Ocular complications of neurological therapy

Presumed topiramate-induced retinopathy in a 58-year-old woman

We present a case of presumed topiramate-induced retinopathy in a 58-year-old woman who presented with progressive, bilateral visual loss following a 3- to 4-year history of oral topiramate intake for migraine. She reported difficulty with light adaptation, hemeralopia, and color desaturation. Her best-corrected visual acuity was 1/60 (20/1200) in the right eye and 6/18 (20/60) in the left eye, and she performed poorly on Ishihara color plate testing. Anterior segment examination was normal; dilated funduscopy showed mild macular pigmentary changes. Optical coherence tomography revealed subtle thinning and reduced reflectivity of the subfoveal ellipsoid zone and interdigitation zone bilaterally, associated with increased foveal autofluorescence. Humphrey visual field 24-2 revealed central defects. Electrodiagnostic testing showed a reduced and delayed b-wave and a normal a-wave on photopic full-field electroretinogram (ERG), with normal scotopic responses; multifocal ERG revealed reduced responses in the inner 10° in both eyes. She underwent extensive investigations including whole-body computed tomography and positron emission tomography scan, magnetic resonance imaging of the brain, uveitis screening, retinal autoantibody testing, and genetic testing on the retinal dystrophy panel to rule-out other causes for her presentation, all of which were normal or negative.

Ocular Surface Features in Patients with Parkinson Disease on and off Treatment: A Narrative Review

Parkinson disease (PD) is a progressive, neurodegenerative disease of the central nervous system. Visual disturbance is one of the most frequent nonmotor abnormalities referred to by patients suffering from PD at early stages. Furthermore, ocular surface alterations including mainly dry eye and blink reduction represent another common finding in patients with PD. Tears of PD patients show specific alterations related to protein composition, and in vivo confocal microscopy has demonstrated profound changes in different corneal layers in this setting. These changes can be attributed not only to the disease itself, but also to the medications used for its management. In particular, signs of corneal toxicity, both at epithelial and endothelial level, are well described in the literature in PD patients receiving amantadine. Management of PD patients from the ophthalmologist's side requires knowledge of the common, but often underdiagnosed, ocular surface alterations as well as of the signs of drug toxicity. Furthermore, ocular surface biomarkers can be useful for the early diagnosis of PD as well as for monitoring the degree of neural degeneration over time.

Possibilities of monitoring intraocular pressure in children using EASYTON transpalpebral tonometer

Purpose

To compare the effectiveness of transpalpebral scleral tonometry (TPST) and corneal pneumotonometry in children, and assess the discomfort level when measuring intraocular pressure (IOP) by these methods.

Methods

TPST using EASYTON tonometer (Russia) and pneumotonometry using Reichert 7 Non-contact AutoTonometer (USA) have been sequentially performed on 84 eyes (42 children aged 5–14, ave. 9.3 ± 2.7), including 64 myopic eyes (-0.5 to 6.75D), 18 hyperopic eyes (+ 0.75 to + 3.75D), and 2 emmetropic eyes. We assessed tolerance to the procedure on a five-point scale using a questionnaire which listed several criteria: discomfort, presence of pain, fear or anxiety during the procedure, the child's resistance to measurement.

Results

EASYTON tonometry demonstrated repeatability of IOP indicators when measuring the same eye three times sequentially and almost the same IOP level in paired eyes of isometropic children. Pneumotonometry reveals a greater individual data variability and a more pronounced asymmetry of the paired eyes’ indicators. IOP measured using the TPST was 18.3 ± 2.3 mmHg across the whole group, 18.2 ± 2.3 mmHg in myopic, and 18.5 ± 2.3 mmHg in hyperopic children. With pneumotonometry, the corresponding indicators were 17.1 ± 3.9 mmHg, 16.9 ± 3.8 mmHg, and 18.2 ± 4.0 mmHg. The average score for the TPST (4.64 ± 0.60 points) was significantly higher than that for pneumotonometry (3.85 ± 0.90 points) (p < 0.05).

Conclusions

TPST provides broader possibilities for IOP control in pediatric practice, yielding more reliable and accurate results than pneumotonometry, eliminating the influence of corneal thickness and irregularity on the measurement result, and ensuring a calmer behavior and more comfort of children during the procedure.

Olanzapine-Induced Acute Angle Closure

Patient: Male, 59-year-old

Final Diagnosis: Acute angle closure

Symptoms: Pain • red eye

Medication: —

Clinical Procedure: —

Specialty: Ophthalmology

A STROBE-compliant case-control study: Effects of cumulative doses of topical atropine on intraocular pressure and myopia progression

Topical atropine has become a mainstream treatment of myopia throughout East and Southeast Asia, but it is uncertain whether long-term topical atropine therapy induces intraocular pressure (IOP) elevation and subsequent development of glaucoma. We then prospectively examined the effects of long-term atropine treatment on IOP.Our case series collected 186 myopic children who were younger than 16 years of age. Complete ocular examination data, IOP and refractive status measurements beginning in 2008 were collected for all participants. Participants were divided into two groups: 121 children who received atropine therapy at various concentrations were classified as the treated group, whereas 65 children who did not receive atropine therapy were classified as the untreated (reference) group. In the treated group, clinicians prescribed different concentrations of atropine eye drops according to their discretion with regard to the severity of myopia on each visit of the patient. We then calculated the cumulative dose of atropine therapy from 2008 to the patients' last follow-up in 2009. Furthermore, the treated group was then further divided into low- and high-refractive-error groups of nearly equal size for further analysis.There were no significant differences for the baseline refractive errors and IOPs between the treated and untreated groups. Both the low- and high-cumulative atropine dosage subgroups showed significantly lower myopic progression than the untreated group, but there was no significant difference between the two subgroups in terms of different cumulative dosages. All groups, including the untreated group, showed an increase of mean IOP at the last follow-up, but both low- and high-cumulative atropine dosage subgroups experienced a smaller increase of IOP. The mean IOP of all atropine-treated groups showed no significant increase in either low- or high-refractive-error eyes.This study revealed that topical atropine eye drops do not induce ocular hypertension and are effective for slowing the progression of myopia. The treatment effects are not correlated with the cumulative atropine dosages.

Corneal Edema Associated With Systemic Dopaminergic Agents

PURPOSE

To describe the development and resolution of corneal edema in 3 patients who were exposed to compounds that stimulate dopaminergic pathways.

METHODS

We conducted a review of the literature on bilateral corneal edema secondary to amantadine use and report a case series of corneal edema seen in an outpatient ophthalmology specialty clinic, shortly after exposure to agents that enhance dopamine transmission.

RESULTS

Cases 1 and 2 report a 25-year-old man with attention-deficit hyperactivity disorder and a 73-year-old man with Parkinson disease who were placed on dopaminergic medications to treat their conditions. The former was administered methylphenidate and the latter patient was administered ropinirole. Both patients developed corneal edema soon afterward. Case 3 is a 67-year-old man with a recent exposure to resin from Euphorbia resinifera, a cactus in his garden. After cessation of the offending medications and treatment for exposure to resiniferatoxin, the corneal edema progressively resolved and visual acuity returned to baseline in all 3 cases.

CONCLUSIONS

Methylphenidate, ropinirole, and resiniferatoxin have different mechanisms of actions but have a common end point leading to increased dopamine. We believe that these agents are linked with the reversible corneal edema seen in our 3 patients. This strongly correlates with previous studies that have linked amantadine, a drug that blocks dopamine reuptake, to reversible corneal edema.

A Review of Corneal Endotheliitis and Endotheliopathy: Differential Diagnosis, Evaluation, and Treatment

The corneal endothelium plays an integral role in regulating corneal hydration and clarity. Endotheliitis, defined as inflammation of the corneal endothelium, may disrupt endothelial function and cause subsequent visual changes. Corneal endotheliitis is characterized by corneal edema, the presence of keratic precipitates, anterior chamber inflammation, and occasionally limbal injection, neovascularization, and co-existing or superimposed uveitis. The disorder is classified into four subgroups: linear, sectoral, disciform, and diffuse. Its etiology is extensive and, although commonly viral, may be medication-related, procedural, fungal, zoological, environmental, or systemic. Not all cases of endothelial dysfunction leading to corneal edema are inflammatory in nature. Therefore, it is imperative that practitioners consider a broad differential for patients presenting with possible endotheliitis, as well as familiarize themselves with appropriate diagnostic and therapeutic modalities.

Incidence and Types of Pediatric Nystagmus

PURPOSE

To report the incidence, prevalent subtypes, and clinical characteristics of pediatric nystagmus diagnosed over a 30-year period.

DESIGN

Retrospective, population-based study.

METHODS

Using the Rochester Epidemiology Project, we reviewed the medical records of all children (<19 years) diagnosed as residents in Olmsted County, Minnesota, with any form of nystagmus from January 1, 1976, through December 31, 2005.

RESULTS

Seventy-one children were diagnosed during the 30-year period, yielding an annual incidence of 6.72 per 100,000 younger than 19 years (95% confidence interval [CI], 5.15-8.28) Infantile nystagmus, onset by 6 months, comprised 62 (87.3%) of the study patients, corresponding to a birth prevalence of 1 in 821. The median age at diagnosis for the cohort was 12.7 months (range, 0 days to 18.6 years) and 42 subjects (59.2%) were male. The main types of nystagmus, in declining order, were nystagmus associated with retinal/optic nerve disease in 23 (32.4%), idiopathic or congenital motor nystagmus in 22 (31.0%), manifest latent nystagmus or latent nystagmus in 17 (24.0%), and 2 (2.8%) each associated with Chiari malformation, medication use, tumor of the central nervous system, and no diagnosis. Developmental delay was diagnosed in 31 (43.6%), strabismus in 25 (35.2%), and amblyopia in 10 (14.1%). Eighty percent had 20/40 (or equivalent) or better vision at presentation in at least 1 eye.

CONCLUSIONS

This study provides population-based data on incidence and clinical characteristics of childhood nystagmus in North America. Idiopathic and nystagmus associated with retinal/optic nerve disease were the most common presentations, with most patients having good vision. Developmental delay, strabismus, and amblyopia were common in this cohort.

Effects of topical atropine on intraocular pressure and myopia progression: a prospective comparative study

Background

Myopia-related maculopathy is one of the leading causes of blindness in the world. The prevalence of myopia has been reported as high as 90 % in some Asian countries. Therefore, controlling myopia progression is an urgent public issue. The purpose of this study is to evaluate the effects of topical atropine with different concentrations on intraocular pressure measurements and myopia progression in school-aged children in Taiwan.

Methods

Fifty-six myopic children were divided into three groups: 32 children were treated with 0.125 % atropine eyedrop; 12 of them were treated with 0.25 % atropine eye drop and another 12 served as a control group. IOP, auto-refractor and manifest refraction were measured at baseline and every 3 months following treatment for one year.

Results

There were no significant differences for the mean age, gender and baseline IOPs among the three groups. During the follow up period, no significant IOP difference was found among three groups. The change between final and baseline mean IOPs also revealed no significant differences: 0.54 mmHg, −1.28 mmHg, −0.33 mmHg for the 0.125 % atropine, 0.25 % atropine and control groups. The baseline mean spherical equivalent similarly did not differ significantly among groups but the control group showed a significant myopic progression compared to the 0.125 % atropine group 6 months after treatment, and persisted for one year. The change between final and baseline mean spherical equivalents were −0.05 D, 0 D, −1.05 D for the 0.125 % atropine, 0.25 % atropine and control groups, with both atropine-treated groups showing significant myopic retardation compared to the control group.

Conclusions

Topical use of low concentration atropine for one year does not induce ocular hypertension and is effective for retarding myopic progression. However, further large scale studies with longer follow up period is necessary to validate the long term safety and efficacy.

Trial registration

ISRCTN33002849, 2016/01/19, retrospectively registered.

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.

Acquired oculomotor nerve paresis with cyclic spasms in a young woman, a rare subtype of neuromyotonia

BACKGROUND

To report an unusual case of cyclic oculomotor nerve paresis and spasms, which developed 5 years following brain radiotherapy for cerebellar medulloblastoma.

METHODS

Observational case report.

RESULTS

The cyclic oculomotor nerve paresis and spasms resolved in our patient when treated with carbamazepine. However, because of severe photophobia and tearing, carbamazepine had to be discontinued leading to reappearance of the eye movement disorder.

CONCLUSION

Cyclic oculomotor nerve paresis and spasms appear to be a delayed effect of radiotherapy and respond to carbamazepine therapy. It may be a rare form of ocular neuromyotonia.

Predicting chemical ocular toxicity using a combinatorial QSAR approach

Regulatory agencies require testing of chemicals and products to protect workers and consumers from potential eye injury hazards. Animal screening, such as the rabbit Draize test, for potential environmental toxicants is time-consuming and costly. Therefore, virtual screening using computational models to tag potential ocular toxicants is attractive to toxicologists and policy makers. We have developed quantitative structure-activity relationship (QSAR) models for a set of small molecules with animal ocular toxicity data compiled by the National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods. The data set was initially curated by removing duplicates, mixtures, and inorganics. The remaining 75 compounds were used to develop QSAR models. We applied both k nearest neighbor and random forest statistical approaches in combination with Dragon and Molecular Operating Environment descriptors. Developed models were validated on an external set of 34 compounds collected from additional sources. The external correct classification rates (CCR) of all individual models were between 72 and 87%. Furthermore, the consensus model, based on the prediction average of individual models, showed additional improvement (CCR = 0.93). The validated models could be used to screen external chemical libraries and prioritize chemicals for in vivo screening as potential ocular toxicants.

Ocular adverse effects of common psychotropic agents: a review

All psychotropic medications have the potential to induce numerous and diverse unwanted ocular effects. Visual adverse effects can be divided into seven major categories: eyelid and keratoconjunctival disorders; uveal tract disorders; accommodation interference; angle-closure glaucoma; cataract/pigmentary deposits in the lens and cornea; retinopathy; and other disorders. The disorders of the eyelid and of the keratoconjunctiva are mainly related to phenothiazines and lithium. Chlorpromazine, at high dosages, can commonly cause abnormal pigmentation of the eyelids, interpalpebral conjunctiva and cornea. It can also cause a more worrisome but rarer visual impairment, namely corneal oedema. Lithium can rarely lead to a bothersome eye irritation by affecting sodium transport. Uveal tract problems are mainly associated with tricyclic antidepressants (TCAs), typical antipsychotics, topiramate and selective serotonin reuptake inhibitors (SSRIs). TCAs, typical antipsychotics and SSRIs can all cause mydriasis that is often transient and with no major consequences, but that can promote closure of angles in susceptible patients. Topiramate has been frequently associated with a number of significant ocular symptoms including acquired myopia and angle-closure glaucoma. Problems with accommodation are related to TCAs and to low-potency antipsychotics. TCAs cause transient blurred vision in up to one-third of patients. Angle-closure glaucoma is a serious condition that has been mainly associated with TCAs, low-potency antipsychotics, topiramate and, to a lesser extent, SSRIs. When patients with narrow angles are given TCAs, they all appear to experience induction of glaucomatous attacks. Antipsychotics and SSRIs may lead to an added risk of developing angle-closure glaucoma, but only in predisposed eyes. Topiramate can lead to an allergic-type reaction whereby structures of the lens and ciliary body are displaced, which results in angle-closure glaucoma. Cataractous changes can result from antipsychotics, mainly from high dosages of chlorpromazine or thioridazine. These two drugs, when used at high dosages and for prolonged periods, frequently cause lenticular opacifications. Retinopathy has been shown to be related to high dosages of typical antipsychotics, mainly chlorpromazine and thioridazine. The frequency of occurrence of retinal effects seems to be proportional to the total amount of drug used over a long period of time. Other visual problems of special concern are the ocular dystonias, other eye movement disorders, and decreased ability to perceive colours and to discriminate contrast. Ocular dystonias can occur with antipsychotics (especially high-potency ones), carbamazepine (especially in polytherapy), topiramate and, rarely, with SSRIs. Disturbance in various eye movements is frequently seen with benzodiazepines, antiepileptic drugs and lithium. Impairment in the perception of colours and the discrimination of contrasts has been shown to occur not uncommonly with carbamazepine and lorazepam. Thus, typical antipsychotics, TCAs, lithium, benzodiazepines, carbamazepine, topiramate and SSRIs appear to produce most of the currently recognized ocular problems. Psychiatrists, ophthalmologists and patients need to be aware of and prepared for any medication-induced adverse effect. Early prevention and intervention can avoid most of the serious and potentially irreversible ocular toxicities.

Bilateral reversible corneal edema associated with amantadine use

PURPOSE

In this article, we report a case of bilateral severe reversible corneal edema caused by amantadine therapy.

CASE

A 39-year-old women was referred to us for evaluation of bilateral corneal edema. Her past medical history was significant for multiple sclerosis, anorexia, and seizures. She developed painless progressive bilateral loss of vision for the past 6 months. She was evaluated by several ophthalmologists elsewhere who felt that the patient's visual loss was secondary to a nutritional deficiency as opposed to related to multiple sclerosis. She was started on vitamin B-12 medication without improvement in her symptoms. She was then evaluated by neuro-ophthalmology. The examination revealed severe bilateral corneal edema and was referred to our corneal service for further evaluation of her corneal condition. Our examination revealed best corrected visual acuity of 20/400 bilaterally. Corneal thickness was 940 microm in the right eye and 802 microm in the left. Color vision was intact. Conjunctivas were white bilaterally. Cornea evaluation revealed diffuse stromal edema and Descemet's folds and microcystic subepithelial edema with to guttae noted. Anterior chambers were deep and quiet. A specular microscopy revealed significant pleomorphism and polymegathism with an endothelial cell count of 1,504 cells in the right eye and 1,596 in the left eye.

RESULTS

Review of the patient's medical information revealed therapy with amantadine 2 months prior to the appearance of the patient's symptoms as a means to control the patient's tremors. The patient experienced rapid resolution of the corneal edema within the next 2 months after discontinuation of the agent with recovery of best corrected visual acuity of 20/40 in the right eye and 20/30 in the left.

CONCLUSIONS

In cases of unexplained corneal edema and in the absence of any identifiable ocular cause, a review of toxic effects of systemic medications should be performed. Early diagnosis may prevent irreversible endothelial damage. Amantadine can cause endothelial failure and needs to be considered as part of the differential diagnosis of corneal edema.

Corneal endothelial dysfunction associated with amantadine toxicity

PURPOSE

To describe bilateral corneal endothelial dysfunction in a patient with Parkinson disease who was treated with long-term amantadine.

METHODS

We employed an A-B-A-B single-subject research design that included clinical history, clinical findings, photographic images, and specular microscopic findings of ocular changes.

RESULTS

A 52-year-old woman with Parkinson disease who had taken amantadine for 6 years had bilateral corneal edema for 2 months at baseline. After cessation of amantadine, the edema resolved, and the endothelial cell densities were <or=600/mm. Corneal edema recurred when the administration of amantadine was resumed. Therefore, amantadine was permanently discontinued and the cornea cleared again.

CONCLUSIONS

Amantadine can cause reversible corneal edema but can irreversibly reduce the density of endothelial cells.

Zebrafish based assays for the assessment of cardiac, visual and gut function--potential safety screens for early drug discovery

INTRODUCTION

Safety pharmacology is integral to the non-clinical safety assessment of new chemical entities prior to first administration to humans. The zebrafish is a well established model organism that has been shown to be relevant to the study of human diseases. The potential role of zebrafish in safety pharmacology was evaluated using reference compounds in three models assessing cardiac, visual and intestinal function.

METHODS

Compound toxicity was first established in zebrafish to determine the non toxic concentration of a blinded set of 16 compounds. In the cardiac assay, zebrafish larvae at 3 days post fertilisation (d.p.f.) were exposed to compounds for 3 h before measurement of the atrial and ventricular rates. To investigate visual function, the optomotor response was assessed in 8 d.p.f. larvae following a 5 day compound exposure. In the intestinal function assay, the number of gut contractions was measured in 7 d.p.f. larvae after a 1 h compound exposure. Finally, compound uptake was determined for 9 of the 16 compounds to measure the concentration of compound absorbed by the zebrafish larvae.

RESULTS

Seven compounds out of nine produced an expected effect that was statistically significant in the cardiac and visual functions assays. In the gut contraction assay, six out of ten compounds showed a statistically significant effect that was also the expected result whilst two displayed anticipated but non-significant effects. The compound uptake method was used to determine larval tissue concentrations and allowed the identification of false negatives when compound was poorly absorbed into the zebrafish.

DISCUSSION

Overall, results generated in three zebrafish larvae assays demonstrated a good correlation between the effects of compounds in zebrafish and the data available from other in vivo models or known clinical adverse effects. These results suggest that for the cardiac, intestinal and visual function, zebrafish assays have the potential to predict adverse drug effects and supports their possible role in early safety assessment of novel compounds.

Neuro-ophthalmology

Neuro-ophthalmologic disorders arise from all areas of the neuro-ophthalmologic tract. They may be expressed simply as loss of vision or double vision, or as complex syndromes or systemic illnesses, depending on the location and type of lesion. Problems may occur anywhere along the visual pathway, including the brainstem, cavernous sinus, subarachnoid space, and orbital apex, and may affect adjacent structures also. A firm understanding of the neuroanatomy and neurophysiology of the eye is essential to correct diagnosis.

Medical management of brain tumor patients

Brain tumors can present challenging medical problems. Seizures, peritumoral edema, venous thromboembolism, fatigue, and cognitive dysfunction can complicate the treatment of patients who have primary or metastatic brain tumors. Effective medical management results in decreased morbidity and mortality and improved quality of life for affected patients.

Decreased cortical inhibition and yet cerebellar pathology in ‘familial cortical myoclonic tremor with epilepsy’

Cortical hyperexcitability is a feature of "familial cortical myoclonic tremor with epilepsy" (FCMTE). However, neuropathological investigations in a single FCMTE patient showed isolated cerebellar pathology. Pathological investigations in a second FCMTE patient, reported here, confirmed cerebellar Purkinje cell degeneration and a normal sensorimotor cortex. Subsequently, we sought to explore the nature of cerebellar and motor system pathophysiology in FCMTE. Eye movement recordings and transcranial magnetic stimulation performed in six related FCMTE patients showed impaired saccades and smooth pursuit and downbeat nystagmus upon hyperventilation, as in patients with spinocerebellar ataxia type 6. In FCMTE patients short-interval intracortical inhibition (SICI) was significantly reduced. Resting motor threshold, recruitment curve, silent period, and intracortical facilitation were normal. The neuropathological and ocular motor abnormalities indicate cerebellar involvement in FCMTE patients. Decreased SICI is compatible with intracortical GABA(A)-ergic dysfunction. Cerebellar and intracortical functional changes could result from a common mechanism such as a channelopathy. Alternatively, decreased cortical inhibition may be caused by dysfunction of the cerebello-thalamo-cortical loop as a result of primary cerebellar pathology.

Les effets indésirables des antituberculeux: épidémiologie, mécanismes et conduite à tenir

Tuberculosis, what ever its localization, is an infectious disease which can be totally cured by combining antitubercular drugs. Current therapeutic regimens with isoniazid, rifampicin, pyrazinamide, ethambutol, and streptomycin have proved successful in treating tuberculosis. However, they are associated to a high rate of adverse effects that can lead to therapeutic failure. Understanding the nature and the severity of these adverse effects allows for their appropriate management. Toxic neuropathy and hepatitis are the most common adverse reactions to isoniazid. Rifampicin is generally well tolerated but some severe immuno-allergic reactions may occur in case of intermittent regimen. Pyrazinamide-induced liver injury is rare but sometimes lethal. Joint affections, usually due to hyperuricemia, are more frequent but easily manageable. The major adverse effect related to ethambutol is ocular optic neuropathy. It occurs dose-dependently and can be irreversible. Finally, administration of streptomycin is potentially associated with renal and cochleo-vestibular toxicity that might be milder than when induced by other aminoglycosides. The management of antituberculosis-induced adverse effects depends on parameters related to the adverse effect itself and to the administrated drug.

Vigabatrin transport across the human intestinal epithelial (Caco-2) brush-border membrane is via the H+ -coupled amino-acid transporter hPAT1

The aim of this investigation was to determine if the human proton-coupled amino-acid transporter 1 (hPAT1 or SLC36A1) is responsible for the intestinal uptake of the orally-administered antiepileptic agent 4-amino-5-hexanoic acid (vigabatrin). The Caco-2 cell line was used as a model of the human small intestinal epithelium. Competition experiments demonstrate that [3H]GABA uptake across the apical membrane was inhibited by vigabatrin and the GABA analogues trans-4-aminocrotonic acid (TACA) and guvacine, whereas 1-(aminomethyl)cyclohexaneacetic acid (gabapentin) had no affect. Experiments with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF)-loaded Caco-2 cells demonstrate that apical exposure to vigabatrin and TACA induce comparable levels of intracellular acidification (due to H+/amino-acid symport) to that generated by GABA, suggesting that they are substrates for a H+ -coupled absorptive transporter such as hPAT1. In hPAT1 and mPAT1-expressing Xenopus laevis oocytes [3H]GABA uptake was inhibited by vigabatrin, TACA and guvacine, whereas gabapentin failed to inhibit [3H]GABA uptake. In Na+ -free conditions, vigabatrin and TACA evoked similar current responses (due to H+/amino-acid symport) in hPAT1-expressing oocytes under voltage-clamp conditions to that induced by GABA (whereas no current was observed in water-injected oocytes) consistent with the ability of these GABA analogues to inhibit [3H]GABA uptake. This study demonstrates that hPAT1 is the carrier responsible for the uptake of vigabatrin across the brush-border membrane of the small intestine and emphasises the therapeutic potential of hPAT1 as a delivery route for orally administered, clinically significant GABA-related compounds.

Localizing forms of nystagmus: Symptoms, diagnosis, and treatment

Nystagmus is a rhythmic oscillation of the eyes that may be acquired or congenital. The symptoms of acquired nystagmus include blurred vision and oscillopsia. Most patients with congenital nystagmus do not have oscillopsia symptoms. Several forms of nystagmus have localizing value and any neuroimaging should be directed to the topographic localization suggested by the morphology of the nystagmus and any accompanying localizing signs. Several optical, medical, and surgical treatments have been used with some success in specific forms of nystagmus.