the potassium voltage-gated channel subfamily Q member 2 (KCNQ2) polypeptide chain. The mutation locations for various genetic variants were marked, ^awith the self-limited group indicated in blue, ^bwhile the developmental and epileptic encephalopathy group was highlighted in red.

Fig. 2.

Overview of (A, C) variant locations and (B, D) mutation types identified in patients with potassium voltage-gated channel subfamily Q member 2 (KCNQ2)-related epilepsy: self-limited and developmental and epileptic encephalopathy (DEE) phenotypes. SeLNE, self-limited neonatal epilepsy; SeLFNE, self-limited familial neonatal epilepsy; SeLFNIE, self-limited familial neonatal-infantile epilepsy.

Table 1.

Classification of KCNQ2-related epilepsy phenotypes of patients in the study cohort

Variable	No. of patients (n=20)
Self-limited (n=9)
Neonatal epilepsy	4
Familial neonatal epilepsy	4
Familial neonatal-infantile epilepsy	1
DEE (n=11)
Neonatal onset	5
Non-neonatal onset	6

KCNQ2, potassium voltage-gated channel subfamily Q member 2; DEE, developmental and epileptic encephalopathy.

Table 2.

Genetic variants and clinical phenotypes in patients with KCNQ2-related epilepsy

Patient	Nucleotide change	Amino acid change	Domain	Mutation type	Phenotype	Reported	Classification
1	c.740C>T	p.Ser247Leu	S5	Missense	SeLNE	EE [14]	Pathogenic
2	c.792C>A	p.Tyr264X	Pore loop	Nonsense	SeLNE	No	Pathogenic
3	c.881C>T	p.Ala294Val	S6	Missense	SeLNE	DEE [15]	Pathogenic
4	c.1611del	p.Val538SerfsTer27	C-terminal	Frameshift	SeLNE	DD, ID [16]	Pathogenic
5	c.998G>A	p.Arg333Gln	C-terminal	Missense	SeLFNE	BFNI [17]	Pathogenic
6	c.1160dup	p.Leu388AlafsTer13	C-terminal	Frameshift	SeLFNE	No	Not provided
7	c.1342C>T	p.Arg448X	C-terminal	Nonsense	SeLFNE	BFNC [18]	Pathogenic
8	c.1771C>T	p.Gln591Ter	C-terminal	Nonsense	SeLFNE	BFNS [19]	Not provided
9	c.1771C>T	p.Gln591Ter	C-terminal	Nonsense	SeLFNIE	BFNS [19]	Not provided
10	c.602G>A	p.Arg201His	S4	Missense	Neo-DEE	DEE [10,20]	Pathogenic
11	c.611A>G	p.Gln204Arg	S4	Missense	DEE	No	Pathogenic
12	c.628C>T	p.Arg210Cys	S4	Missense	DEE	EE, DE [21]	Pathogenic
13	c.727C>G	p.Leu243Val	S5	Missense	Neo-DEE	EE [22]	Pathogenic/Likely pathogenic
14	c.766G>T	p.Gly256Trp	S5	Missense	Neo-DEE	EE [23]	Pathogenic
15	c.773A>G	p.Asn258Ser	Pore loop	Missense	DEE	BFNC [24,25]	Not provided
16	c.997C>T	p.Arg333Trp	C-terminal	Missense	DEE	DEE [26]	Pathogenic
17	c.1054delTC	p.Ser352fs	C-terminal	Deletion	DEE	No	Not provided
18	c.1163T>C	p.Leu388Pro	C-terminal	Missense	DEE	No	Not provided
19	c.1657C>T	p.Arg553Trp	C-terminal	Missense	Neo-DEE	BFNS [27], DEE [26]	Pathogenic
20	c.1657C>T	p.Arg553Trp	C-terminal	Missense	Neo-DEE	BFNS [27], DEE [26]	Pathogenic

KCNQ2, potassium voltage-gated channel subfamily Q member 2; SeLNE, self-limited neonatal epilepsy; EE, epileptic encephalopathy; DEE, developmental and epileptic encephalopathy; DD, developmental delay; ID, intellectual disability; SeLFNE, self-limited familial neonatal epilepsy; BFNI, benign familial neonatal infantile; BFNC, benign familial neonatal convulsion; BFNS, benign familial neonatal seizure; SeLFNIE, self-limited familial neonatal-infantile epilepsy; Neo-DEE, neonatal-onset developmental and epileptic encephalopathy; DE, developmental encephalopathy.

Table 3.

Clinical information and functional outcomes in patients with KCNQ2-related epilepsy

Patient	Sex	Age at onset (day)	EEG at onset	Brain MRI at onset	Effective treatment	Seizure outcome	Comorbidity	FSS
1	F	4	BS	Normal	DPH	Free for >1 yr	No	6
2	M	4	Normal	Normal	CBZ	Free for >1 yr	No	6
3	M	2	Focal ED	Normal	DPH	Free for >1 yr	No	6
4	F	3	Normal	Normal	DPH	Free for >1 yr	No	6
5	F	3	Focal ED	Normal	PHB	Free for >1 yr	No	6
6	M	7	Normal	Normal	VPA	Free for >1 yr	No	6
7	F	3	Focal ED	Normal	PHB	Free for >1 yr	No	6
8	M	3	Focal ED	Normal	CLB	Free for >1 yr	No	6
9	F	124	Focal ED	Normal	LEV	Free for >1 yr	No	6
10	F	5	Multifocal ED	Normal	VGB	Monthly seizures	Movement disorder	10
11	F	107	BS+Multifocal ED	Normal	PER	Free for >1 yr	Movement disorder, DD	15
12	F	2,396	Generalized	Normal	LTG	Free for >1 yr	ID, ASD	7
13	M	1	Normal	Normal	None	Monthly seizures	DD	8
14	M	2	BS+Multifocal ED	Normal	DPH	Free for >1 yr	DD	7
15	F	136	Multifocal ED	Normal	OXC, TPM	Weekly seizures	DD, ADHD, movement disorder	14
16	M	1,973	Focal ED	Normal	DPH	Free for >1 yr	ID	7
17	F	61	Normal	Normal	None	Free for >1 yr	ASD	9
18	M	4,388	Slow, focal ED	Normal	LEV	Yearly seizures	ID	6
19	F	2	Multifocal ED	Normal	VGB	Daily seizures	No	6
20	M	3	Normal	Normal	None	Free for >1 yr	ID	8

KCNQ2, potassium voltage-gated channel subfamily Q member 2; EEG, electroencephalography; MRI, magnetic resonance imaging; FSS, Functional Status Scale; F, female; BS, burst suppression; DPH, phenytoin; M, male; CBZ, carbamazepine; ED, epileptic discharges; PHB, phenobarbital; VPA, valproic acid; CLB, clobazam; LEV, levetiracetam; VGB, vigabatrin; PER, perampanel; DD, developmental delay; LTG, lamotrigine; ID, intellectual disability; ASD, autism spectrum disorder; OXC, oxcarbazepine; TPM, topiramate; ADHD, attention deficit hyperactivity disorder.

Table 4.

Functional Status Score outcomes of pediatric patients with KCNQ2-related epilepsy

Variable	Value (n=20)
FSS
6 (normal)	11
7-12 (mild dysfunction)	7
13-18 (moderate dysfunction)	2
FSS patient group
All patients (n=20)	7.6 (6-15)
Self-limited (n=9)	6
DEE (n=11)	8.8 (6-15)

Values are presented as number or mean (range).

KCNQ2, potassium voltage-gated channel subfamily Q member 2; FSS, Functional Status Scale; DEE, developmental and epileptic encephalopathy.

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