Severe Relapse of Epilepsy after Vigabatrin Withdrawal: For How Long Should We Treat Symptomatic Infantile Spasms?

Fifteen years of real-world data on the use of vigabatrin in individuals with infantile epileptic spasms syndrome

OBJECTIVE

This study was undertaken to evaluate our treatment algorithm for infantile epileptic spasms syndrome (IESS) used between 2000 and 2018. We initiated vigabatrin (VGB), and steroids were added if the electroclinical response (spasms and electroencephalogram [EEG]) to VGB was not obtained or incomplete.

METHODS

Individuals with IESS treated with VGB were recruited from our hospital clinical data warehouse based on electronic health records (EHRs) generated since 2009 and containing relevant keywords. We confirmed the diagnosis of IESS. Clinical, EEG, imaging, and biological data were extracted from the EHRs. We analyzed factors associated with short-term response, time to response, relapse, time to relapse of spasms, and the presence of spasms at last follow-up.

RESULTS

We collected data from 198 individuals (female: 46.5%, IESS onset: 6 [4.5-10.3] months, follow-up: 4.6 [2.5-7.6] years, median [Q1-Q3]) including 129 (65.2%) with identifiable etiology. VGB was started 17 (5-57.5) days after IESS diagnosis. A total of 113 individuals were responders (57.1% of the cohort), 64 with VGB alone and 38 with VGB further combined with steroids (56.6% and 33.6% of responders, respectively). Among responders, 33 (29%) experienced relapses of spasms, mostly those with later onset of spasms (p = .002) and those who received VGB for <24 months after spasms cessation compared to a longer duration on VGB (45% vs. 12.8%, p = .003). At follow-up, 92 individuals were seizure-free (46.5% of the whole cohort), including 26 free of therapy (13.1%). One hundred twelve individuals (56.6%) were still receiving VGB, with a duration of 3.2 (1.75-5.7) years.

SIGNIFICANCE

Our sequential protocol introducing VGB then adding steroids is an effective alternative to a combined VGB-steroids approach in IESS. It avoids steroid-related adverse events, as well as those from VGB-steroid combination. According to our data, a period of 7 days seems sufficient to assess VGB response and enables the addition of steroids rapidly if needed. Continuing VGB for 2 years may balance the risk of relapse and treatment-induced adverse events.

Tuberous sclerosis complex and epilepsy in infancy: prevention and early diagnosis

Numerous studies showed that epilepsy represents a high burden in Tuberous Sclerosis Complex (TSC), affecting 63 to 78% of the patients. Epilepsy will be refractory to medication in over 60% of cases in early presentations, and accompanied by intellectual disabilities and/or autism spectrum disorders. The emerging experimental and clinical data suggest that the molecular and cellular changes triggered by seizures, particularly during the first weeks of life, can be limited by early action. Making any effort to avoid or delay epilepsy onset is a promising pathway to improve global outcome for TSC patients, although it is not possible to tidy up the specific roles of seizures, interictal abnormalities, and cortical abnormalities upon neurodevelopment. Early diagnosis of epilepsy can be made during a "symptomatic phase," shortly after the onset of seizures (focal seizures or spasms), revealing the TSC in a young infant. As soon as the diagnosis is made, a treatment with Vigabatrin is now recommended. The diagnosis of epilepsy can also be performed during a "presymptomatic phase", with the improvement of fetal and neonatal diagnosis of TSC. Recent studies demonstrated a significant delay of more than 3 months between the detection of EEG abnormalities and the first clinical seizures, which allows to consider a preventive treatment. Beside vigabatrin, mTOR inhibitors may have a place in this early management. The last recommendations about early detection and treatment of epilepsy in TSC will be detailed in this review. © 2022 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

Pharmacotherapy for Seizures in Tuberous Sclerosis Complex

Epilepsy is one of the main symptoms affecting the lives of individuals with tuberous sclerosis complex (TSC), causing a high rate of morbidity. Individuals with TSC can present with various types of seizures, epilepsies, and epilepsy syndromes that can coexist or appear in relation to age. Focal epilepsy is the most frequent epilepsy type with two developmental and epileptic encephalopathies: infantile spasms syndrome and Lennox-Gastaut syndrome. Active screening and early management of epilepsy is recommended in individuals with TSC to limit its consequences and its impact on quality of life, cognitive outcome and the economic burden of the disease. The progress in the knowledge of the mechanisms underlying epilepsy in TSC has paved the way for new concepts in the management of epilepsy related to TSC. In addition, we are moving from traditional "reactive" and therapeutic choices with current antiseizure medications used after the onset of seizures, to a proactive approach, aimed at predicting and preventing epileptogenesis and the onset of epilepsy with vigabatrin, and to personalized treatments with mechanistic therapies, namely mechanistic/mammalian target of rapamycin inhibitors. Indeed, epilepsy linked to TSC is one of the only epilepsies for which a predictive and preventive approach can delay seizure onset and improve seizure response. However, the efficacy of such interventions on long-term cognitive and psychiatric outcomes is still under investigation.

Stiripentol and vigabatrin current roles in the treatment of epilepsy

INTRODUCTION

Stiripentol and vigabatrin are the two anticonvulsant drugs currently approved in severe infantile-onset epilepsies, respectively Dravet syndrome and infantile spasms.

AREAS COVERED

For both, the indication was discovered by chance thanks to an exploratory study. Both demonstrated indisputable efficacy through randomized-controlled trials. Stiripentol as adjunctive therapy to clobazam and valproate performed better than placebo, and vigabatrin as first-line monotherapy better than the reference steroid therapy in spasms due to tuberous sclerosis. At one-year treatment vigabatrin and steroids were equally efficient in the other etiologies of spasms. However, it took more than 20 years for both drugs to be approved world-wide.

EXPERT OPINION

Stiripentol suffered from pharmacokinetic potentiation of clobazam, thus raising the question whether it was efficient per se. Finally, animal models and pharmacogenetic data on CYP2C19 confirmed its specific anticonvulsant effect. Stiripentol (in comedication with clobazam and valproate) is therefore to be recommended for Dravet patients. Vigabatrin was found to have a frequent and irreversible retinal toxicity, which required an alternative visual testing to be detected in young children. Today the benefit/risk ratio of vigabatrin as first-line is considered to be positive in infantile spasms, given the severity of this epilepsy and the lack of a safer alternative therapy.

Optimal management of seizures associated with tuberous sclerosis complex: current and emerging options

Seizures are clinically significant manifestations associated with 79%-90% of patients with tuberous sclerosis complex. Often occurring within the first year of life in the form of infantile spasms, seizures interfere with neuropsychiatric, social, and cognitive development and carry significant individual and societal consequences. Prompt identification and treatment of seizures is an important focus in the overall management of tuberous sclerosis complex patients. Medical management, either after seizure onset or prophylactically in infants with electroencephalographic abnormalities, is considered first-line therapy. Vigabatrin and adrenocorticotropic hormone have emerged over the past few decades as mainstay pharmacologic modalities. Furthermore, emerging research on mammalian target of rapamycin inhibitors demonstrated promise for the management of seizures and subependymal giant cell astrocytoma. For appropriate surgical candidates with an epileptogenic zone associated with one or more glioneuronal hamartomas, ideally in noneloquent cortex, resective surgery can be considered, which provides a cure in 56% of patients. For medically refractory patients who do not meet criteria for curative surgery, palliative surgical approaches focused on reducing seizure burden, in the form of corpus callosotomy and vagus nerve stimulation, are alternative management options. Lastly, the ketogenic diet, a reemerging therapy based on the anticonvulsant effects of ketone bodies, can be utilized independently or in conjunction with other treatment modalities for the management of difficult-to-treat seizures.

Epileptic spasms in tuberous sclerosis complex

PURPOSE

To characterize epileptic spasms (ES) occurring after the age of two years in patients with tuberous sclerosis complex (TSC), particularly treatment response to vigabatrin (VGB), which is extremely effective for infantile spasms (IS) in TSC.

METHODS

The authors retrospectively reviewed 19 patients with TSC and ES. Medical records were assessed for clinical and treatment data, neurocognitive, EEG, MRI data, and genetic analyses.

RESULTS

Of 391 patients with TSC, 19 (4.8%) had ES. Of those with detailed clinical data, six had infantile spasms that persisted after 2 years old, six recurred after an initial remission of infantile spasms (range 2-24 years old), and four occurred de novo over the age of two (range 2-20 years old). All concurrently had other seizure types. One had hypsarrhythmia on EEG. All had brain MRI stigmata typical of TSC. Thirteen had a mutation in TSC2, and one in TSC1. Six patients became spasm-free with medication treatment, including four with VGB, one with VGB in combination with the low glycemic index dietary treatment, and one with felbamate. Five became spasm-free after epilepsy surgery. VGB was not effective for seven patients. The majority continued to have refractory epilepsy.

CONCLUSIONS

ES are not uncommon in patients with TSC, especially those with TSC2 mutations. ES in TSC occur in the setting of other seizure types and refractory epilepsy. Hypsarrhythmia is rare. VGB can be effective, but the success of VGB for ES in TSC is not equivalent to that of IS in TSC.

Treatment strategies

There has been important progress in the identification of antiepileptic compounds and their indications in children over the past 15 years: their number has doubled and specific pediatric trials are being performed to document their effect according to seizures and syndromes as well as their tolerability in pediatrics. The improved understanding of pharmacokinetics and drug-drug interactions has helped to optimize treatment. Specific issues specific of infants have also been studied although new antiepileptic drugs are still dramatically lacking for this age group. Before reaching a syndromic diagnosis, the choice of a first- line agent goes to compounds with the largest range of efficacy and least identified risks. Subsequent choices are mainly based on the epilepsy syndrome and seizure type in addition to good clinical practice to determine dose, adverse effect profile, risk of aggravating seizures and drug interactions, clinician's experience, cultural habits, and availability of drugs. If there are several options, preference is given to the compound that exhibits the best risk/benefit ratio, or the most rapid titration when seizure frequency is the major issue. For new antiepileptic compounds, price is often a limiting factor in countries with poor insurance coverage. Third generation anti-epileptic drugs are emerging which also seem to be promising.

Balancing clinical benefits of vigabatrin with its associated risk of vision loss

Vigabatrin is an effective and well-tolerated antiepileptic drug (AED) for the treatment of refractory complex partial seizures (rCPS) and infantile spasms (IS), but its benefits must be evaluated in conjunction with its risk of retinopathy with the development of peripheral visual field defects (pVFDs). Vigabatrin should be considered for rCPS if a patient has failed appropriate trials of other AEDs or is not a suitable candidate for other AEDs, is not an optimal surgical candidate, and continues to experience debilitating effects from seizures. Vigabatrin is indicated as monotherapy for pediatric patients with IS. Its efficacy in achieving improved seizure control should be apparent within 12 weeks in patients with rCPS and within 2-4 weeks after attaining appropriate dosage for patients with IS. Because 12 weeks is well less than the known time of onset of visual defects, the risk of developing pVFDs may be minimized by discontinuing vigabatrin early during the course of therapy for patients with inadequate response. Appropriate vision screening is recommended at baseline, every 3 months during continued vigabatrin treatment, and at 3-6 months after discontinuation (if therapy has spanned more than a few months). If a pVFD is detected at any point and the decision is made to discontinue therapy, the pVFD is not likely to progress after discontinuation of vigabatrin. Although some patients will be at risk of retinopathy, vigabatrin is an appropriate treatment option for patients who achieve substantial clinical benefit, especially given the severe consequences of rCPS and uncontrolled IS. While retinopathy with the development of pVFDs is a serious adverse event, it is not life-threatening and its risk can be effectively managed.

Vigabatrin therapy for infantile spasms: review of major trials in Europe, Canada, and the United States; and recommendations for dosing

Infantile spasms (IS) are a unique and severe form of epilepsy associated with poor neurologic and developmental outcomes. The refractory spasms and abnormal electroencephalogram (EEG) patterns associated with the condition are believed to have a progressively detrimental impact. Therefore, rapid and complete control of spasms is the primary goal of treatment. Well-controlled clinical trials in Europe, Canada, and the United States have demonstrated that vigabatrin is efficacious and generally well-tolerated as monotherapy for IS. Several key studies, including pivotal trials that led to United States approval of vigabatrin in 2009, as well as comparative trials of vigabatrin and hormonal treatment, are the focus of this review. All studies assessed spasm cessation - usually as the primary endpoint - and adverse events. Vigabatrin dosages generally ranging from 100 to 150 mg/kg/day demonstrated efficacy to decrease or eradicate spasms and eliminate hypsarrhythmic EEG in patients with newly diagnosed IS. Several studies demonstrated long-term sustainability of spasm freedom with no negative impact on developmental outcomes. Vigabatrin was generally well-tolerated with few severe adverse events. Visual field defects cannot be adequately assessed in infants and young children, so this potential adverse effect was not evaluated in children with spasms. Notably, the time to response with vigabatrin was very rapid, generally occurring within 2 weeks of initial treatment. This allows for early treatment modification as needed. For infants who respond well to vigabatrin, treatment duration up to 6 months appears to be appropriate for realizing spasm freedom while limiting potential risks of adverse events and recurrences.

Infantile spasms: review of the literature and personal experience

This epileptic disorder has become a classic topic for neuropediatricians and the interest is documented by the large number of publications on this subject.The relative frequency among the epileptic syndromes is an another reason why not only neuropediatricians but also general pediatricians must be fully informed about diagnostic, clinical, imaging and genetic aspects.Early diagnosis is of paramount importance in order to obtain even complete results in patients with so called idiopathic situations. A number of problems are still to be solved. There is no agreement on the type and the schedule of treatment. A common denominator about this problem is not jet available even if some advances in this regard have been accomplished. Of paramount importance is an accurate clinical and laboratory examination as a prerequisite regarding prognosis and results of therapy in every single case.However, even if more than 170 years have elapsed since the first communication of dr. West on the peculiar syndrome that his child was suffering of, the interest of scientists on this subject has now been enriched and rewarded.

Justification of vigabatrin administration in West syndrome patients? Warranting a re-consideration for improvement in their quality of life

West syndrome (WS) or infantile spasms (IS) is a severe epileptic syndrome associated with poor prognosis and increased morbidity. The exact etio-pathogenesis of the disorder still remains elusive ant therefore the management continues to pose a challenge to the clinicians. Currently, adreno-corticotrophic hormone (ACTH), steroids and vigabatrin (VGB) form the mainstay of its treatment. However, the recent detection of an irreversible visual field defect observed in as high as 30-50% of children treated with vigabatrin has raised concern over the drug's usage. This brief paper is intended to highlight the significance of the irreversible visual toxicity in an already existent mentally challenged state in WS patients, which can lead to a worsening in the disability status of such patients. Therefore, based on the enhancement of handicap by VGB administration it is recommended that a comprehensive review be performed on its continuation in WS patients in order to prevent further deterioration of their quality of life (QOL).