Optical coherence tomography in neuromyelitis optica spectrum disorders: potential advantages for individualized monitoring of progression and therapy

Retinal Changes in Double-Antibody Seronegative Neuromyelitis Optica Spectrum Disorders

BACKGROUND AND OBJECTIVES

To systematically describe the clinical picture of double-antibody seronegative neuromyelitis optica spectrum disorders (DN-NMOSD) with specific emphasis on retinal involvement.

METHODS

Cross-sectional data of 25 people with DN-NMOSD (48 eyes) with and without a history of optic neuritis (ON) were included in this study along with data from 25 people with aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorder (AQP4-NMOSD, 46 eyes) and from 25 healthy controls (HCs, 49 eyes) for comparison. All groups were matched for age and sex and included from the collaborative retrospective study of retinal optical coherence tomography (OCT) in neuromyelitis optica (CROCTINO). Participants underwent OCT with central postprocessing and local neurologic examination and antibody testing. Retinal neurodegeneration was quantified as peripapillary retinal nerve fiber layer thickness (pRNFL) and combined ganglion cell and inner plexiform layer thickness (GCIPL).

RESULTS

This DN-NMOSD cohort had a history of [median (inter-quartile range)] 6 (5; 9) attacks within their 5 ± 4 years since onset. Myelitis and ON were the most common attack types. In DN-NMOSD eyes after ON, pRNFL (p < 0.001) and GCIPL (p = 0.023) were thinner compared with eyes of HCs. Even after only one ON episode, DN-NMOSD eyes already had considerable neuroaxonal loss compared with HCs. In DN-NMOSD eyes without a history of ON, pRNFL (p = 0.027) and GCIPL (p = 0.022) were also reduced compared with eyes of HCs. However, there was no difference in pRNFL and GCIPL between DN-NMOSD and AQP4-NMOSD for the whole group and for subsets with a history of ON and without a history of ON-as well as between variances of retinal layer thicknesses.

DISCUSSION

DN-NMOSD is characterized by severe retinal damage after ON and attack-independent retinal neurodegeneration. Most of the damage occurs during the first ON episode, which highlights the need for better diagnostic markers in DN-NMOSD to facilitate an earlier diagnosis as well as for effective and early treatments. In this study, people with DN-NMOSD presented with homogeneous clinical and imaging findings potentially suggesting a common retinal pathology in these patients.

Comparison of ocular changes in multiple sclerosis and neuromyelitis optica spectrum disorder patients

Purpose

To explore ocular changes in patients with MS and NMOSD via SD-OCT and PVEP analysis.

Methods

From August 2020 to July 2021, 82 patients (164 eyes) diagnosed with MS, 59 patients (118 eyes) diagnosed with NMOSD and 50 healthy controls (100 eyes) were retrospectively selected. SD-OCT and PVEP were performed to compare retinal nerve fibre layer (RNFL) thickness around the optic disc, ganglion cell inner plexiform layer (GCIPL) thickness in the macula and P100 latency and amplitude between the disease groups and the control group.

Results

In the NMOSD and MS groups, the thickness of the GCIPL quadrants in eyes with optic neuritis was thinner than that in eyes without optic neuritis, and the amplitude of the P100 wave decreased. In addition, in eyes with optic neuritis, patients with NMOSD have thinner RNFL thicknesses in the temporal and superior quadrants than patients with MS, and the thickness of the GCIPL is thinner in each region. In eyes without optic neuritis, patients with MS have thinner nasal RNFL than do those with NMOSD.

Conclusion

SD-OCT and VEP may be useful for monitoring and distinguishing pathological changes in MS and NMOSD patients.

Delimiting MOGAD as a disease entity using translational imaging

The first formal consensus diagnostic criteria for myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) were recently proposed. Yet, the distinction of MOGAD-defining characteristics from characteristics of its important differential diagnoses such as multiple sclerosis (MS) and aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorder (NMOSD) is still obstructed. In preclinical research, MOG antibody-based animal models were used for decades to derive knowledge about MS. In clinical research, people with MOGAD have been combined into cohorts with other diagnoses. Thus, it remains unclear to which extent the generated knowledge is specifically applicable to MOGAD. Translational research can contribute to identifying MOGAD characteristic features by establishing imaging methods and outcome parameters on proven pathophysiological grounds. This article reviews suitable animal models for translational MOGAD research and the current state and prospect of translational imaging in MOGAD.

Modeling MOG Antibody-Associated Disorder and Neuromyelitis Optica Spectrum Disorder in Animal Models: Visual System Manifestations

BACKGROUND AND OBJECTIVES

Mechanisms of visual impairment in aquaporin 4 antibody (AQP4-IgG) seropositive neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein antibody (MOG-IgG)-associated disorder (MOGAD) are incompletely understood. The respective impact of optic nerve demyelination and primary and secondary retinal neurodegeneration are yet to be investigated in animal models.

METHODS

Active MOG35-55 experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6Jrj mice, and monoclonal MOG-IgG (8-18C5, murine), recombinant AQP4-IgG (rAb-53, human), or isotype-matched control IgG (Iso-IgG, human) was administered 10 days postimmunization. Mobility impairment was scored daily. Visual acuity by optomotor reflex and ganglion cell complex thickness (GCC, 3 innermost retinal layers) by optical coherence tomography (OCT) were longitudinally assessed. Histopathology of optic nerve and retina was investigated during presymptomatic, acute, and chronic disease phases for immune cells, demyelination, complement deposition, natural killer (NK) cell, AQP4, and astrocyte involvement, retinal ganglion cells (RGCs), and Müller cell activation. Groups were compared by nonparametric tests with a p value <0.05 indicating statistical significance.

RESULTS

Visual acuity decreased from baseline to chronic phase in MOG-IgG (mean ± standard error of the mean: 0.54 ± 0.01 to 0.46 ± 0.02 cycles/degree, p < 0.05) and AQP4-IgG EAE (0.54 ± 0.01 to 0.43 ± 0.02, cycles/degree, p < 0.05). Immune cell infiltration of optic nerves started in presymptomatic AQP4-IgG, but not in MOG-IgG EAE (5.85 ± 2.26 vs 0.13 ± 0.10 macrophages/region of interest [ROI] and 1.88 ± 0.63 vs 0.15 ± 0.06 T cells/ROI, both p < 0.05). Few NK cells, no complement deposition, and stable glial fibrillary acid protein and AQP4 fluorescence intensity characterized all EAE optic nerves. Lower GCC thickness (Spearman correlation coefficient r = -0.44, p < 0.05) and RGC counts (r = -0.47, p < 0.05) correlated with higher mobility impairment. RGCs decreased from presymptomatic to chronic disease phase in MOG-IgG (1,705 ± 51 vs 1,412 ± 45, p < 0.05) and AQP4-IgG EAE (1,758 ± 14 vs 1,526 ± 48, p < 0.01). Müller cell activation was not observed in either model.

DISCUSSION

In a multimodal longitudinal characterization of visual outcome in animal models of MOGAD and NMOSD, differential retinal injury and optic nerve involvement were not conclusively clarified. Yet optic nerve inflammation was earlier in AQP4-IgG-associated pathophysiology. Retinal atrophy determined by GCC thickness (OCT) and RGC counts correlating with mobility impairment in the chronic phase of MOG-IgG and AQP4-IgG EAE may serve as a generalizable marker of neurodegeneration.

Update on the diagnosis and treatment of neuromyelits optica spectrum disorders (NMOSD) - revised recommendations of the Neuromyelitis Optica Study Group (NEMOS). Part I: Diagnosis and differential diagnosis

The term 'neuromyelitis optica spectrum disorders' (NMOSD) is used as an umbrella term that refers to aquaporin-4 immunoglobulin G (AQP4-IgG)-positive neuromyelitis optica (NMO) and its formes frustes and to a number of closely related clinical syndromes without AQP4-IgG. NMOSD were originally considered subvariants of multiple sclerosis (MS) but are now widely recognized as disorders in their own right that are distinct from MS with regard to immunopathogenesis, clinical presentation, optimum treatment, and prognosis. In part 1 of this two-part article series, which ties in with our 2014 recommendations, the neuromyelitis optica study group (NEMOS) gives updated recommendations on the diagnosis and differential diagnosis of NMOSD. A key focus is on differentiating NMOSD from MS and from myelin oligodendrocyte glycoprotein antibody-associated encephalomyelitis (MOG-EM; also termed MOG antibody-associated disease, MOGAD), which shares significant similarity with NMOSD with regard to clinical and, partly, radiological presentation, but is a pathogenetically distinct disease. In part 2, we provide updated recommendations on the treatment of NMOSD, covering all newly approved drugs as well as established treatment options.

Optical coherence tomography angiography measurements in multiple sclerosis: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Recent literature on multiple sclerosis (MS) demonstrates the growing implementation of optical coherence tomography-angiography (OCT-A) to discover potential qualitative and quantitative changes in the retina and optic nerve. In this review, we analyze OCT-A studies in patients with MS and examine its utility as a surrogate or precursor to changes in central nervous system tissue.

METHODS

PubMed and EMBASE were systematically searched to identify articles that applied OCT-A to evaluate the retinal microvasculature measurements in patients with MS. Quantitative data synthesis was performed on all measurements which were evaluated in at least two unique studies with the same OCT-A devices, software, and study population compared to controls. A fixed-effects or random-effects model was applied for the meta-analysis based on the heterogeneity level.

RESULTS

The study selection process yielded the inclusion of 18 studies with a total of 1552 evaluated eyes in 673 MS-associated optic neuritis (MSON) eyes, 741 MS without optic neuritis (MSNON eyes), and 138 eyes without specification for the presence of optic neuritis (ON) in addition to 1107 healthy control (HC) eyes. Results indicated that MS cases had significantly decreased whole image superficial capillary plexus (SCP) vessel density when compared to healthy control subjects in the analyses conducted on Optovue and Topcon studies (both P < 0.0001). Likewise, the whole image vessel densities of deep capillary plexus (DCP) and radial peripapillary capillary (RPC) were significantly lower in MS cases compared to HC (all P < 0.05). Regarding optic disc area quadrants, MSON eyes had significantly decreased mean RPC vessel density compared to MSNON eyes in all quadrants except for the inferior (all P < 0.05). Results of the analysis of studies that used prototype Axsun machine revealed that MSON and MSNON eyes both had significantly lower ONH flow index compared to HC (both P < 0.0001).

CONCLUSIONS

This systematic review and meta-analysis of the studies reporting OCT-A measurements of people with MS confirmed the tendency of MS eyes to exhibit reduced vessel density in the macular and optic disc areas, mainly in SCP, DCP, and RPC vessel densities.

Diagnostic value of intereye difference metrics for optic neuritis in aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorders

BACKGROUND

The novel optic neuritis (ON) diagnostic criteria include intereye differences (IED) of optical coherence tomography (OCT) parameters. IED has proven valuable for ON diagnosis in multiple sclerosis but has not been evaluated in aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorders (AQP4+NMOSD). We evaluated the diagnostic accuracy of intereye absolute (IEAD) and percentage difference (IEPD) in AQP4+NMOSD after unilateral ON >6 months before OCT as compared with healthy controls (HC).

METHODS

Twenty-eight AQP4+NMOSD after unilateral ON (NMOSD-ON), 62 HC and 45 AQP4+NMOSD without ON history (NMOSD-NON) were recruited by 13 centres as part of the international Collaborative Retrospective Study on retinal OCT in Neuromyelitis Optica study. Mean thickness of peripapillary retinal nerve fibre layer (pRNFL) and macular ganglion cell and inner plexiform layer (GCIPL) were quantified by Spectralis spectral domain OCT. Threshold values of the ON diagnostic criteria (pRNFL: IEAD 5 µm, IEPD 5%; GCIPL: IEAD: 4 µm, IEPD: 4%) were evaluated using receiver operating characteristics and area under the curve (AUC) metrics.

RESULTS

The discriminative power was high for NMOSD-ON versus HC for IEAD (pRNFL: AUC 0.95, specificity 82%, sensitivity 86%; GCIPL: AUC 0.93, specificity 98%, sensitivity 75%) and IEPD (pRNFL: AUC 0.96, specificity 87%, sensitivity 89%; GCIPL: AUC 0.94, specificity 96%, sensitivity 82%). The discriminative power was high/moderate for NMOSD-ON versus NMOSD-NON for IEAD (pRNFL: AUC 0.92, specificity 77%, sensitivity 86%; GCIP: AUC 0.87, specificity 85%, sensitivity 75%) and for IEPD (pRNFL: AUC 0.94, specificity 82%, sensitivity 89%; GCIP: AUC 0.88, specificity 82%, sensitivity 82%).

CONCLUSIONS

Results support the validation of the IED metrics as OCT parameters of the novel diagnostic ON criteria in AQP4+NMOSD.

The Acute Optic Neuritis Network (ACON): Study protocol of a non-interventional prospective multicenter study on diagnosis and treatment of acute optic neuritis

Optic neuritis (ON) often occurs at the presentation of multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD), and myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD). The recommended treatment of high-dose corticosteroids for ON is based on a North American study population, which did not address treatment timing or antibody serostatus. The Acute Optic Neuritis Network (ACON) presents a global, prospective, observational study protocol primarily designed to investigate the effect of time to high-dose corticosteroid treatment on 6-month visual outcomes in ON. Patients presenting within 30 days of the inaugural ON will be enrolled. For the primary analysis, patients will subsequently be assigned into the MS-ON group, the aquapotin-4-IgG positive ON (AQP4-IgG+ON) group or the MOG-IgG positive ON (MOG-IgG+ON) group and then further sub-stratified according to the number of days from the onset of visual loss to high-dose corticosteroids (days-to-Rx). The primary outcome measure will be high-contrast best-corrected visual acuity (HC-BCVA) at 6 months. In addition, multimodal data will be collected in subjects with any ON (CIS-ON, MS-ON, AQP4-IgG+ON or MOG-IgG+ON, and seronegative non-MS-ON), excluding infectious and granulomatous ON. Secondary outcomes include low-contrast best-corrected visual acuity (LC-BCVA), optical coherence tomography (OCT), magnetic resonance imaging (MRI) measurements, serum and cerebrospinal fluid (CSF) biomarkers (AQP4-IgG and MOG-IgG levels, neurofilament, and glial fibrillary protein), and patient reported outcome measures (headache, visual function in daily routine, depression, and quality of life questionnaires) at presentation at 6-month and 12-month follow-up visits. Data will be collected from 28 academic hospitals from Africa, Asia, the Middle East, Europe, North America, South America, and Australia. Planned recruitment consists of 100 MS-ON, 50 AQP4-IgG+ON, and 50 MOG-IgG+ON. This prospective, multimodal data collection will assess the potential value of early high-dose corticosteroid treatment, investigate the interrelations between functional impairments and structural changes, and evaluate the diagnostic yield of laboratory biomarkers. This analysis has the ability to substantially improve treatment strategies and the accuracy of diagnostic stratification in acute demyelinating ON.

Trial registration

ClinicalTrials.gov, identifier: NCT05605951.

Visual function and disability are associated with microcystic macular edema, macular and peripapillary vessel density in patients with neuromyelitis optica spectrum disorder

Purpose

To assess macular and peripapillary vessel density and neurodegeneration in eyes with and without microcystic macular edema (MME) in neuromyelitis optica spectrum disorder (NMOSD) patients while investigating their association with visual impairment and disease disability.

Methods

This is a cross-sectional study. A total of 52 eyes from 29 NMOSD patients were recruited, including 8 eyes with MME from 7 patients. Optical coherence tomography angiography (OCTA) images were analyzed to quantify the radial papillary capillary density (RPCD), and the density of macular microvascular network in both the superficial retinal capillary plexus (SRCP) and the deep retinal capillary plexus (DRCP). Thicknesses of the neural retinal layers centered on the fovea and the optic nerve head were also collected by OCT. Best-corrected visual acuity (BCVA) and Expanded Disability Status Scale (EDSS) scores were assessed for all patients. Microvascular densities and retinal sublayer thicknesses were compared among groups, and correlations of these vascular and structural parameters with BCVA and EDSS scores were determined.

Results

Patients with NMOSD and MME had significantly decreased visual acuity and worse EDSS score than patients without MME (P = 0.01 and 0.002, respectively). The vessel density in SRCP and RPCD were significantly lower in eyes with MME and ON compared to that of eyes with ON but without MME and eyes without MME or ON. Impairment of visual acuity and disease severity were significantly negatively associated with the reduction of SRCP vessel density and RPCD but were not related to DRCP vessel density.

Conclusions

MME were correlated with worse visual impairment and disability in NMOSD patients. Sparse SRCP vessel density and RPCD were observed in NMOSD MME eyes and correlated with worse BCVA and EDSS scores.

Diagnostik der Neuromyelitis-optica-Spektrum-Erkrankung (NMOSD) und der MOG-Antikörper-assoziierten Erkrankung (MOGAD)

Die Aquaporin-4-Antikörper-positive Neuromyelitis-optica-Spektrum-Erkrankung (engl. NMOSD) und die Myelin-Oligodendrozyten-Glykoprotein-Antikörper-assoziierte Erkrankung (engl. MOGAD) sind Autoimmunerkrankungen des zentralen Nervensystems. Typische Erstmanifestationen sind bei Erwachsenen Optikusneuritis und Myelitis. Eine Beteiligung auch von Hirn und Hirnstamm, spätestens im weiteren Verlauf, ist häufig. Während die NMOSD nahezu immer schubförmig verläuft, nimmt die MOGAD gelegentlich einen monophasischen Verlauf. Die Differenzialdiagnostik ist anspruchsvoll und stützt sich auf u. a. auf radiologische und serologische Befunde. Die Abgrenzung von der häufigeren neuroinflammatorischen Erkrankung, Multiple Sklerose (MS), ist von erheblicher Bedeutung, da sich Behandlung und langfristige Prognose von NMOSD, MOGAD und MS wesentlich unterscheiden. Die vielfältigen Symptome und die umfangreiche Diagnostik machen eine enge Zusammenarbeit zwischen Ophthalmologie, Neurologie und Radiologie erforderlich. Dieser Artikel gibt einen Überblick über typische MRT-Befunde und die serologische Antikörperdiagnostik bei NMOSD und MOGAD. Zwei illustrative Fallberichte aus der ärztlichen Praxis ergänzen die Darstellung.

Structure-function correlates of vision loss in neuromyelitis optica spectrum disorders

Optic neuritis (ON) in neuromyelitis optica spectrum disorders (NMOSD) regularly leads to more profound vision loss compared to multiple sclerosis (MS) and myelin-oligodendrocyte-glycoprotein-antibody associated disease (MOGAD). Here we investigate ON-related vision loss in NMOSD compared to MS and MOGAD in order to identify neuroaxonal and retinal contributors to visual dysfunction. In this retrospective study we included patients with aquaporin-4-antibody seropositive NMOSD (n = 28), MOGAD (n = 14), MS (n = 29) and controls (n = 14). We assessed optic nerve damage and fovea morphometry by optical coherence tomography. Visual function was assessed as high (HCVA) and low contrast visual acuity (LCVA), and visual fields' mean deviation (MD). In all diseases, lower visual function was associated with peripapillary retinal nerve fiber layer (pRNFL) and ganglion cell and inner plexiform layer (GCIP) thinning following a broken stick model, with pRNFL and GCIP cutoff point at ca. 60 µm. HCVA loss per µm pRNFL and GCIP thinning was stronger in NMOSD compared with MOGAD. Foveal inner rim volume contributed to MD and LCVA in NMOSD eyes, only. Together these data supports that visual dysfunction in NMOSD is associated with neuroaxonal damage beyond the effect seen in MS and MOGAD. A primary retinopathy, respectively Müller cell pathology, may contribute to this effect.

Correlation of IgH-CDR3 Immune Repertoire Diversity Test in Peripheral Blood of Neuromyelitis Spectrum Diseases

Neuroretinitis spectrum disorder (NMOSD) is generally regarded as an acute or subacute inflammatory demyelinating disease of the central nervous system, mainly involving the optic nerve and spinal cord, mediated by humoral immunity. To address these questions, this work established an immunomic library of the heavy chain complementarity determinant 3 (gHI-CDR3) of peripheral blood lymphocyte B cell receptors. The library was established in patients with a spectrum of neurosyphilis-retinitis disorders. Six NMOSD patients and six healthy volunteers were recruited, and the NMOSD group was divided into an early-onset group and a stable group according to treatment conditions. The IgH-CDR3 gene fragment cultured in vitro was amplified by multiplex PCR technology, and the gene was sequenced by the second-generation high-throughput sequencing technology, and the statistical analysis was carried out by the method without reference. The quantity, type, and diversity of IgH-CDR3 in peripheral blood B lymphocytes of NMOSD patients were significantly lower than those of normal group (P > 0.05); the variation of IgH-CDR3 sequence in the initial stage of treatment was higher than that in the stable stage (P > 0.05); the replication frequency of the characteristic gene "CASSICLGSGCGGYYYGMDVW" was significantly increased in patients at the initial stage of NMOSD treatment (P < 0.05). The conclusion was that the gene expression and gene expression analysis of NMOSD patients could accurately judge the condition of NMOSD patients, evaluate their efficacy, and provide new molecular targets and new theoretical basis for clinical application.

Optic Neuritis-Independent Retinal Atrophy in Neuromyelitis Optica Spectrum Disorder

BACKGROUND

A limited number of studies have investigated the presence of ongoing disease activity independent of clinical relapses in neuromyelitis optica spectrum disorder (NMOSD), and data are conflicting. The objective of our study was to examine whether patients with aquaporin-4 (AQP4)-IgG seropositive NMOSD exhibit progressive retinal neuroaxonal loss, independently of optic neuritis (ON) attacks.

METHODS

In this single-center, longitudinal study, 32 AQP4-IgG+ NMOSD patients and 48 healthy controls (HC) were followed with serial spectral-domain optical coherence tomography and visual acuity (VA) assessments. NMOSD patients with ON less than 6 months before baseline were excluded, whereas data from patients with ON during follow-up were censored at the last visit before ON. VA worsening was defined as a decrease in monocular letter acuity ≥5 letters for high-contrast VA and ≥7 letters for low-contrast VA. Analyses were performed with mixed-effects linear regression models adjusted for age, sex, and race.

RESULTS

The median follow-up duration was 4.2 years (interquartile range: 1.8-7.5). Relative to HC, NMOSD eyes had faster peripapillary retinal nerve fiber layer (pRNFL) (β = -0.25 µm/year faster, 95% confidence interval [CI]: -0.45 to -0.05, P = 0.014) and GCIPL thinning (β = -0.09 µm/year faster, 95% CI: -0.17 to 0, P = 0.05). This difference seemed to be driven by faster pRNFL and GCIPL thinning in NMOSD eyes without a history of ON compared with HC (GCIPL: β = -0.15 µm/year faster; P = 0.005; pRNFL: β = -0.43 µm/year faster, P < 0.001), whereas rates of pRNFL (β: -0.07 µm/year, P = 0.53) and GCIPL (β = -0.01 µm/year, P = 0.90) thinning did not differ between NMOSD-ON and HC eyes. Nine NMOSD eyes had VA worsening during follow-up.

CONCLUSIONS

In this longitudinal study, we observed progressive pRNFL and GCIPL atrophy in AQP4-IgG+ NMOSD eyes unaffected by ON. These results support that subclinical involvement of the anterior visual pathway may occur in AQP4-IgG+ NMOSD.

Clinical and neuroimaging findings in MOGAD-MRI and OCT

Myelin oligodendrocyte glycoprotein antibody-associated disorders (MOGAD) are rare in both children and adults, and have been recently suggested to be an autoimmune neuroinflammatory group of disorders that are different from aquaporin-4 autoantibody-associated neuromyelitis optica spectrum disorder and from classic multiple sclerosis. In-vivo imaging of the MOGAD patient central nervous system has shown some distinguishing features when evaluating magnetic resonance imaging of the brain, spinal cord and optic nerves, as well as retinal imaging using optical coherence tomography. In this review, we discuss key clinical and neuroimaging characteristics of paediatric and adult MOGAD. We describe how these imaging techniques may be used to study this group of disorders and discuss how image analysis methods have led to recent insights for consideration in future studies.

A comparative study of alteration in retinal layer segmentation alteration by SD-OCT in neuromyelitis optica spectrum disorders: A systematic review and meta-analysis

Background

To evaluate the feature of different retinal layer segmentation in neuromyelitis optica spectrum disorders (NMOSD) with spectral-domain optical coherence tomography (SD-OCT) and to compare it with that in multiple sclerosis (MS), healthy controls (HC), and idiopathic optic neuritis (ION).

Methods

We retrieved four electronic databases, including Pubmed, Embase, Cochrane Library, and Web of Science from inception to September 1st, 2021. A meta-analysis was performed to compare different retinal layer segmentation thicknesses between patients with or without a history of optic neuritis (ON) in NMOSD and the control group, including patients with MS, HC, and ION.

Results

Forty-two studies were included and the interval between the last ON onset and examination was greater than 3 months. Compared with that in HC eyes, the loss of retinal nerve fiber layer (RNFL) and macular ganglion cell and inner plexiform layer (GC-IPL) was serious in NMOSD eye especially after ON. Moreover, compared with that in ION eyes or MS-related-ON eyes, the injury to the peripapillary retinal nerve fiber layer (pRNFL) was severe in NMOSD-related-ON eyes. In addition, the correlation coefficient between pRNFL and prognostic visual acuity was 0.43. However, the one-arm study revealed the inner nuclear layer (INL) was thickened in NMOSD-related-ON eyes compared with HC eyes.

Conclusions

Inclusion of the RNFL and macular GC-IPL is recommended for monitoring disease progression and attention should be paid to changes in the INL.

Retinal optical coherence tomography and magnetic resonance imaging in neuromyelitis optica spectrum disorders and MOG-antibody associated disorders: an updated review

INTRODUCTION

Neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein IgG antibody-associated disorders (MOGAD) comprise two groups of rare neuroinflammatory diseases that cause attack-related damage to the central nervous system (CNS). Clinical attacks are often characterized by optic neuritis, transverse myelitis, and to a lesser extent, brainstem encephalitis/area postrema syndrome. Retinal optical coherence tomography (OCT) is a non-invasive technique that allows for in vivo thickness quantification of the retinal layers. Apart from OCT, magnetic resonance imaging (MRI) plays an increasingly important role in NMOSD and MOGAD diagnosis based on the current international diagnostic criteria. Retinal OCT and brain/spinal cord/optic nerve MRI can help to distinguish NMOSD and MOGAD from other neuroinflammatory diseases, particularly from multiple sclerosis, and to monitor disease-associated CNS-damage.

AREAS COVERED

This article summarizes the current status of imaging research in NMOSD and MOGAD, and reviews the clinical relevance of OCT, MRI and other relevant imaging techniques for differential diagnosis, screening and monitoring of the disease course.

EXPERT OPINION

Retinal OCT and MRI can visualize and quantify CNS damage in vivo, improving our understanding of NMOSD and MOGAD pathology. Further efforts on the standardization of these imaging techniques are essential for implementation into clinical practice and as outcome parameters in clinical trials.

Retinal Optical Coherence Tomography in Neuromyelitis Optica

Background and Objectives

To determine optic nerve and retinal damage in aquaporin-4 antibody (AQP4-IgG)-seropositive neuromyelitis optica spectrum disorders (NMOSD) in a large international cohort after previous studies have been limited by small and heterogeneous cohorts.

Methods

The cross-sectional Collaborative Retrospective Study on retinal optical coherence tomography (OCT) in neuromyelitis optica collected retrospective data from 22 centers. Of 653 screened participants, we included 283 AQP4-IgG–seropositive patients with NMOSD and 72 healthy controls (HCs). Participants underwent OCT with central reading including quality control and intraretinal segmentation. The primary outcome was thickness of combined ganglion cell and inner plexiform (GCIP) layer; secondary outcomes were thickness of peripapillary retinal nerve fiber layer (pRNFL) and visual acuity (VA).

Results

Eyes with ON (NMOSD-ON, N = 260) or without ON (NMOSD-NON, N = 241) were assessed compared with HCs (N = 136). In NMOSD-ON, GCIP layer (57.4 ± 12.2 μm) was reduced compared with HC (GCIP layer: 81.4 ± 5.7 μm, p < 0.001). GCIP layer loss (−22.7 μm) after the first ON was higher than after the next (−3.5 μm) and subsequent episodes. pRNFL observations were similar. NMOSD-NON exhibited reduced GCIP layer but not pRNFL compared with HC. VA was greatly reduced in NMOSD-ON compared with HC eyes, but did not differ between NMOSD-NON and HC.

Discussion

Our results emphasize that attack prevention is key to avoid severe neuroaxonal damage and vision loss caused by ON in NMOSD. Therapies ameliorating attack-related damage, especially during a first attack, are an unmet clinical need. Mild signs of neuroaxonal changes without apparent vision loss in ON-unaffected eyes might be solely due to contralateral ON attacks and do not suggest clinically relevant progression but need further investigation.

Impaired motion perception is associated with functional and structural visual pathway damage in multiple sclerosis and neuromyelitis optica spectrum disorders

Background:

Decreased motion perception has been suggested as a marker for visual pathway demyelination in optic neuritis (ON) and/or multiple sclerosis (MS).

Objectives:

To examine the influence of neuro-axonal damage on motion perception in MS and neuromyelitis optica spectrum disorders (NMOSD).

Methods:

We analysed motion perception with numbers-from-motion (NFM), visual acuity, (multifocal (mf)) VEP, optical coherence tomography in patients with MS (n = 38, confirmatory cohort n = 43), NMOSD (n = 13) and healthy controls (n = 33).

Results:

NFM was lower compared with controls in MS (B = −12.37, p < 0.001) and NMOSD (B = −34.5, p < 0.001). NFM was lower in ON than in non-ON eyes (B = −30.95, p = 0.041) in NMOSD, but not MS. In MS and NMOSD, lower NFM was associated with worse visual acuity (B = −139.4, p < 0.001/B = −77.2, p < 0.001) and low contrast letter acuity (B = 0.99, p = 0.002/B = 1.6, p < 0.001), thinner peripapillary retinal nerve fibre layer (B = 1.0, p < 0.001/ B = 0.92, p = 0.016) and ganglion cell/inner plexiform layer (B = 64.8, p < 0.001/B = 79.5, p = 0.006), but not with VEP P100 latencies. In the confirmatory MS cohort, lower NFM was associated with thinner retinal nerve fibre layer (B = 1.351, p < 0.001) and increased mfVEP P100 latencies (B = −1.159, p < 0.001).

Conclusions:

Structural neuro-axonal visual pathway damage is an important driver of motion perception impairment in MS and NMOSD.

A window into the future? MRI for evaluation of neuromyelitis optica spectrum disorder throughout the disease course

Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing, inflammatory disease of the central nervous system marked by relapses often associated with poor recovery and long-term disability. Magnetic resonance imaging (MRI) is recognized as an important tool for timely diagnosis of NMOSD as, in combination with serologic testing, it aids in distinguishing NMOSD from possible mimics. Although the role of MRI for disease monitoring after diagnosis is not as well established, MRI may provide important prognostic information and help differentiate between relapses and pseudorelapses. Increasing evidence of subclinical disease activity and the emergence of newly approved, highly effective immunotherapies for NMOSD adjure us to re-evaluate MRI as a tool to guide optimal treatment selection and escalation throughout the disease course. In this article we review the role of MRI in NMOSD diagnosis, prognostication, disease monitoring, and treatment selection.

Optical coherence tomography angiography helps distinguish multiple sclerosis from AQP4-IgG-seropositive neuromyelitis optica spectrum disorder

INTRODUCTION

The aim was to characterize the optical coherence tomography (OCT) angiography measures in patients with multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) and to evaluate their disease discrimination capacity.

METHODS

Patients with MS (n = 83) and AQP4-IgG-seropositive NMOSD (n = 91) with or without a history of optic neuritis, together with healthy controls (n = 34), were imaged. The main outcome measures were peripapillary retinal nerve fiber layer (pRNFL) thickness, macular ganglion cell-inner plexiform layer (GC-IPL) thickness, macular vessel density (VD), and perfusion density (PD) in the superficial capillary plexus. Diagnostic accuracy was assessed using the area under the receiver operating characteristics curve.

RESULTS

Compared with patients with MS, those with NMOSD had a significantly smaller average thickness of the pRNFL and GC-IPL (80.0 [59.0; 95.8] μm versus 92.0 [80.2; 101] μm, p < .001; 68.0 [56.0; 81.0] μm, versus 74.5 [64.2; 81.0] μm, p < .001) and significantly smaller whole VD and PD areas (15.6 [12.6; 17.0] mm^-1 versus 16.7 [14.8; 17.7] mm^-1 , p < .001; 0.38 [0.31; 0.42] mm^-1 versus 0.40 [0.37; 0.43] mm^-1 , p < .01). The combination of structural parameters (average thickness of the pRNFL and GC-IPL) with microvascular parameters (temporal-inner quadrant of VD, temporal-inner, nasal-inferior, and nasal-outer quadrant of PD) was revealed to have a good diagnostic capability for discriminating between NMOSD and MS.

CONCLUSIONS

OCT angiography reveals different structural and microvascular retinal changes in MS and AQP4-IgG-seropositive NMOSD. These combined structural and microvascular parameters might be promising biomarkers for disease diagnosis.

[Differential diagnostics of autoimmune inflammatory spinal cord diseases]

Myelitis is an acute or subacute inflammatory syndrome of the spinal cord. Myelopathy, often used as a synonym and presenting with similar symptoms in clinical practice, can be caused by numerous, not primarily inflammatory etiologies and might also show a progressive disease course. Within the last decade the spectrum of autoimmune myelitis was significantly broadened as was the spectrum of diagnostic methods. Apart from the characteristic example of multiple sclerosis with short-length myelitis and neuromyelitis optica spectrum disorders with longitudinally extensive transverse myelitis, multiple rare but important differential diagnoses should also be considered. Magnetic resonance imaging and laboratory analyses of serum antibodies and cerebrospinal fluid are the most important diagnostic methods and are fundamental for rapid treatment decisions, subsequently with better prognosis. This article reviews representative diseases within the spectrum of autoimmune spinal cord diseases and their differential diagnoses.

Foveal changes in aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorder are independent of optic neuritis and not overtly progressive

BACKGROUND AND PURPOSE

Foveal changes were reported in aquaporin-4 antibody (AQP4-Ab) seropositive neuromyelitis optica spectrum disorder (NMOSD) patients; however, it is unclear whether they are independent of optic neuritis (ON), stem from subclinical ON or crossover from ON in fellow eyes. Fovea morphometry and a statistical classification approach were used to investigate if foveal changes in NMOSD are independent of ON and progressive.

METHODS

This was a retrospective longitudinal study of 27 AQP4-IgG + NMOSD patients (49 eyes; 15 ON eyes and 34 eyes without a history of ON [NON eyes]), follow-up median (first and third quartile) 2.32 (1.33-3.28), and 38 healthy controls (HCs) (76 eyes), follow-up median (first and third quartile) 1.95 (1.83-2.54). The peripapillary retinal nerve fibre layer thickness and the volume of combined ganglion cell and inner plexiform layer as measures of neuroaxonal damage from ON were determined by optical coherence tomography. Nineteen foveal morphometry parameters were extracted from macular optical coherence tomography volume scans. Data were analysed using orthogonal partial least squares discriminant analysis and linear mixed effects models.

RESULTS

At baseline, foveal shape was significantly altered in ON eyes and NON eyes compared to HCs. Discriminatory analysis showed 81% accuracy distinguishing ON vs. HCs and 68% accuracy in NON vs. HCs. NON eyes were distinguished from HCs by foveal shape parameters indicating widening. Orthogonal partial least squares discriminant analysis discriminated ON vs. NON with 76% accuracy. In a follow-up of 2.4 (20.85) years, no significant time-dependent foveal changes were found.

CONCLUSION

The parafoveal area is altered in AQP4-Ab seropositive NMOSD patients suggesting independent neuroaxonal damage from subclinical ON. Longer follow-ups are needed to confirm the stability of the parafoveal structure over time.

Lateral geniculate nucleus volume changes after optic neuritis in neuromyelitis optica: A longitudinal study

•

LGN correlates with structural markers of the anterior and posterior visual pathway.

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LGN volume may reduce after an episode of ON, shown in four patients.

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LGN volume does not change over time in the absence of ON episodes.

•

Our findings argue against occult neurodegeneration in the visual pathway in NMO.

Objectives

Lateral geniculate nucleus (LGN) volume is reduced after optic neuritis (ON) in neuromyelitis optica spectrum disorders (NMOSD). We aimed at a longitudinal assessment of LGN volume in NMOSD.

Methods

Twenty-nine patients with aquaporin 4-IgG seropositive NMOSD (age: 47.8 ± 14.6 years (y), female: n = 27, history of ON (NMO-ON): n = 17, median time since ON: 3[1.2–12.1]y) and 18 healthy controls (HC; age: 39.3 ± 15.8y; female: n = 13) were included. Median follow-up was 4.1[1.1–4.7]y for patients and 1.7[0.9–3.2]y for HC. LGN volume was measured using a multi-atlas-based approach of automated segmentation on 3 Tesla magnetic resonance images. Retinal optical coherence tomography and probabilistic tractography of the optic radiations (OR) were also performed.

Results

At baseline, NMO-ON patients had lower LGN volumes (395.4 ± 48.9 mm³) than patients without ON (NMO-NON: 450.7 ± 55.6 mm³; p = 0.049) and HC (444.5 ± 61.5 mm³, p = 0.025). LGN volume was associated with retinal neuroaxonal loss and microstructural OR damage. Longitudinally, there was no change in LGN volumes in the absence of ON, neither in all patients (B = −0.6, SE = 1.4, p = 0.670), nor in NMO-ON (B = −0.8, SE = 1.6, p = 0.617) and NMO-NON (B = 1.7, SE = 3.5, p = 0.650). However, in four patients with new ON during follow-up, LGN volume was reduced at last visit (median time since ON: 2.6 [1.8–3.9] y) compared to the measurement before ON (352 ± 52.7 vs. 371.1 ± 55.9 mm³; t = −3.6, p = 0.036).

Conclusion

Although LGN volume is reduced after ON in NMOSD, this volume loss is not progressive over longer follow-up or independent of ON. Thus, our findings -at least in this relatively small cohort- do not support occult neurodegeneration of the afferent visual pathway in NMOSD.

Recent advances and future directions on the use of optical coherence tomography in neuro-ophthalmology

Optical coherence tomography (OCT) is a noninvasive imaging technique used to qualitatively and quantitatively analyze various layers of the retina. OCT of the retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) is particularly useful in neuro-ophthalmology for the evaluation of patients with optic neuropathies and retrochiasmal visual pathway disorders. OCT allows for an objective quantification of edema and atrophy of the RNFL and GCIPL, which may be evident before obvious clinical signs and visual dysfunction develop. Enhanced depth imaging OCT allows for visualization of deep structures of the optic nerve and has emerged as the gold standard for the detection of optic disc drusen. In the evaluation of compressive optic neuropathies, OCT RNFL and GCIPL thicknesses have been established as the most important visual prognostic factor. There is increasing evidence that inclusion of OCT as part of the diagnostic criteria for multiple sclerosis (MS) increases its sensitivity. Moreover, OCT of the RNFL and GCIPL may be helpful in the early detection and monitoring the treatment of conditions such as MS and Alzheimer's disease. OCT is an important aspect of the neuro-ophthalmologic assessment and its use is likely to increase moving forward.

Optical Coherence Tomography Angiography (OCTA) in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorder

Vascular changes are increasingly recognized as important factors in the pathophysiology of neuroinflammatory disease, especially in multiple sclerosis (MS). The relatively novel technology of optical coherence tomography angiography (OCTA) images the retinal and choroidal vasculature non-invasively and in a depth-resolved manner. OCTA provides an alternative quantitative measure of retinal damage, by measuring vascular density instead of structural atrophy. Preliminary results suggest OCTA is sensitive to retinal damage in early disease stages, while also having less of a "floor-effect" compared with commonly used OCT metrics, meaning it can pick up further damage in a severely atrophied retina in later stages of disease. Furthermore, it may serve as a surrogate marker for vascular pathology in the central nervous system. Data to date consistently reveal lower densities of the retinal microvasculature in both MS and neuromyelitis optica spectrum disorder (NMOSD) compared with healthy controls, even in the absence of prior optic neuritis. Exploring the timing of vascular changes relative to structural atrophy may help answer important questions about the role of hypoperfusion in the pathophysiology of neuroinflammatory disease. Finally, qualitative characteristics of retinal microvasculature may help discriminate between different neuroinflammatory disorders. There are however still issues regarding image quality and development of standardized analysis methods before OCTA can be fully incorporated into clinical practice.

Atypical Neuromyelitis Optica Spectrum Disorder With Diffuse Cerebral Abnormalities: A Case Report

The recent expansion of the radiological criteria and the use of a highly specific biomarker, anti-aquaporin 4-IgG (AQP4 IgG), has significantly improved the ability of clinicians to provide a timely and accurate diagnosis for neuromyelitis optica spectrum disorder (NMOSD), especially when faced with an abnormal disease presentation. Here, we report on the 5-year clinical experience of a 69-year-old right-handed African American woman who initially presented following symptoms suggestive of transient global amnesia. Her clinical history was only remarkable for a single episode of visual decline with poor recovery experienced 35 years prior, with prior unrevealing serological investigations. Brain MRI features were significant for diffuse, bilateral white matter abnormalities throughout the supratentorial, deep gray matter, and infratentorial regions. Spinal cord imaging studies were within normal limits with no intramedullary high-signal abnormalities identified. Serological studies were significant for the presence of anti-aquaporin 4-IgG. The clinical features were supportive of the diagnosis of NMOSD. The data provided here highlight both the clinical and radiological heterogeneity of NMOSD.

Optical Coherence Tomography in Neuromyelitis Optica spectrum disorder and Multiple Sclerosis: A population-based study

BACKGROUND

The aim of this study was to identify and compare the characteristics of retinal nerve layers using spectral domain-optical coherence tomography (SD-OCT) in neuromyelitis optica spectrum disorder (NMOSD), relapsing-remitting multiple sclerosis (RRMS) and healthy controls (HCs).

METHODS

It is a cross-sectional population-based study in Isfahan, Iran. We enrolled 98 participants including 45 NMOSD patients (90 eyes), 35 RRMS patients (70 eyes) and 18 HCs (36 eyes). Evaluation criteria were thickness of different sectors in peripapillary retinal nerve fiber layer (pRNFL) and intra-retinal layers around the macula. History of previous optic neuritis (ON) was obtained through chart review and medical record.

RESULTS

Without considering ON, total macular, ganglion cell layer (GCL) and pRNFL were significantly thinner in both groups of patients compared to HCs. On macular examination, GCL and total macular thickness were significantly thinner than HCs in all NMOSD and RRMS eyes with and without history of ON. While there was no significant difference between MS-ON and MS without a history of ON in the macular measures, the reduction in total macular and GCL thickness was significantly greater in NMOSD-ON compared to NMOSD without a history of ON. Also in NMOSD-ON eyes, the RNFL, GCL, IPL and GCIPL layers were significantly thinner than that of MS-ON. On the other hand, the pRNFL study showed significant thinning of all quadrants in the RRMS and NMOSD groups relative to HCs. While the decrease of pRNFL thickness in the eyes of NMOSD-ON and MS with and without a previous history of ON was significantly greater than that of HCs, no difference was observed between NMOSD without ON and HCs. In addition, in NMOSD patients, pRNFL was significantly thinner in eyes with history of ON compared to non ON-eyes. Furthermore, in patients with a history of ON, reduction in all sectors of pRNFl (except in T) was significantly greater in NMOSD compared to MS patients.

CONCLUSION

Our findings showed that although macular and retinal damage occurred in both NMOSD and RRMS patients without significant differences, the severity of injury in eyes with history of ON was significantly higher in NMOSD compared to MS patients, that could be considered as a marker to distinguish them. In addition, our results confirmed the absence of subclinical optic nerve involvement in NMOSD unlike MS patients.

Neuromyelitis optica spectrum disorders

The disease concept of Neuromyelitis Optica Spectrum Disorders(NMOSD) has undergone a significant change over the last two decades including the detection of Myelin Oligodendrocyte Glycoprotein(MOG) antibody in patients who are seronegative for aquaporin-4 antibody. Aquaporin-4 antibody positive NMOSD is now regarded as an immune astrocytopathy. Conversely, MOG antibody associated disease is known to target myelin rather than astrocytes, leading to an NMOSD syndrome with distinct clinical and radiological features. Incorporation of clinical features like area postrema syndrome, brainstem syndrome, diencephalic syndrome and cortical manifestations as core clinical characteristics into the revised diagnostic criteria has widened the clinical spectrum of NMOSD. With the development of these criteria, it is possible to make the diagnosis at an earlier stage so that effective immunosuppression can be instituted promptly for a better long-term prognosis. Newer therapeutic agents have been introduced for aquaporin-4 seropositive NMOSD disease; however, challenges remain in treating seronegative disease because of limited treatment options.

Cohort profile: a collaborative multicentre study of retinal optical coherence tomography in 539 patients with neuromyelitis optica spectrum disorders (CROCTINO)

PURPOSE

Optical coherence tomography (OCT) captures retinal damage in neuromyelitis optica spectrum disorders (NMOSD). Previous studies investigating OCT in NMOSD have been limited by the rareness and heterogeneity of the disease. The goal of this study was to establish an image repository platform, which will facilitate neuroimaging studies in NMOSD. Here we summarise the profile of the Collaborative OCT in NMOSD repository as the initial effort in establishing this platform. This repository should prove invaluable for studies using OCT to investigate NMOSD.

PARTICIPANTS

The current cohort includes data from 539 patients with NMOSD and 114 healthy controls. These were collected at 22 participating centres from North and South America, Asia and Europe. The dataset consists of demographic details, diagnosis, antibody status, clinical disability, visual function, history of optic neuritis and other NMOSD defining attacks, and OCT source data from three different OCT devices.

FINDINGS TO DATE

The cohort informs similar demographic and clinical characteristics as those of previously published NMOSD cohorts. The image repository platform and centre network continue to be available for future prospective neuroimaging studies in NMOSD. For the conduct of the study, we have refined OCT image quality criteria and developed a cross-device intraretinal segmentation pipeline.

FUTURE PLANS

We are pursuing several scientific projects based on the repository, such as analysing retinal layer thickness measurements, in this cohort in an attempt to identify differences between distinct disease phenotypes, demographics and ethnicities. The dataset will be available for further projects to interested, qualified parties, such as those using specialised image analysis or artificial intelligence applications.

Emerging drugs for the treatment of neuromyelitis optica

INTRODUCTION

Evidence-based treatment options for neuromyelitis optica spectrum disorders (NMOSD) patients are beginning to enter the market. Where previously, there was only the exclusive use of empiric and off-label immunosuppressants in this rare and devastating central nervous system autoimmune disease.

AREAS COVERED

In accordance to expanding pathogenetic insights, drugs in phase II and III clinical trials are presented in the context of the current treatment situation for acute attacks and immunopreventative strategies in NMOSD. Some such drugs are the 2019-approved complement inhibitor eculizumab, other compounds in late development include its modified successor ravulizumab, IL-6 receptor antibody satralizumab, CD19 targeting antibody inebilizumab and the TACI-Fc fusion protein telitacicept.

EXPERT OPINION

Moving from broad immunosuppression to tailored treatment strategies, the prospects for efficient NMOSD therapy are positive. For the first time in this disease, class I treatment evidence is available, but long-term data will be necessary to confirm the overall promising study results of the compounds close to approval. While drug development still centers around AQP4 antibody seropositive patients, current and future research requires consideration of possible diverging treatment demands for the smaller group of seronegative patients and patients with presence of MOG antibodies.

Pain in NMOSD and MOGAD: A Systematic Literature Review of Pathophysiology, Symptoms, and Current Treatment Strategies

Neuromyelitis optica spectrum disorders (NMOSDs) and myelin oligodendrocyte glycoprotein-antibody-associated disease (MOGAD) are autoimmune inflammatory disorders of the central nervous system (CNS). Pain is highly prevalent and debilitating in NMOSD and MOGAD with a severe impact on quality of life, and there is a critical need for further studies to successfully treat and manage pain in these rare disorders. In NMOSD, pain has a prevalence of over 80%, and pain syndromes include neuropathic, nociceptive, and mixed pain, which can emerge in acute relapse or become chronic during the disease course. The impact of pain in MOGAD has only recently received increased attention, with an estimated prevalence of over 70%. These patients typically experience not only severe headache, retrobulbar pain, and/or pain on eye movement in optic neuritis but also neuropathic and nociceptive pain. Given the high relevance of pain in MOGAD and NMOSD, this article provides a systematic review of the current literature pertaining to pain in both disorders, focusing on the etiology of their respective pain syndromes and their pathophysiological background. Acknowledging the challenge and complexity of diagnosing pain, we also provide a mechanism-based classification of NMOSD- and MOGAD-related pain syndromes and summarize current treatment strategies.

Investigation of Visual System Involvement in Spinocerebellar Ataxia Type 14

Spinocerebellar ataxia type 14 (SCA-PRKCG, formerly SCA14) is a rare, slowly progressive disorder caused by conventional mutations in protein kinase Cγ (PKCγ). The disease usually manifests with ataxia, but previous reports suggested PRKCG variants in retinal pathology. To systematically investigate for the first time visual function and retinal morphology in patients with SCA-PRKCG. Seventeen patients with PRKCG variants and 17 healthy controls were prospectively recruited, of which 12 genetically confirmed SCA-PRKCG patients and 14 matched controls were analyzed. We enquired a structured history for visual symptoms. Vision-related quality of life was obtained with the National Eye Institute Visual Function Questionnaire (NEI-VFQ) including the Neuro-Ophthalmic Supplement (NOS). Participants underwent testing of visual acuity, contrast sensitivity, visual fields, and retinal morphology with optical coherence tomography (OCT). Measurements of the SCA-PRKCG group were analyzed for their association with clinical parameters (ataxia rating and disease duration). SCA-PRKCG patients rate their vision-related quality of life in NEI-VFQ significantly worse than controls. Furthermore, binocular visual acuity and contrast sensitivity were worse in SCA-PRKCG patients compared with controls. Despite this, none of the OCT measurements differed between groups. NEI-VFQ and NOS composite scores were related to ataxia severity. Additionally, we describe one patient with a genetic variant of uncertain significance in the catalytic domain of PKCγ who, unlike all confirmed SCA-PRKCG, presented with a clinically silent epitheliopathy. SCA-PRKCG patients had reduced binocular vision and vision-related quality of life. Since no structural retinal damage was found, the pathomechanism of these findings remains unclear.

Altered fovea in AQP4-IgG-seropositive neuromyelitis optica spectrum disorders

Objective

To investigate disease-specific foveal shape changes in patients with neuromyelitis optica spectrum disorders (NMOSDs) using foveal morphometry.

Methods

This cross-sectional study included macular spectral domain optical coherence tomography scans of 52 eyes from 28 patients with aquaporin-4 immunoglobulin G (AQP4-IgG)-seropositive NMOSD, 116 eyes from 60 patients with MS, and 123 eyes from 62 healthy controls (HCs), retrospectively, and an independent confirmatory cohort comprised 33/33 patients with NMOSD/MS. The fovea was characterized using 3D foveal morphometry. We included peripapillary retinal nerve fiber layer (pRNFL) thickness and combined macular ganglion cell and inner plexiform layer (GCIPL) volume to account for optic neuritis (ON)-related neuroaxonal damage.

Results

Group comparison showed significant differences compared with HC in the majority of foveal shape parameters in NMOSD, but not MS. Pit flat disk area, average pit flat disk diameter, inner rim volume, and major slope disk length, as selected parameters, showed differences between NMOSD and MS (p value = 0.017, 0.002, 0.005, and 0.033, respectively). This effect was independent of ON. Area under the curve was between 0.7 and 0.8 (receiver operating characteristic curve) for discriminating between NMOSD and MS. Pit flat disk area and average pit flat disk diameter changes independent of ON were confirmed in an independent cohort.

Conclusions

Foveal morphometry reveals a wider and flatter fovea in NMOSD in comparison to MS and HC. Comparison to MS and accounting for ON suggest this effect to be at least in part independent of ON. This supports a primary retinopathy in AQP4-IgG–seropositive NMOSD.

Visualizing the Central Nervous System: Imaging Tools for Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders

Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) are autoimmune central nervous system conditions with increasing incidence and prevalence. While MS is the most frequent inflammatory CNS disorder in young adults, NMOSD is a rare disease, that is pathogenetically distinct from MS, and accounts for approximately 1% of demyelinating disorders, with the relative proportion within the demyelinating CNS diseases varying widely among different races and regions. Most immunomodulatory drugs used in MS are inefficacious or even harmful in NMOSD, emphasizing the need for a timely and accurate diagnosis and distinction from MS. Despite distinct immunopathology and differences in disease course and severity there might be considerable overlap in clinical and imaging findings, posing a diagnostic challenge for managing neurologists. Differential diagnosis is facilitated by positive serology for AQP4-antibodies (AQP4-ab) in NMOSD, but might be difficult in seronegative cases. Imaging of the brain, optic nerve, retina and spinal cord is of paramount importance when managing patients with autoimmune CNS conditions. Once a diagnosis has been established, imaging techniques are often deployed at regular intervals over the disease course as surrogate measures for disease activity and progression and to surveil treatment effects. While the application of some imaging modalities for monitoring of disease course was established decades ago in MS, the situation is unclear in NMOSD where work on longitudinal imaging findings and their association with clinical disability is scant. Moreover, as long-term disability is mostly attack-related in NMOSD and does not stem from insidious progression as in MS, regular follow-up imaging might not be useful in the absence of clinical events. However, with accumulating evidence for covert tissue alteration in NMOSD and with the advent of approved immunotherapies the role of imaging in the management of NMOSD may be reconsidered. By contrast, MS management still faces the challenge of implementing imaging techniques that are capable of monitoring progressive tissue loss in clinical trials and cohort studies into treatment algorithms for individual patients. This article reviews the current status of imaging research in MS and NMOSD with an emphasis on emerging modalities that have the potential to be implemented in clinical practice.

Optic chiasm measurements may be useful markers of anterior optic pathway degeneration in neuromyelitis optica spectrum disorders

OBJECTIVES

We aimed to evaluate optic chiasm (OC) measures as potential imaging marker for anterior optic pathway damage assessment in the context of neuromyelitis optica spectrum disorders (NMOSD).

MATERIALS AND METHOD

This cross-sectional study included 39 patients exclusively with aquaporin 4-IgG seropositive NMOSD of which 25 patients had a history of optic neuritis (NMOSD-ON) and 37 age- and sex-matched healthy controls (HC). OC heights, width, and area were measured using standard 3D T1-weighted MRI. Sensitivity of these measures to detect neurodegeneration in the anterior optic pathway was assessed in receiver operating characteristics analyses. Correlation coefficients were used to assess associations with structural measures of the anterior optic pathway (optic nerve dimensions, retinal ganglion cell loss) and clinical measures (visual function and disease duration).

RESULTS

OC heights and area were significantly smaller in NMOSD-ON compared to HC (NMOSD-ON vs. HC p < 0.0001). An OC area smaller than 22.5 mm² yielded a sensitivity of 0.92 and a specificity of 0.92 in separating chiasms of NMOSD-ON from HC. OC area correlated well with structural and clinical measures in NMOSD-ON: optic nerve diameter (r = 0.4, p = 0.047), peripapillary retinal nerve fiber layer thickness (r = 0.59, p = 0.003), global visual acuity (r = - 0.57, p = 0.013), and diseases duration (r = - 0.5, p = 0.012).

CONCLUSION

Our results suggest that OC measures are promising and easily accessible imaging markers for the assessment of anterior optic pathway damage.

KEY POINTS

• Optic chiasm dimensions were smaller in neuromyelitis optica spectrum disorder patients compared to healthy controls. • Optic chiasm dimensions are associated with retinal measures and visual dysfunction. • The optic chiasm might be used as an easily accessible imaging marker of neurodegeneration in the anterior optic pathway with potential functional relevance.

Effectiveness of subcutaneous tocilizumab in neuromyelitis optica spectrum disorders

BACKGROUND

Tocilizumab (TCZ), a humanized monoclonal antibody against the interleukin-6 receptor, is approved for treatment of rheumatoid arthritis and several other immune-mediated disorders. Off-label use of the intravenous formulation of tocilizumab for Neuromyelitis Optica Spectrum Disorder (NMOSD) decreased relapse rates in two small case series. However, treatment protocol that requires frequent intravenous infusions may adversely affect adherence to therapy, especially in the more disabled patients, thereby reducing effectiveness. A subcutaneous formulation of tocilizumab was shown to be noninferior to the IV formulation for approved rheumatologic diseases. The effectiveness of subcutaneous TCZ for NMOSD is unknown.

METHODS

We retrospectively reviewed clinical, radiological and serological data on all NMOSD patients who received subcutaneous TCZ in two tertiary referral centers between 2014-2019.

RESULTS

Twelve NMOSD patients who received at least 6 months of subcutaneous TCZ were identified. Eleven were female; mean age was 46.9 ± 14.5 years and mean disease duration was 6.6 ± 4.6 years. Seven patients were seropositive for AQP-4 antibodies, two - for MOG-IgG antibodies, and three were doubly seronegative. During subcutaneous TCZ treatment, eight patients (66.6%) were relapse-free, one patient (8.3%) experienced 1 relapse, two patients (16.6%) - 2 relapses, and one patient (8.3%) - 3 relapses. The median relapse rate within 1 year after starting subcutaneous TCZ - 0 (interquartile range =1.75-0) - was significantly lower than in the year prior to treatment initiation (2, interquartile range = 4.0-0.25; p = 0.04). Overall, the annual relapse rate (ARR) decreased from a median of 2 (interquartile range = 5.75-1.29) prior to subcutaneous TCZ to 0 (interquartile range= = 1.0-0) on treatment (p = 0.0015). One TCZ-treated patient died following a severe myelitis attack.

CONCLUSIONS

Effectiveness of subcutaneous TCZ in NMOSD appears to be similar to that reported for the IV formulation and has an advantage of at-home administration. Prospective, comparative studies of subcutaneous TCZ for NMOSD are warranted.

The Detection of Retina Microvascular Density in Subclinical Aquaporin-4 Antibody Seropositive Neuromyelitis Optica Spectrum Disorders

Purpose: To use optical coherence tomography (OCT) and OCT angiography (OCT-A) to measure changes in the retinal structure and microvasculature of patients with aquaporin-4 antibody-positive, neuromyelitis optica spectrum disorder (NMOSD) with a history of optic neuritis (NMOSD+ON) and those without it (NMOSD–ON).

Methods: A total of 27 aquaporin-4 antibody-positive NMOSD patients and 31 age- and gender-matched healthy control (HC) participants were included. In 27 NMOSD patients, 19 of them had a history of optic neuritis (ON) and 8 of them had no history of ON. Peripapillary retinal nerve fiber layer (pRNFL) thickness and macular ganglion cell and inner plexiform layer (GCIPL) thickness were measured by OCT. Radial peripapillary capillary density (RPCD) and macular superficial vessel density (MSVD) were measured by OCT-A. Comparisons of retinal structural and microvascular parameters between the cohorts were performed using generalized estimating equation (GEE) models. Diagnostic accuracy was evaluated by the area under the receiver operating characteristics curve (AROC).

Results: In NMOSD+ON eyes, the GCIPL and pRNFL thicknesses, 48.6 ± 7.1 and 61.7 ± 25.1 μm, respectively, were significantly thinner than in HC eyes (P < 0.001 for both). However, in NMOSD–ON eyes, the GCIPL and pRNFL thicknesses were not significantly thinner than in HC eyes (P > 0.05 for both). In NMOSD+ON eyes, the RPCD and MSVD, 37.8 ± 7.1 and 36.7 ± 5.0%, respectively, were significantly less dense than HC eyes (P < 0.001 for both). Similarly, the RPCD and MSVD in NMOSD–ON eyes, 49.0 ± 2.8 and 43.9 ± 4.2%, respectively, were also less dense than in HC eyes (P < 0.029 for RPCD, P < 0.023 for MSVD). The highest AROC, 0.845 (sensitivity = 88.5%, specificity = 78.0%), was achieved by the logistic regression combination of all of the variables, i.e., pRNFL, GCIPL, RPCD, and MSVD.

Conclusions: Retinal microvascular changes were present in NMOSD–ON eyes. The combination of retinal structural and microvascular parameters might be helpful to discriminate NMOSD–ON eyes from HC eyes.

Central Sleep Apnea Syndrome Can Complicate Neuromyelitis Optica Spectrum Disorder: A Case Report

Neuromyelitis optica spectrum disorder is a rare, relapsing autoimmune disease of the central nervous system. Various initial presentations can delay diagnosis and treatment. A 14-year-old girl was admitted to the emergency department owing to respiratory insufficiency. Repeated history-taking and neuroimaging revealed an area postrema syndrome. A diagnosis of neuromyelitis optica spectrum disorder with positive aquaporin-4 antibodies has finally been established. The patient improved significantly with immunosuppressive therapy. However, her 3-year follow-up still showed sleep-disordered breathing requiring nocturnal bilevel positive airway pressure therapy. We report an original case of NMOSD leading to persistent central sleep apnea syndrome.

Retinal correlates of neurological disorders

Considering the retina as an extension of the brain provides a platform from which to study diseases of the nervous system. Taking advantage of the clear optical media of the eye and ever-increasing resolution of modern imaging techniques, retinal morphology can now be visualized at a cellular level in vivo. This has provided a multitude of possible biomarkers and investigative surrogates that may be used to identify, monitor and study diseases until now limited to the brain. In many neurodegenerative conditions, early diagnosis is often very challenging due to the lack of tests with high sensitivity and specificity, but, once made, opens the door to patients accessing the correct treatment that can potentially improve functional outcomes. Using retinal biomarkers in vivo as an additional diagnostic tool may help overcome the need for invasive tests and histological specimens, and offers the opportunity to longitudinally monitor individuals over time. This review aims to summarise retinal biomarkers associated with a range of neurological conditions including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and prion diseases from a clinical perspective. By comparing their similarities and differences according to primary pathological processes, we hope to show how retinal correlates can aid clinical decisions, and accelerate the study of this rapidly developing area of research.

Suggestions for improving the design of clinical trials in multiple sclerosis-results of a systematic analysis of completed phase III trials

This manuscript reviews the primary and secondary endpoints of pivotal phase III trials with immunomodulatory drugs in multiple sclerosis (MS). Considering the limitations of previous trial designs, we propose new standards for the planning of clinical trials, taking into account latest insights into MS pathophysiology and patient-relevant aspects. Using a systematic overview of published phase III (pivotal) trials performed as part of application for drug market approval, we evaluate the following characteristics: trial duration, number of trial participants, comparators, and endpoints (primary, secondary, magnetic resonance imaging outcome, and patient-reported outcomes). From a patient perspective, the primary and secondary endpoints of clinical trials are only partially relevant. High-quality trial data pertaining to efficacy and safety that stretch beyond the time frame of pivotal trials are almost non-existent. Understanding of long-term benefits and risks of disease-modifying MS therapy is largely lacking. Concrete proposals for the trial designs of relapsing (remitting) multiple sclerosis/clinically isolated syndrome, primary progressive multiple sclerosis, and secondary progressive multiple sclerosis (e.g., study duration, mechanism of action, and choice of endpoints) are presented based on the results of the systematic overview. Given the increasing number of available immunotherapies, the therapeutic strategy in MS has shifted from a mere "relapse-prevention" approach to a personalized provision of medical care as to the choice of the appropriate drugs and their sequential application over the course of the disease. This personalized provision takes patient preferences as well as disease-related factors into consideration such as objective clinical and radiographic findings but also very burdensome symptoms such as fatigue, depression, and cognitive impairment. Future trial designs in MS will have to assign higher relevance to these patient-reported outcomes and will also have to implement surrogate measures that can serve as predictive markers for individual treatment response to new and investigational immunotherapies. This is an indispensable prerequisite to maximize the benefit of individual patients when participating in clinical trials. Moreover, such appropriate trial designs and suitable enrolment criteria that correspond to the mode of action of the study drug will facilitate targeted prevention of adverse events, thus mitigating risks for individual study participants.

Normative Data and Minimally Detectable Change for Inner Retinal Layer Thicknesses Using a Semi-automated OCT Image Segmentation Pipeline

Neurodegenerative and neuroinflammatory diseases regularly cause optic nerve and retinal damage. Evaluating retinal changes using optical coherence tomography (OCT) in diseases like multiple sclerosis has thus become increasingly relevant. However, intraretinal segmentation, a necessary step for interpreting retinal changes in the context of these diseases, is not standardized and often requires manual correction. Here we present a semi-automatic intraretinal layer segmentation pipeline and establish normative values for retinal layer thicknesses at the macula, including dependencies on age, sex, and refractive error. Spectral domain OCT macular 3D volume scans were obtained from healthy participants using a Heidelberg Engineering Spectralis OCT. A semi-automated segmentation tool (SAMIRIX) based on an interchangeable third-party segmentation algorithm was developed and employed for segmentation, correction, and thickness computation of intraretinal layers. Normative data is reported from a 6 mm Early Treatment Diabetic Retinopathy Study (ETDRS) circle around the fovea. An interactive toolbox for the normative database allows surveying for additional normative data. We cross-sectionally evaluated data from 218 healthy volunteers (144 females/74 males, age 36.5 ± 12.3 years, range 18-69 years). Average macular thickness (MT) was 313.70 ± 12.02 μm, macular retinal nerve fiber layer thickness (mRNFL) 39.53 ± 3.57 μm, ganglion cell and inner plexiform layer thickness (GCIPL) 70.81 ± 4.87 μm, and inner nuclear layer thickness (INL) 35.93 ± 2.34 μm. All retinal layer thicknesses decreased with age. MT and GCIPL were associated with sex, with males showing higher thicknesses. Layer thicknesses were also positively associated with each other. Repeated-measurement reliability for the manual correction of automatic intraretinal segmentation results was excellent, with an intra-class correlation coefficient >0.99 for all layers. The SAMIRIX toolbox can simplify intraretinal segmentation in research applications, and the normative data application may serve as an expandable reference for studies, in which normative data cannot be otherwise obtained.

Imaging markers of disability in aquaporin-4 immunoglobulin G seropositive neuromyelitis optica: a graph theory study

Neuromyelitis optica spectrum disorders lack imaging biomarkers associated with disease course and supporting prognosis. This complex and heterogeneous set of disorders affects many regions of the central nervous system, including the spinal cord and visual pathway. Here, we use graph theory-based multimodal network analysis to investigate hypothesis-free mixed networks and associations between clinical disease with neuroimaging markers in 40 aquaporin-4-immunoglobulin G antibody seropositive patients (age = 48.16 ± 14.3 years, female:male = 36:4) and 31 healthy controls (age = 45.92 ± 13.3 years, female:male = 24:7). Magnetic resonance imaging measures included total brain and deep grey matter volumes, cortical thickness and spinal cord atrophy. Optical coherence tomography measures of the retina and clinical measures comprised of clinical attack types and expanded disability status scale were also utilized. For multimodal network analysis, all measures were introduced as nodes and tested for directed connectivity from clinical attack types and disease duration to systematic imaging and clinical disability measures. Analysis of variance, with group interactions, gave weights and significance for each nodal association (hyperedges). Connectivity matrices from 80% and 95% F-distribution networks were analyzed and revealed the number of combined attack types and disease duration as the most connected nodes, directly affecting changes in several regions of the central nervous system. Subsequent multivariable regression models, including interaction effects with clinical parameters, identified associations between decreased nucleus accumbens (β = −0.85, P = 0.021) and caudate nucleus (β = −0.61, P = 0.011) volumes with higher combined attack type count and longer disease duration, respectively. We also confirmed previously reported associations between spinal cord atrophy with increased number of clinical myelitis attacks. Age was the most important factor associated with normalized brain volume, pallidum volume, cortical thickness and the expanded disability status scale score. The identified imaging biomarker candidates warrant further investigation in larger-scale studies. Graph theory-based multimodal networks allow for connectivity and interaction analysis, where this method may be applied in other complex heterogeneous disease investigations with different outcome measures.

Review: Recent advances in the understanding of the pathophysiology of neuromyelitis optica spectrum disorder

Neuromyelitis optica is an autoimmune inflammatory disorder of the central nervous system that preferentially targets the spinal cord and optic nerve. Following the discovery of circulating antibodies against the astrocytic aquaporin 4 (AQP4) water channel protein, recent studies have expanded our knowledge of the unique complexities of the pathogenesis of neuromyelitis optica and its relationship with the immune response. This review describes and summarizes the recent advances in our understanding of the molecular mechanisms underlying neuromyelitis optica disease pathology and examines their potential as therapeutic targets. Additionally, we update the most recent research by proposing major unanswered questions regarding how peripheral AQP4 antibodies are produced and their entry into the central nervous system, the causes of AQP4-IgG-seronegative disease, why peripheral AQP4-expressing organs are spared from damage, and the impact of this disease on pregnancy.

Optical coherence tomography in myelin-oligodendrocyte-glycoprotein antibody-seropositive patients: a longitudinal study

Background

Serum antibodies against myelin-oligodendrocyte-glycoprotein (MOG-IgG) are detectable in a proportion of patients with acute or relapsing neuroinflammation. It is unclear, if neuro-axonal damage occurs only in an attack-dependent manner or also progressively. Therefore, this study aimed to investigate longitudinally intra-retinal layer changes in eyes without new optic neuritis (ON) in MOG-IgG-seropositive patients.

Methods

We included 38 eyes of 24 patients without ON during follow-up (F/U) [median years (IQR)] 1.9 (1.0–2.2) and 56 eyes of 28 age- and sex-matched healthy controls (HC). The patient group’s eyes included 18 eyes without (Eye^ON-) and 20 eyes with history of ON (Eye^ON+). Using spectral domain optical coherence tomography (OCT), we acquired peripapillary retinal nerve fiber layer thickness (pRNFL) and volumes of combined ganglion cell and inner plexiform layer (GCIP), inner nuclear layer (INL), and macular volume (MV). High-contrast visual acuity (VA) was assessed at baseline.

Results

At baseline in Eye^ON-, pRNFL (94.3 ± 15.9 μm, p = 0.36), INL (0.26 ± 0.03 mm³, p = 0.11), and MV (2.34 ± 0.11 mm³, p = 0.29) were not reduced compared to HC; GCIP showed thinning (0.57 ± 0.07 mm³; p = 0.008), and VA was reduced (logMAR 0.05 ± 0.15 vs. − 0.09 ± 0.14, p = 0.008) in comparison to HC. Longitudinally, we observed pRNFL thinning in models including all patient eyes (annual reduction − 2.20 ± 4.29 μm vs. − 0.35 ± 1.17 μm, p = 0.009) in comparison to HC. Twelve Eye^ON- with other than ipsilateral ON attacks ≤ 6 months before baseline showed thicker pRNFL at baseline and more severe pRNFL thinning in comparison to 6 Eye^ON- without other clinical relapses.

Conclusions

We observed pRNFL thinning in patients with MOG-IgG during F/U, which was not accompanied by progressive GCIP reduction. This effect could be caused by a small number of Eye^ON- with other than ipsilateral ON attacks within 6 months before baseline. One possible interpretation could be a reduction of the swelling, which could mean that MOG-IgG patients show immune-related swelling in the CNS also outside of an attack’s target area.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1521-5) contains supplementary material, which is available to authorized users.

Devic's index case: A critical reappraisal - AQP4-IgG-mediated neuromyelitis optica spectrum disorder, or rather MOG encephalomyelitis?

In 1894, Eugène Devic (1858-1930) and his doctoral student Fernand Gault (1873-1936) reported on a patient with optic neuritis (ON) and myelitis and proposed the name "neuro-myélite optique" for this syndrome. Subsequently, Devic became the eponym of neuromyelitis optica (NMO), which was then referred to as "Devic's syndrome", "Devic's disease" or "Morbus Devic". Thereby, the case became a historical index case of NMO. For many decades little attention was paid to NMO, which most authors considered a clinical variant of multiple sclerosis. However, the discovery of pathogenic antibodies to aquaporin-4 at the beginning of the 21st century revived interest in the syndrome, and AQP4-IgG-positive NMO spectrum disorders (NMOSD) are now studied as prototypical autoimmune diseases. More recently, antibodies to full-length myelin oligodendrocyte glycoprotein (MOG) have been detected in patients with ON as well as in patients with myelitis, some of whom exhibit a clinical phenotype very similar to that described by Devic. This raises the question of whether Devic's patient might have suffered from MOG encephalomyelitis rather than classic NMOSD. In this article, we summarise and discuss the available evidence for and against that hypothesis. We also discuss differential diagnoses and the question whether Devic's patient, who worked as a hatter and had initially been admitted for nervous hyperexcitability and tremor, might have suffered from co-existing erethism ('mad hatter disease'), which is caused by chronic occupational exposure to mercury.

Epidemiology of neuromyelitis optica spectrum disorder in Denmark (1998-2008, 2007-2014)

Epidemiological studies of the uncommon disorder neuromyelitis optica spectrum disorder (NMOSD) may be difficult to interpret because of the evolving nature of diagnostic criteria, differences in the definition and accuracy of NMOSD diagnosis, the completeness of case ascertainment, and variability in assays for the disease-specific biomarker aquaporin-4 (AQP4)-IgG. A sub-group of patients with the clinical syndrome NMOSD lack detectable AQP4-IgG and in these cases an accurate diagnosis requires precise diagnostic algorithms and longitudinal follow-up. Consecutive sets of criteria for NMO/NMOSD have been introduced during the two last decades. Such criteria need validation in different populations. Detection of other autoantibodies, such as IgG specific for myelin oligodendrocyte glycoprotein or for glial fibrillary acidic protein in a sub-group of AQP4-IgG-negative NMOSD patients, has improved over the past decade and may lead to overlap of the clinical syndromes/phenotypes. This review begins by summarizing current knowledge on the widening clinical spectrum of NMOSD. Subsequently, we describe two epidemiological studies from Denmark carried out in two different decades (1998-2008 and 2007-2014) and comment on the differences in study design, patient ascertainment, and interpretation of results. These factors may explain some of the observed differences, reflecting the complexity and providing a clear example of this development.

The role of Optical Coherence Tomography in Parkinsonism: A critical review

Optical coherence tomography (OCT) has been evaluated as a tool to assess retinal changes in various neurodegenerative disorders. Parkinson's disease (PD), is a neurodegenerative disorder wherein dopaminergic deficiency results in some of the symptoms. As retina also has high concentration of dopamine, it would be of interest for both the clinician as well as the basic scientist to know if there is a correlation between the clinical features and the retinal changes. The objective of this review is to critically evaluate the literature and study the utility of OCT as a tool to evaluate retinal changes in PD.