Neuro-ophthalmology

Bouffard MA, Nathavitharana RR, Yassa DS, Torun N. Re-Treatment With Ethambutol After Toxic Optic Neuropathy. J Neuroophthalmol 2017;37(1):40-42.Abstract

There are no data in the literature regarding the safety of re-treatment with ethambutol for recurrent mycobacterial infection after prior ethambutol-induced optic neuropathy. We describe a patient who developed optic neuropathy attributed to ethambutol, recovered fully after drug withdrawal, and tolerated a 14-month long re-treatment 10 years later without developing recurrent optic neuropathy.

Cestari DM, Gaier ED, Bouzika P, Blachley TS, De Lott LB, Rizzo JF, Wiggs JL, Kang JH, Pasquale LR, Stein JD. Demographic, Systemic, and Ocular Factors Associated with Nonarteritic Anterior Ischemic Optic Neuropathy. Ophthalmology 2016;123(12):2446-2455.Abstract

OBJECTIVE: Nonarteritic anterior ischemic optic neuropathy (NAION) is a devastating ocular condition causing permanent vision loss. Little is known about risk factors for developing this disease. We assessed demographic, systemic, and ocular factors associated with NAION. DESIGN: Retrospective longitudinal cohort study. PARTICIPANTS: Beneficiaries between 40 and 75 years old without NAION at baseline enrolled in a large U.S. managed care network. METHODS: Enrollees were monitored continuously for ≥2 years between 2001 and 2014 to identify those newly diagnosed with NAION (International Classification of Diseases, 9th Revision, Clinical Modification [ICD-9-CM] code 377.41). All persons were under ophthalmic surveillance and all cases had ≥1 confirmatory ICD-9-CM code for NAION during follow-up. MAIN OUTCOME MEASURES: Multivariable Cox regression modeling was used to generate hazard ratios (HRs) with 95% confidence intervals (CIs) to describe the statistical relationship between selected demographic characteristics, systemic and ocular conditions, and the hazard of developing NAION. RESULTS: Of 1 381 477 eligible enrollees, 977 (0.1%) developed NAION during a mean ± standard deviation (SD) follow-up of 7.8±3.1 years. The mean ± SD age for NAION cases at the index date was 64.0±9.2 years vs. 58.4±9.4 years for the remainder of the beneficiaries. After adjustment for confounding factors, each additional year older was associated with a 2% increased hazard of NAION (HR = 1.02; 95% CI: 1.01-1.03). Female subjects had a 36% decreased hazard of developing NAION (HR = 0.64; 95% CI: 0.55-0.74) compared with male subjects. Compared with whites, Latinos had a 46% decreased hazard of developing NAION (HR = 0.54; 95% CI: 0.36-0.82), whereas African ancestry was not significantly associated with NAION (HR = 0.91; 95% CI: 0.72-1.15). Systemic diseases associated with NAION included hypertension (HR = 1.62; 95% CI: 1.26-2.07) and hypercoagulable states (HR = 2.46; 95% CI: 1.51-4.00). Although diabetes mellitus (DM) was not significantly associated with NAION compared with those without DM (P = 0.45), patients with end-organ involvement from DM had a 27% increased hazard of NAION relative to those with uncomplicated DM (HR = 1.27; 95% CI: 1.01-1.59). Ocular diseases associated with NAION were age-related macular degeneration (HR = 1.29; 95% CI: 1.08-1.54) and retinal vein occlusion (HR = 3.94; 95% CI: 3.11-4.99). CONCLUSIONS: Our study identified several modifiable risk factors that may be associated with NAION. Should future studies confirm these findings, they may offer opportunities to prevent or treat this debilitating condition.

Chun BY, Rizzo JF. Dominant optic atrophy: updates on the pathophysiology and clinical manifestations of the optic atrophy 1 mutation. Curr Opin Ophthalmol 2016;Abstract

PURPOSE OF REVIEW: Review recent advances in clinical and experimental studies of dominant optic atrophy (DOA) to better understand the complexities of pathophysiology caused by the optic atrophy 1 (OPA1) mutation. RECENT FINDINGS: DOA is the most commonly diagnosed inherited optic atrophy, causing progressive bilateral visual loss that begins early in life. During the past 25 years, there has been substantial progress in the understanding of the clinical, genetic, and pathophysiological basis of this disease. The histopathological hallmark of DOA is the primary degeneration of retinal ganglion cells, preferentially in the papillomacular bundle, which results temporal optic disc pallor and cecocentral scotomata in patients with DOA. Loss of OPA1 protein function by OPA1 gene mutations causes mitochondrial dysfunction because of the loss of mitochondrial fusion, impaired mitochondrial oxidative phosphorylation, increases in reactive oxygen species, and altered calcium homeostasis. These factors lead to apoptosis of retinal ganglion cells by a haploinsufficiency mechanism. SUMMARY: Improved understanding of the pathophysiology of DOA provides insights that can be used to develop therapeutic approaches to the DOA.

Gaier ED, Torun N. The enigma of nonarteritic anterior ischemic optic neuropathy: an update for the comprehensive ophthalmologist. Curr Opin Ophthalmol 2016;Abstract

PURPOSE OF REVIEW: Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common cause of acute optic nerve injury, and frequently presents to comprehensive ophthalmologists. We review the typical and atypical clinical features and current literature on various treatment modalities for NAION. RECENT FINDINGS: The epidemiology and clinical presentation of this disease can be variable, making a definitive diagnosis difficult in many cases. In addition, the differential diagnoses for this disorder, although comprising much less prevalent entities, are quite broad and can have substantial systemic implications if these alternatives go unrecognized. NAION has many systemic associations and comorbidities that deserve inquiry when the diagnosis is made. There are currently no widely accepted, evidence-based treatments for NAION. All recommendations made to patients to reduce their risk of sequential eye involvement, including avoidance of potential nocturnal hypotension, erectile dysfunction medication, and treatment of obstructive sleep apnea, have theoretical bases. SUMMARY: NAION is a common cause of acute vision loss in adult and older patients, and thus, comprehensive ophthalmologists need to be able to diagnose and appropriately manage this disorder. We anticipate fruitful results from current and future trials aimed at neuroprotection in the affected eye and prevention of sequential eye involvement.

Gómez-Laberge C, Smolyanskaya A, Nassi JJ, Kreiman G, Born RT. Bottom-Up and Top-Down Input Augment the Variability of Cortical Neurons. Neuron 2016;91(3):540-7.Abstract

Neurons in the cerebral cortex respond inconsistently to a repeated sensory stimulus, yet they underlie our stable sensory experiences. Although the nature of this variability is unknown, its ubiquity has encouraged the general view that each cell produces random spike patterns that noisily represent its response rate. In contrast, here we show that reversibly inactivating distant sources of either bottom-up or top-down input to cortical visual areas in the alert primate reduces both the spike train irregularity and the trial-to-trial variability of single neurons. A simple model in which a fraction of the pre-synaptic input is silenced can reproduce this reduction in variability, provided that there exist temporal correlations primarily within, but not between, excitatory and inhibitory input pools. A large component of the variability of cortical neurons may therefore arise from synchronous input produced by signals arriving from multiple sources.

Vodopivec I, Cho TA, Rizzo JF, Frosch MP, Sims KB. Mitochondrial Encephalopathy and Optic Neuropathy Due to m.10158 MT-ND3 Complex I Mutation Presenting in an Adult Patient: Case Report and Review of the Literature. Neurologist 2016;21(4):61-5.Abstract

INTRODUCTION: Establishing a diagnosis of mitochondrial disease in adults remains a clinician's challenge. We report a case of syndrome reminiscent of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) in an adult patient who carries m.10158T>C mutation in complex I respiratory chain gene MT-ND3 (mitochondrially encoded NADH dehydrogenase 3). CASE REPORT: This 26-year-old man from Thailand presented with new-onset headaches, seizures, stroke-like episodes, and poor vision due to optic neuropathy and cortical blindness. Instead of expected mutations in the mitochondrial tRNA gene that are frequently associated with MELAS, the mutation in MT-ND3 with variable tissue heteroplasmy (blood 5.3%, muscle 89.5%) was demonstrated. The patient's clinical features, blood biomarkers, neuroimaging findings, muscle biopsy with histochemical and functional in vitro analysis, and genetic studies were analyzed and compared with all previously reported ND3 disease cases. CONCLUSIONS: ND3 disease due to m.10158T>C mutation was previously described only in patients with Leigh or Leigh-like syndrome. Our findings thus indicate that ND3 disease can manifest with atypical phenotype in adults. The diagnosis of mitochondrial disease caused by other than typical MELAS-associated mutations in adults with stroke-like episodes, headaches, and seizures should be considered. An analysis of tissue other than blood, which is more likely to harbor a tissue-specific mitochondrial DNA mutation at a measurable level, may be necessary for diagnosis.

Davies EC, Jakobiec FA, Stagner AM, Rizzo JF. An Atypical Case of Lymphocytic Panhypophysitis in a Pregnant Woman. J Neuroophthalmol 2016;36(3):313-6.Abstract

We describe a case of lymphocytic panhypophysitis (LPH) in a 30-year-old woman presenting with throbbing headaches and vision changes during her third trimester. LPH is the rarest subclassification of lymphocytic hypophysitis; it is typically found in males and has not previously been associated with pregnancy. Anterior and posterior pituitary deficits together with headaches should raise a high degree of suspicion regarding the possibility of LPH. The atypical magnetic resonance imaging finding of a heterogeneous pituitary mass additionally raised concern about pituitary apoplexy. Tissue from a transsphenoidal biopsy permitted diagnosis of lymphocytic hypophysitis. There was infiltration of the pituitary gland by small B and T lymphocytes. Resolution of the visual symptoms occurred after the biopsy and treatment with intravenous steroids.

Gaier ED, Boudreault K, Rizzo JF, Falardeau J, Cestari DM. Atypical Optic Neuritis. Curr Neurol Neurosci Rep 2015;15(12):76.Abstract

Classic demyelinative optic neuritis is associated with multiple sclerosis and typically carries a good prognosis for visual recovery. This disorder is well characterized with respect to its presentation and clinical features by baseline data obtained through the optic neuritis treatment trial and numerous other studies. Atypical optic neuritis entails clinical manifestations that deviate from this classic pattern of features. Clinical signs and symptoms that deviate from the typical presentation should prompt consideration of less common etiologies. Atypical features to consider include lack of pain, simultaneous or near-simultaneous onset, lack of response to or relapse upon tapering from corticosteroids, or optic nerve head or peripapillary hemorrhages. The most important alternative etiologies to consider and the steps towards their respective diagnostic evaluations are suggested for these atypical features.

Meyer Zu Horste G, Derksen A, Stassart R, Szepanowski F, Thanos M, Stettner M, Boettcher C, Lehmann HC, Hartung H-P, Kieseier BC. Neuronal ADAM10 Promotes Outgrowth of Small-Caliber Myelinated Axons in the Peripheral Nervous System. J Neuropathol Exp Neurol 2015;74(11):1077-85.Abstract

The regulation of myelination and axonal outgrowth in the peripheral nervous system is controlled by a complex signaling network involving various signaling pathways. Members of the A Disintegrin And Metalloproteinase (ADAM) family are membrane-anchored proteinases with both proteolytic and disintegrin characteristics that modulate the function of signaling molecules. One family member, ADAM17, is known to influence myelination by cleaving and thus regulating one of the key signals, neuregulin-1, which controls peripheral nervous system myelination. A similar function for ADAM10 had been suggested by previous in vitro studies. Here, we assessed whether ADAM10 exerts a similar function in vivo and deleted ADAM10 in a cell type-specific manner in either neurons or Schwann cells. We found that ADAM10 is not required in either Schwann cells or neurons for normal myelination during development or for remyelination after injury. Instead, ADAM10 is required specifically in neurons for the outgrowth of myelinated small-fiber axons in vitro and after injury in vivo. Thus, we report for the first time a neuron-intrinsic function of ADAM10 in axonal regeneration that is distinct from that of the related protein family member ADAM17 and that may have implications for targeting ADAM function in nervous system diseases.

Karki P, Kim C, Smith K, Son D-S, Aschner M, Lee E. Transcriptional Regulation of the Astrocytic Excitatory Amino Acid Transporter 1 (EAAT1) via NF-κB and Yin Yang 1 (YY1). J Biol Chem 2015;290(39):23725-37.Abstract

Astrocytic glutamate transporter excitatory amino acid transporter (EAAT) 1, also known as glutamate aspartate transporter (GLAST) in rodents, is one of two glial glutamate transporters that are responsible for removing excess glutamate from synaptic clefts to prevent excitotoxic neuronal death. Despite its important role in neurophysiological functions, the molecular mechanisms of EAAT1 regulation at the transcriptional level remain to be established. Here, we report that NF-κB is a main positive transcription factor for EAAT1, supported by the following: 1) EAAT1 contains two consensus sites for NF-κB, 2) mutation of NF-κB binding sites decreased EAAT1 promoter activity, and 3) activation of NF-κB increased, whereas inhibition of NF-κB decreased EAAT1 promoter activity and mRNA/protein levels. EGF increased EAAT1 mRNA/protein levels and glutamate uptake via NF-κB. The transcription factor yin yang 1 (YY1) plays a role as a critical negative regulator of EAAT1, supported by the following: 1) the EAAT1 promoter contains multiple consensus sites for YY1, 2) overexpression of YY1 decreased EAAT1 promoter activity and mRNA/protein levels, and 3) knockdown of YY1 increased EAAT1 promoter activity and mRNA/protein levels. Manganese decreased EAAT1 expression via YY1. Epigenetic modifiers histone deacetylases (HDACs) served as co-repressors of YY1 to further decrease EAAT1 promoter activity, whereas inhibition of HDACs reversed manganese-induced decrease of EAAT1 expression. Taken together, our findings suggest that NF-κB is a critical positive regulator of EAAT1, mediating the stimulatory effects of EGF, whereas YY1 is a negative regulator of EAAT1 with HDACs as co-repressors, mediating the inhibitory effects of manganese on EAAT1 regulation.

Peeler CE, De Lott LB, Nagia L, Lemos J, Eggenberger ER, Cornblath WT. Clinical Utility of Acetylcholine Receptor Antibody Testing in Ocular Myasthenia Gravis. JAMA Neurol 2015;72(10):1170-4.Abstract

IMPORTANCE: The sensitivity of acetylcholine receptor (AChR) antibody testing is thought to be lower in ocular myasthenia gravis (OMG) compared with generalized disease, although estimates in small-scale studies vary. There is little information in the literature about the implications of AChR antibody levels and progression from OMG to generalized myasthenia gravis. OBJECTIVES: To test the hypothesis that serum AChR antibody testing is more sensitive in OMG than previously reported and to examine the association between AChR antibody levels and progression from OMG to generalized myasthenia gravis. DESIGN, SETTING, AND PARTICIPANTS: A retrospective, observational cohort study was conducted of 223 patients (mean [SD] age, 59.2 [16.4] years; 139 [62.3%] male) diagnosed with OMG between July 1, 1986, and May 31, 2013, at 2 large, academic medical centers. MAIN OUTCOMES AND MEASURES: Baseline characteristics, OMG symptoms, results of AChR antibody testing, and progression time to generalized myasthenia gravis (if this occurred) were recorded for each patient. Multiple logistic regression was used to measure the association between all clinical variables and antibody result. Kaplan-Meier survival analysis was performed to examine time to generalization. RESULTS: Among the 223 participants, AChR antibody testing results were positive in 158 participants (70.9%). In an adjusted model, increased age at diagnosis (odds ratio [OR], 1.03; 95% CI, 1.01-1.04; P = .007) and progression to generalized myasthenia gravis (OR, 2.92; 95% CI, 1.18-7.26; P = .02) were significantly associated with positive antibody test results. Women were less likely to have a positive antibody test result (OR, 0.36; 95% CI, 0.19-0.68; P = .002). Patients who developed symptoms of generalized myasthenia gravis had a significantly higher mean (SD) antibody level than those who did not develop symptoms of generalized myasthenia gravis (12.7 [16.5] nmol/L vs 4.2 [7.9] nmol/L; P = .002). CONCLUSIONS AND RELEVANCE: We demonstrate a higher sensitivity of AChR antibody testing than previously reported in the largest cohort of patients with OMG available to date. Older age, male sex, and progression to generalized myasthenia gravis were significantly associated with a positive antibody test result. In addition, to our knowledge, this is the first report of an association between high AChR antibody levels and progression from OMG to generalized disease.

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