Pyridoxine-dependent seizures: findings from recent studies pose new questions

MOLECULAR MECHANISMS UNDERLYING THERAPEUTIC ACTION OF VITAMIN B6

The aim of the study was to analyze the molecular mechanisms that determine the possibility of using vitamin B6 in clinical practice for the correction of various pathological conditions.

Materials and methods. Information retrieval (Scopus, PubMed) and library (eLibrary) databases were used as research tools. In some cases, the ResearchGate application was used for a semantic search. The analysis and generalization of the scientific literature on the topic of research, covering the period from 1989 to the present, has been carried out in the work.

Results. It has been shown that all chemical forms of vitamin B6 are able to penetrate the membranes of most cells by free diffusion, while forming phosphorylated forms inside. Pyridoxal phosphate is a biologically important metabolite that is directly involved as a cofactor in a variety of intracellular reactions. Requirements for this cofactor depend on the age, sex and condition of the patient. Pregnancy and lactation play a special role in the consumption of vitamin B6. In most cases, a balanced diet will provide an acceptable level of this vitamin. At the same time, its deficiency leads to the development of a number of pathological conditions, including neurodegenerative diseases, inflammations and diabetes. Negative manifestations from the central nervous system are also possible with an excessive consumption of B6.

Conclusion. Replenishment of the vitamin B6 level in case of its identified deficiency is a necessary condition for the successful treatment of the central nervous system diseases, diabetes and correction of patients’ immune status. At the same time, it is necessary to observe a balanced intake of this cofactor in order to avoid negative effects on metabolism in case of its excess.

The spectrum of pyridoxine dependent epilepsy across the age span: A nationwide retrospective observational study

BACKGROUND

Pyridoxine-dependent epilepsy (PDE) is a rare seizure disorder usually presenting with neonatal seizures. Most cases are caused by biallelic pathogenic ALDH7A1variants. While anti-seizure medications are ineffective, pyridoxine provides seizure control, and dietary interventions may be of benefit. As the natural history beyond adolescence is insufficiently explored, our study aimed to assess the spectrum of PDE at various ages in Norway.

METHODS

Patients were ascertained by contacting all Norwegian paediatric, neurological, and neurohabilitation departments and relevant professional societies. Medical records were collected and reviewed.

RESULTS

We identified 15 patients treated for PDE; 13 had ALDH7A1 variants (PDE-ALDH7A1), one had PNPO deficiency, and in one, aetiology remained obscure. Of those with PDE-ALDH7A1, 12 were alive at time of study; five were > 18 years old and six were < 4 years. Median age was 10 years (range 2 months-53 years). Estimated minimum prevalence was 6.3/million among children and 1.2/million among adults. Ten had seizure onset on the first day of life. Perinatal complications and neuroradiological abnormalities suggested additional seizure aetiologies in several patients. Pyridoxine had immediate effect in six, while six had delayed (>1 h) or uncertain effect. Median delay from first seizure to continuous treatment was 11 days (range 0-42). Nine experienced breakthrough seizures with intercurrent disease or due to pyridoxine discontinuation. Cognitive outcomes ranged from normal to severe intellectual disability. The condition appeared to remain stable in adult life.

SIGNIFICANCE

We found a much higher prevalence of PDE-ALDH7A1 in children relative to adults, suggesting previous underdiagnosis and early mortality. Perinatal complications are common and can delay diagnosis and initiation of pyridoxine treatment. Lifelong and continuous treatment with pyridoxine is imperative. Due to better diagnostics and survival, the number of adult patients is expected to rise.

High-dose pyridoxine treatment for inherited glycosylphosphatidylinositol deficiency

OBJECTIVE

We aimed to assess the efficacy and safety of high-dose pyridoxine treatment for seizures and its effects on development in patients with inherited glycosylphosphatidylinositol deficiencies (IGDs).

METHODS

In this prospective open-label multicenter pilot study, we enrolled patients diagnosed with IGDs using flow cytometry and/or genetic tests. The patients received oral pyridoxine (20-30 mg/kg/day) for 1 year, in addition to previous treatment.

RESULTS

All nine enrolled patients (mean age: 66.3 ± 44.3 months) exhibited marked decreases in levels of CD16, a glycosylphosphatidylinositol-anchored protein, on blood granulocytes. The underlying genetic causes of IGDs were PIGO, PIGL, and unknown gene mutations in two, two, and five patients, respectively. Six patients experienced seizures, while all patients presented with developmental delay (mean developmental age: 11.1 ± 8.1 months). Seizure frequencies were markedly (>50%) and drastically (>90%) reduced in three and one patients who experienced seizures, respectively. None of the patients presented with seizure exacerbation. Eight of nine patients exhibited modest improvements in development (P = 0.14). No adverse events were observed except for mild transient diarrhea in one patient.

CONCLUSION

One year of daily high-dose pyridoxine treatment was effective in the treatment of seizures in more than half of our patients with IGDs and modestly improved development in the majority of them. Moreover, such treatment was reasonably safe. These findings indicate that high-dose pyridoxine treatment may be effective against seizures in patients with IGDs, although further studies are required to confirm our findings. (University Hospital Medical Information Network Clinical Trials Registry [UMIN-CTR] number: UMIN000024185.).

A case of pyridoxine-dependent epilepsy with novel ALDH7A1 mutations

Pyridoxine-dependent epilepsy (PDE) is a rare autosomal-recessive disorder typically presenting with neonatal seizures and is sometimes difficult to diagnose, because the clinical features mimic those of birth asphyxia. A Japanese newborn boy presented with pulmonary haemorrhage and convulsions on the day of birth. Brain computed tomography showed diffuse, but mild, low-density cerebral white matter and a thin subdural hematoma in the posterior fossa. He did not have thrombocytopenia or coagulopathy. His respiratory status improved with conservative treatment, but his convulsions were persistent even after prescription of several antiepileptic drugs. His serum and cerebrospinal fluid showed decreased vitamin B6 vitamers and increased upstream metabolites of α-aminoadipic semialdehyde dehydrogenase, strongly suggesting a diagnosis of PDE; the epileptic spasms ceased after administration of intravenous pyridoxal phosphate hydrate. Gene analysis revealed novel compound heterozygous mutations in ALDH7A1 that included NM_001182.4:[c.1196G > T] and [c.1200 + 1G > A]. Atypical birth asphyxia with persistent neonatal seizure should prompt vitamin B6/metabolite screening.

Role of pyridoxine in GABA synthesis and degradation in the hippocampus

Pyridoxal-5'-phosphate, the active form of vitamin B₆, is associated with activities of several enzymes and the treatment of various neurological disorders. Here, we investigated the effects of pyridoxine on the immunoreactivity and protein levels of γ-aminobutyric acid (GABA)-synthesizing and degradation enzymes such as glutamic acid decarboxylase (GAD), GABA transaminase (GABA-T), and succinic semialdehyde dehydrogenase (SSADH), in the hippocampus of mice. The mice intraperitonially received physiological saline and 350 mg/kg pyridoxine, twice a day for 21 days, and were euthanized 2 h after the final dose. In the vehicle-treated group, we observed GAD67 immunoreactivity in the stratum pyramidale of the CA1 and CA3 region, Schaffer collateral, polymorphic layer, and outer granule cell layer of the dentate gyrus. Pyridoxine administration significantly increased GAD67 immunoreactivity, while significantly decreasing GABA-T immunoreactivity in pyridoxine-treated mouse hippocampi (CA1 region and dentate gyrus). In the stratum lacunosum-moleculare of CA1 region, GABA-T immunoreactivity was significantly increased in the pyridoxine-treated group compared to that in the vehicle-treated group, although GAD67 immunoreactivity was similarly observed in these groups. Alternatively, there were no significant differences in SSADH immunoreactivity in any regions of the hippocampus between the vehicle- and pyridoxine-treated groups. Western blot analysis showed significant increases in GAD67 and GABA-T protein levels in the pyridoxine-treated group compared with those in the vehicle-treated group. Therefore, pyridoxine administration facilitates GABA turnover in mouse hippocampus by modulating the GABA-synthesizing and degradation enzymes.

Pyridoxine and pancreatic acinar cells: transport physiology and effect on gene expression profile

Pyridoxine (vitamin B₆), an essential micronutrient for normal cell physiology, plays an important role in the function of the exocrine pancreas. Pancreatic acinar cells (PACs) obtain vitamin B₆ from circulation, but little is known about the mechanism involved in the uptake process; limited information also exists on the effect of pyridoxine availability on the gene expression profile in these cells. We addressed both these issues in the current investigation using mouse-derived pancreatic acinar 266-6 cells (PAC 266-6) and human primary PACs (hPACs; obtained from organ donors), together with appropriate physiological and molecular (RNA-Seq) approaches. The results showed [³H]pyridoxine uptake to be 1) pH and temperature (but not Na⁺) dependent, 2) saturable as a function of concentration, 3) cis-inhibited by unlabeled pyridoxine and its close structural analogs, 4) trans-stimulated by unlabeled pyridoxine, 5) regulated by an intracellular Ca²⁺/calmodulin-mediated pathway, 6) adaptively-regulated by extracellular substrate (pyridoxine) availability, and 7) negatively impacted by exposure to cigarette smoke extract. Vitamin B₆ availability was found (by means of RNA-Seq) to significantly (FDR < 0.05) modulate the expression profile of many genes in PAC 266-6 cells (including those that are relevant to pancreatic health and development). These studies demonstrate, for the first time, the involvement of a regulatable and specific carrier-mediated mechanism for pyridoxine uptake by PACs; the results also show that pyridoxine availability exerts profound effects on the gene expression profile in mammalian PACs.

Neuropathological Mechanisms of Seizures in Autism Spectrum Disorder

This manuscript reviews biological abnormalities shared by autism spectrum disorder (ASD) and epilepsy. Two neuropathological findings are shared by ASD and epilepsy: abnormalities in minicolumn architecture and γ-aminobutyric acid (GABA) neurotransmission. The peripheral neuropil, which is the region that contains the inhibition circuits of the minicolumns, has been found to be decreased in the post-mortem ASD brain. ASD and epilepsy are associated with inhibitory GABA neurotransmission abnormalities including reduced GABA_A and GABA_B subunit expression. These abnormalities can elevate the excitation-to-inhibition balance, resulting in hyperexcitablity of the cortex and, in turn, increase the risk of seizures. Medical abnormalities associated with both epilepsy and ASD are discussed. These include specific genetic syndromes, specific metabolic disorders including disorders of energy metabolism and GABA and glutamate neurotransmission, mineral and vitamin deficiencies, heavy metal exposures and immune dysfunction. Many of these medical abnormalities can result in an elevation of the excitatory-to-inhibitory balance. Fragile X is linked to dysfunction of the mGluR5 receptor and Fragile X, Angelman and Rett syndromes are linked to a reduction in GABA_A receptor expression. Defects in energy metabolism can reduce GABA interneuron function. Both pyridoxine dependent seizures and succinic semialdehyde dehydrogenase deficiency cause GABA deficiencies while urea cycle defects and phenylketonuria cause abnormalities in glutamate neurotransmission. Mineral deficiencies can cause glutamate and GABA neurotransmission abnormalities and heavy metals can cause mitochondrial dysfunction which disrupts GABA metabolism. Thus, both ASD and epilepsy are associated with similar abnormalities that may alter the excitatory-to-inhibitory balance of the cortex. These parallels may explain the high prevalence of epilepsy in ASD and the elevated prevalence of ASD features in individuals with epilepsy.

Metabolic and mitochondrial disorders associated with epilepsy in children with autism spectrum disorder

Autism spectrum disorder (ASD) affects a significant number of individuals in the United States, with the prevalence continuing to grow. A significant proportion of individuals with ASD have comorbid medical conditions such as epilepsy. In fact, treatment-resistant epilepsy appears to have a higher prevalence in children with ASD than in children without ASD, suggesting that current antiepileptic treatments may be suboptimal in controlling seizures in many individuals with ASD. Many individuals with ASD also appear to have underlying metabolic conditions. Metabolic conditions such as mitochondrial disease and dysfunction and abnormalities in cerebral folate metabolism may affect a substantial number of children with ASD, while other metabolic conditions that have been associated with ASD such as disorders of creatine, cholesterol, pyridoxine, biotin, carnitine, γ-aminobutyric acid, purine, pyrimidine, and amino acid metabolism and urea cycle disorders have also been associated with ASD without the prevalence clearly known. Interestingly, all of these metabolic conditions have been associated with epilepsy in children with ASD. The identification and treatment of these disorders could improve the underlying metabolic derangements and potentially improve behavior and seizure frequency and/or severity in these individuals. This paper provides an overview of these metabolic disorders in the context of ASD and discusses their characteristics, diagnostic testing, and treatment with concentration on mitochondrial disorders. To this end, this paper aims to help optimize the diagnosis and treatment of children with ASD and epilepsy. This article is part of a Special Issue entitled "Autism and Epilepsy".

Current treatment and management of pyridoxine-dependent epilepsy

OPINION STATEMENT

Pyridoxine-dependent epilepsy (PDE) is a rare autosomal recessive disorder and is considered as a prototypical form of metabolic epilepsy. Characterized by recurrent seizures in the prenatal, neonatal, and/or postnatal periods that are resistant to conventional anti-epileptic drugs, PDE is responsive to pharmacological dosages of pyridoxine. Presently, however, there are no clear dose recommendations for long-term treatment. While pyridoxine supplementation is the first line of treatment and should be initiated in all confirmed PDE patients at an early age, various other treatment strategies are emerging. These include a lysine-restricted diet and arginine fortification. These will be discussed in light of current evidence, together with recommendations for best management of patients with this rare but treatable metabolic epilepsy, and future research and collaborative efforts, including the International PDE Consortium.

Early diagnosis of pyridoxine-dependent epilepsy: video-EEG monitoring and biochemical and genetic investigation

Pyridoxine-dependent epilepsy (PDE) is a rare autosomal recessive metabolic disease. A delay of treatment may affect outcome and early initiation of pyridoxine based on effective diagnosis is crucial to ensure good cognitive outcome in neonates. A consensus for the diagnosis of PDE is based on refractive seizures and responsiveness to pyridoxine, however, a growing body of evidence suggests that additional elements should be considered which include biochemical data, genetic screening, and EEG monitoring. We present a case study of a neonate with PDE, who presented with misleading clinical presentation and a novel mutation in the antiquitin (ALDH7A1) gene (A294V), and highlight important aspects in order to consider the definition of diagnosis and management of PDE in the light of more recent data.

Clinical, biochemical, and molecular studies in pyridoxine-dependent epilepsy. Antisense therapy as possible new therapeutic option

PURPOSE

Pyridoxine-dependent epilepsy seizure (PDE; OMIM 266100) is a disorder associated with severe seizures that can be controlled pharmacologically with pyridoxine. In the majority of patients with PDE, the disorder is caused by the deficient activity of the enzyme α-aminoadipic semialdehyde dehydrogenase (antiquitin protein), which is encoded by the ALDH7A1 gene. The aim of this work was the clinical, biochemical, and genetic analysis of 12 unrelated patients, mostly from Spain, in an attempt to provide further valuable data regarding the wide clinical, biochemical, and genetic spectrum of the disease.

METHODS

The disease was confirmed based on the presence of α-aminoadipic semialdehyde (α-AASA) in urine measured by liquid chromatography tandem mass spectrometry (LC-MS/MS) and pipecolic acid (PA) in plasma and/or cerebrospinal fluid (CSF) measured by high performance liquid chromatography (HPLC)/MS/MS and by sequencing analysis of messenger RNA (mRNA) and genomic DNA of ALDH7A1.

KEY FINDINGS

Most of the patients had seizures in the neonatal period, but they responded to vitamin B6 administration. Three patients developed late-onset seizures, and most patients showed mild-to-moderate postnatal developmental delay. All patients had elevated PA and α-AASA levels, even those who had undergone pyridoxine treatment for several years. The clinical spectrum of our patients is not limited to seizures but many of them show associated neurologic dysfunctions such as muscle tone alterations, irritability, and psychomotor retardation. The mutational spectrum of the present patients included 12 mutations, five already reported (c.500A>G, c.919C>T, c.1429G>C c.1217_1218delAT, and c.1482-1G>T) and seven novel sequence changes (c.75C>T, c.319G>T, c.554_555delAA, c.757C>T, c.787 + 1G>T, c.1474T>C, c.1093-?_1620+?). Only one mutation, p.G477R (c.1429G>C), was recurrent; this was detected in four different alleles. Transcriptional profile analysis of one patient's lymphoblasts and ex vivo splicing analysis showed the silent nucleotide change c.75C>T to be a novel splicing mutation creating a new donor splice site inside exon 1. Antisense therapy of the aberrant mRNA splicing in a lymphoblast cell line harboring mutation c.75C>T was successful.

SIGNIFICANCE

The present results broaden our knowledge of PDE, provide information regarding the genetic background of PDE in Spain, afford data of use when making molecular-based prenatal diagnosis, and provide a cellular proof-of concept for antisense therapy application.

Pyridoxine and pyridoxalphosphate-dependent epilepsies

To date we know of four inborn errors of autosomal recessive inheritance that lead to vitamin B6-dependent seizures. Among these, pyridoxine-dependent seizures due to antiquitin deficiency is by far the most common, although exact incidence data are lacking. In PNPO deficiency, samples have to be collected prior to treatment, while PDE, hyperprolinemia type II and congenital HPP can be diagnosed while on vitamin B6 supplementation. A vitamin B6 withdrawal for diagnostic purposes is nowadays only indicated in patients with a clear vitamin B6 response but normal biochemical work-up. In the presence of therapy-resistant neonatal seizures, early consideration of a vitamin B6 trial over 3 consecutive days is crucial in order to prevent irreversible brain damage. While PLP would be effective in all four disorders, pyridoxine fails to treat seizures in PNPO deficiency. As PLP is unlicensed within Europe and North America, pyridoxine is widely used as the first line drug, but if it is ineffective it should be followed by a trial with PLP, especially in neonates. As severe apnea has been described in responders, resuscitation equipment should be at hand during a first pyridoxine/PLP administration. Patients and parents have to be informed about the lifelong dependency and recurrence risks in forthcoming pregnancies.

Pyridoxine dependent epilepsy and antiquitin deficiency: clinical and molecular characteristics and recommendations for diagnosis, treatment and follow-up

Antiquitin (ATQ) deficiency is the main cause of pyridoxine dependent epilepsy characterized by early onset epileptic encephalopathy responsive to large dosages of pyridoxine. Despite seizure control most patients have intellectual disability. Folinic acid responsive seizures (FARS) are genetically identical to ATQ deficiency. ATQ functions as an aldehyde dehydrogenase (ALDH7A1) in the lysine degradation pathway. Its deficiency results in accumulation of α-aminoadipic semialdehyde (AASA), piperideine-6-carboxylate (P6C) and pipecolic acid, which serve as diagnostic markers in urine, plasma, and CSF. To interrupt seizures a dose of 100 mg of pyridoxine-HCl is given intravenously, or orally/enterally with 30 mg/kg/day. First administration may result in respiratory arrest in responders, and thus treatment should be performed with support of respiratory management. To make sure that late and masked response is not missed, treatment with oral/enteral pyridoxine should be continued until ATQ deficiency is excluded by negative biochemical or genetic testing. Long-term treatment dosages vary between 15 and 30 mg/kg/day in infants or up to 200 mg/day in neonates, and 500 mg/day in adults. Oral or enteral pyridoxal phosphate (PLP), up to 30 mg/kg/day can be given alternatively. Prenatal treatment with maternal pyridoxine supplementation possibly improves outcome. PDE is an organic aciduria caused by a deficiency in the catabolic breakdown of lysine. A lysine restricted diet might address the potential toxicity of accumulating αAASA, P6C and pipecolic acid. A multicenter study on long term outcomes is needed to document potential benefits of this additional treatment. The differential diagnosis of pyridoxine or PLP responsive seizure disorders includes PLP-responsive epileptic encephalopathy due to PNPO deficiency, neonatal/infantile hypophosphatasia (TNSALP deficiency), familial hyperphosphatasia (PIGV deficiency), as well as yet unidentified conditions and nutritional vitamin B6 deficiency. Commencing treatment with PLP will not delay treatment in patients with pyridox(am)ine phosphate oxidase (PNPO) deficiency who are responsive to PLP only.

Intestinal absorption of water-soluble vitamins in health and disease

Our knowledge of the mechanisms and regulation of intestinal absorption of water-soluble vitamins under normal physiological conditions, and of the factors/conditions that affect and interfere with theses processes has been significantly expanded in recent years as a result of the availability of a host of valuable molecular/cellular tools. Although structurally and functionally unrelated, the water-soluble vitamins share the feature of being essential for normal cellular functions, growth and development, and that their deficiency leads to a variety of clinical abnormalities that range from anaemia to growth retardation and neurological disorders. Humans cannot synthesize water-soluble vitamins (with the exception of some endogenous synthesis of niacin) and must obtain these micronutrients from exogenous sources. Thus body homoeostasis of these micronutrients depends on their normal absorption in the intestine. Interference with absorption, which occurs in a variety of conditions (e.g. congenital defects in the digestive or absorptive system, intestinal disease/resection, drug interaction and chronic alcohol use), leads to the development of deficiency (and sub-optimal status) and results in clinical abnormalities. It is well established now that intestinal absorption of the water-soluble vitamins ascorbate, biotin, folate, niacin, pantothenic acid, pyridoxine, riboflavin and thiamin is via specific carrier-mediated processes. These processes are regulated by a variety of factors and conditions, and the regulation involves transcriptional and/or post-transcriptional mechanisms. Also well recognized now is the fact that the large intestine possesses specific and efficient uptake systems to absorb a number of water-soluble vitamins that are synthesized by the normal microflora. This source may contribute to total body vitamin nutrition, and especially towards the cellular nutrition and health of the local colonocytes. The present review aims to outline our current understanding of the mechanisms involved in intestinal absorption of water-soluble vitamins, their regulation, the cell biology of the carriers involved and the factors that negatively affect these absorptive events.

The genotypic and phenotypic spectrum of pyridoxine-dependent epilepsy due to mutations in ALDH7A1

Pyridoxine-dependent epilepsy is a disorder associated with severe seizures that may be caused by deficient activity of α-aminoadipic semialdehyde dehydrogenase, encoded by the ALDH7A1 gene, with accumulation of α-aminoadipic semialdehyde and piperideine-6-carboxylic acid. The latter reacts with pyridoxal-phosphate, explaining the effective treatment with pyridoxine. We report the clinical phenotype of three patients, their mutations and those of 12 additional patients identified in our clinical molecular laboratory. There were six missense, one nonsense, and five splice-site mutations, and two small deletions. Mutations c.1217_1218delAT, I431F, IVS-1(+2)T > G, IVS-2(+1)G > A, and IVS-12(+1)G > A are novel. Some disease alleles were recurring: E399Q (eight times), G477R (six times), R82X (two times), and c.1217_1218delAT (two times). A systematic review of mutations from the literature indicates that missense mutations cluster around exons 14, 15, and 16. Nine mutations represent 61% of alleles. Molecular modeling of missense mutations allows classification into three groups: those that affect NAD+ binding or catalysis, those that affect the substrate binding site, and those that affect multimerization. There are three clinical phenotypes: patients with complete seizure control with pyridoxine and normal developmental outcome (group 1) including our first patient; patients with complete seizure control with pyridoxine but with developmental delay (group 2), including our other two patients; and patients with persistent seizures despite pyridoxine treatment and with developmental delay (group 3). There is preliminary evidence for a genotype-phenotype correlation with patients from group 1 having mutations with residual activity. There is evidence from patients with similar genotypes for nongenetic factors contributing to the phenotypic spectrum.

Antenatal treatment in two Dutch families with pyridoxine-dependent seizures

Incidental reports suggest that antenatal treatment of pyridoxine dependent seizures (PDS) may improve neurodevelopmental outcome of affected patients. Two families with PDS are reported, both with two affected siblings. Antenatal treatment with pyridoxine was instituted during the second pregnancy in each family (50 and 60 mg daily from 3 and 10 weeks of gestation, respectively). Perinatal characteristics and neurodevelopmental outcome at 4 (Family A) and 12 (Family B) years of age were compared between the untreated and treated child within each family. Meconium-stained amniotic fluid was present in both first pregnancies and abnormal foetal movements were noticed in one. In the treated infants, pregnancy and birth were uncomplicated. In family A, postnatal pyridoxine supplementation prevented neonatal seizures. Both children in family A were hypotonic and started walking after 2 years of age; both had white matter changes on MRI, and the first child was treated for squint. IQ was 73 and 98 in the antenatally untreated and treated child, respectively. The second child in family B developed seizures on the seventh day, because pyridoxine maintenance therapy had not been instituted after birth. Seizures responded rapidly to pyridoxine supplementation. MRI showed large ventricles and a mega cisterna magna. IQ was 80 and 106 in the antenatally untreated and treated child respectively. Both children had normal motor development. These results suggest that antenatal pyridoxine supplementation may be effective in preventing intrauterine seizures, decreasing the risk of complicated birth and improving neurodevelopmental outcome in PDS.

New treatment paradigms in neonatal metabolic epilepsies

Neonatal seizures represent a major challenge among the epilepsies vis-à-vis seizure classification, electroclinical correlation, inherent excitability of neocortex, ontogenic characteristics of neurotransmitter receptors, and responsiveness to standard antiepileptic drugs. Each of these factors renders neonatal seizures more difficult to treat, and therapy has been a vexing area for recent advances in this seizure category. Conversely, specific metabolic disorders have very special therapeutic considerations in the clinical setting of neonatal seizures which require a high index of clinical suspicion and rapid intervention for a successful outcome. The prototype is pyridoxine dependency, although pyridoxal 5'-phosphate dependency is a recently recognized but treatable neonatal epilepsy that deserves earmarked distinction. Clinicians must remain vigilant for these possibilities, including atypical cases where apparent seizure-free intervals may occur. Folinic acid-dependent seizures are allelic with pyridoxine dependency. Serine-dependent seizures and glucose transporter deficiency may present with neonatal seizures and have specific therapy. A vital potassium channel regulated by serum ATP/ADP ratios in the pancreas and brain may be mutated with a resultant neuroendocrinopathy characterized by development delay, epilepsy, and neonatal diabetes (DEND). This requires oral hypoglycaemic therapy, and not insulin, for neurological responsiveness. The startle syndrome of hyperekplexia, which mimics neonatal epilepsy, has been associated with laryngospasm and sudden death but is treated with benzodiazepines.

Pyridoxine uptake by colonocytes: a specific and regulated carrier-mediated process

The water-soluble vitamin B6 (pyridoxine) is important for normal cellular functions, growth, and development. The vitamin is obtained from two exogenous sources: a dietary source, which is absorbed in the small intestine, and a bacterial source, where the vitamin is synthesized in significant quantities by the normal microflora of the large intestine. Evidence exists to suggest the bioavailability of the latter source of the vitamin, but nothing is known about the mechanism involved and its regulation. In this study, we addressed these issues using young adult mouse colonic epithelial (YAMC) cells and human colonic apical membrane vesicles (AMV) as models and using [3H]pyridoxine as the uptake substrate. The results showed the initial rate of [3H]pyridoxine uptake by YAMC cells to be 1) energy- and temperature- (but not Na-) dependent and to occur without metabolic alteration in the transported substrate; 2) saturable as a function of concentration with an apparent Km and Vmax of 2.1 +/- 0.5 muM and 53.4 +/- 4.3 pmol.mg protein(-1).3 min(-1), respectively; 3) cis-inhibited by unlabeled pyridoxine and its structural analogs, but not by the unrelated compounds theophylline, penicillamine, and isoniazid; 4) trans-stimulated by unlabeled pyridoxine; 5) amiloride sensitive; and 6) regulated by extracellular and intracellular factors. Uptake of pyridoxine by native human colonic AMV was also found to involve a carrier-mediated process. These studies demonstrate, for the first time, the functional existence of a specific and regulatable carrier-mediated process for pyridoxine uptake by mammalian colonocytes.

Pyridoxine-dependent epilepsy initially responsive to phenobarbital

Pyridoxine-dependent epilepsy is a rare autossomal recessive disorder characterized by recurrent seizures that are not controlled by anticonvulsant medications but remits after administration of pyridoxine. We report on a 30 day-old girl who presented with seizures during the first day of life, initially responsive to anticonvulsant therapy, which remitted within two weeks. Seizures were characterized as multifocal myoclonic jerks of upper and lower limbs associated with buccal-lingual oral movements and eyelid blinking. Laboratory and neuroimaging studies were normal. Electroencephalographic record demonstrated a abnormal background activity with high-voltage epileptic discharges and a burst-suppression pattern. The seizures ceased after oral administration of pyridoxine, but recurred after withdrawal, confirming the diagnosis.

The role of nitric oxide in the anticonvulsant effects of pyridoxine on penicillin-induced epileptiform activity in rats

The present study was conducted to identify the role of nitric oxide (NO) in the anticonvulsant effects of pyridoxine hydrochloride on penicillin-induced epileptiform activity in rats. A single microinjection of penicillin (500 units) into the left sensorimotor cortex induced epileptiform activity within 2-4 min, progressing to full seizure activity lasting about 3-5h. Thirty minutes after penicillin injection, 20, 40, 80, and 160 mg/kg of pyridoxine hydrochloride was administered intraperitoneally (i.p.). Pyridoxine significantly reduced the frequency of penicillin-induced epileptiform activity. A low dose of pyridoxine (40 mg/kg) was the most effective in reducing both the frequency and amplitude of epileptiform activity. The effect of systemic administration of nitric oxide synthase (NOS) inhibitors, non-selective N(G)-nitro-L-arginine methyl ester (L-NAME), selective neuronal NOS inhibitor, 7-nitroindazole (7-NI) and NO substrate, L-arginine on anticonvulsive effects of pyridoxine was investigated. The administration of L-arginine (500 mg/kg, i.p.) and 7-NI (25 and 50 mg/kg, i.p.) significantly decreased the frequency of epileptiform electrocorticographical (ECoG) activity while administration of L-NAME (60 mg/kg, i.p.) and the inactive form of arginine (D-arginine) did not influence it. The administration of L-NAME (60 mg/kg, i.p.) 15 min before pyridoxine (40 mg/kg i.p.) application reversed the anticonvulsant effects of pyridoxine whereas 7-NI (25 and 50 mg/kg, i.p.) did not influence it. The same dose of its inactive enantiomer N(G)-nitro-D-arginine methyl ester (d-NAME) failed to reverse the anticonvulsant effects of pyridoxine. The administration of L-arginine (500 mg/kg, i.p.) did not affect the frequency of epileptiform ECoG activity in the pyridoxine administered group. L-arginine did not reverse the anticonvulsant effect of 7-NI in the penicillin and pyridoxine administered groups. The results of present study indicate that the inhibitory effect on the anticonvulsant activity of pyridoxine against penicillin-induced epileptiform activity was produced by L-NAME, not by 7-NI, and is probably not related to the decrease of NOS activity in the brain.

Allelic and non-allelic heterogeneities in pyridoxine dependent seizures revealed by ALDH7A1 mutational analysis

Pyridoxine dependent seizure (PDS) is a disorder of neonates or infants with autosomal recessive inheritance characterized by seizures, which responds to pharmacological dose of pyridoxine. Recently, mutations have been identified in the ALDH7A1 gene in Caucasian families with PDS. To elucidate further the genetic background of PDS, we screened for ALDH7A1 mutations in five PDS families (patients 1-5) that included four Orientals. Diagnosis as having PDS was confirmed by pyridoxine-withdrawal test. Exon sequencing analysis of patients 1-4 revealed eight ALDH7A1 mutations in compound heterozygous forms: five missense mutations, one nonsense mutation, one point mutation at the splicing donor site in intron 1, and a 1937-bp genomic deletion. The deletion included the entire exon 17, which was flanked by two Alu elements in introns 16 and 17. None of the mutations was found in 100 control chromosomes. In patient 5, no mutation was found by the exon sequencing analysis. Furthermore, expression level or nucleotide sequences of ALDH7A1 mRNA in lymphoblasts were normal. Plasma pipecolic acid concentration was not elevated in patient 5. These observations suggest that ALDH7A1 mutation is unlikely to be responsible for patient 5. Abnormal metabolism of GABA/glutamate in brain has long been suggested as the underlying pathophysiology of PDS. CSF glutamate concentration was elevated during the off-pyridoxine period in patient 3, but not in patient 2 or 5. These results suggest allelic and non-allelic heterogeneities of PDS, and that the CSF glutamate elevation does not directly correlate with the presence of ALDH7A1 mutations.

Pyridoxine-dependent seizures: a family phenotype that leads to severe cognitive deficits, regardless of treatment regime

The neuropsychological and clinical histories of three male siblings affected by pyridoxine-dependent seizures with known homozygous antiquitin mutations are presented. Neuropsychological evaluation is reported from when the siblings were 11, 9, and 7 years of age. Two of the siblings had received early pyridoxine treatment (antenatal, 2-4 wks into pregnancy) and one had received late treatment (2mo postnatal). However, there was no differential effect on cognitive outcome, with all three siblings having moderate to severe learning disability. Unlike previously reported cases that received early postnatal treatment, none of the siblings had relatively preserved non-verbal cognitive skills. Equally, their intellectual performance over time did not increase above the 1st centile despite high maintenance doses of vitamin B6 (range 16-26 mg/kg/d), and mild sensory neuropathy was reported on nerve conduction studies. The findings in these siblings challenge assumptions that early and high dose pyridoxine treatment can benefit cognition in this population and suggest routine electromyography monitoring may be beneficial.

Biochemical and molecular characterization of 18 patients with pyridoxine-dependent epilepsy and mutations of the antiquitin (ALDH7A1) gene

Patients with pyridoxine dependent epilepsy (PDE) present with early-onset seizures resistant to common anticonvulsants. According to the benefit of pyridoxine (vitamin B(6)) and recurrence of seizures on pyridoxine withdrawal, patients so far have been classified as having definite, probable, or possible PDE. Recently, PDE has been shown to be caused by a defect of alpha-amino adipic semialdehyde (AASA) dehydrogenase (antiquitin) in the cerebral lysine degradation pathway. The accumulating compound piperideine-6-carboxylic acid (P6C) was shown to inactivate pyridoxalphosphate (PLP) by a Knoevenagel condensation. Pipecolic acid (PA) and AASA are markedly elevated in urine, plasma, and cerebrospinal fluid (CSF) and thus can be used as biomarkers of the disease. We have investigated 18 patients with neonatal seizure onset, who have been classified as having definite (11), probable (four), or possible (three) PDE. All patients had elevated PA and AASA in plasma (and urine) while on treatment with individual dosages of pyridoxine. Within this cohort, molecular analysis identified 10 novel mutations (six missense mutations, one nonsense mutation, two splice site mutations) within highly conserved regions of the antiquitin gene. Seven mutations were located in exonic sequences and two in introns 7 and 17. Furthermore, a novel deletion of exon 7 was identified. Two of the 36 alleles investigated require further investigation. A known mutation (p.Glu399Gln) was found with marked prevalence, accounting for 12 out of 36 alleles (33%) within our cohort. Pyridoxine withdrawal is no longer needed to establish the diagnosis of "definite" PDE. Administration of pyridoxine in PDE may not only correct secondary PLP deficiency, but may also lead to a reduction of AASA (and P6C) as presumably toxic compounds.

Pyridoxine-dependent seizures: new genetic and biochemical clues to help with diagnosis and treatment

PURPOSE OF REVIEW

Pyridoxine dependency is an uncommon but important cause of intractable seizures presenting in infancy and early childhood. This paper discusses recent clinical, biochemical and genetic studies and how the findings should change our approach in evaluating young patients with antiepileptic drug-resistant seizures.

RECENT FINDINGS

Originally thought to be due to abnormal binding of pyridoxal phosphate to glutamic acid decarboxylase resulting in decreased gamma-aminobutyric acid, mutations in the gene encoding this enzyme have been ruled out. While linkage to 5q31 has been demonstrated, a disease-causing gene in that region has not been identified. Further haplotype analysis of six affected kindreds has demonstrated genetic heterogeneity for this rare disorder. Other studies demonstrate that some children with intractable seizures respond to pyridoxal phosphate rather than pyridoxine, including a rare form of neonatal epileptic encephalopathy shown to be due to mutations in the PNPO gene for pyridox(am)ine 5'-phosphate oxidase. While the biochemical explanation for this finding is not clear, elevated pipecolic acid levels may serve as a diagnostic marker for patients with pyridoxine-dependent seizures.

SUMMARY

The results of these studies should prompt clinicians to adopt new strategies for diagnosis and therapy for young patients with intractable seizures. Levels of both pipecolic acid and certain metabolites shown to be elevated in patients with PNPO mutations should be measured, and therapeutic trials of pyridoxal phosphate as well as pyridoxine should be considered early in the course of the management of infants and young children with intractable seizures.

Folinic acid-responsive seizures initially responsive to pyridoxine

This report presents a male who developed clonic seizures on the day he was born. The next day, the diagnosis of pyridoxine-dependent seizures was made. However, contradictory to this diagnosis, seizures reappeared despite treatment with pyridoxine. Seizures ceased after folinic acid was initiated. The clinical and biochemical characteristics of folinic acid-responsive seizures are reviewed. Treatment with folinic acid should be considered in neonatal seizures of unknown origin that do not respond to pyridoxine, or manifest a transient response to pyridoxine.

Hospital pharmacy and emergency department availability of parenteral pyridoxine

OBJECTIVES

Pyridoxine is a recommended antidote that should be available in emergency departments (EDs). A pediatric use of this preparation is the treatment of acute seizures secondary to pyridoxine dependency or responsiveness. Two cases of children with pyridoxine-dependent and pyridoxine-responsive seizures whose treatment was affected by the unavailability of pyridoxine in local EDs are presented. These cases prompted the development of a survey to ascertain the availability of parenteral pyridoxine in the pharmacies and EDs of both children's and general hospitals in the United States.

METHODS

A survey of 203 pharmacy directors in 100 pediatric hospitals (42 self-governing and 58 within a hospital) and 103 general hospitals was conducted. The questionnaire asked for the number of licensed beds and whether injectable pyridoxine was on the formulary and stocked by the ED.

RESULTS

The overall response rate was 73% (83% pediatric and 64% general hospitals). Injectable pyridoxine was on the formulary of 99% of pediatric hospitals and 91% of general hospitals (P = 0.044). Of those hospitals that had pyridoxine on the formulary, the availability of injectable pyridoxine in EDs was low in both pediatric (20.7%) and general hospitals (16.7%).

CONCLUSIONS

Given the number of possible uses of parenteral pyridoxine in the ED, it is suggested that there is a case for all pediatric and general hospital pharmacies to have it on the formulary and further for all EDs in these hospitals to have injectable pyridoxine available for immediate use.

Genetic heterogeneity for autosomal recessive pyridoxine-dependent seizures

Pyridoxine-dependent seizure (PDS) is a rare autosomal recessive intractable seizure disorder only controlled by a daily supplementation of pharmacological doses of pyridoxine (Vitamin B6). Although glutamate decarboxylase utilizes pyridoxal phosphate as a cofactor during conversion of the excitatory amino acid, glutamate, to the inhibitory neurotransmitter, gamma-amino butyric acid (GABA), several studies have failed to demonstrate a linkage to either of the glutamate-decarboxylase-encoding genes (GAD1 and GAD2) and PDS excluding involvement of this functional candidate. However, in 2000, a locus for PDS was mapped to a 5 cM interval at chromosome 5q31 in four consanguineous and one multisib pedigree (Z(max)=8.43 at theta=0 for marker D5S2017) [Cormier-Daire et al. in Am J Hum Genet 67(4):991-993 2000]. We undertook molecular genetic studies of six nonconsanguineous North American families, using up to ten microsatellite markers to perform haplotype segregation analysis of the 5q31 locus. Assignment to the chromosome 5q PDS locus was excluded in one of the six North American PDS pedigrees, as chromosome 5q31 haplotypes were incompatible with linkage to this locus. The remaining five PDS pedigrees showed haplotype segregation consistent with linkage to 5q31, generating a maximum combined lod score of 1.87 (theta=0) at marker D5S2011. In this study, we establish genetic heterogeneity for PDS, catalog 21 genes within the originally defined PDS interval, and identify additional recombinations that indicate a higher priority interval, containing just 11 genes.

Nonpharmacological treatment options for epilepsy

Approximately one third of children with epilepsy have persistent seizures despite trials of multiple antiepileptic medications. For some of these patients, epilepsy surgery may provide freedom from seizures. However, in many cases, epilepsy surgery is not a viable treatment option. Nonpharmacological approaches are a useful adjunct to help manage seizures in these children. This review examines the role of vagus nerve stimulation, the ketogenic diet, and various forms of EEG biofeedback therapy in children with intractable epilepsy. Although the mechanism of action is not known precisely for any of these adjunctive therapies, they add an important and evolving dimension to the management of difficult to control epilepsy in children. In addition, pyridoxine-dependent seizures are discussed as an example of an etiology of refractory seizures that responds well to replacement therapy.

Neonatal seizures: to treat or not to treat?

The immature brain is intrinsically hyperexcitable, a feature that, despite being crucial for learning, synaptogenesis and neuronal plasticity, predisposes the neonate to seizures. Seizures represent the most common neurologic manifestation of impaired brain function in this age group. Importantly, although seizure-induced neuronal injury is minimal in the "healthy" neonatal brain, the "metabolically-compromised" brain appears more vulnerable. Even in the "healthy" brain, however, seizures result in impaired learning, enhanced susceptibility to further seizures, and increased risk of brain injury with seizures later in life, as a result of altered hippocampal circuitry. Given these findings, an aggressive approach to neonatal seizures appears warranted. However, our current conventional therapies (including phenobarbital, phenytoin, and benzodiazepines), even when used in combination, are often ineffective in controlling seizures. Lidocaine may yield better efficacy but requires more study. Recent animal data suggest that alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) antagonists such as topiramate may have a neuroprotective role. However, further work is needed to confirm the safety of excitatory amino acid antagonists in neonates because there remains a prevailing concern that such agents may impair normal neurodevelopmental processes.

Pyridoxal phosphate is better than pyridoxine for controlling idiopathic intractable epilepsy

AIM

To study the difference between pyridoxine (PN) and its active form, pyridoxal phosphate, (PLP) in control of idiopathic intractable epilepsy in children.

METHODS

Among 574 children with active epilepsy, 94 (aged 8 months to 15 years) were diagnosed with idiopathic intractable epilepsy for more than six months. All received intravenous PLP 10 mg/kg, then 10 mg/kg/day in four divided doses. If seizures recurred within 24 hours, another dose of 40 mg/kg was given, followed by 50 mg/kg/day in four divided doses. For those patients whose seizures were totally controlled, PLP was replaced by the same dose of oral PN. If the seizure recurred, intravenous PLP was infused followed by oral PLP 50 mg/kg/day.

RESULTS

Fifty seven patients had generalised seizures (of whom 13 had infantile spasms) and 37 had focal seizure. Eleven had dramatic and sustained responses to PLP; of these, five also responded to PN. Within six months of treatment with PLP or PN, five of the 11 patients were seizure free and had their previous antiepileptic medicine tapered off gradually. Two were controlled with pyridoxine and the other three needed PLP to maintain seizure freedom. The remaining six responders needed PLP exclusively for seizure control. Six of the 11 responders to PLP had infantile spasms (46%); four of them needed PLP exclusively. The other five responders were in the remaining 81 patients with other seizure type.

CONCLUSIONS

PLP could replace PN in the treatment of intractable childhood epilepsy, particularly in the treatment of infantile spasms.

Clinical aspects of the disorders of GABA metabolism in children

PURPOSE OF REVIEW

There has been increased recognition of the pediatric neurotransmitter disorders. This review focuses on the clinical disorders of GABA metabolism.

RECENT FINDINGS

The known clinical disorders of GABA metabolism are pyridoxine dependent epilepsy, GABA-transaminase deficiency, SSADH deficiency, and homocarnosinosis. Pyridoxine dependent epilepsy is diagnosed clinically but potentially more common presentations, with later and atypical features, widen the spectrum. No gene locus has been confirmed; the pathophysiology may involve alterations in PLP transport, binding to GAD, or other PLP-dependent pathways. SSADH deficiency is associated with developmental delay, prominent language deficits, hypotonia, ataxia, hyporeflexia, and seizures. Increased detection is reported when specific ion monitoring is used for GHB on urine organic acids. The most consistent MRI abnormality is increased signal in the globus pallidus. MR spectroscopy has demonstrated the first example of increased endogenous GABA in human brain parenchyma in this disorder. GABA-transaminase deficiency and homocarnosinosis appear to be very rare but require CSF for detection, thus allowing for the possibility that these entities, as in the other pediatric neurotransmitter disorders, are underrecognized.

SUMMARY

The disorders of GABA metabolism require an increased index of clinical suspicion. Pyridoxine dependent epilepsy is a treatable condition with a potentially widening clinical spectrum, but with a prognosis dependent on early intervention. SSADH deficiency has a heterogeneous spectrum and requires careful urine organic acid testing for screening, followed by enzymatic confirmation allowing appropriate prognostic and genetic counseling.

Recent advances in carrier-mediated intestinal absorption of water-soluble vitamins

Significant progress has been made in recent years toward understanding the mechanisms and regulation of intestinal absorption of water-soluble vitamins from the diet, especially those that are transported by a specialized carrier-mediated mechanism (i.e., ascorbic acid, biotin, folate, riboflavin, thiamin, and pyridoxine). The driving force involved in the uptake events and the molecular identity of the systems involved have been identified for a number of these vitamins. In addition, information about regulation of the uptake process of these micronutrients by intracellular and extracellular factors has been forthcoming. Furthermore, the 5' regulatory region of the genes that encode a number of these transporters has been characterized, thus providing information about transcriptional regulation of the transport events. Also of interest is the identification of existence of carrier-mediated mechanisms in human colonocytes that are capable of absorbing some of the vitamins that are synthesized by normal microflora of the large intestine. Although the contribution of the latter source of vitamins toward overall host nutrition is not clear and requires further investigations, it is highly likely that it does contribute toward the cellular homeostasis of these vitamins in the localized colonocytes.

Pharmacorefractory status epilepticus due to low vitamin B6 levels during pregnancy

We report a patient with pyridoxine-dependent epileptic seizures during early childhood. She had been completely seizure free for 23 years until she became pregnant. During the week 14 of her pregnancy, status epilepticus developed and was refractory to antiepileptic drugs but responded to intravenous administration of vitamin B6. Vitamin B6 levels were found to be decreased during pregnancy, although the patient reported continued and regular oral supplementation. Possible reasons for decreased vitamin B6 levels leading to status epilepticus are discussed.

A carrier-mediated mechanism for pyridoxine uptake by human intestinal epithelial Caco-2 cells: regulation by a PKA-mediated pathway

Vitamin B6 is essential for cellular functions and growth due to its involvement in important metabolic reactions. Humans and other mammals cannot synthesize vitamin B6 and thus must obtain this micronutrient from exogenous sources via intestinal absorption. The intestine, therefore, plays a central role in maintaining and regulating normal vitamin B6 homeostasis. Due to the water-soluble nature of vitamin B6 and the demonstration that transport of other water-soluble vitamins in intestinal epithelial cells involves specialized carrier-mediated mechanisms, we hypothesized that transport of vitamin B6 in these cells is also carrier mediated in nature. To test this hypothesis, we examined pyridoxine transport in a model system for human enterocytes, the human-derived intestinal epithelial Caco-2 cells. The results showed pyridoxine uptake to be 1) linear with time for up to 10 min of incubation and to occur with minimal metabolic alteration in the transported substrate, 2) temperature and energy dependent but Na+ independent, 3) pH dependent with higher uptake at acidic compared with alkaline pHs, 4) saturable as a function of concentration (at buffer pH 5.5 but not 7.4) with an apparent Michaelis-Menten constant (Km) of 11.99 +/- 1.41 microM and a maximal velocity (Vmax) of 67.63 +/- 3.87 pmol. mg protein-1. 3 min-1, 5) inhibited by pyridoxine structural analogs (at buffer pH 5.5 but not 7.4) but not by unrelated compounds, and 6) inhibited in a competitive manner by amiloride with an apparent inhibitor constant (Ki) of 0.39 mM. We also examined the possible regulation of pyridoxine uptake by specific intracellular regulatory pathways. The results showed that whereas modulators of PKC, Ca+2/calmodulin (CaM), and nitric oxide (NO)-mediated pathways had no effect on pyridoxine uptake, modulators of PKA-mediated pathway were found to cause significant reduction in pyridoxine uptake. This reduction was mediated via a significant inhibition in the Vmax, but not the apparent Km, of the pyridoxine uptake process. These results demonstrate, for the first time, the involvement of a specialized carrier-mediated mechanism for pyridoxine uptake by intestinal epithelial cells. This system is pH dependent and amiloride sensitive and appears to be under the regulation of an intracellular PKA-mediated pathway.

Treatment Strategies for Myoclonic Seizures and Epilepsy Syndromes with Myoclonic Seizures

Despite the availability of numerous treatment options, the diagnosis and treatment of myoclonic seizures continue to be challenging. Based on clinical experience, valproate and benzodiazepines have historically been used to treat myoclonic seizures. However, many more treatment options exist today, and the clinician must match the appropriate treatment with the patient's epilepsy syndrome and its underlying etiology. Comorbidities and other medications must also be considered when making decisions regarding treatment. Rarely, some antiepileptic drugs may exacerbate myoclonic seizures. Most epileptic myoclonus can be treated pharmacologically, but some cases respond better to surgery, the ketogenic diet, or vagus nerve stimulation. Because myoclonic seizures can be difficult to treat, clinicians should be flexible in their approach and tailor therapy to each patient.