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Adam MP, Bick S, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025.

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Adam MP, Bick S, Mirzaa GM, et al., editors.
Seattle (WA):University of Washington, Seattle; 1993-2025.

KCNT1-Related Epilepsy

, MD, PhD,, MD, MSCE,, PhD, and, PhD.

Author Information and Affiliations
, MD, PhD
Department of Pediatrics
Ann and Robert H Lurie Children's Hospital of Chicago
Chicago, Illinois
, MD, MSCE
Department of Neurology
Division of Child Neurology
University of Rochester School of Medicine
Rochester, New York
, PhD
Department of Pharmacology
University of Buffalo
Buffalo, New York
, PhD
Department of Neurology
Feinberg School of Medicine
Northwestern University
Chicago, Illinois

Initial Posting:.

Estimated reading time: 25 minutes

Summary

Clinical characteristics.

KCNT1-related epilepsy is most often associated with two phenotypes: epilepsy of infancy with migrating focal seizures (EIMFS) andautosomal dominant nocturnal frontal lobe epilepsy (ADNFLE).

  • EIMFS is characterized by seizures, typically focal and asynchronous, beginning in the first six months of life with associated developmental plateau or regression. Autonomic manifestations (e.g., perioral cyanosis, flushing, apnea) are common. Seizures are intractable to multiple anticonvulsants and progress to become nearly continuous by age six to nine months.
  • ADNFLE is characterized by clusters of nocturnal motor seizures that vary from simple arousals to hyperkinetic events with tonic or dystonic features. Individuals withKCNT1-related ADNFLE are more likely to develop seizures at a younger age, have cognitive comorbidity, and display psychiatric and behavioral problems than individuals with ADNFLE resulting from other causes.

Less common seizure phenotypes in individuals withKCNT1-related epilepsy include West syndrome, Ohtahara syndrome, early myoclonic encephalopathy, leukodystrophy and/or leukoencephalopathy, focal epilepsy, and multifocal epilepsy. Additional neurologic features include hypotonia, microcephaly developing by age 12 months, strabismus, profound developmental delay, and additional movement disorders. Other systemic manifestations including pulmonary hemorrhage caused by prominent systemic-to-pulmonary collateral arteries or cardiac arrhythmia have been reported.

Diagnosis/testing.

The diagnosis ofKCNT1-related epilepsy is established in aproband with intractable epilepsy and aheterozygouspathogenic variant inKCNT1 identified bymolecular genetic testing.

Management.

Treatment of manifestations: KCNT1-related epilepsy is often refractory to conventional anticonvulsants; stiripentol, benzodiazepines, levetiracetam, and the ketogenic diet have all been well tolerated with limited success; quinidine has been used as an off-label anticonvulsant with success in some individuals; in rare cases of pulmonary hemorrhage as a result of systemic pulmonary collaterals, embolization has been recommended; developmental support is appropriate.

Surveillance: EEG at intervals determined by seizure frequency and progression, for evaluation of new involuntary movements or unexplained, paroxysmal changes in vital signs, or following adjustments to an anticonvulsant regimen; monitoring of development.

Agents/circumstances to avoid: For individuals with ADNFLE, activities in which a sudden loss of consciousness could lead to injury or death should be avoided (e.g., bathing, swimming, driving, or working/playing at heights).

Pregnancy management: For women with ADNFLE, a discussion of the risks and benefits of using a given anti-seizure medication during pregnancy should ideally take place before conception. Transitioning to a lower-risk medication prior to pregnancy may be possible.

Genetic counseling.

KCNT1-related epilepsy is inherited in anautosomal dominant manner. The majority of affected individuals representsimplex cases (i.e., a single occurrence in a family) resulting from ade novo KCNT1pathogenic variant. The proportion of cases caused by ade novo pathogenic variant varies byphenotype. All individuals diagnosed withKCNT1-related epilepsy of infancy with migrating focal seizures (EIMFS) have the disorder as the result of ade novo pathogenic variant or an inherited variant from an unaffected parent with somatic and/orgermline mosaicism. Some individuals diagnosed withKCNT1-related autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) have an affected parent. Each child of an individual withKCNT1-related epilepsy has a 50% chance of inheriting the pathogenic variant, and intrafamilial clinical variability and reducedpenetrance have been reported. Prenatal testing for a pregnancy at increased risk andpreimplantation genetic testing are possible if the pathogenic variant in the family is known.

Diagnosis

No formal diagnostic criteria forKCNT1-related epilepsy have been published to date.

KCNT1-related epilepsy is most often associated with two phenotypes: epilepsy of infancy with migrating focal seizures (EIMFS) andautosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). Less often,KCNT1 pathogenic variants are associated with epilepsy with variable presentation.

Suggestive Findings

KCNT1-related epilepsy of infancy with migrating focal seizures (EIMFS)should be suspected in individuals with the following history and findings:

  • Normal prenatal course and birth without history, clinical features, or imaging suggestive of traumatic, anoxic, vascular, or infectious injury
  • Sporadic, asynchronous focal seizures arising independently from either hemisphere with patterns of intracortical "migration" occurring by age six months, with subsequent escalation of seizure frequency
  • Developmental plateau or regression following the onset of seizures
  • Intractability to anticonvulsant medication

KCNT1-relatedautosomal dominant nocturnal frontal lobe epilepsy (ADNFLE)should be suspected in individuals with the following history and findings:

  • Frequent brief, nocturnal seizures
  • Mild-to-moderate intellectual disability
  • Psychiatric disease (e.g., depression, anxiety, suicidality, attention-deficit/hyperactivity disorder)
  • Family history of ADNFLE or EIMFS

KCNT1-related epilepsy has been less frequently identified in individuals with the following phenotypes:

  • West syndrome
  • Ohtahara syndrome (early-infantile epileptic encephalopathy)
  • Early myoclonic encephalopathy
  • Leukodystrophy/leukoencephalopathy
  • Focal epilepsy
  • Multifocal epilepsy

Establishing the Diagnosis

The diagnosis ofKCNT1-related epilepsyis established in aproband with intractable epilepsy and aheterozygous pathogenic (orlikely pathogenic) variant inKCNT1 identified bymolecular genetic testing (seeTable 1).

Note: (1) Per ACMG/AMP variant interpretation guidelines, the terms "pathogenic variant" and "likely pathogenic variant" are synonymous in a clinical setting, meaning that both are considered diagnostic and can be used for clinical decision making [Richards et al 2015]. Reference to "pathogenic variants" in thisGeneReview is understood to include likely pathogenic variants. (2) Identification of aheterozygousKCNT1 variant ofuncertain significance does not establish or rule out the diagnosis.

Because thephenotype ofKCNT1-related epilepsy is indistinguishable from many other inherited disorders with epilepsy, recommendedmolecular genetic testing approaches include use of amultigene panel orcomprehensivegenomic testing.

Note: (1) Single-gene testing (sequence analysis ofKCNT1) is rarely useful and typically NOT recommended. (2)KCNT1-related epilepsy is postulated to occur through again-of-function mechanism. Large intragenic deletions andduplication have not been reported; testing for intragenic deletions or duplication is not indicated.

A seizuremultigene panel that includesKCNT1 and other genes of interest (seeDifferential Diagnosis) is most likely to identify the genetic cause of the condition while limiting identification of pathogenic variants and variants ofuncertain significance in genes that do not explain the underlyingphenotype. Note: (1) The genes included in the panel and the diagnosticsensitivity of the testing used for eachgene vary by laboratory and are likely to change over time. (2) Some multigene panels may include genes not associated with the condition discussed in thisGeneReview. (3) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focusedexome analysis that includes genes specified by the clinician. (4) Methods used in a panel may includesequence analysis,deletion/duplication analysis, and/or other non-sequencing-based tests.

For an introduction to multigene panels clickhere. More detailed information for clinicians ordering genetic tests can be foundhere.

Comprehensivegenomic testing (which does not require the clinician to determine whichgene[s] are likely involved) is another good option.Exome sequencing is most commonly used;genome sequencing is also possible.

For an introduction to comprehensivegenomic testing clickhere. More detailed information for clinicians ordering genomic testing can be foundhere.

Table 1.

Molecular Genetic Testing Used inKCNT1-Related Epilepsy

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Gene 1MethodProportion of Pathogenic Variants 2 Identified by Method
KCNT1Sequence analysis 3100% 4
Gene-targeteddeletion/duplication analysis 5None reported 4, 6
1.
2.

SeeMolecular Genetics for information on variants detected in thisgene.

3.

Sequence analysis detects variants that are benign,likely benign, ofuncertain significance,likely pathogenic, or pathogenic. Variants may includemissense,nonsense, andsplice site variants and small intragenic deletions/insertions; typically,exon or whole-gene deletions/duplications are not detected. For issues to consider in interpretation ofsequence analysis results, clickhere.

4.
5.

Gene-targeteddeletion/duplication analysis detects intragenic deletions or duplications. Methods used may include a range of techniques such asquantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and agene-targeted microarray designed to detect single-exon deletions or duplications.

6.

Clinical Characteristics

Clinical Description

KCNT1-related epilepsy encompasses a range of epilepsy syndromes. The most common phenotypes reported in individuals withKCNT1-related epilepsy are epilepsy of infancy with migrating focal seizures (EIMFS) andautosomal dominant nocturnal frontal lobe epilepsy (ADNFLE).

Epilepsy Phenotype

EIMFS is an early-infantile epileptic encephalopathy characterized by seizures beginning in the first six months of life with associated developmental plateau or regression. The seizures are primarily focal motor, variably with secondary generalization, but also include tonic, clonic, tonic-clonic, myoclonic, and epileptic spasms [McTague et al 2013]. Autonomic manifestations (e.g., perioral cyanosis, flushing, apnea) are common. Seizures progress to become nearly continuous by age six to nine months. Seizures are intractable to multiple anticonvulsants. Rarely, status epilepticus at onset has been described [Zamponi et al 2008]. The characteristic feature on EEG is focal ictal discharges that migrate across contiguous cortical regions and arise independently at multiple foci. An increase in amplitude and frontal predominance over time with post-ictal and interictal suppression has been noted [McTague et al 2018].

Additional neurologic features reported in individuals withKCNT1-related EIMFS include hypotonia (axial>appendicular), decreased head growth with microcephaly developing by age 12 months, strabismus, and profound developmental delay with rare ability to ambulate or verbalize. Additional reported movement disorders include choreoathetosis, dyskinesias, and focal and generalized dystonia.

Prognosis for individuals withKCNT1-related EIMFS is currently unknown.

ADNFLE is characterized by clusters of nocturnal motor seizures that vary from simple arousals to hyperkinetic events with tonic or dystonic features (seeAutosomal Dominant Nocturnal Frontal Lobe Epilepsy). Individuals withKCNT1-related ADNFLE are more likely to develop seizures before adolescence, have cognitive comorbidity, and display psychiatric and behavioral problems than are individuals with ADNFLE resulting from other causes.

Less common epilepsy phenotypes in individuals with aKCNT1pathogenic variant include:

  • West syndrome
  • Ohtahara syndrome (early-infantile epileptic encephalopathy)
  • Early myoclonic encephalopathy
  • Leukodystrophy/leukoencephalopathy
  • Focal or multifocal epilepsy

Brain MRI and/or CT examination is often normal prior to seizure onset, though recent studies have noted variable delayed myelination, hippocampal volume loss, and cerebellar atrophy [McTague et al 2018]. Temporal lobe pathology as a cause versus consequence has been noted in two individuals withKCNT1-related temporal lobe epilepsy [Hansen et al 2017].

Other. Prenatal history, birth, and neonatal history prior to seizure onset are normal, with no notabledysmorphic features.

Pulmonary Hemorrhage

Three individuals withKCNT1-related EIMFS were reported to have prominent systemic-to-pulmonary collateral artery formation and subsequent pulmonary hemorrhage that developed between age four and 19 months [Kawasaki et al 2017]. Evaluation for pulmonary hemorrhage should be considered if an individual develops acute respiratory failure, heart failure, or hemoptysis.

Cardiac Arrhythmia

Brugada syndrome was reported in one individual with ade novo KCNT1 variant [Juang et al 2014]. An individual with confirmedfamilialKCNT1-related epilepsy and an unspecified cardiac arrhythmia was reported byMøller et al [2015].

Genotype-Phenotype Correlations

There is some evidence for agenotype-phenotype correlation. However, disparate phenotypes (e.g., ADNFLE, EIMFS) have been identified in family members with the samepathogenic variant.

EIMFS. The majority of pathogenic variants associated with EIMFS occur in either the S5 transmembranedomain or the regulator of potassium conductance domains within the C-terminus.

ADNFLE-related pathogenic variants are concentrated in the NAD+ bindingdomain or more distal C-terminus.

Specific correlations between genetic variant and seizure burden, developmental impairment, or medication responsiveness have not yet been elucidated.

Penetrance

Penetrance is reported to be 100% forKCNT1-related EIMFS [Barcia et al 2012,Heron et al 2012] but is reported as reduced inKCNT1-related epilepsy with other seizure phenotypes [Møller et al 2015].

Nomenclature

In the initial description of EIMFS,Coppola et al [1995] described his cohort of globally arrested infants with frequent focal, "migrating" seizures that were medically intractable as malignant migrating partial seizures of infancy (MMPSI); it has also been variably referred to as migrating partial epilepsy of infancy (MPEI). In 2010, the International League Against Epilepsy reclassified this epilepsy syndrome as EIMFS [Berg et al 2010].

Prevalence

The prevalence ofKCNT1-related epilepsy is unknown. To date, 88 probands withKCNT1-related epilepsy have been reported in the literature.

Genetically Related (Allelic) Disorders

No phenotypes other than those discussed in thisGeneReview are known to be associated withgermline pathogenic variants inKCNT1.

Differential Diagnosis

Phenotypic and EEG features associated withKCNT1 pathogenic variants are not sufficient to diagnoseKCNT1-related epilepsy. All genes known to be associated with early-infantile epileptic encephalopathy (>30 have been identified; seeOMIM Phenotypic Series) should be included in the differential diagnosis ofKCNT1-related epilepsy including other genes less commonly associated with epilepsy of infancy with migrating focal seizures (SCN1A,SCN2A,SLC12A5,SLC25A22,TBC1D24,PLCB1) andautosomal dominant nocturnal frontal lobe epilepsy (CHRNA4,CHRNB2,DEPDC5,CRH).

Note: At seizure onset, it is most important to distinguishKCNT1-related epilepsy from potentially treatable causes of early infantile-onset epileptic encephalopathy, such as neurometabolic disorders, CNS infection, structural brain lesions, and other syndromes (seeTable 2).

Table 2.

Treatable Disorders Associated with Early Infantile-Onset Epileptic Encephalopathy

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ConditionsGene(s)MOIClinical FindingsTreatment
Neuro-
metabolic
disorders
Pyridoxine-dependent epilepsyALDH7A1AR
  • ↑ plasma & urine alpha-aminoadipic semialdehyde
  • ↑ plasma & CSF pipecolic acid
Seizures/encephalopathy responsive to pyridoxine
Pyridoxamine 5'-phosphate oxidase deficiency (OMIM610090)PNPOAR
  • Lactic acidemia
  • Hypoglycemia
Seizures/encephalopathy responsive to pyridoxal 5-prime phosphate
Biotinidase deficiencyBTDAR
  • Deficient biotinidase enzyme activity in serum or plasma
  • Ketolactic acidosis, organic aciduria, hyperammonemia
  • Skin rash, alopecia, recurrent viral or fungal infections
Lifelong biotin supplementation
Glucose transporter 1 deficiency syndromeSLC2A1AD
AR
  • ↓ CSF glucose concentration
  • Absence seizures beginning age <3
Ketogenic diet

Creatine deficiency syndromes

GAMT
GATM
SLC6A8
AR
XL
  • Cerebral creatine deficiency on brain MR spectroscopy
  • Suggestive ratio of guanidinoacetate, creatine, &/or creatinine in plasma & urine
Creatine monohydrate supplementation
Holocarboxylase synthetase deficiency (OMIM253270)HLCSAR
  • Ketolactic acidosis, organic aciduria, hyperammonemia
  • Skin rash, alopecia
Responsive to biotin
Serine biosynthesis disordersPHGDH
PSAT1
PSPH
AR
  • Congenital or acquired microcephaly,congenital cataracts
  • ↓ plasma & CSF serine
L-serine & glycine supplementation can reduce seizures, improve psychomotor symptoms, & prevent progression depending on subtype
OtherInfection of the CNSNAMRI, blood culture &/or lumbar puncture suggestive of infectionAntibiotic, antiviral, or antifungal therapy
Structural brain lesionsNA(Multi)focal lesions on brain MRI

Tuberous sclerosis complex

TSC1
TCS2
  • MRI brain lesions (subependymal nodules, subependymal giant cell astrocytomas, tubers, focal cortical dysplasias)
  • Cardiac rhabdomyoma, skin lesions, retinal lesions, renal lesions
Consideration of mTOR inhibitor for astrocytoma, additional seizure reduction
ARX-associated encephalopathy (OMIM308350)ARXEnlarged ventricles & T2-weighted signals in basal ganglia on brain MRI

AD =autosomal dominant; AR =autosomal recessive; MOI =mode of inheritance; NA = not applicable; XL =X-linked

Management

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed withKCNT1-related epilepsy, the evaluations summarized in this section (if not performed as part of the evaluation that led to the diagnosis) are recommended:

  • Prolonged video EEG monitoring to evaluate electroclinical and electrographic seizure burden in consultation with a pediatric epileptologist
  • Evaluation by a movement disorder specialist if dictated by clinical presentation
  • Consideration of echocardiogram to evaluate for pulmonary collaterals
  • Electrocardiogram (EKG) to evaluate for cardiac rhythm abnormalities
  • Cognitive and behavioral assessment
  • Physical, occupational, and speech therapy evaluation
  • Consultation with a clinical geneticist and/or genetic counselor

Treatment of Manifestations

Seizures.KCNT1-related epilepsy is often refractory to conventional anticonvulsants.

  • Stiripentol in combination with abenzodiazepine (commonly clonazepam or clobazam), levetiracetam, and theketogenic diet have all been well tolerated with limited success [Hmaimess et al 2006,Caraballo et al 2008,Cilio et al 2009,McTague et al 2018].
  • Vagal nerve stimulator (VNS) has not been shown to be effective [Zamponi et al 2008].
  • Quinidine. Seizure control and developmental progression with off-label use of quinidine was reported in an individual withKCNT1pathogenic variant p.Arg428Gln [Bearden et al 2014], prompting subsequent treatment trials in individuals with the same and other pathogenic variants with negative results [Mullen et al 2018] and pro-arrhythmic cardiotoxicity. Potential explanations for this variable responsiveness include genetic/epigenetic modifiers ofKCNT1 as well as polymorphisms in P-glycoprotein transporters, which actively shuttle quinidine across the blood-brain barrier [Liu et al 2015]. The limited efficacy may also be narrowed by epilepsy type, as a small, randomized, placebo-controlled, crossover clinical trial ofKCNT1-related ADNFLE showed no efficacy [Mullen et al 2018]. It has also been suggested that quinidine administered after age four years may be less effective [Abdelnour et al 2018]. In addition, given the increased risk for arrhythmia associated with quinidine treatment, some individuals are not able to achieve adequate serum levels because of the development of life-threating cardiac rhythm abnormalities, thus limiting its utility.
  • Caregivers. For information on non-medical interventions and coping strategies for parents or caregivers of children diagnosed with epilepsy, seeEpilepsy Foundation Toolbox.

Pulmonary collaterals and pulmonary hemorrhage. Embolization of systemic pulmonary collateral arteries has been used with limited success [Kawasaki et al 2017].

Developmental Delay / Intellectual Disability Management Issues

The following information represents typical management recommendations for individuals with developmental delay / intellectual disability in the United States; standard recommendations may vary from country to country.

Ages 0-3 years. Referral to an early intervention program is recommended for access to occupational, physical, speech, and feeding therapy. In the US, early intervention is a federally funded program available in all states.

Ages 3-5 years. In the US, developmental preschool through the local public school district is recommended. Before placement, an evaluation is made to determine needed services and therapies and an individualized education plan (IEP) is developed.

Ages 5-21 years

  • In the US, an IEP based on the individual's level of function should be developed by the local public school district. Affected children are permitted to remain in the public school district until age 21.
  • Discussion about transition plans including financial, vocation/employment, and medical arrangements should begin at age 12 years. Developmental pediatricians can provide assistance with transition to adulthood.

All ages. Consultation with a developmental pediatrician is recommended to ensure the involvement of appropriate community, state, and educational agencies and to support parents in maximizing quality of life.

Consideration of private supportive therapies based on the affected individual's needs is recommended. Specific recommendations regarding type of therapy can be made by a developmental pediatrician.

In the US:

  • Developmental Disabilities Administration (DDA) enrollment is recommended. DDA is a public agency that provides services and support to qualified individuals. Eligibility differs by state but is typically determined by diagnosis and/or associated cognitive/adaptive disabilities.
  • Families with limited income and resources may also qualify for supplemental security income (SSI) for their child with a disability.

Motor Dysfunction

Gross motor dysfunction

  • Physical therapy is recommended to maximize mobility.
  • Consider use of durable medical equipment as needed (e.g., wheelchairs, walkers, bath chairs, orthotics, adaptive strollers).

Fine motor dysfunction. Occupational therapy is recommended for difficulty with fine motor skills that affect adaptive function such as feeding, grooming, dressing, and writing.

Oral motor dysfunction. Assuming that the individual is safe to eat by mouth, feeding therapy (typically from an occupational or speech therapist) is recommended for affected individuals who have difficulty feeding as a result of poor oral motor control.

Communication issues. Consider evaluation for alternative means of communication (e.g.,augmentative and alternative communication [AAC]) for individuals who have expressive language difficulties.

Social/Behavioral Concerns

Children may qualify for and benefit from interventions used in treatment of autism spectrum disorder, including applied behavior analysis (ABA). ABA therapy is targeted to the individual child's behavioral, social, and adaptive strengths and weaknesses and is typically performed one on one with a board-certified behavior analyst.

Consultation with a developmental pediatrician may be helpful in guiding parents through appropriate behavior management strategies or providing prescription medications (e.g., to treat attention-deficit/hyperactivity disorder) when necessary.

Concerns about serious aggressive or destructive behavior can be addressed by a pediatric psychiatrist.

Surveillance

EEG is recommended at intervals determined by seizure frequency and progression, for evaluation of new involuntary movements or unexplained, paroxysmal changes in vital signs, or following adjustments to an anticonvulsant regimen.

Developmental evaluation and initiation of therapies is recommended at time of diagnosis if not already begun.

Following initial EKG and echocardiogram, there is no indication to repeat cardiac monitoring or cardiopulmonary imaging unless clinically indicated or following initiation of quinidine therapy.

Agents/Circumstances to Avoid

No anticonvulsants have been noted to exacerbateKCNT1-related epilepsy.

For individuals with ADNFLE, activities in which a sudden loss of consciousness could lead to injury or death should be avoided (e.g., bathing, swimming, driving, or working/playing at heights).

Evaluation of Relatives at Risk

It is appropriate to clarify the genetic status of apparently asymptomatic at-risk relatives of an affected individual bymolecular genetic testing for theKCNT1pathogenic variant in the family. Family members who are found to have aheterozygousKCNT1 pathogenic variant are at risk for seizures and cardiac arrhythmias, and thus appropriate screening should be performed.

SeeGenetic Counseling for issues related to testing of at-risk relatives forgenetic counseling purposes.

Pregnancy Management

In general, women with epilepsy or a seizure disorder from any cause are at greater risk for mortality during pregnancy than pregnant women without a seizure disorder; use of anti-seizure medication during pregnancy reduces this risk. However, exposure to anti-seizure medication (e.g., valproate, phenobarbital, topiramate) may increase the risk for adverse fetal outcome (depending on the drug used, the dose, and the stage of pregnancy at which medication is taken). Nevertheless, the risk of an adverse outcome to the fetus from anti-seizure medication exposure is often less than that associated with exposure to an untreated maternal seizure disorder. Therefore, use of anti-seizure medication to treat a maternal seizure disorder during pregnancy is typically recommended. Discussion of the risks and benefits of using a given anti-seizure medication during pregnancy should ideally take place prior to conception. Transitioning to a lower-risk medication prior to pregnancy may be possible [Sarma et al 2016].

SeeMotherToBaby for further information on medication use during pregnancy.

Therapies Under Investigation

SearchClinicalTrials.gov in the US andEU Clinical Trials Register in Europe for information on clinical studies for a wide range of diseases and conditions.

Genetic Counseling

Genetic counseling is the process of providing individuals and families withinformation on the nature, mode(s) of inheritance, and implications of genetic disorders to help themmake informed medical and personal decisions. The following section deals with geneticrisk assessment and the use of family history and genetic testing to clarify geneticstatus for family members; it is not meant to address all personal, cultural, orethical issues that may arise or to substitute for consultation with a geneticsprofessional. —ED.

Mode of Inheritance

KCNT1-related epilepsy is inherited in anautosomal dominant manner.

Risk to Family Members

Parents of aproband

Sibs of aproband. The risk to the sibs of the proband depends on the clinical/genetic status of the proband's parents:

Offspring of aproband. Each child of an individual withKCNT1-related epilepsy has a 50% chance of inheriting theKCNT1pathogenic variant.

Other family members. The risk to other family members depends on the status of theproband's parents: if a parent has theKCNT1pathogenic variant, the parent's family members may be at risk.

Related Genetic Counseling Issues

See Management,Evaluation of Relatives at Risk for information on evaluating at-risk relatives for the purpose of early diagnosis and treatment.

Considerations in families with an apparentde novopathogenic variant. When neither parent of aproband with anautosomal dominant condition has the pathogenic variant identified in the proband or clinical evidence of the disorder, the pathogenic variant is likelyde novo. However, non-medical explanations includingalternate paternity or maternity (e.g., with assisted reproduction) and undisclosed adoption could also be explored.

Family planning

  • The optimal time for determination of genetic risk and discussion of the availability of prenatal/preimplantation genetic testing is before pregnancy.
  • It is appropriate to offergenetic counseling (including discussion of potential risks to offspring and reproductive options) to young adults who are affected or at risk.

DNA banking. Because it is likely that testing methodology and our understanding of genes, pathogenic mechanisms, and diseases will improve in the future, consideration should be given to banking DNA from probands in whom a molecular diagnosis has not been confirmed (i.e., the causative pathogenic mechanism is unknown). For more information, seeHuang et al [2022].

Prenatal Testing and Preimplantation Genetic Testing

Once theKCNT1pathogenic variant has been identified in an affected family member, prenatal andpreimplantation genetic testing are possible.

Differences in perspective may exist among medical professionals and within families regarding the use of prenatal andpreimplantation genetic testing. While most health care professionals would consider use of prenatal and preimplantation genetic testing to be a personal decision, discussion of these issues may be helpful.

Resources

GeneReviews staff has selected the following disease-specific and/or umbrellasupport organizations and/or registries for the benefit of individuals with this disorderand their families. GeneReviews is not responsible for the information provided by otherorganizations. For information on selection criteria, clickhere.

Molecular Genetics

Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.

Table A.

KCNT1-Related Epilepsy: Genes and Databases

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Data are compiled from the following standard references:gene fromHGNC;chromosomelocus fromOMIM;protein fromUniProt.For a description of databases (Locus Specific, HGMD, ClinVar) to which links are provided, clickhere.

Table B.

OMIM Entries for KCNT1-Related Epilepsy (View All in OMIM)

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608167POTASSIUM CHANNEL, SUBFAMILY T, MEMBER 1; KCNT1
614959DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 14; DEE14
615005EPILEPSY, NOCTURNAL FRONTAL LOBE, 5; ENFL5

Gene structure.KCNT1 is located atchromosome 9q34.3. Although a long and short isoform have been reported in humans, the long isoform (Slack-B) composed of 31 exons is thought to encode the predominantly expressed functional protein and has been more extensively studied. With 1,235 amino acids, it is the largest potassium channel identified thus far. As studies in animals have revealed five spliceisoforms with different expression patterns and physiologic properties, additional expression studies are necessary in humans to better definegene expression.

Pathogenic variants. All pathogenic variants reported to date aremissense variants associated with an epilepsyphenotype, with the exception of two missense variants identified in individuals with cardiac conduction abnormalities [Juang et al 2014,Møller et al 2015]. Whereas most variants in neonates are associated with EIMFS, other phenotypes within the spectrum of infantile-onset epilepsy (e.g., West syndrome or EIEE not consistent with EIMFS) have been reported [Allen et al 2016,Fukuoka et al 2017].

The majority of ADNFLE-associated variants have also been observed in individuals with an EIMFSphenotype, consistent withvariable expressivity [Heron et al 2012,Ishii et al 2013,Steinlein 2014,Møller et al 2015].

Table 3.

KCNT1 Variants Discussed in ThisGeneReview

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Associated PhenotypeDNA Nucleotide ChangePredicted Protein ChangeReference Sequences
EIMFSc.769C>Gp.His257AspNM_020822​.2
NP_065873​.2
c.785G>Ap.Arg262Gln
c.808C>Gp.Gln270Glu
c.811G>Tp.Val271Phe
c.820C>Ap.Leu274Ile
c.1038C>Gp.Phe364Leu
c.1225C>Tp.Pro409Ser
c.1420C>Tp.Arg474Cys
c.1429G>Ap.Ala477Thr
c.1504T>Gp.Phe502Val
c.1546A>Gp.Met516Val
c.1885G>Ap.Lys629Glu
c.1887G>Cp.Lys629Asn
c.2280C>Gp.Ile760Met
c.2687T>Ap.Met896Lys
c.2771C>Tp.Pro924Leu
c.2797C>Gp.Arg933Gly
c.2800G>Ap.Ala934Thr
c.2839A>Gp.Lys947Glu
c.2849G>Ap.Arg950Gln
Temporal lobe epilepsyc.398G>Ap.Arg133His
c.3320G>Ap.Arg1107His
ADNFLEc.862G>Ap.Gly288Ser
c.2386T>Cp.Tyr796His
c.2688G>Ap.Met896Ile
ADNFLE, EIMFSc.2849G>Ap.Arg950Gln
ADNFLE, EIMFS, multifocal epilepsyc.1018G>Ap.Val340Met
c.1193G>Ap.Arg398Gln
EIMFS, multifocal epilepsyc.1283G>Ap.Arg428Gln
EIEEc.1799G>Ap.Arg600Gln
EIMFS, West syndrome, EIEEc.1421G>Ap.Arg474His
EIMFS, West syndromec.1955G>Tp.Gly652Val
West syndrome, leukodystrophyc.2718G>Tp.Gln906His
EIMFS, ADNFLE, focal epilepsy, cardiac arrhythmiac.2782C>Tp.Arg928Cys
EIEE, delayed myelination, leukodystrophyc.2794T>Ap.Phe932Ile
Multifocal epilepsyc.2882G>Ap.Arg961His
Brugada syndromec.3317G>Ap.Arg1106Gln

Variants listed in the table have been provided by the authors.GeneReviews staff have not independently verified the classification of variants.

GeneReviews follows the standard naming conventions of the Human Genome Variation Society (varnomen​.hgvs.org). SeeQuick Reference for an explanation of nomenclature.

Normalgene product.KCNT1 encodes one of the two known sodium-activated potassium channels, termed the slack ("sequence like A calcium-activated K"; previously known as Slo2.2 and KCa4.1) channel [Joiner et al1998]. Current nomenclature now refers to KCNT1 as KNa1.1 [Kaczmarek et al 2017].

While KNa1.1 possesses six transmembrane domains and a poredomain between the S5 and S6 transmembrane domains, similar to other voltage-gated potassium channels, its C-terminus is disproportionately large. The C-terminus comprises:

  • Two regulators of conductance of K+ (RCK) domains that form a ring on the cytoplasmic face of the channel, which, in the presence of sodium, undergoes a conformational shift to expose the electrostatic channel pore [Hite et al 2015];
  • An NAD+ bindingdomain in the C-terminus, which, in the presence of increased NAD+ concentrations, reduces the sodium requirement of the channel [Tamsett et al 2009].

The C-terminus regulates channel opening by interaction with fragile X mental retardation protein (FMRP) [Zhang et al 2012].

KCNT1 expression is robust throughout the CNS in brain stem nuclei, the cerebellum, and the olfactory bulb and less strongly in the hippocampus and frontal cortex [Bhattacharjee et al 2002,Rizzi et al 2016].

Abnormalgene product. Of the variants studied functionally, all confer again-of-function channelphenotype regardless of the type of associated epilepsy [reviewed inMøller et al 2015,Lim et al 2016,McTague et al 2018], with the exception of p.Phe932Ile, which confers aloss-of-function channel phenotype [Vanderver et al 2014].

Although the majority of variants associated withKCNT1-related EIMFS andKCNT1-related ADNFLE cluster in different regions of the channel (seeFigure 1), there is insufficient evidence to predictgenotype-phenotype correlation. Clinical variability is expected.

Figure 1. . Pathogenic variants identified in KCNT1-related epilepsy cluster in the S5 transmembrane and the Regulators of Potassium (RCK) domains of the channel protein.

Figure 1.

Pathogenic variants identified inKCNT1-related epilepsy cluster in the S5 transmembrane and the Regulators of Potassium (RCK) domains of the channel protein. Generated from an image drawn using Protter open-source software [Omasits et al 2014]

Several mechanisms of channel dysfunction have been described. Some variants cause a shift in time spent in subconductance states, either secondary to loss of PKC-dependent regulation [Barcia et al 2012] or because of enhanced cooperativity of channels leading to increased open channel probability [Kim et al 2014]. Other pathogenic variants appear hypersensitive to intracellular sodium and thus more likely to be in an open state [Tang et al 2016]. Further research is needed to determine the impact of an enhanced potassium conductance on neuronal firing within regions of the developing brain susceptible to epileptogenesis.

Chapter Notes

Author Notes

TheKCNT1 Registry includes individuals with epilepsy and known or suspected pathogenic variants inKCNT1. The registry is an ongoing natural history study ofKCNT1-related epilepsy. Individuals interested in participating in theKCNT1 Registry should contact Dr David Bearden at david_bearden@urmc.rochester.edu.

Revision History

  • 20 September 2018 (tg) Review posted live
  • 28 February 2018 (jlr) Original submission

References

Literature Cited

  • AbdelnourE, GallentineW, McDonaldM, SachdevM, JiangYH, MikatiMA. Does age affect response to quinidine in patients with KCNT1 mutations? Report of three new cases and review of the literature.Seizure.2018;55:1-3. [PubMed: 29291456]
  • AllenNM, ConroyJ, ShahwanA, LynchB, CorreaRG, PenaSD, McCrearyD, MagalhãesTR, EnnisS, LynchSA, KingMD. Unexplained early onset epileptic encephalopathy: exome screening and phenotype expansion.Epilepsia.2016;57:e12-7 [PubMed: 26648591]
  • BarciaG, FlemingMR, DeligniereA, GazulaVR, BrownMR, LangouetM, ChenH, KronengoldJ, AbhyankarA, CilioR, NitschkeP, KaminskaA, BoddaertN, CasanovaJL, DesguerreI, MunnichA, DulacO, KaczmarekLK, ColleauxL, NabboutR. De novo gain-of-function KCNT1 channel mutations cause malignant migrating partial seizures of infancy.Nat Genet.2012;44:1255-9. [PMC free article: PMC3687547] [PubMed: 23086397]
  • BeardenD, StrongA, EhnotJ, DiGiovineM, DlugosD, GoldbergEM. Targeted treatment of migrating partial seizures of infancy with quinidine.Ann Neurol.2014;76:457-61. [PubMed: 25042079]
  • BergAT, BerkovicSF, BrodieMJ, BuchhalterJ, CrossJH, van Emde BoasW, EngelJ, FrenchJ, GlauserTA, MathernGW, MoshéSL, NordliD, PlouinP, SchefferIE. Revised terminology and concepts for organization of seizures and epilepsies: report of the ILAE Commission on Classification and Terminology, 2005-2009.Epilepsia.2010;51:676-85. [PubMed: 20196795]
  • BhattacharjeeA, GanL, KaczmarekLK. Localization of the Slack potassium channel in the rat central nervous system.J Comp Neurol.2002;454:241-54. [PubMed: 12442315]
  • CaraballoRH, FontanaE, DarraF, CassarL, NegriniF, FioriniE, ArroyoH, FerraroS, FejermanN, Dalla BernardinaB. Migrating focal seizures in infancy: analysis of the electroclinical patterns in 17 patients.J Child Neurol.2008;23:497-506. [PubMed: 18230844]
  • CilioMR, BianchiR, BalestriM, OnofriA, GiovanniniS, Di CapuaM, VigevanoF. Intravenous levetiracetam terminates refractory status epilepticus in two patients with migrating partial seizures in infancy.Epilepsy Res.2009;86:66-71. [PubMed: 19520548]
  • CoppolaG, PlouinP, ChironC, RobainO, DulacO. Migrating partial seizures in infancy: a malignant disorder with developmental arrest.Epilepsia.1995; 36: 1017-24. [PubMed: 7555952]
  • FukuokaM, KukiI, KawawakiH, OkazakiS, KimK, HattoriY, TsujiH, NukuiM, InoueT, YoshidaY, UdaT, KimuraS, MogamiY, SuzukiY, OkamotoN, SaitsuH, MatsumotoN.Quinidine therapy for West syndrome with KCNTI mutation: a case report.Brain Dev.2017; 39: 80-3. [PubMed: 27578169]
  • HansenN, WidmanG, HattingenE, ElgerCE, KunzWS. Mesial temporal lobe epilepsy associated with KCNT1 mutation.Seizure.2017; 45: 181-3. [PubMed: 28081520]
  • HeronSE, SmithKR, BahloM, NobiliL, KahanaE, LicchettaL, OliverKL, MazaribA, AfawiZ, KorczynA, PlazziG, PetrouS, BerkovicSF, SchefferIE, DibbensLM. Missense mutations in the sodium-gated potassium channel gene KCNT1 cause severe autosomal dominant nocturnal frontal lobe epilepsy.Nat Genet.2012; 44: 1188-90. [PubMed: 23086396]
  • HiteRK, YuanP, LiZ, HsuingY, WalzT, MacKinnonR. Cryo-electron microscopy structure of the Slo2.2 Na(+)-activated K(+) channel.Nature.2015; 527: 198-203. [PMC free article: PMC4886347] [PubMed: 26436452]
  • HmaimessG, KadhimH, NassogneMC, BonnierC, van RijckevorselK. Levetiracetam in a neonate with malignant migrating partial seizures.Pediatr Neurol.2006; 34: 55-9. [PubMed: 16376281]
  • HuangSJ, AmendolaLM, SternenDL. Variation among DNA banking consent forms: points for clinicians to bank on.J Community Genet.2022;13:389-97. [PMC free article: PMC9314484] [PubMed: 35834113]
  • IshiiA, ShiodaM, OkumuraA, KidokoroH, SakauchiM, ShimadaS, ShimizuT, OsawaM, HiroseS, YamamotoT.A recurrent KCNT1 mutation in two sporadic cases with malignant migrating partial seizures in infancy.Gene.2013; 531: 467-71. [PubMed: 24029078]
  • JoinerWJ, TangMD, WangLY, DworetzkySI, BoissardCG, GanL, GribkoffVK, KaczmarekLK. Formation of intermediate-conductance calcium-activated potassium channels by interaction of Slack and Slo subunits.Nat Neurosci.1998; 1: 462-9. [PubMed: 10196543]
  • JuangJM, LuTP, LaiLC, HoCC, LiuYB, TsaiCT, LinLY, YuCC, ChenWJ, ChiangFT, YehSF, LaiLP, ChuangEY, LinJL. Disease-targeted sequencing of ion channel genes identifies de novo mutations in patients with non-familial Brugada syndrome.Sci Rep.2014; 4: 6733. [PMC free article: PMC4206841] [PubMed: 25339316]
  • KaczmarekLK, AldrichRW, ChandyKG, GrissmerS, WeiAD, WulffH. International Union of Basic and Clinical Pharmacology. C. Nomenclature and properties of calcium-activated and sodium-activated potassium channels.Pharmacol Rev.2017; 69: 1-11. [PMC free article: PMC11060434] [PubMed: 28267675]
  • KawasakiY, KukiI, EharaE, MurakamiY, OkazakiS, KawawakiH, HaraM, WatanabeY, KishimotoS, SudaK, SaitsuH, MatsumotoN.Three cases of KCNT1 mutations: malignant migrating partial seizures in infancy with massive systemic to pulmonary collateral arteries.J Pediatr.2017; 191: 270-4. [PubMed: 28987752]
  • KimGE, KronengoldJ, BarciaG, QuraishiIH, MartinHC, BlairE, TaylorJC, DulacO, ColleauxL, NabboutR, KaczmarekLK. Human slack potassium channel mutations increase positive cooperativity between individual channels.Cell Rep.2014; 9: 1661-72. [PMC free article: PMC4294418] [PubMed: 25482562]
  • LimCX, RicosMG, DibbensLM, HeronSE. KCNT1 mutations in seizure disorders: the phenotypic spectrum and functional effects.J Med Genet.2016; 53: 217-25. [PubMed: 26740507]
  • LiuL, CollierAC, LinkJM, DominoKB, MankoffDA, EaryJF, SpiekermanCF, HsiaoP, DeoAK, UnadkatJD. Modulation of P-glycoprotein at the human blood-brain barrier by quinidine or rifampin treatment: a positron emission tomography imaging study.Drug Metab Dispos.2015; 43: 1795-804. [PMC free article: PMC4613948] [PubMed: 26354948]
  • McTagueA, AppletonR, AvulaS, CrossJH, KingMD, JacquesTS, BhateS, CroninA, CurranA, DesurkarA, FarrellMA, HughesE, JeffersonR, LascellesK, LivingstonJ, MeyerE, McLellanA, PoduriA, SchefferIE, SpintyS, KurianMA, KneenR. Migrating partial seizures of infancy: expansion of the electroclinical, radiological and pathological disease spectrum.Brain.2013; 136: 1578-91. [PMC free article: PMC3634200] [PubMed: 23599387]
  • McTagueA, NairU, MalhotraS, MeyerE, TrumpN, GazinaEV, PapandreouA, NgohA, AckermannS, AmbegaonkarG, AppletonR, DesurkarA, EltzeC, KneenR, KumarAV, LascellesK, MontgomeryT, RameshV, SamantaR, ScottRH, TanJ, WhitehouseW, PoduriA, SchefferIE, ChongWKK, CrossJH, TopfM, PetrouS, KurianMA. Clinical and molecular characterization of KCNT1-related severe early-onset epilepsy.Neurology.2018; 90: e55-e66. [PMC free article: PMC5754647] [PubMed: 29196579]
  • MøllerRS, HeronSE, LarsenLH, LimCX, RicosMG, BaylyMA, van KempenMJ, KlinkenbergS, AndrewsI, KelleyK, RonenGM, CallenD, McMahonJM, YendleSC, CarvillGL, MeffordHC, NabboutR, PoduriA, StrianoP, BagliettoMG, ZaraF, SmithNJ, PridmoreC, GardellaE, NikanorovaM, DahlHA, GellertP, SchefferIE, GunningB, Kragh-OlsenB, DibbensLM. Mutations in KCNT1 cause a spectrum of focal epilepsies.Epilepsia.2015; 56: e114-20. [PMC free article: PMC5915334] [PubMed: 26122718]
  • MullenSA, CarneyPW, RotenA, ChingM, LightfootPA, ChurilovL, NairU, LiM, BerkovicSF, PetrouS, SchefferIE. Precision therapy for epilepsy due to KCNT1 mutations: a randomized trial of oral quinidine.Neurology.2018; 90: e67-e72. [PubMed: 29196578]
  • OhbaC, KatoM, TakahashiN, OsakaH, ShiiharaT, TohyamaJ, NabatameS, AzumaJ, FujiiY, HaraM, TsurusawaR, InoueT, OgataR, WatanabeY, TogashiN, KoderaH, NakashimaM, TsurusakiY, MiyakeN, TanakaF, SaitsuH, MatsumotoN.De novo KCNT1 mutations in early-onset epileptic encephalopathy.Epilepsia.2015; 56: e121-8. [PubMed: 26140313]
  • OmasitsU, AhrensCH, MüllerS, WollscheidB. Protter: interactive protein feature visualization and integration with experimental proteomic data.Bioinformatics.2014;30:884-6. [PubMed: 24162465]
  • RichardsS, AzizN, BaleS, BickD, DasS, Gastier-FosterJ, GrodyWW, HegdeM, LyonE, SpectorE, VoelkerdingK, RehmHL, et al.Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology.Genet Med.2015;17:405-24. [PMC free article: PMC4544753] [PubMed: 25741868]
  • RizziS, KnausHG, SchwarzerC. Differential distribution of the sodium-activated potassium channels slick and slack in mouse brain.J Comp Neurol.2016; 524: 2093-116. [PMC free article: PMC4982087] [PubMed: 26587966]
  • SarmaAK, KhandkerN, KurczewskiL, BrophyGM. Medical management of epileptic seizures: challenges and solutions.Neuropsychiatr Dis Treat.2016;12:467-85 [PMC free article: PMC4771397] [PubMed: 26966367]
  • SteinleinOK. Genetic heterogeneity in familial nocturnal frontal lobe epilepsy.Prog Brain Res.2014; 213: 1-15. [PubMed: 25194481]
  • TamsettTJ, PicchioneKE, BhattacharjeeA. NAD+ activates KNa channels in dorsal root ganglion neurons.J Neurosci.2009; 29: 5127-34. [PMC free article: PMC6665483] [PubMed: 19386908]
  • TangQY, ZhangFF, XuJ, WangR, ChenJ, LogothetisDE, ZhangZ. Epilepsy-related slack channel mutants lead to channel over-activity by two different mechanisms.Cell Rep.2016; 14: 129-39. [PMC free article: PMC4706775] [PubMed: 26725113]
  • VanderverA, SimonsC, SchmidtJL, PearlPL, BloomM, LavensteinB, MillerD, GrimmondSM, TaftRJ. Identification of a novel de novo p.Phe932Ile KCNT1 mutation in a patient with leukoencephalopathy and severe epilepsy.Pediatr Neurol.2014; 50: 112-4. [PMC free article: PMC4303471] [PubMed: 24120652]
  • ZamponiN, RychlickiF, CorpaciL, CesaroniE, TrignaniR.Vagus nerve stimulation (VNS) is effective in treating catastrophic 1 epilepsy in very young children.Neurosurg Rev.2008; 31: 291-7. [PubMed: 18446391]
  • ZhangY, BrownMR, HylandC, ChenY, KronengoldJ, FlemingMR, KohnAB, MorozLL, KaczmarekLK. Regulation of neuronal excitability by interaction of fragile X mental retardation protein with slack potassium channels.J Neurosci.2012; 32: 15318-27. [PMC free article: PMC3518385] [PubMed: 23115170]
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