Magnetic resonance imaging abnormalities associated with vigabatrin in patients with epilepsy

Vigabatrin-associated brain magnetic resonance imaging abnormalities and clinical symptoms in infants with tuberous sclerosis complex

OBJECTIVE

Previous retrospective studies have reported vigabatrin-associated brain abnormalities on magnetic resonance imaging (VABAM), although clinical impact is unknown. We evaluated the association between vigabatrin and predefined brain magnetic resonance imaging (MRI) changes in a large homogenous tuberous sclerosis complex (TSC) cohort and assessed to what extent VABAM-related symptoms were reported in TSC infants.

METHODS

The Dutch TSC Registry and the EPISTOP cohort provided retrospective and prospective data from 80 TSC patients treated with vigabatrin (VGB) before the age of 2 years and 23 TSC patients without VGB. Twenty-nine age-matched non-TSC epilepsy patients not receiving VGB were included as controls. VABAM, specified as T2/fluid-attenuated inversion recovery hyperintensity or diffusion restriction in predefined brain areas, were examined on brain MRI before, during, and after VGB, and once in the controls (at approximately age 2 years). Additionally, the presence of VABAM accompanying symptoms was evaluated.

RESULTS

Prevalence of VABAM in VGB-treated TSC patients was 35.5%. VABAM-like abnormalities were observed in 13.5% of all patients without VGB. VGB was significantly associated with VABAM (risk ratio [RR] = 3.57, 95% confidence interval [CI] = 1.43-6.39), whereas TSC and refractory epilepsy were not. In all 13 VGB-treated patients with VABAM for whom posttreatment MRIs were available, VABAM entirely resolved after VGB discontinuation. The prevalence of symptoms was 11.7% in patients with VABAM or VABAM-like MRI abnormalities and 4.3% in those without, implicating no significant association (RR = 2.76, 95% CI = .68-8.77).

SIGNIFICANCE

VABAM are common in VGB-treated TSC infants; however, VABAM-like abnormalities also occurred in children without either VGB or TSC. The cause of these MRI changes is unknown. Possible contributing factors are abnormal myelination, underlying etiology, recurrent seizures, and other antiseizure medication. Furthermore, the presence of VABAM (or VABAM-like abnormalities) did not appear to be associated with clinical symptoms. This study confirms that the well-known antiseizure effects of VGB outweigh the risk of VABAM and related symptoms.

Symptomatic vigabatrin-associated MRI toxicity is associated with simultaneous hormonal therapy among patients with infantile spasms

Vigabatrin-associated brain abnormalities on MRI (VABAM) are observed in approximately 20% of children who receive vigabatrin for treatment of infantile epileptic spasms syndrome. Although usually reversible and asymptomatic, VABAM is occasionally symptomatic. Whereas asymptomatic VABAM appears to be dose-dependent, symptomatic VABAM is possibly associated with co-administration of vigabatrin and hormonal therapy (i.e., corticosteroids or adrenocorticotropic hormone). With retrospective study of a cohort of vigabatrin-treated children, we evaluated candidate risk factors for VABAM. Among 108 children with detailed vigabatrin exposure data, we identified VABAM in 17 children (11 symptomatic). Symptomatic VABAM was strongly associated with simultaneous exposure to hormonal therapy (p = 0.001). Neither symptomatic nor asymptomatic VABAM were associated with peak vigabatrin dose. Although these data support the hypothesis that symptomatic VABAM risk is higher with coadministration of vigabatrin and hormonal therapy, this study does not establish a causal link. Further study is warranted to better understand the pathogenesis of VABAM and devise strategies to mitigate risk. Clinicians should carefully weigh the potential risk of symptomatic vigabatrin toxicity against the known benefit of vigabatrin and hormonal therapy coadministration. PLAIN LANGUAGE SUMMARY: Several case reports suggest that the combination of vigabatrin and hormonal therapy for treatment of infantile spasms may provoke an adverse reaction known as symptomatic vigabatrin MRI toxicity (sVABAM, which includes characteristic changes on MRI images and associated symptoms). In response to these reports, we studied a large single-center cohort of children with infantile spasms and determined that combination therapy is indeed statistically associated with sVABAM. However, we have not proven that combination therapy actually causes sVABAM. Further study is needed to clarify the nature of sVABAM and risk factors thereof.

Tuberous sclerosis complex: Diagnostic features, surveillance, and therapeutic strategies

Tuberous sclerosis complex (TSC) is a rare neurocutaneous disorder of mTOR pathway dysregulation resulting from pathogenic variants in the TSC1 or TSC2 genes. Expression of this disorder may involve abnormal tissue growth and dysfunction within the brain, kidneys, heart, lungs, eyes, skin, bones, and teeth. Neurological manifestations can include subependymal giant cell astrocytomas (SEGAs), high rates of infantile spasms, drug-resistant epilepsy, developmental delay, cognitive impairment, autism spectrum disorder, and other neurobehavioral manifestations. Here we review the potential clinical manifestations of TSC by system, recommended diagnostic and surveillance testing, genetic testing, currently available therapeutic options, and considerations for education and social support resources given the unique challenges of this multi-system disorder.

Epileptic spasms relapse is associated with response latency but not conventional attributes of post-treatment EEG

OBJECTIVE

Relapse of epileptic spasms after initial treatment of infantile epileptic spasms syndrome (IESS) is common. However, past studies of small cohorts have inconsistently linked relapse risk to etiology, treatment modality, and EEG features upon response. Using a large single-center IESS cohort, we set out to quantify the risk of epileptic spasms relapse and identify specific risk factors.

METHODS

We identified all children with epileptic spasms at our center using a clinical EEG database. Using the electronic medical record, we confirmed IESS syndrome classification and ascertained treatment, response, time to relapse, etiology, EEG features, and other demographic factors. Relapse-free survival analysis was carried out using Cox proportional hazards regression.

RESULTS

Among 599 children with IESS, 197 specifically responded to hormonal therapy and/or vigabatrin (as opposed to surgery or other second-line treatments). In this study, 41 (21%) subjects exhibited relapse of epileptic spasms within 12 months of response. Longer duration of IESS prior to response (>3 months) was strongly associated with shorter latency to relapse (hazard ratio = 3.11; 95% CI 1.59-6.10; p = 0.001). Relapse was not associated with etiology, developmental status, or any post-treatment EEG feature.

SIGNIFICANCE

This study suggests that long duration of IESS before response is the single largest clinical predictor of relapse risk, and therefore underscores the importance of prompt and successful initial treatment. Further study is needed to evaluate candidate biomarkers of epileptic spasms relapse and identify treatments to mitigate this risk.

PLAIN LANGUAGE SUMMARY

Relapse of infantile spasms is common after initially successful treatment. With study of a large group of children with infantile spasms, we determined that relapse is linked to long duration of infantile spasms. In contrast, relapse was not associated with the cause of infantile spasms, developmental measures, or EEG features at the time of initial response. Further study is needed to identify tools to predict impending relapse of infantile spasms.

The vigabatrin-associated brain abnormalities on MRI and their differential diagnosis

Vigabatrin is an anti-epileptic drug that inhibits the enzyme γ-aminobutyric acid (GABA)-transaminase. The anticonvulsant effect of vigabatrin involves increasing GABA levels and attenuating glutamate-glutamine cycling. Vigabatrin indications include infantile spasms and refractory focal seizures. Despite having a significant role in paediatric epileptology, vigabatrin has adverse effects, such as retinal toxicity, in up to 30% of patients after 1 year of use and brain abnormalities on magnetic resonance imaging (MRI). The percentage of patients with brain abnormalities on MRI varies between 22-32% of children using vigabatrin to treat infantile spasms. Risk factors for presenting these imaging abnormalities are cryptogenic infantile spasms, age <12 months old, high dosage, and possible concomitant hormonal therapy. Clinically, these abnormalities are usually asymptomatic. Histopathological analysis reveals white matter vacuolation and intramyelinic oedema. The typical findings of vigabatrin-associated brain abnormalities on MRI are bilateral and have a symmetrical hyperintense signal on T2-weighted imaging, with diffusion restriction, that often compromise the globi pallidi, thalami, subthalamic nuclei, cerebral peduncles, midbrain, dorsal brainstem, including the medial longitudinal fasciculi, and dentate nuclei of the cerebellum. In this article, the authors intend to review the clinical manifestations, histopathological features, imaging aspects, and differential diagnosis of vigabatrin-associated brain abnormalities on MRI.

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.

Magnetic Resonance Imaging-Based Distribution and Reversibility of Lesions in Pediatric Vigabatrin-Related Brain Toxicity

BACKGROUND

We aimed to systematically characterize the magnetic resonance imaging (MRI) findings in vigabatrin-related neurotoxicity in children and determine the reversibility of lesions based on follow-up images.

METHODS

We evaluated children with a history of refractory seizures who had a brain MRI while on vigabatrin therapy. We included available brain MRI studies before vigabatrin therapy initiation, during vigabatrin treatment, and after vigabatrin was discontinued. A pediatric neuroradiologist systematically assessed images on T2/fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging /apparent diffusion coefficient sequences to identify hyperintense lesions and/or restricted diffusion. The frequency of abnormal signal at each location was determined, as well as the reversibility of these after vigabatrin discontinuation.

RESULTS

MRIs of 43 patients were reviewed: 13 before vigabatrin initiation, 18 during treatment, and 12 after vigabatrin discontinuation. In the MRIs acquired during vigabatrin treatment, most lesions on T2/FLAIR occurred in the globus pallidi, thalami, and midbrain. Correspondingly, the most common locations for restricted diffusion were the globus pallidi, thalami, and subthalamic nuclei. On MRI after vigabatrin discontinuation, complete resolution of lesions on T2/FLAIR in all patients was seen in the midbrain, dentate nuclei, subthalamic nuclei, and hypothalami. Complete resolution of restricted diffusion was observed in the globus pallidi, midbrain, dentate nuclei, hippocampi, anterior commissure, and hypothalami.

CONCLUSION

Globus pallidi and thalami are the most commonly affected structures in vigabatrin-related toxicity, and most vigabatrin-related neuroimaging findings are reversible.

Efficacy and safety of vigabatrin in patients with tuberous sclerosis complex and infantile epileptic spasm syndrome: a systematic review

INTRODUCTION

Tuberous sclerosis complex (TSC) is a common genetic cause of epilepsy. Infantile epileptic spasm syndrome (IESS) is often the presenting neurologic feature, progressively evolving into refractory epilepsy. Vigabatrin (VGB) is often used in clinical practice as a first-line therapy in TSC with IESS. This systematic review aims to collect and analyze the efficacy data about VGB in TSC cases with IESS, in order to evaluate the strength of evidence in the literature.

METHODS

A systematic search of trials, observational studies, and case series involving patients with TSC and IESS treated with VGB was performed using MEDLINE, CENTRAL, and the US NIH Clinical Trials Registry. Single case studies, animal and non-English language studies were excluded. Seventeen studies were selected, of which 3 were RCTs and 14 were observational studies.

RESULTS

An overall response rate of 67% (231/343 responders) resulted from the analysis, with a spasm-free rate restricted to RCTs of 88% (29/33 subjects).

CONCLUSIONS

Although all the studies analyzed reported beneficial effects of VGB in TSC patients with IESS, with higher response rates in comparison to non-TSC subjects with IESS, a low level of evidence and high heterogeneity do not guarantee sufficient strength for therapeutic recommendations.

Neuroimaging in mitochondrial disease

The anatomic complexity of the brain in combination with its high energy demands makes this organ specifically vulnerable to defects of mitochondrial oxidative phosphorylation. Therefore, neurodegeneration is a hallmark of mitochondrial diseases. The nervous system of affected individuals typically shows selective regional vulnerability leading to distinct patterns of tissue damage. A classic example is Leigh syndrome, which causes symmetric alterations of basal ganglia and brain stem. Leigh syndrome can be caused by different genetic defects (>75 known disease genes) with variable disease onset ranging from infancy to adulthood. Other mitochondrial diseases are characterized by focal brain lesions, which is a core feature of MELAS syndrome (mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes). Apart from gray matter, also white matter can be affected by mitochondrial dysfunction. White matter lesions vary depending on the underlying genetic defect and may progress into cystic cavities. In view of the recognizable patterns of brain damage in mitochondrial diseases, neuroimaging techniques play a key role in diagnostic work-up. In the clinical setting, magnetic resonance imaging (MRI) and MR spectroscopy (MRS) are the mainstay of diagnostic work-up. Apart from visualization of brain anatomy, MRS allows the detection of metabolites such as lactate, which is of specific interest in the context of mitochondrial dysfunction. However, it is important to note that findings like symmetric basal ganglia lesions on MRI or a lactate peak on MRS are not specific, and that there is a broad range of disorders that can mimic mitochondrial diseases on neuroimaging. In this chapter, we will review the spectrum of neuroimaging findings in mitochondrial diseases and discuss important differential diagnoses. Moreover, we will give an outlook on novel biomedical imaging tools that may provide interesting insights into mitochondrial disease pathophysiology.

Vigabatrin-associated brain abnormalities on MRI in tuberous sclerosis complex patients with infantile spasms: are they preventable?

Background

Vigabatrin (VGB) is currently the most widely prescribed first-line medication for individuals with infantile spasms (IS) and especially for those with tuberous sclerosis complex (TSC), with demonstrated efficacy. Meanwhile, its adverse events, such as vigabatrin-associated brain abnormalities on magnetic resonance imaging (MRI; VABAM), have also been widely reported.

Objectives

The objectives of this study were to observe the occurrences of VABAM in patients with IS caused by TSC (IST) and further explore the associated risk factors.

Methods

Children with IS receiving VGB were recruited from our institution; clinical, imaging, and medication data were collected. Cerebral MRI was reviewed to determine the occurrence of VABAM. Group comparisons (IS caused by TSC and other etiologies) were performed; subgroup analyses on IST were also performed. Next, a retrospective cohort study of children taking VGB was conducted to explore risk/protective factors associated with VABAM.

Results

The study enrolled 172 children with IS who received VGB. VABAM was observed in 38 patients (22.1%) with a peak dosage of 103.5 ± 26.7 mg/kg/day. Subsequent analysis found the incidence of VABAM was significantly lower in the 80 patients with IST than in the 92 patients with IS caused by other etiologies (10% versus 32.6%, p-value < 0.001). In subgroup analyses within the IST cohort, VABAM was significantly lower in children who received concomitant rapamycin therapy. Univariate and multivariate logistic regression analysis of the 172 IS children showed that treatment with rapamycin was the independent factor associated with a lower risk of VABAM; similar results were observed in the survival analysis.

Conclusion

The incidence of VABAM was significantly lower in IST patients. Further research is needed to examine the mechanisms that underlie this phenomenon and to determine if treatment with rapamycin may reduce the risk of VABAM.

Neuroimaging in cerebellar ataxia in childhood: A review

Ataxia is one of the most common pediatric movement disorders and can be caused by a large number of congenital and acquired diseases affecting the cerebellum or the vestibular or sensory system. It is mainly characterized by gait abnormalities, dysmetria, intention tremor, dysdiadochokinesia, dysarthria, and nystagmus. In young children, ataxia may manifest as the inability or refusal to walk. The diagnostic approach begins with a careful clinical history including the temporal evolution of ataxia and the inquiry of additional symptoms, is followed by a meticulous physical examination, and, depending on the results, is complemented by laboratory assays, electroencephalography, nerve conduction velocity, lumbar puncture, toxicology screening, genetic testing, and neuroimaging. Neuroimaging plays a pivotal role in either providing the final diagnosis, narrowing the differential diagnosis, or planning targeted further workup. In this review, we will focus on the most common form of ataxia in childhood, cerebellar ataxia (CA). We will discuss and summarize the neuroimaging findings of either the most common or the most important causes of CA in childhood or present causes of pediatric CA with pathognomonic findings on MRI. The various pediatric CAs will be categorized and presented according to (a) the cause of ataxia (acquired/disruptive vs. inherited/genetic) and (b) the temporal evolution of symptoms (acute/subacute, chronic, progressive, nonprogressive, and recurrent). In addition, several illustrative cases with their key imaging findings will be presented.

Vigabatrin-associated brain abnormalities on MRI and other neurological symptoms in patients with West syndrome

OBJECTIVES

Report a series of children with West syndrome (WS) treated with vigabatrin (VGB) who developed characteristic MRI alterations. In the majority, these adverse events were asymptomatic; however, some of the patients developed movement disorders and acute encephalopathy.

METHODS

This is a retrospective analysis of our epilepsy clinical and EEG database of 288 patients with WS seen between 2014 and 2020. All patients who received VGB alone or with concomitant therapies, such as adrenocorticotropic hormone (ACTH), high-dose oral corticosteroids, ketogenic diet, valproate, levetiracetam, or topiramate, were evaluated.

RESULTS

In 44 of 288 patients with WS receiving VGB, MRI findings compatible with VGB-associated brain abnormalities were identified; median age at diagnosis was 6.29 months (range, 2 weeks to 11 months). The etiology of WS with vigabatrin-associated brain abnormalities on MRI (VABAM) was unknown in 22 (52.27%), genetic in seven (15.9%), genetic-structural in three (6.8%), structural malformative in three others (6.8%), and structural acquired in eight patients (18.2%). Vigabatrin-associated brain abnormalities on MRI was asymptomatic in 25 of 44 patients. Ten of 44 (22.7%) infants were reported to have had a movement disorder (choreoathetosis, dystonic posturing). Nine of 42 infants exhibited progressive psychomotor deterioration associated with signs and symptoms of encephalopathy.

CONCLUSION

MRI abnormalities were observed in infants treated with VGB and they appeared to be dose dependent. In our study common locations for MRI abnormalities included globi pallidi and brainstem, followed by thalami and dentate nuclei. Risk factors for the development of VABAM may include age younger than 11 months and higher VGB dose of VGB (>165 mg/kg/day). Vigabatrin-associated brain abnormalities on MRI usually resolved following VGB discontinuation, probably after a period of 3 months.

Bilateral Structural Network Abnormalities in Epilepsy Associated With Bottom-of-Sulcus Dysplasia

BACKGROUND AND OBJECTIVES

To identify white matter fiber tracts that exhibit structural abnormality in patients with bottom-of-sulcus dysplasia (BOSD) and investigate their association with seizure activity.

METHODS

Whole-brain fixel-based analysis of diffusion MRI data was performed to identify white matter fiber tracts with significant reductions in fiber density and cross-section in patients with BOSD (n = 20) when compared to healthy control participants (n = 40). Results from whole-brain analysis were used to investigate the association of fiber tract abnormality with seizure frequency and epilepsy duration.

RESULTS

Despite the focal nature of the dysplasia, patients with BOSD showed widespread abnormality in white matter fiber tracts, including the bilateral corticospinal, corticothalamic, and cerebellothalamic tracts, superior longitudinal fasciculi, corpus callosum (body), and the forceps major. This pattern of bilateral connectivity reduction was not related to the laterality of the lesion. Exploratory post hoc analyses showed that high seizure frequency was associated with greater reduction in fiber density at the forceps major, bilateral corticospinal, and cerebellothalamic tracts.

DISCUSSION

We demonstrate evidence of a bilaterally distributed, specific white matter network that is vulnerable to disruption in BOSD. The degree of tract abnormality is partly related to seizure activity, but additional contributors such as the genetic background and effects of treatment or environment have not been excluded.

Trends and Costs Associated With the Diagnosis and Treatment of Infantile Spasms: A 10-Year Multicenter Retrospective Review

OBJECTIVE

Early treatment of infantile spasms (IS) may be imperative for improvement of neurodevelopmental outcomes. Existing studies have led to inconclusive recommendations with variation in treatment. Our objective was to determine the national average cost, initial diagnostic workup, treatments, and hospital length of stay for patients with IS.

METHODS

This retrospective cohort study was designed to review data of patients < 2 years from 43 non-profit institutions. Data obtained included patient demographics, length of stay, admission cost, and treatments used from 2004 to 2014. Cost data were collected and adjusted to 2014 dollars, the year data were analyzed.

RESULTS

A total of 6183 patients met study criteria (n = 3382, 55% male). Three-quarters of patients (n = 4684, 76%) had an electroencephalogram, 56.4% had brain imaging (n = 3487), and 17% (n = 1050) underwent a lumbar puncture. Medication for IS was initiated during inpatient hospital stay in two-thirds of all patients (n = 4139, 67%). Most patients were initiated on corticotropin (n = 2066, 33%) or topiramate (n = 1804, 29%). Average length of stay was 5.8 days with an average adjusted cost of $18,348. Over time there was an 86.6% increase in cost from an average $12,534.54 (2004) to $23,391.20 (2014), a significant change (p < 0.01). This correlated with an increase in average length of stay.

CONCLUSIONS

Variability exists in diagnostic workup and pharmacotherapy initiated for IS, which may lead to differences in the cost of hospital stay. Further studies may help determine contributing factors to increased cost and improve health care utilization for IS patients.

Risk of vigabatrin-associated brain abnormalities on MRI: A retrospective and controlled study

OBJECTIVE

Vigabatrin (VGB) is the first-line treatment for infantile spasms (IS). Previous studies have shown that VGB exposure may cause vigabatrin-associated brain abnormalities on magnetic resonance imaging (MRI) (VABAM). Based on previous studies, this study aimed to go further to explore the possible risk factors and the incidence of VABAM. In addition, diffusion-weighted imaging (DWI) and T2-weighted imaging (T2WI) were compared to explore whether DWI should be used as a routine examination sequence when MRI is performed in children receiving VGB.

METHODS

Children with IS receiving VGB were selected as the study subjects. Whether VABAM occurred or not was categorized as the VABAM group and the non-VABAM group, respectively. Their general clinical data and medication exposure were collected. The possible risk factors of VABAM and different MRI sequences were compared and statistically analyzed.

RESULTS

A total of 77 children with IS were enrolled in the study, of which 25 (32.5%) developed VABAM. Twenty-three of the 25 VABAM cases have a peak dosage of VGB between 50 and 150 mg/kg/day. The earliest observation time of VABAM was 30 days. Regression analysis of relevant risk factors showed that the peak dosage of VGB was the risk factor for VABAM. Comparison between different MRI sequences showed that DWI is more sensitive than T2WI to the evaluation of VABAM.

SIGNIFICANCE

In our study, the occurrence of VABAM was 32.5%, indicating a higher incidence than in most previous reports. In addition, we once again verified that the peak dosage of VGB was the risk factor of VABAM. Caution should be exercised that our data also suggest that VABAM may occur even using the conventional dosage of VGB (ie, 50-150 mg/kg/day). Therefore, even when using the conventional dosage of VGB, regular MRI examination should be required. Furthermore, DWI sequence should be used as a routine examination sequence when MRI is performed in children with IS who are receiving VGB.

A Review of the Selected and Newer Antiseizure Medications Used in Childhood Epilepsies

There have been additions of newer antiseizure medications in the armamentarium of clinicians for the management of epilepsy. The newer antiseizure medications have advantages of better tolerability, lesser adverse effects, and minimal drug interactions in comparison with conventional antiseizure medications. However, high cost and availability are concerns. There are also peculiar pharmacokinetic and pharmacodynamic considerations for the pediatric age, particularly in the context of age-dependent electroclinical syndromes and precision-based medicine. This review attempts to provide a comprehensive and pragmatic update on newer antiseizure medications.

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.

Hippocampal Involvement With Vigabatrin-Related MRI Signal Abnormalities in Patients With Infantile Spasms: A Novel Finding

BACKGROUND

In a subset of infants exhibiting typical vigabatrin-related magnetic resonance imaging (MRI) changes, the authors observed additional hippocampal signal abnormalities. The authors investigated occurrence and significance of additional signal abnormalities.

METHODS

A retrospective review of infantile spasms patients with typical vigabatrin-related MRI abnormalities was performed. Atypical features included signal changes unilaterally or at previously unreported sites. Comparisons were made between patients with and without atypical features.

RESULTS

In all, 26/55 (47%) exhibited typical vigabatrin-related MRI changes, with additional signal abnormalities in the hippocampi in 6 of 26. On follow-up, evolution of hippocampal signal changes paralleled changes at typical locations in 4 patients. Two patients, clinically well, without follow-up MRI. Patients with and without additional hippocampal signal changes did not differ with respect to clinical factors, including seizure status. One patient had unilateral thalamic/cerebral peduncle signal abnormality along with typical vigabatrin changes.

CONCLUSIONS

Hippocampal changes seen in subset of patients with typical vigabatrin-related changes may be attributable to vigabatrin exposure in the appropriate circumstance.

Magnetic resonance imaging pattern recognition in childhood bilateral basal ganglia disorders

Bilateral basal ganglia abnormalities on MRI are observed in a wide variety of childhood disorders. MRI pattern recognition can enable rationalization of investigations and also complement clinical and molecular findings, particularly confirming genomic findings and also enabling new gene discovery. A pattern recognition approach in children with bilateral basal ganglia abnormalities on brain MRI was undertaken in this international multicentre cohort study. Three hundred and five MRI scans belonging to 201 children with 34 different disorders were rated using a standard radiological scoring proforma. In addition, literature review on MRI patterns was undertaken in these 34 disorders and 59 additional disorders reported with bilateral basal ganglia MRI abnormalities. Cluster analysis on first MRI findings from the study cohort grouped them into four clusters: Cluster 1-T2-weighted hyperintensities in the putamen; Cluster 2-T2-weighted hyperintensities or increased MRI susceptibility in the globus pallidus; Cluster 3-T2-weighted hyperintensities in the globus pallidus, brainstem and cerebellum with diffusion restriction; Cluster 4-T1-weighted hyperintensities in the basal ganglia. The 34 diagnostic categories included in this study showed dominant clustering in one of the above four clusters. Inflammatory disorders grouped together in Cluster 1. Mitochondrial and other neurometabolic disorders were distributed across clusters 1, 2 and 3, according to lesions dominantly affecting the striatum (Cluster 1: glutaric aciduria type 1, propionic acidaemia, 3-methylglutaconic aciduria with deafness, encephalopathy and Leigh-like syndrome and thiamine responsive basal ganglia disease associated with SLC19A3), pallidum (Cluster 2: methylmalonic acidaemia, Kearns Sayre syndrome, pyruvate dehydrogenase complex deficiency and succinic semialdehyde dehydrogenase deficiency) or pallidum, brainstem and cerebellum (Cluster 3: vigabatrin toxicity, Krabbe disease). The Cluster 4 pattern was exemplified by distinct T1-weighted hyperintensities in the basal ganglia and other brain regions in genetically determined hypermanganesemia due to SLC39A14 and SLC30A10. Within the clusters, distinctive basal ganglia MRI patterns were noted in acquired disorders such as cerebral palsy due to hypoxic ischaemic encephalopathy in full-term babies, kernicterus and vigabatrin toxicity and in rare genetic disorders such as 3-methylglutaconic aciduria with deafness, encephalopathy and Leigh-like syndrome, thiamine responsive basal ganglia disease, pantothenate kinase-associated neurodegeneration, TUBB4A and hypermanganesemia. Integrated findings from the study cohort and literature review were used to propose a diagnostic algorithm to approach bilateral basal ganglia abnormalities on MRI. After integrating clinical summaries and MRI findings from the literature review, we developed a prototypic decision-making electronic tool to be tested using further cohorts and clinical practice.

Vigabatrin-related adverse events for the treatment of epileptic spasms: systematic review and meta-analysis

Objective: Although vigabatrin (VGB) is effective and well tolerated for the treatment of epileptic spasms, there are safety concerns. The aim of this systematic review and metaanalysis was to assess adverse events of VGB for the treatment of epileptic spasms. Methods: MEDLINE, EMBASE, and Cochrane databases were searched. The population was infants treated with VGB for epileptic spasms. The outcomes were VGB-related adverse events. Meta-analyses of VGB-related MRI abnormalities, retinal toxicity as measured by electroretinogram (ERG), visual field defect as measured by perimetry, and other adverse events were conducted. Results: Fifty-seven articles were included in the systematic review. The rate of VGB-related MRI abnormalities was 21% (95% CI: 15-29%). Risk factors for MRI abnormalities were age younger than 12 months and higher VGB dose. VGB-related retinal toxicity and visual field defect occurred in 29% (95% CI: 7-69%) and 28% (95% CI: 4-78%) respectively. Other adverse events occurred in 23% (95% CI: 16-34%), consisting predominantly of central nervous system symptoms, and the majority of these did not require therapeutic modification. Conclusion: This study will inform physicians and families on the risk profile of VGB for the treatment of epileptic spasms and will help decisions on treatment options.

Fulminant vigabatrin toxicity during combination therapy with adrenocorticotropic hormone for infantile spasms: Three cases and review of the literature

Vigabatrin (VGB), adrenocorticotropic hormone (ACTH), and prednisone are first-line treatments for infantile spasms (IS). A recent study reported benefits from the use of combination VGB and hormonal therapy over hormonal treatment alone in IS. We describe three patients with IS who developed acute encephalopathy with extrapyramidal symptoms, vigabatrin-associated brain abnormalities on magnetic resonance imaging (VABAM), and death in one patient shortly after initiation of therapy with VGB and ACTH. A literature review supports increased risk of fulminant, symptomatic VABAM in patients receiving VGB in association with hormonal therapy, raising concerns regarding its safety in IS.

Infantile Spasms: Outcome in Clinical Studies

Children with infantile spasms are likely to have a poor outcome. Outcome measures for infantile spasms include primary response to treatment, relapse of spasms, neurological development, death, and progression to another type of epilepsy (Consensus Statements of the WEST Delphi Group 2004). This review is based mainly on prospective studies and emphasizes data about the current first-line drugs, adrenocorticotropic hormone, vigabatrin, and prednisolone, taking into account the proportion of patients with known and unknown etiology, which has a very strong effect on seizure outcome. In most studies, hormonal treatment (adrenocorticotropic hormone or prednisolone) is the optimal monotherapy, except for patients with tuberous sclerosis complex, in whom vigabatrin appears superior. Combination therapy (hormones plus vigabatrin) may well be more effective than either agent alone. The underlying etiology is the most important prognostic factor. In studies with a long follow-up (up to 50 years), a favorable cognitive outcome has been observed in approximately one quarter of patients and complete seizure freedom in one-third. Autism is relatively frequent, and premature mortality is high throughout life. Modifiable prognostic factors include early recognition of the spasms with prompt treatment, short duration of hypsarrhythmia, prompt treatment of relapses of spasms and multifocal epileptic discharges, and early treatment of adverse effects. It is hoped that eventually advanced genetics and molecular data will allow an understanding of the pathogenetic mechanisms of many specific etiologies to allow disease-specific treatment such as is emerging for tuberous sclerosis.

Treatment of infantile spasms: why do we know so little?

INTRODUCTION

Infantile spasm (IS) is an epileptic syndrome with typical onset within the first 2 years of life. This condition might be caused by several etiologies. IS is associated with pathological neuronal networks; however, definite hypotheses on neurobiological processes are awaited.

AREAS COVERED

Changes in NMDA and GABA_B receptors and increase of Ca²⁺ conductance are some of the possible pathophysiological mechanisms. Animal models can help, but most have only some features of IS. Outcome is strongly affected by etiology and the timing of treatment, which relies still on ACTH, oral steroids, and vigabatrin. No significant differences in terms of efficacy have been documented, though a combination of ACTH and vigabatrin seems to be associated with better long-term outcomes. Despite the increasing knowledge about the etiology and pathophysiology of IS, in the last years, no new treatment approaches have been recognized to be able to modify the neurobiological process underlying IS. Precision medicine has far to come in IS.

EXPERT OPINION

Recently, no new therapeutic options for IS have emerged, probably due to the lack of reliable animal models and to the extreme variability in etiologies. Consequently, the outlook for patients and families is poor and early recognition and intervention remain research priorities.

Synthetic pharmaceutical grade cannabidiol for treatment of refractory infantile spasms: A multicenter phase-2 study

PURPOSE

Limited data suggest that cannabidiol (CBD) may be effective for treatment of refractory infantile spasms (IS). This study was designed to more rigorously evaluate the efficacy and safety of synthetic CBD in the treatment of IS.

METHODS

Children six to 36 months of age with IS that failed treatment with both adrenocorticotropic hormone (ACTH) and vigabatrin (VGB) were eligible for enrollment. Children receiving clobazam were excluded. After baseline overnight video-electroencephalography (vEEG) to confirm diagnosis and ascertain hypsarrhythmia, patients were treated with synthetic CBD oral solution (20 mg/kg/day). Overnight video-EEG was repeated after 14 days, and both baseline and repeat video-EEGs were completely de-identified and reviewed in a pairwise fashion by an independent, blinded pediatric electroencephalographer. The primary efficacy endpoint was freedom from spasms and hypsarrhythmia on day 14.

RESULTS

Nine patients were enrolled, comprising an older (median age = 23 months) cohort with long-standing IS (median duration = 13 months) and numerous prior treatment failures (median = 6). One patient responded to therapy and eight patients exhibited neither clinical nor electrographic response.

CONCLUSIONS

The immediate but temporary response in a single patient suggests that CBD oral solution is not particularly effective in highly refractory cases, but may, nevertheless, be effective in younger patients with shorter durations of IS. Further study, examining both short- and long-term outcomes, is warranted to further evaluate the efficacy and safety of CBD oral solution in the treatment of IS.

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.

High vigabatrin dosage is associated with lower risk of infantile spasms relapse among children with tuberous sclerosis complex

After initially successful treatment of infantile spasms, the long-term cumulative risk of relapse approaches 50%, and there is no established protocol to mitigate this risk. Although vigabatrin may be an effective means to prevent relapse, there is little guidance as to ideal duration and dosage. Using a cohort of children with infantile spasms and tuberous sclerosis complex (TSC), we evaluated the potential association of post-response VGB treatment and the rate of infantile spasms relapse. Patients with infantile spasms and clinical response to vigabatrin were identified among a multicenter prospective observational cohort of children with TSC. For each patient we recorded dates of infantile spasms onset, response to vigabatrin, relapse (if any), and quantified duration and dosage of vigabatrin after response. Time to relapse as a function of vigabatrin exposure was evaluated using survival analyses. We identified 50 children who responded to VGB. During a median follow-up of 16.6 months (IQR 10.3-22.9), 12 (24%) patients subsequently relapsed after a median of 7.8 months (IQR 3.1-9.6). Relapse occurred after VGB discontinuation in four patients, and during continued VGB treatment in the remaining eight cases. In survival analyses, risk of relapse was unaffected by the presence or absence of VGB treatment (HR 0.31, 95%CI 0.01-28.4, P =  0.61), but weighted-average dosage was associated with marked reduction in relapse risk: Each 50 mg/kg/d increment in dosage was associated with 61% reduction in risk (HR 0.39, 95%CI 0.17 - 0.90, P =  0.026). This study suggests that the risk of infantile spasms relapse in TSC may be reduced by high-dose vigabatrin treatment.

West Syndrome: A Review and Guide for Paediatricians

West syndrome (WS), also known as infantile spasms, occurs in infancy with a peak between 4 and 7 months. Spasms, neurodevelopmental regression and hypsarrhythmia on electroencephalogram (EEG) basically define WS. The International League Against Epilepsy commission classifies the aetiologies of WS into genetic, structural, metabolic and unknown. Early diagnosis and a shorter lag time to treatment are essential for the overall outcome of WS patients. These goals are feasible with the addition of brain magnetic resonance imaging (MRI) and genetic and metabolic testing. The present work analysed the medical literature on WS and reports the principal therapeutic protocols of its management. Adrenocorticotropic hormone (ACTH), vigabatrin (VGB) and corticosteroids are the first-line treatments for WS. There is no unique therapeutic protocol for ACTH, but most of the evidence suggests that low doses are as effective as high doses for short-term treatment, which is generally 2 weeks followed by dose tapering. VGB is generally administered at doses from 50 to 150 mg/kg/day, but its related retinal toxicity, which occurs in 21-34% of infants, is most frequently observed when treatment periods last longer than 6 months. Among corticosteroids, a treatment of 14 days of oral prednisolone (40-60 mg/day) has been considered effective and well tolerated. Considering that an early diagnosis and a shorter lag time to treatment are essential for successful outcomes in these patients, further studies on efficacy of the different therapeutic approaches with evaluation of final outcome after cessation of therapy are needed.

Efficacy and safety of vigabatrin in Japanese patients with infantile spasms: Primary short-term study and extension study

Vigabatrin was approved for the treatment of infantile spasms by the US Food and Drug Administration, but not in Japan at the time of initiating this clinical study because of concerns about irreversible peripheral visual field defects (VFDs). This study evaluated the efficacy and safety of vigabatrin for Japanese patients with infantile spasms. Of 15 patients (aged ≥4weeks and <2years) enrolled, with the exception of two patients who did not receive vigabatrin, 13 were treated with a titrated dosage of vigabatrin (50-150mg/kg/day; limited to 3000mg/day). Twelve out of 13 patients receiving vigabatrin had spasms that were treatment refractory; these patients were concurrently treated with at least one other antiepileptic drug. One patient received vigabatrin monotherapy. Eight of the 13 patients (61.5% [95% CI: 31.6-86.1%]) had a ≥50% reduction during the dose-adjustment phase compared with baseline in the frequency of spasms, with efficacy maintained through a 2-week maintenance phase. Spasms disappeared in six out of nine patients (66.7% [95% CI: 29.9-92.5%]) who transitioned to the maintenance phase and hypsarrhythmia on electroencephalography also resolved in four patients. Hypsarrhythmia was improved in another two patients. Six out of seven patients who continued treatment through Week 32 of an extension study reported ongoing efficacy for vigabatrin. The most common adverse events (AEs) were psychiatric disorders and nervous system disorders (n=8; 61.5%) that were generally mild in severity. No treatment-related peripheral VFDs were observed. No severe AEs or AEs resulting in discontinuation of vigabatrin therapy were reported. An abnormality in magnetic resonance images was observed in one patient during the extension period. Vigabatrin was deemed to be clinically effective and well tolerated in Japanese patients with infantile spasms.

The Pharmacology and Toxicology of Third-Generation Anticonvulsant Drugs

Epilepsy is a neurologic disorder affecting approximately 50 million people worldwide, or about 0.7% of the population [1]. Thus, the use of anticonvulsant drugs in the treatment of epilepsy is common and widespread. There are three generations of anticonvulsant drugs, categorized by the year in which they were developed and released. The aim of this review is to discuss the pharmacokinetics, drug-drug interactions, and adverse events of the third generation of anticonvulsant drugs. Where available, overdose data will be included. The pharmacokinetic properties of third-generation anticonvulsant drugs include relatively fewer drug-drug interactions, as well as several unique and life-threatening adverse events. Overdose data are limited, so thorough review of adverse events and knowledge of drug mechanism will guide expectant management of future overdose cases. Reporting of these cases as they occur will be necessary to further clarify toxicity of these drugs.

Central tegmentum tract hyperintensities in pediatric neurological patients: Incidence or coincidence

AIM

The central tegmental tract hyperintensities (CTTH) have been found in many different pediatric neurological conditions. There is only scarce data about the value of this radiological phenomenon. In this study we aimed to show the neurological conditions associated with this radiological finding.

MATERIALS AND METHODS

We performed a retrospective analysis of all pediatric brain MRI's between 2013 and 2015. After finding those patients with CTTH, we evaluated them in the pediatric neurology clinic.

RESULTS

There were 41 out of 1464 brain MRI's with CTTH with 2.8% prevalence. Thirty four patients (23 male, age range 3months-98months) were available for evaluation. CTTH were present in mainly younger age group. There were many different neurological conditions associated with CTTH. These included brain tumors, epilepsy, developmental delay, metabolic disorders and genetic syndromes.

CONCLUSION

CTTH is found in many different pediatric neurological conditions. Further neuropathological and prospective MRI and clinical studies are needed to better understand this interesting radiological finding.

Magnetic resonance imaging patterns of treatment-related toxicity in the pediatric brain: an update and review of the literature

Treatment-related neurotoxicity is a potentially life-threatening clinical condition that can represent a diagnostic challenge. Differentiating diagnoses between therapy-associated brain injury and recurrent disease can be difficult, and the immediate recognition of neurotoxicity is crucial to providing correct therapeutic management, ensuring damage reversibility. For these purposes, the knowledge of clinical timing and specific treatment protocols is extremely important for interpreting MRI patterns. Neuroradiologic findings are heterogeneous and sometimes overlapping, representing the compounding effect of the different treatments. Moreover, MRI patterns can be acute, subacute or delayed and involve different brain regions, depending on (1) the mechanism of action of the specific medication and (2) which brain regions are selectively vulnerable to specific toxic effects. This review illustrates the most common radiologic appearance of radiotherapy, chemotherapy and medication-associated brain injury in children, with special focus on the application of advanced MRI techniques (diffusion, perfusion and proton spectroscopy) in the diagnosis of the underlying processes leading to brain toxicity.

Emerging Antiepileptic Drugs for Severe Pediatric Epilepsies

The medical management of the epilepsy syndromes of early childhood (eg, infantile spasms, Dravet syndrome, and Lennox-Gastaut syndrome) is challenging; and requires careful evaluation, classification, and treatment. Pharmacologic therapy continues to be the mainstay of management for these children, and as such it is important for the clinician to be familiar with the role of new antiepileptic drugs. This article reports the clinical trial data and personal experience in treating the severe epilepsies of childhood with the recently Food and Drug Administration-approved new antiepileptic drugs (vigabatrin, rufinamide, perampanel, and clobazam) and those in clinical trials (cannabidiol, stiripentol, and fenfluramine). Genetic research has also identified an increasing number of pediatric developmental and seizure disorders that are possibly treatable with targeted drug therapies, focused on correcting underlying neural dysfunction. We highlight recent genetic advances, and how they affect our treatment of some of the genetic epilepsies, and speculate on the use of targeted genetic treatment (precision medicine) in the future.

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.

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.

Vigabatrin as First-Line Treatment for Infantile Spasms Not Related to Tuberous Sclerosis Complex

BACKGROUND

Infantile spasms are a rare, catastrophic, age-specific seizure disorder of infancy. Adrenocorticotropic hormone or vigabatrin have been recommended for the short-term treatment of infantile spasms by the Child Neurology Society/American Academy of Neurology practice parameter.

OBJECTIVE

This retrospective study reviewed the Hospital for Sick Children's experience with the short-term efficacy of vigabatrin as first-line treatment for infantile spasms not related to tuberous sclerosis complex.

METHOD

We performed a single-center, retrospective analysis of all cases of newly diagnosed infantile spasms between January 2010 and September 2013. Duration of follow-up was at least 6 months from treatment initiation.

RESULTS

Eighteen of the 61 infants (30%) had a clinical and electrographic response to vigabatrin therapy within 4 weeks of treatment. Of the vigabatrin responders, 2/18 (11%) relapsed. At final follow-up after initiation of vigabatrin therapy, 17/61 (27%) of the vigabatrin responders were free of all clinical seizure types. Normal development at the time of infantile spasms diagnosis was statistically associated with vigabatrin response.

CONCLUSION

These findings do not support our hypothesis that vigabatrin is effective as first-line, short-term treatment of infantile spasms in non-tuberous sclerosis complex patients. However, when used in this setting, vigabatrin is most effective in children with normal development at the time of diagnosis. These findings may assist clinicians in the optimal treatment choice for children at the first presentation of infantile spasms not related to tuberous sclerosis complex.

Disorders of GABA metabolism: SSADH and GABA-transaminase deficiencies

Clinical disorders known to affect inherited gamma-amino butyric acid (GABA) metabolism are autosomal recessively inherited succinic semialdehyde dehydrogenase and GABA-transaminase deficiency. The clinical presentation of succinic semialdehyde dehydrogenase deficiency includes intellectual disability, ataxia, obsessive-compulsive disorder and epilepsy with a nonprogressive course in typical cases, although a progressive form in early childhood as well as deterioration in adulthood with worsening epilepsy are reported. GABA-transaminase deficiency is associated with a severe neonatal-infantile epileptic encephalopathy.

Brain MRI findings with vigabatrin therapy: case report and literature review

Infantile spasm or West syndrome is a pediatric epileptic disorder characterized by flexor and/or extensor spasms beginning in childhood. Vigabatrin is an effective medical therapy for infantile spasm but has pronounced, potentially worrisome imaging findings in patients receiving therapy. We present the case of an 8-month-old infant with such brain magnetic resonance imaging findings after treatment initiation. In this article, we highlight the imaging changes and discuss the differential diagnosis along with the required follow-up.

A novel mutation of ALDH5A1 gene associated with succinic semialdehyde dehydrogenase deficiency

Succinic semialdehyde dehydrogenase deficiency is a rare autosomal recessive metabolic disorder affecting γ-aminobutyric acid degradation. We described a boy with a severe phenotype of succinic semialdehyde dehydrogenase deficiency and novel mutations of ALDH5A1 gene. He was referred because of developmental delay, focal seizures, and choreoathetosis at 6 months of age. The diagnosis of succinic semialdehyde dehydrogenase deficiency was confirmed by increased level of γ-hydroxybutyric acid in urine and novel compound heterozygous mutations in the ALDH5A1 gene. His seizures were successfully controlled. However, the patient showed a slowly progressive clinical course with severe neurologic deficits. A magnetic resonance imaging (MRI) revealed abnormal high intensities in the putamen and globus pallidi on T2-weighted images when he was 6 months old, and more diffuse abnormal signal intensities over bilateral hemispheres were noted when he was 3 years old.

Toxic leukoencephalopathies, including drug, medication, environmental, and radiation-induced encephalopathic syndromes

Toxic leukoencephalopathies can be secondary to the exposure to a wide variety of exogenous agents, including cranial irradiation, chemotherapy, antiepileptic agents, drugs of abuse, and environmental toxins. There is no typical clinical picture, and patients can present with a wide array of signs and symptoms. Involvement of white matter is a key finding in this scenario, although in some circumstances other high metabolic areas of the central nervous system can also be affected. Magnetic resonance (MR) imaging usually discloses bilateral and symmetric white matter areas of hyperintense signal on T2-weighted and fluid-attenuated inversion recovery images, and signs of restricted diffusion are associated in the acute stage. In most cases, the changes are reversible, especially with prompt recognition of the disease and discontinuation of the noxious agent. Either the MR or clinical features may be similar to several nontoxic entities, such as demyelinating diseases, leukodystrophies, hepatic encephalopathy, vascular disease, hypoxic-ischemic states, and others. A high index of suspicion should be maintained whenever a patient presents recent onset of neurologic deficit, searching the risk of exposure to a neurotoxic agent. Getting to know the most frequent MR appearances and mechanisms of action of causative agents may help to make an early diagnosis and begin therapy, improving outcome. In this review, some of the most important causes of leukoencephalopathies are presented; as well as other 2 related conditions: strokelike migraine attacks after radiation therapy syndrome and reversible splenial lesions.

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.

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.