Vigabatrin therapy in infantile spasms: Solving one problem and inducing another?

Visual field defects after vigabatrin treatment during infancy: retrospective population-based study

AIM

To investigate the prevalence of vigabatrin-attributed visual field defect (VAVFD) in infantile spasms and the utility of optical coherence tomography (OCT) in detecting vigabatrin-related damage.

METHOD

We examined visual fields by Goldmann or Octopus perimetry and the thickness of peripapillary retinal nerve fiber layer (RNFL) with spectral-domain OCT at school age or adolescence.

RESULTS

Out of 88 patients (38 females, mean age at study 15y, SD 4y 3mo, range 6y 4mo-23y 3mo [n=65] or deceased [n=21] or moved abroad [n=2]) exposed to vigabatrin in infancy, 28 were able to perform formal visual field testing. Two had visual field defect from structural causes. We found mild VAVFD in four patients and severe VAVFD in one patient. Median vigabatrin treatment duration for those with normal visual field was 11 months compared to 19 months for those with VAVFD (p=0.04). OCT showed concomitant attenuated RNFL in three children with VAVFD, and was normal in one. The temporal half of the peripapillary RNFL was significantly thinner in the VAVFD group compared to the normal visual field group.

INTERPRETATION

The overall prevalence of VAVFD is lower after exposure in infancy compared to 52% which has been reported after exposure in adulthood. The risk increases with longer treatment duration. Further studies should identify infants particularly susceptible to VAVFD and clarify the role of OCT.

Clinical profile of children with West syndrome: A retrospective chart review

Background:

This study was intended to document the clinical profile and treatment outcome of West syndrome in children attending a tertiary care centre in Northern India.

Methods:

Data were collected by a retrospective chart review of children diagnosed with West syndrome between January 2017 to January 2018. Information was recorded pertaining to the age at onset and presentation, etiology, and associated co-morbidities; results of electroencephalography (EEG) and neuroimaging; treatment given; and final outcome. The following drugs were used for treatment: ACTH (n = 7), prednisolone (n = 17), vigabatrin (n = 25), sodium valproate (n = 28), clonazepam (n = 30), and levetiracetam (n = 13) and modified Atkins diet (n = 7). The response was categorized as spasm cessation, partial improvement (>50% improvement), or no improvement.

Results:

Records of 30 children (21 boys) were analyzed. The median (IQR) age at onset was 4 (3, 6.5) months. The median (IQR) lag time to treatment was 5 (2,14) months. Eight (26%) were premature, 2 (7%) were small for gestational age, birth asphyxia in 56%, neonatal encephalopathy in 62%. EEG findings were hypsarrhythmia in 13 (43.3%) children and modified hypsarrhythmia in 9 (30%) children. MRI finding was periventricular leukomalacia (54.1%), cystic encephalomalacia (13.8%), normal MRI (20.7%) and one had arrested hydrocephalus. There was no improvement with valproate (93%), clonazepam (89%), levetiracetam (78%). Cessation of spasm was achieved with vigabatrin (28%), prednisolone (38.2%), ACTH (42.8%). Hypsarrhythmia resolved with improvement in of background and other epileptiform abnormalities in 17 children.

Conclusion:

The present research highlights favourable response of West syndrome to oral steroids, vigabatrin and ACTH with limited role of conventional antiepileptic drugs like sodium valporate, levetiracetam and clonazepam. Primary care physician plays a vital role in early recognition and treatment of epileptic spasm.

Reliability of Handheld Optical Coherence Tomography in Children Younger Than Three Years of Age Undergoing Vigabatrin Treatment for Childhood Epilepsy

Purpose

Vigabatrin-associated retinal toxicity manifests as reduction in the clinical electroretinogram and retinal nerve fiber layer (RNFL) thinning. This observational investigation of RNFL thickness in young vigabatrin-treated children was to identify intravisit and intervisit reliabilities of peripapillary RNFL thickness measurements performed with Envisu (optical coherence tomography) OCT. Secondarily, a longitudinal assessment investigated the presence and extent of RNFL thinning.

Methods

We measured the handheld OCT in sedated children to evaluate the RNFL thickness using segmentation software. Intraclass correlation coefficient (ICC) statistics identified intravisit and intervisit reliabilities for RNFL thickness.

Results

Twenty-nine children (10.1 ± 6.0 months old) underwent handheld optical coherence tomography (OCT). Fourteen of these completed follow-up assessments. Intravisit reliability was good for the right eye (ICCs = 0.82-0.98) and the left eye (ICCs = 0.75-0.89) for each of the 4 retinal quadrants. Inter-visit ICCs for each of the 4 retinal quadrants were good (ICC = 0.82-0.98). There was no consistent change in RNFL thickness longitudinally.

Conclusions

In this pediatric cohort, RNFL thickness measures using handheld OCT provided good reliability within a single visit and between consecutive visits supporting its use as an adjunctive tool in the clinical setting. Further long-term follow-up is required to understand RNFL thickness changes in this specific population and its association with vigabatrin toxicity.

Translational Relevance

The findings of good reliability and clinical feasibility would provide an opportunity for the handheld OCT to monitor reliably for vigabatrin-associated retinal toxicity in children who often show noncompliance to traditional testing approaches.

Treatment of infantile spasms

The treatment of infantile spasms is challenging, especially in the context of the following: (1) a severe phenotype with high morbidity and mortality; (2) the urgency of diagnosis and successful early response to therapy; and (3) the paucity of effective, safe, and well-tolerated therapies. Even after initially successful treatment, relapse risk is substantial and the most effective therapies pose considerable risk with long-term administration. In evaluating any treatment for infantile spasms, the key short-term outcome measure is freedom from both epileptic spasms and hypsarrhythmia. In contrast, the most important long-term outcomes are enduring seizure-freedom and measures of intellectual performance in later childhood and adulthood. First-line treatment options-namely hormonal therapy and vigabatrin-display moderate to high efficacy but also exhibit substantial side-effect burdens. Data on efficacy and safety of each class of therapy, as well as the combination of these therapies, are reviewed in detail. Specific hormonal therapies (adrenocorticotropic hormone and various corticosteroids) are contrasted. Those etiologies that prompt specific therapies are reviewed briefly, as are an array of second-line therapies supported by less-compelling data. The ketogenic diet is discussed in greater detail, with a focus on the limitations of numerous available studies that generally suggest that it is efficacious. Special discussion is allocated to cannabidiol-the investigational therapy that has received the most attention, and which is already in use in the form of various artisanal cannabis extracts. Finally, a treatment algorithm reflecting the concepts and controversies discussed in this review is presented.

A lack of clinically apparent vision loss among patients treated with vigabatrin with infantile spasms: The UCLA experience

BACKGROUND

Vigabatrin (VGB) is one of two FDA-approved medications for treatment of infantile spasms. Despite demonstrated efficacy, its use has been curtailed by reports indicating a substantial risk of VGB-associated visual field loss (VAVFL). As these reports have conflicted with our clinical observations in routine practice, we systematically reviewed the experiences of patients treated with VGB at UCLA to estimate the prevalence of clinically apparent VAVFL.

METHODS

Patients with video-EEG-confirmed infantile spasms evaluated at our center between February 2007 and February 2014 were retrospectively identified. Among patients with VGB exposure, we documented relevant clinical factors and determined the duration of therapy, peak dosage, and cumulative dosage. Based on a review of serial neurologic and ophthalmologic reports and aided by electroretinography (ERG) assessments when available, we ascertained whether each patient had evidence of clinically apparent vision impairment (i.e., recognized by a neurologist or ophthalmologist during any follow-up visit) and whether or not the vision loss was attributed to VGB exposure (i.e., evidence of bilateral, symmetric, and peripheral visual field loss), either by the treating physician or on retrospective review by the study team.

RESULTS

During the study period, 257 patients with video-EEG-confirmed infantile spasms were identified. One hundred and forty-three (56%) patients received VGB. Although visual loss of any cause was common among patients with (31%) and without (32%) VGB exposure, there were no cases in which visual field defects were plausibly linked to VGB. We estimate that the risk of clinically significant VAVFL does not exceed 3.2% (95% CI upper bound). Vision loss was never characterized as exclusively peripheral and was always better explained by other causes (e.g., hemianopsia following hemispherectomy and cortical vision impairment after hypoxic ischemic encephalopathy). Precise quantitative exposure data were available for 104 (73%) patients treated with VGB, among whom the median duration of treatment was 8.6 (IQR: 3.7-16.2) months, the median peak dosage was 141.5 (IQR: 104.8-166.0) mg/kg/day, and the median cumulative dosage was 314 (IQR: 140.8-645.7) grams.

CONCLUSIONS

We found that the risk of clinically apparent vision loss is quite low among young children treated for infantile spasms. Our estimate of risk contrasts with prior studies and likely reflects our ascertainment of vision loss without the aid of perimetry or serial ERG, the short treatment duration, and the relatively young age of our patients. In the treatment of infantile spasms, risk-benefit assessment should consider both the low prevalence of ERG-identified VAVFL among patients with brief (<6-9months) exposure and the very low prevalence of clinically apparent VAVFL in this population.

Recent advances in the pharmacotherapy of infantile spasms

Adrenocorticotrophic hormone (ACTH), oral corticosteroids and vigabatrin are now first-line treatments for infantile spasms in the US and Europe. There is now increased knowledge regarding the role of ACTH, corticosteroids and vigabatrin (e.g. efficacy, doses, side effects, treatment in specific aetiological subtypes of infantile spasms), and other antiepileptic drugs (i.e. topiramate, valproate, zonisamide, sulthiame, levetiracetam, lamotrigine, pyridoxine, ganaxolone), as well as adjunctive flunarizine and novel drugs not yet in clinical use for infantile spasms (i.e. pulse rapamycin and melanocortin receptor agonists). The existence of a latent period, weeks to months following a precipitating brain insult, raises the possibility of preventive interventions. Recent experimental data emerging from animal models of infantile spasms have provided optimism that new and innovative treatments can be developed, and knowledge that drug treatment can affect long-term cognitive outcome is increasing. The aim of this article is to review recent developments in the pharmacotherapy of infantile spasms and to highlight the practical implications of the latest research.

Recent and Emerging Anti-seizure Drugs: 2013

OPINION STATEMENT

Recent and emerging pharmacotherapies have become available for use within the last 4 years to enhance our ability to manage people with epilepsy (PWE). More antiseizure drug (ASD) choices allow greater opportunity to match a unique medicine with each patient from the time of first seizure and for drug-resistant epilepsy. Balancing the efficacy, safety, and tolerability of an ASD is unique for each person and epilepsy syndrome. This tailored approach to effectiveness includes seven new ASDs that have become available since 2009 to treat PWE expanding our armamentarium to more than two dozen ASDs in the US that are now available for use. "Which ASD is best?" is still a complex challenge that remains to be answered. Until the ASD is found that is a panacea for everyone, the role of new AEDs in the treatment of epilepsy lies in the hands of the clinician to address the overall needs of the person first and foremost. In this paper, the newest and emerging ASDs in 2013 are reviewed focusing on the pharmacology, efficacy, and adverse effects. Each ASD has benefits and risks and the ultimate role in clinical use will be established over time as experience with each agent grows.

Antiepileptic drugs 2012: recent advances and trends

There are now 24 antiepileptic drugs (AEDs) approved for use in epilepsy in the United States by the Food and Drug Administration. A literature search was conducted using PubMed, MEDLINE, and Google for all English-language articles that discuss newly approved AEDs and the use of AEDs in epilepsy in the United States from January 1, 2008, through December 31, 2011. Five new agents were identified that have come onto the market within the past 2 years. Moreover, 3 trends involving AEDs have become clinically important and must be considered by all who treat patients with epilepsy. These trends include issues of generic substitution of AEDs, pharmacogenomics predicting serious adverse events in certain ethnic populations, and the issue of the suicide risk involving the entire class of AEDs. This article discusses the most recent AEDs approved for use in the United States and the 3 important trends shaping the modern medical management of epilepsy.

Retinal disorders

The retina represents part of the central nervous system (CNS). After modifying the neural signal, the axon of the last neuron enters the optic nerve and leaves the eye. In most cases of retinal disease leading to visual loss, the diagnosis will be made by an ophthalmologist after examining the ocular fundus. Some retinal disorders, however, might not be detectable at the time of examination. Those patients will be referred to a neurologist for "unexplained visual loss" when suspecting a lesion behind the optic nerve. Moreover, knowledge of potential retinal abnormalities is useful for the neurologist when seeing patients with CNS disease, which can manifest itself also in the retina. This chapter aims to give an overview about retinal disorders causing no or only few retinal abnormalities, those associated with neurological diseases, as well as the most important retinal diseases involving the tissues of the ocular fundus (vitreous body, retina, pigment epithelium, and the choroid). The most frequently used examination techniques and diagnostic tools are described. Tumors, vascular disease, especially diabetic retinopathy, age-related macular degeneration, chorioretinal inflammatory and toxic disorders, paraneoplastic retinopathies, inherited retinal dystrophies, and retinal involvement in CNS disease such as phakomatoses and multiple sclerosis are discussed.