Antiepileptic drugs and visual function

Ocular hemodynamics in epileptic children treated with antiepileptic drugs

PURPOSE

To evaluate the quantitative measurements obtained for vessel density (VD) of the optic nerve head, macula, peripapillary retinal nerve fibre layer (p-RNFL) and total retinal thicknesses (Trt) by optical coherence tomography angiography (OCT-A) and the choroidal vascular structure using an image binarization method in children with epilepsy using three different antiepileptic drugs (AEDs) and to compare these measurements with healthy participants.

METHODS

This observational, cross-sectional study included 124 patients divided into 4 groups: Group-1: patients receiving carbamazepine(n = 30), group-2: patients receiving levetiracetam (n = 31), group-3: patients receiving valproic acid (n = 32), and group 4: healthy controls (n = 31).A fully automated microstructural analysis of the VD of the retinal superficial capillary plexus (SCP), deep capillary plexus (DCP), and the choriocapillaris (CC) layers and radial peripapillary capillary, and Trt, p-RNFL thickness were analyzed by using OCT-A. Enhanced depth imaging (EDI)-OCT scans of the macula were obtained and the images were binarized using the ImageJ software.

RESULTS

The mean age, gender distribution and the duration of epilepsy were similar in all groups. Evaluation of the p-RNFL thickness and perifoveal Trt between the groups showed a statistically significant difference in all quadrants.The p-RNFL thickness was lower in patients receiving carbamazepine and valproic acid. The lowest values of the luminal area and choroidal vascular index (CVI) were found in patients receiving valproic acid; comparison with matched healthy controls showed statistically significant differences.

CONCLUSION

Valproic acid and carbamazepine are associated with thinning of the p-RNFL in epilepsy patients, but the macular and radial peripapillary VD were not affected.However, a reduction of choroidal vascular blood flow was found in epilepsy patients taking valproic acid.

Effects of sodium valproate and levetiracetam on posterior segment parameters in children with epilepsy

PURPOSE

To evaluate changes in posterior segment parameters in pediatric patients with epilepsy using sodium valproate or levetiracetam monotherapy for at least 12 months.

METHODS

This study included 45 children with generalized epilepsy aged 6-17 years and 32 age- and gender-matched healthy subjects. The patients were assigned to three groups: Group 1 included patients using valproate monotherapy at a dose of 20-40 mg/kg/day, group 2 included patients using levetiracetam monotherapy at a dose of 20-40 mg/kg/day, and group 3 consisted of healthy controls. Peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell layer-inner plexiform layer (mGCIPL) thicknesses were measured using spectral-domain optical coherence tomography (OCT).

RESULTS

No significant differences were noted between the groups regarding age, gender distribution, visual acuity, spherical equivalent, and intraocular pressure (p > 0.05). The average and temporal, nasal, and superior quadrants RNFL values were significantly thinner in group 1 than in group 2 (p = 0.001, p = 0.023, p = 0.011, and p = 0.001, respectively) and group 3 (p < 0.001, p = 0.032, p < 0.001, and p = 0.001, respectively). The OCT parameters were similar in groups 2 and 3 (p > 0.05). A negative correlation was observed in group 1 between only the average mGCIPL and the treatment dose (r =  - 0.501). In group 2, no significant correlation was found between OCT parameters and the duration of epilepsy treatment, dose of treatment, and age at treatment onset values (p > 0.05).

CONCLUSION

These findings support that there is an association between sodium valproate treatment and the reduction of RNFL thickness in epilepsy. Levetiracetam treatment appears to be a safe option, but care should be taken regarding ocular side effects that may occur with long-term and high-dose use of sodium valproate.

Evaluation of ganglion cell complex and retinal nerve fiber layer thinning in epilepsy patients

Purpose

This study aimed to compare the perimacular ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (RNFL) thickness measurements of epileptic and healthy individuals.

Methods

The right eyes of 38 epileptic and 38 healthy individuals who had been using antiepileptic drugs (AEDs) for at least 1 year were included in the study. Central macular thickness, perimacular GCC thickness and volume, and peripapillary retinal nerve fiber layers were measured by optical coherence tomography (OCT) device. Perimacular 1, 3, and 6 mm circle diameters of Early Treatment of Diabetic Retinopathy Study (ETDRS.

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were selected for GCC measurements.

Results

In epilepsy patients, GCC was significantly lower in the 3 mm superior quadrant and 6 mm in all quadrants compared to the control group (P < 0.05). RNFL was significantly thinner in epilepsy patients only in the temporal-inferior quadrant (P < 0.05). There was no significant difference between the patients who received AEDs as monotherapy and polytherapy (P > 0.05).

Conclusion

We found that epilepsy patients had significant thinning in the GCC layers and temporal-inferior quadrant of RNFL compared to the control group. Our findings from the study show that early retinal changes in epilepsy patients, especially perimacular GCC layers, can be followed up with OCT.

Epidemiology of eye diseases among children with disability in rural Bangladesh: a population-based cohort study

AIM

To describe the epidemiology of eye diseases among children with disability in rural Bangladesh.

METHOD

We established a population-based cohort of children with disability using the key informant method. Children younger than 18 years with disability (i.e. physical, visual, hearing, speech, epilepsy) were included. We used detailed ophthalmological assessments following World Health Organization (WHO) protocols by a multidisciplinary team including an ophthalmologist, optometrist, physician, and physiotherapist. Visual impairment, blindness, and severe visual impairment (SVI) were defined by following WHO categories.

RESULTS

Between October 2017 and February 2018, 1274 children were assessed (43.6% female; median [interquartile range] age 9y 10mo [6y -13y 7mo]). Overall, 6.5% (n=83) had blindness/SVI, and 5.6% (n=71) had visual impairment. In the group with blindness/SVI, 47% (n=39) had cortical blindness; of those, 79.5% (n=31) had cerebral palsy (CP). The other main anatomical sites of abnormalities in this group included lens (13.3%, n=11), cornea (10.8%, n=9), and optic nerve (9.6%, n=8). In the group with visual impairment, 90.1% (n=64) had refractive error. Overall, 83.1% (n=69) and 78.8% (n=56) of those with blindness/SVI and visual impairment had avoidable causes. Most children with blindness/SVI and visual impairment lacked access to education.

INTERPRETATION

The burden of blindness/SVI/visual impairment is high among children with disability in rural Bangladesh, mostly due to avoidable causes. Overrepresentation of CP and cortical blindness in the group with blindness/SVI and refractive error in the group with visual impairment highlights the need for integration of ophthalmology assessment, eye care, and refraction services in comprehensive health care for children with disability including CP in rural Bangladesh.

Visual surround suppression in people with epilepsy correlates with attentional-executive functioning, but not with epilepsy or seizure types

PURPOSE

Following reports that an index of visual surround suppression (SI) may serve as a biomarker for an imbalance of cortical excitation and inhibition in different psychiatric and neurological disorders including epilepsy, we evaluated whether SI is associated with seizure susceptibility, seizure spread, and inhibitory effects of antiseizure medication (ASM).

METHODS

In this prospective controlled study, we examined SI with a motion discrimination task in people with genetic generalized epilepsy (GGE) and focal epilepsy with and without focal to bilateral tonic-clonic seizures. Cofactors such as GABAergic ASM, attentional-executive functioning, and depression were taken into account.

RESULTS

Data of 45 patients were included in the final analysis. Suppression index was not related to epilepsy or seizure type, GABAergic ASM treatment or mood. However, SI correlated with attentional-executive functioning (r = 0.32), which in turn was associated with ASM load (r = -0.38). Repeated task administration (N = 7) proved a high stability over a one-week interval (r_tt = 0.89).

CONCLUSIONS

Our results do not support the hypothesis that SI is a reliable biomarker for mechanisms related to inhibition of seizure spread or seizure frequency, i.e., it does not seem to reflect inhibitory capacities in epilepsy. Likewise, SI did not differentiate GGE from focal epilepsy, nor was it influenced by ASM load or mode of action. Thus, in epilepsy, no added value of including SI to routine diagnostics can be concluded.

Retinal ganglion cell complex and visual evoked potentials in levetiracetam treatment

PURPOSE

To examine central macular, RNFL (retinal nerve fibre layer), GCC (ganglion cell complex) thicknesses; and VEPs (visual evoked potential) in epileptic patients using levetiracetam for at least one year.

MATERIALS AND METHODS

Sixteen focal epileptic patients receiving levetiracetam monotherapy and 16 healthy subjects were included in the study. Central macular, RNFL and GCC thicknesses according to spectral domain OCT (optical coherence tomography); and VEPs parameters were compared between patients and healthy subjects.

RESULTS

The mean age of patient and control groups were 40 ± 16 and 38 ± 12 years respectively (p > 0.05). The patient group was on levetiracetam therapy for 64 ± 45 (12-168) months. Central macular thickness was thinner in the patient group (p = 0.008). There was no difference among groups regarding RNFL thicknesses. GCC thicknesses in all quadrants were similar among groups, except the superior quadrant; which was thinner in the patient group (p = 0.03). P100 amplitude in 30 min pattern was lower in the patient group (p = 0.04). N135 latency in 15 min (p = 0.03) and 7 min patterns (p = 0.01) was longer in the patient group.

CONCLUSION

Central macular and GCC thicknesses; and VEP parameters in patients receiving levetiracetam treatment may differ from healthy subjects.

Antiepileptic drug therapy in the elderly: a clinical pharmacological review

Seizure disorder is the third most common neurological disorder in the elderly after stroke and dementia. With the increasing geriatric population, the situation of clinicians seeing more and more elderly epilepsy patients is very likely. Not only is the diagnosis of epilepsy tedious in the elderly, its management raises many challenging issues for the treating physicians. Altered physiology, age-related decline in organ function, and plasma protein binding and altered pharmacodynamics make the elderly patients with seizure disorder a difficult group to treat. This is further complicated by the presence of comorbidities and polypharmacy which increase the chances of drug interactions. The adverse effects that might be tolerated well in younger populations may be disastrous for the aged. Although the newer antiepileptic drugs are found to have a favorable safety profile, there is relative scarcity of randomized-controlled trials involving older and newer antiepileptics in the geriatric population. This review tries to compile the available literature on management of epilepsy in the elderly population including evidence of safety and efficacy of newer and older antiepileptics with special reference to the 'geriatric giants'. It also deals with the interactions between antiepileptic medications and other commonly prescribed drugs in the elderly such as anti-hypertensives and antiischemic agents. The recommended guidelines of various international bodies are also analyzed from the perspective of elderly with seizure disorder.

Attenuation of retinal nerve fibre layer in people with epilepsy receiving valproate

OBJECTIVES

Valproate (VPA) is one of the most frequently used anti-epileptic drugs (AEDs) worldwide. Its effects in decreasing the retinal nerve fibre layer (RNFL) thickness remain debatable. We aimed to evaluate the effect of VPA usage on the RNFL in comparison with other AEDs and no AED usage in people with epilepsy (PWE).

METHODS

In this observational case-control study, PWE were enrolled and divided into three groups: PWE 1) receiving VPA monotherapy throughout their clinical course; 2) receiving an AED other than VPA as monotherapy; and 3) who never took any AED. RNFL thickness of the right eye was measured by optical coherence tomography (OCT). In each individual, disease-related information was recorded.

RESULTS

A total of 86 individuals (51 males; median age, 25 years) with an average epilepsy duration of 6.88 years were enrolled. No difference in the demographics except for sex was noted between the groups. The average RNFL thickness in 26 individuals who had received VPA (group I) was 93.73 ± 9.24 μm, which was significantly lower than the corresponding values for the 31 individuals who received other single AED regimens (group II; 99.71 ± 8.50 μm; p = 0.031) or the 29 individuals who never used any AED (group III; 102.79 ± 8.05 μm; p = 5.67 × 10^-4), especially in the superior and inferior quadrants. The RNFL attenuation was significantly correlated with the epilepsy duration in groups II and III (r = 0.351, p = 0.006). However, no correlation between epilepsy duration, cumulative dosage of VPA, duration of treatment with VPA and RNFL thickness was found in group Ⅰ.

CONCLUSION

These preliminary findings suggest an association between VPA usage and reduction of retinal thickness in PWE, especially in the superior and inferior quadrants. Epilepsy itself might also be another risk factor for RNFL attenuation. Further studies need to confirm this finding and to unravel the underlying mechanism.

An investigation of the ocular toxic effects of levetiracetam therapy in children with epilepsy

OBJECTIVE

To investigate the potential toxic effects of levetiracetam monotherapy on ocular tissues in cases of pediatric epilepsy using optical coherence tomography (OCT).

METHODS

Thirty epileptic children (group 1) receiving levetiracetam monotherapy at a dosage of 20-40 mg/kg/day for at least 1 year with a first diagnosis of epilepsy and 30 age- and gender-matched healthy children (group 2) were included in the study. In addition to a detailed eye examination, peripapillary retinal nerve fiber layer (RNFL) thickness, ganglion cell complex (GCC) thickness, foveal thickness (FT), and central corneal thickness (CCT) were measured in all children by means of spectral domain OCT. The data obtained from the two groups were then subjected to statistical analysis.

RESULTS

The mean age of both groups was 12 ± 3.64 years [1-12]. The mean duration of levetiracetam in group 1 was 24.07 ± 12.82 months. Mean RNFL values in groups 1 and 2 were 106.1 ± 10.42 and 104.98 ± 10.04 μm, mean GCC values were 94.72 ± 6.26 and 94.4 ± 6 μm, mean FT values were 240.73 ± 17.94 and 240.77 ± 15.97 μm, and mean CCT values were 555.1 ± 44.88 and 540.97 ± 32.65 μm, respectively. No significant difference was determined between the two groups in terms of any parameter. Best corrected visual acuity values of the subjects in both groups were 10/10, and no color vision or visual field deficit was determined.

CONCLUSION

Levetiracetam monotherapy causes no significant function or morphological change in ocular tissues in pediatric epilepsies.

New GABA modulators protect photoreceptor cells from light-induced degeneration in mouse models

No clinically approved therapies are currently available that prevent the onset of photoreceptor death in retinal degeneration. Signaling between retinal neurons is regulated by the release and uptake of neurotransmitters, wherein GABA is the main inhibitory neurotransmitter. In this work, novel 3-chloropropiophenone derivatives and the clinical anticonvulsants tiagabine and vigabatrin were tested to modulate GABA signaling and protect against light-induced retinal degeneration. Abca4^-/-Rdh8^-/- mice, an accelerated model of retinal degeneration, were exposed to intense light after prophylactic injections of one of these compounds. Imaging and functional assessments of the retina indicated that these compounds successfully protected photoreceptor cells from degeneration to maintain a full-visual-field response. Furthermore, these compounds demonstrated a strong safety profile in wild-type mice and did not compromise visual function or damage the retina, despite repeated administration. These results indicate that modulating inhibitory GABA signaling can offer prophylactic protection against light-induced retinal degeneration.-Schur, R. M., Gao, S., Yu, G., Chen, Y., Maeda, A., Palczewski, K., Lu, Z.-R. New GABA modulators protect photoreceptor cells from light-induced degeneration in mouse models.

Comprehensive review of visual defects reported with topiramate

Objective

The objective of this study was to analyze clinical patterns of visual field defects (VFDs) reported with topiramate treatment and assess possible mechanism of action (MOA) for antiepileptic drug (AED) associated VFDs.

Methods

A comprehensive topiramate database review included preclinical data, sponsor’s clinical trials database, postmarketing spontaneous reports, and medical literature. All treatment-emergent adverse events (TEAEs) suggestive of retinal dysfunction/damage were summarized. Relative risk (RR) was computed from topiramate double-blind, placebo-controlled trials (DBPCTs) data.

Results

Preclinical studies and medical literature review suggested that despite sharing gamma-aminobutyric acid (GABA)-ergic MOA with other AEDs, topiramate treatment was not associated with VFDs. TEAEs suggestive of retinal dysfunction/damage were observed in 0.3%–0.7% of adults and pediatric patients with topiramate (N=4,679) versus ≤0.1% with placebo (N=1,834) in DBPCTs for approved indications (epilepsy and migraine prophylaxis); open-label trials (OLTs) and DBPCTs for investigational indications had similar incidence. Overall, 88% TEAEs were mild or moderate in severity. Serious TEAEs were very rare (DBPCTs: 0%; OLTs: ≤0.1%), and most were not treatment limiting, and resolved. The most common visual TEAEs (approved indications) were VFD, scotoma, and optic atrophy. The incidence of TEAEs in DBPCTs (approved and investigational indications) was higher in topiramate-treated (N=9,169) versus placebo-treated patients (N=5,023; 0.36% vs 0.24%), but the RR versus placebo-treated patients was not significant (RR: 1.51 [95% confidence interval: 0.78, 2.91]).

Conclusion

VFDs do not appear to be a class effect for AEDs with GABA-ergic MOA. The RR for VFDs is not significantly different between topiramate and placebo treatment.

Visual evoked potentials detect cortical processing deficits in Rett syndrome

OBJECTIVE

Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutation of the X-linked MECP2 gene and characterized by developmental regression during the first few years of life. The objective of this study was to investigate if the visual evoked potential (VEP) could be used as an unbiased, quantitative biomarker to monitor brain function in RTT.

METHODS

We recorded pattern-reversal VEPs in Mecp2 heterozygous female mice and 34 girls with RTT. The amplitudes and latencies of VEP waveform components were quantified, and were related to disease stage, clinical severity, and MECP2 mutation type in patients. Visual acuity was also assessed in both mice and patients by modulating the spatial frequency of the stimuli.

RESULTS

Mecp2 heterozygous female mice and RTT patients exhibited a similar decrease in VEP amplitude that was most striking in the later stages of the disorder. RTT patients also displayed a slower recovery from the principal peak of the VEP response that was impacted by MECP2 mutation type. When the spatial frequency of the stimulus was increased, both patients and mice displayed a deficit in discriminating smaller patterns, indicating lower visual spatial acuity in RTT.

INTERPRETATION

VEP is a method that can be used to assess brain function across species and in children with severe disabilities like RTT. Our findings support the introduction of standardized VEP analysis in clinical and research settings to probe the neurobiological mechanism underlying functional impairment and to longitudinally monitor progression of the disorder and response to treatment.

An Evaluation of Peripapillary Retinal Nerve Fiber Layer Thickness in Children With Epilepsy Receiving Treatment of Valproic Acid

AIM

We investigated the peripapillary retinal nerve fiber layer thickness with optical coherence tomography in epileptic children receiving valproic acid monotherapy.

MATERIALS AND METHODS

The study was conducted on children aged 8-16 years who were undergoing valproic acid monotherapy for epilepsy. The study group comprised a total of 40 children who met the inclusion criteria and 40 healthy age- and sex-matched children as a control group. Children with at least a 1-year history of epilepsy and taking 10-40 mg/kg/day treatment were included in the study. Peripapillary retinal nerve fiber layer thickness measurements were performed using Cirrus HD optical coherence tomography. All children and parents were informed about the study and informed consent was obtained from the parents of all the participants.

RESULTS

The study group included 21 girls and 19 boys with a mean age of 10.6 ± 2.3 years. According to the results of optical coherence tomography measurements, the mean peripapillary retinal nerve fiber layer thickness was 91.6 ± 9.7 in the patient group and 95.5 ± 7.4 μm in the control group (P < 0.05). The superior peripapillary retinal nerve fiber layer thickness was 112.0 ± 13.2 in the patient group and 120.0 ± 14.7 μm in the control group (P < 0.02). According to the results of both measurements, the peripapillary retinal nerve fiber layer thickness was significantly lower in the patient group. Neither color vision loss nor visual field examination abnormality could be documented.

CONCLUSION

According to the optical coherence tomography measurements, the average and superior peripapillary retinal nerve fiber layer thicknesses were thinner in patients with epilepsy who were receiving valproic acid monotherapy compared with healthy children. This situation can lead to undesirable results in terms of eye health. New studies are needed to investigate whether these findings are the result of epilepsy or can be attributed to valproic acid and whether there are adverse effects of valproic acid later in life.

Vitamin U, a novel free radical scavenger, prevents lens injury in rats administered with valproic acid

Valproic acid (2-propyl-pentanoic acid, VPA) is the most widely prescribed antiepileptic drug due to its ability to treat a broad spectrum of seizure types. VPA exhibits various side effects such as organ toxicity, teratogenicity, and visual disturbances. S-Methylmethioninesulfonium is a derivative of the amino acid methionine and it is widely referred to as vitamin U (Vit U). This study was aimed to investigate the effects of Vit U on lens damage parameters of rats exposed to VPA. Female Sprague Dawley rats were divided into four groups. Group I comprised control animals. Group II included control rats supplemented with Vit U (50 mg/kg/day) for 15 days. Group III was given only VPA (500 mg/kg/day) for 15 days. Group IV was given VPA + Vit U (in same dose and time). Vit U was given to rats by gavage and VPA was given intraperitoneally. On the 16th day of experiment, all the animals which were fasted overnight were killed. Lens was taken from animals, homogenized in 0.9% saline to make up to 10% (w/v) homogenate. The homogenates were used for protein, glutathione, lipid peroxidation levels, and antioxidant enzymes activities. Lens lipid peroxidation levels and aldose reductase and sorbitol dehydrogenase activities were increased in VPA group. On the other hand, glutathione levels, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione- S-transferase, and paraoxonase activities were decreased in VPA groups. Treatment with Vit U reversed these effects. This study showed that Vit U exerted antioxidant properties and may prevent lens damage caused by VPA.

The efficacy of gabapentin in children of partial seizures and the blood levels

AIM

To evaluate the long-term efficacy of gabapentin (GBP) and usefulness of measurement of the blood level for the observation of patients that have partial seizures.

METHODS

Thirty patients (20 effective cases and 10 ineffective cases) treated with GBP for the localization related epilepsy had their peak blood levels of GBP. The levels were measured seven time points, one, 6, 12, 18, 24, 30, and 36month after the start of medication. The efficacy of GBP was evaluated at one month after the initiation of medication and every year for 3years, based on the R Ratio and the degree of improvement for the paroxysmal strength and length.

RESULTS

GBP levels were higher in the effective cases than the levels in the ineffective cases 6months after and 1year after the initiation of medication (p<0.05). The level 6months after the start in the effective cases was 5.429±2.384μg/ml (mean±SD), and 5.837±3.217μg/ml after 1year. The cases that were effective for 1year maintained approximately the same efficacy for 3years after the initiation of medication, but there was no correlation between the level and the R Ratio, paroxysmal strength and length.

CONCLUSIONS

No precise definition of the therapeutic range was recognized because of no correlation between GBP level and the improvement of clinical manifestations. We recommend the GBP optimal range that is established the range within 3-8μg/ml (mean; 5μg/ml) as therapeutic target without the side effect.

The effects of vitamin B6 on lens antioxidant system in valproic acid-administered rats

Valproic acid (VPA, 2-propyl pentanoic acid) is a broad-spectrum antiepileptic drug (AED) and is commonly used in the treatment of bipolar disorders and epilepsy. AEDs are known to result in vascular disturbances. Vitamin B6 (Vit B6) is water soluble vitamin essential for normal growth, development, and metabolism. In this study, we aimed to investigate the protective effects of Vit B6 against VPA-induced lens damage in experimental animals. In this study, male 4-month-old, Sprague-Dawley rats were used. The animals were divided into four groups. Group I was intact control animals. Group II rats were administered with Vit B6 (50 mg/kg/day) for 7 days. Group III rats were administered with only VPA (500 mg/kg/day) for 7 days. Group IV was given VPA + Vit B6 (in a same dose and time). Vit B6 was given to rats by gavage and VPA was given by intraperitoneally. On the 8th day of experiment, all of the animals were fasted overnight and then killed under ether anesthesia. Lens tissues were taken from animals, homogenized in 0.9% saline to make up a 10% homogenate. The homogenates was used for glutathione (GSH), lipid peroxidation (LPO), protein levels, and enzyme analysis. In VPA groups, levels of lens GSH and LPO and activities of glutathione- S-transferase, glutathione peroxidase, glutathione reductase, and aldose reductase were increased, while superoxide dismutase activity was decreased. Treatment with Vit B6 reversed these effects. These results demonstrated that administration of Vit B6 is potentially beneficial agent to reduce the lens damage in VPA toxicity, probably by decreasing oxidative stress.

Impact of early life exposure to antiepileptic drugs on neurobehavioral outcomes based on laboratory animal and clinical research

Epilepsy affects approximately 1% of children under the age of 15, making it a very common neurological disorder in the pediatric population (Russ et al., 2012). In addition, ~0.4-0.8% of all pregnant women have some form of epilepsy (Hauser et al., 1996a,b; Borthen et al., 2009; Krishnamurthy, 2012). Despite the potential deleterious effects of antiepileptic drugs (AEDs) on the developing brain, their use is still required for seizure control in pregnant women (Krishnamurthy, 2012), and they represent the standard approach for treating children with epilepsy (Chu-Shore and Thiele, 2010; Quach et al., 2010; Verrotti et al., 2011). Even when AEDs are effective, there are potential side effects, including cognitive and affective changes or altered sleep and appetite. The consequences of AED exposure in development have been studied extensively (Canger et al., 1999; Modi et al., 2011a,b; Oguni, 2011). Despite intensive study, there is still debate about the long-term consequences of early life AED exposure. Here, we consider the evidence to date that AED exposure, either prenatally or in early postnatal life, has significant adverse effects on the developing brain and incorporate studies of laboratory animals as well as those of patients. We also note the areas of research where greater clarity seems critical in order to make significant advances. A greater understanding of the impact of AEDs on somatic, cognitive and behavioral development has substantial value because it has the potential to inform clinical practice and guide studies aimed at understanding the genetic and molecular bases of comorbid pathologies associated with common treatment regimens. Understanding these effects has the potential to lead to AEDs with fewer side effects. Such advances would expand treatment options, diminish the risk associated with AED exposure in susceptible populations, and improve the quality of life and health outcomes of children with epilepsy and children born to women who took AEDs during pregnancy.

Fundal changes in children receiving Vigabatrin

Visual field defects and other abnormalities are reported in patients receiving the newer antiepileptic Vigabatrin (VGB). Field testing in children younger than 6 years and those with mental retardation is difficult. The authors, therefore, studied ophthalmoscopic abnormalities in seven pediatric patients receiving VGB for median duration of 9 month (range, 3-32 months). Abnormal findings were seen in two (33.3%) in the form of surface wrinkling retinopathy and abnormal macular reflexes. The proportion of abnormal findings was in agreement with previous reports. Thus it is concluded that simple ophthalmoscopy by an ophthalmologist picks up the abnormalities due to ocular toxicity of VGB, and helps in rationalizing further AED therapy in the clinic.

Tuberous sclerosis complex: neurological, renal and pulmonary manifestations

Tuberous sclerosis complex (TSC) is an important cause of epilepsy and autism, as well as renal and pulmonary disease in adults and children. Affected individuals are subject to hamartomas in various organ systems which result from constitutive activation of the protein kinase mTOR (mammalian target of rapamycin). The clinical course, prognosis and appropriate therapy for TSC patients are often different from that for individuals with epilepsy, renal tumors, or interstitial lung disease, from other causes. Additionally, TSC serves as a model for other conditions in which the mTOR pathways are also up-regulated. This article reviews the molecular pathophysiology and management of neurological, renal and pulmonary manifestations of the disorder. The use of mTOR inhibitors such as rapamycin and everolimus is discussed and recent clinical trials of these drugs in TSC are reviewed.

Phenytoin-induced visual disturbances mimicking Delirium Tremens in a child

Delirium Tremens is quite rare in children and it is usually caused by withdrawal or abstinence from alcohol, barbiturates and other major tranquilizers. The usual symptoms of Delirium Tremens include severe altered mental status with confusion, delusions, hallucinations, and severe agitation. Although psychosis is a recognized manifestation of Phenytoin toxicity, visual hallucinations are not. This study reports the case of a 4-year-old male with febrile seizures plus syndrome who developed acute complex visual hallucinations and psychomotor agitation early after therapy with intravenous Phenytoin was administered. These visual hallucinations mimicked those linked to Delirium Tremens and were not associated with an encephalopathy or other known neuropsychiatric side effects of this drug. Moreover, the hallucinations occurred while serum Phenytoin concentrations were below therapeutic range. We made an extensive investigation in order to exclude a non-convulsive Status Epilepticus, a Central Nervous System infection, a metabolic disorder, an underlying psychiatric disease and a possible drug toxicity. The temporal relationship between initiation of Phenytoin and onset of visual hallucinations and resolution of symptoms with withdrawal of Phenytoin suggests that the visual disturbances were probably due to that antiepileptic drug.

Taurine deficiency is a cause of vigabatrin-induced retinal phototoxicity

OBJECTIVE

Although vigabatrin irreversibly constricts the visual field, it remains a potent therapy for infantile spasms and a third-line drug for refractory epilepsies. In albino animals, this drug induces a reduction in retinal cell function, retinal disorganization, and cone photoreceptor damage. The objective of this study was to investigate the light dependence of the vigabatrin-elicited retinal toxicity and to screen for molecules preventing this secondary effect of vigabatrin.

METHODS

Rats and mice were treated daily with 40 and 3mg vigabatrin, respectively. Retinal cell lesions were demonstrated by assessing cell function with electroretinogram measurements, and quantifying retinal disorganization, gliosis, and cone cell densities.

RESULTS

Vigabatrin-elicited retinal lesions were prevented by maintaining animals in darkness during treatment. Different mechanisms including taurine deficiency were reported to produce such phototoxicity; we therefore measured amino acid plasma levels in vigabatrin-treated animals. Taurine levels were 67% lower in vigabatrin-treated animals than in control animals. Taurine supplementation reduced all components of retinal lesions in both rats and mice. Among six vigabatrin-treated infants, the taurine plasma level was found to be below normal in three patients and undetectable in two patients.

INTERPRETATION

These results indicate that vigabatrin generates a taurine deficiency responsible for its retinal phototoxicity. Future studies will investigate whether cotreatment with taurine and vigabatrin can limit epileptic seizures without inducing the constriction of the visual field. Patients taking vigabatrin could gain immediate benefit from reduced light exposures and dietetic advice on taurine-rich foods.

Properties of gap junction blockers and their behavioural, cognitive and electrophysiological effects: animal and human studies

Gap junctions play an important role in brain physiology. They synchronize neuronal activity and connect glial cells participating in the regulation of brain metabolism and homeostasis. Gap junction blockers (GJBs) include various chemicals that impair gap junction communication, disrupt oscillatory neuronal activity over a wide range of frequencies, and decrease epileptic discharges. The behavioural and clinical effects of GJBs suggest that gap junctions can be involved in the regulation of locomotor activity, arousal, memory, and breathing. Severe neuropsychiatric side effects suggest the involvement of gap junctions in mechanisms of consciousness. Unfortunately, the available GJBs are not selective and can bind to targets other than gap junctions. Other problems in behavioural studies include the possible adverse effects of GJBs, for example, retinal toxicity and hearing disturbances, changes in blood-brain transport, and the metabolism of other drugs. Therefore, it is necessary to design experiments properly to avoid false, misleading or uninterpretable results. We review the pharmacological properties and electrophysiological, behavioural and cognitive effects of the available gap junction blockers, such as carbenoxolone, glycyrrhetinic acid, quinine, quinidine, mefloquine, heptanol, octanol, anandamide, fenamates, 2-APB, several anaesthetics, retinoic acid, oleamide, spermine, aminosulfonates, and sodium propionate. It is concluded that despite a number of different problems, the currently used gap junction blockers could be useful tools in pharmacology and neuroscience.

Current management of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an important cause of epilepsy, autism, and renal and pulmonary disease in children and adults. The clinical course of TSC and the prognosis and appropriate therapy for TSC patients are often different than that for individuals with epilepsy, renal tumors, or interstitial lung disease from other causes. This article reviews the current therapeutic recommendations for medical and surgical management of neurologic, renal, and pulmonary manifestations of TSC. In addition, recent clinical trials using inhibitors of the mammalian target of rapamycin (mTOR) have demonstrated regression of astrocytomas, angiofibromas, and angiomyoliomas, as well as improved pulmonary function in persons with TSC.

Topiramate: a review of its use in the treatment of epilepsy

Topiramate (Topamax) is a structurally novel broad-spectrum antiepileptic drug (AED) with established efficacy as monotherapy or adjunctive therapy in the treatment of adult and paediatric patients with generalised tonic-clonic seizures, partial seizures with or without generalised seizures, and seizures associated with Lennox-Gastaut syndrome. The incidence and severity of many adverse events, including CNS-related events, may be reduced through the use of slow titration to effective and well tolerated dosages. It is associated with few clinically significant interactions with other drugs, is effective when used with other AEDs, is not associated with drug-induced weight gain and, at lower dosages, does not interfere with the effectiveness of oral contraceptives. Therefore, topiramate is a valuable option as monotherapy or adjunctive therapy in the treatment of epilepsy in adult and paediatric patients.