Clinical efficacy of plasmapheresis in patients with neuromyelitis optica spectrum disorder and effects on circulating anti-aquaporin-4 antibody levels

Clinical Characteristics of Anti-aquaporin 4 Antibody Positive Optic Neuritis in Japan

To investigate the clinical characteristics and the effectiveness of maintenance therapy of anti-AQP4 antibody positive optic neuritis in Japanese patients, medical records from 69 patients (103 eyes) were retrospective reviewed. The status of relapse in patients who received maintenance therapy following acute therapy was compared with that before maintenance therapy in patients who started maintenance therapy ≥6 months after acute therapy. In Japan, anti-AQP4 antibody positive optic neuritis was characterized by older onset age and poor visual outcome. The yearly rate and total number of relapses were lower when maintenance therapy was followed immediately after acute therapy.

Apheresis therapies for NMOSD attacks: A retrospective study of 207 therapeutic interventions

Objective

To analyze whether 1 of the 2 apheresis techniques, therapeutic plasma exchange (PE) or immunoadsorption (IA), is superior in treating neuromyelitis optica spectrum disorder (NMOSD) attacks and to identify predictive factors for complete remission (CR).

Methods

This retrospective cohort study was based on the registry of the German Neuromyelitis Optica Study Group, a nationwide network established in 2008. It recruited patients with neuromyelitis optica diagnosed according to the 2006 Wingerchuk criteria or with aquaporin-4 (AQP4-ab)-antibody-seropositive NMOSD treated at 6 regional hospitals and 16 tertiary referral centers until March 2013. Besides descriptive data analysis of patient and attack characteristics, generalized estimation equation (GEE) analyses were applied to compare the effectiveness of the 2 apheresis techniques. A GEE model was generated to assess predictors of outcome.

Results

Two hundred and seven attacks in 105 patients (87% AQP4-ab-antibody seropositive) were treated with at least 1 apheresis therapy. Neither PE nor IA was proven superior in the therapy of NMOSD attacks. CR was only achieved with early apheresis therapy. Strong predictors for CR were the use of apheresis therapy as first-line therapy (OR 12.27, 95% CI: 1.04-144.91, p = 0.047), time from onset of attack to start of therapy in days (OR 0.94, 95% CI: 0.89-0.99, p = 0.014), the presence of AQP4-ab-antibodies (OR 33.34, 95% CI: 1.76-631.17, p = 0.019), and monofocal attack manifestation (OR 4.71, 95% CI: 1.03-21.62, p = 0.046).

Conclusions

Our findings suggest early use of an apheresis therapy in NMOSD attacks, particularly in AQP4-ab-seropositive patients. No superiority was shown for one of the 2 apheresis techniques.

Classification of evidence

This study provides Class IV evidence that for patients with NMOSD, neither PE nor IA is superior in the treatment of attacks.

Therapeutic plasma exchange in paediatric neurology: a critical review and proposed treatment algorithm

Therapeutic plasma exchange (TPE) has been a key immunotherapeutic strategy in numerous neurological syndromes, predominantly during the acute phase of illness. This paper reviews the indications, strength of evidence, and safety of TPE in children with neurological conditions. The rarity of these immune conditions in children, alongside an often incomplete understanding of their pathobiology, has limited the development of a robust scientific rationale for TPE therapy and the feasibility of conducting larger controlled trials. TPE continues to be used, but is a costly therapy with common adverse effects. Uncertainty remains over how to compare the different TPE methods, the optimal dosage of therapy, and monitoring and integration of TPE with other immunotherapies. Further studies are also required to define the indications and benefits of TPE and assess evolving technologies such as immunoadsorption.

WHAT THIS PAPER ADDS

Studies investigating therapeutic plasma exchange (TPE) are small and mainly uncontrolled. They provide evidence for the efficacy of TPE in childhood neuro-inflammatory conditions. TPE is generally well tolerated provided key adverse effects are anticipated and avoided. Systematic dosing and objective assessment of treatment effect should be priorities for future research.

Short-term effect of additional apheresis on visual acuity changes in patients with steroid-resistant optic neuritis in neuromyelitis optica spectrum disorders

PURPOSE

To evaluate temporal changes in visual acuity in patients with steroid-resistant optic neuritis (ON) in neuromyelitis optica spectrum disorders (NMOSD) after apheresis.

DESIGN

Retrospective observational study, clinical case series SUBJECTS AND METHODS: We reviewed the medical charts of 15 eyes of 9 consecutive patients with ON in NMOSD who underwent apheresis between March 2010 and September 2017. All patients were seropositive for anti-aquaporin 4 (AQP4) antibody and resistant to steroid pulse therapy. Apheresis was performed by either simple plasma exchange or/and immune adsorption therapy.

RESULTS

Twelve eyes (80%) showed improvement with logMAR > 0.3 at 1 month after apheresis. Within 1 month after apheresis therapy, logMAR on average significantly decreased, the magnitude of change being greatest within the first week. Thereafter visual acuity became stable in 10 of the 11 eyes, until 12 months. However, two eyes (12%) showed recurrence of visual acuity reduction 3 months after the cessation of apheresis. There were a few serious complications during and after apheresis, but these were completely treatable.

CONCLUSIONS

Additional apheresis therapy rapidly improves the visual acuity of steroid-resistant seropositive AQP4 ON.

Short delay to initiate plasma exchange is the strongest predictor of outcome in severe attacks of NMO spectrum disorders

INTRODUCTION

Severe attacks of neuromyelitis optica spectrum disorder (NMO-SD) are improved by plasma exchange (PLEX) given as an adjunctive therapy. Initial studies failed to demonstrate a delay of PLEX treatment influenced clinical outcome; however PLEX was always used late. We examine the clinical consequences of delay in PLEX initiation on severe optic neuritis and spinal cord attacks in NMO-SD.

METHODS

All of our patients who suffered attacks of NMO-SD, treated in our centre by PLEX, were retrospectively considered for inclusion. Primary outcome was defined as complete improvement. Secondary poor/good outcomes were respectively defined to be the higher/lower third of Delta-Expanded Disability Status Scale (EDSS) (late minus baseline EDSS). Delays from clinical onset to PLEX initiation were categorised for multivariate analysis.

RESULTS

Of the 60 patients included, NMO-SD criteria (2015) were fulfilled in 92%. One hundred and fifteen attacks were included and received PLEX with a median of 7 days (0-54) after clinical onset. The probability to regain complete improvement continuously decreased from 50% for PLEX given at day 0 to 1%-5% after day 20. Through multivariate analysis, the baseline impairment and PLEX delay were associated with the probability to complete improvement (OR 5.3; 95% CI 1.8 to 15.9). Reducing the PLEX delay also influenced the good secondary outcome but not the poor secondary outcome.

CONCLUSIONS

These results confirm an improved clinical benefit of early initiation of PLEX during severe attacks of NMO-SD. Perceiving PLEX as a rescue therapy only after steroid failure could be deleterious.

Therapeutic Efficacy of Plasma Exchange in Neuromyelitis Optica

Background

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease that selectively affects the optic nerves and spinal cord and generally follows a relapsing course. Therapeutic plasma exchange (TPE) appears to be effective in patients with central nervous system inflammatory demyelinating disease who do not respond to first-line corticosteroid treatment.

Objective

We represent a retrospective review of the use of TPE in the treatment of an acute attack of NMO in five patients who failed to respond to initial immunomodulatory treatment.

Materials and Methods

We evaluated the effect of TPE on the degree of recovery from NMO. It was performed using a single volume plasma exchange with intermittent cell separator (Hemonetics Mobile Collection System plus) by femoral or central line access and scheduled preferably on alternate-day intervals from 8 to 10 days. Both subjective and objective clinical response to TPE was estimated, and final assessment of response was made at the time of the last TPE in the series.

Results

All patients were severely disabled before the initiation of TPE and they were female; with the mean age of these patients was 52.5 years (range = 36-69 years), the median age of NMO diagnosis was 49.4 years (range = 35-65 years), and the median duration of disease was 2.6 years (range = 0-5 years). Out of five patients, three had a history of bilateral optic neuritis, and all patients were anti-against protein aquaporin-4antibody positive. Totally 24 TPE procedures were performed on five patients, the mean time of start of TPE in the acute attack was 18.6 days. Patients were severely disabled at the initiation of TPE (range = expanded disability status scale 6.5-9), and improvement was observed early in the course of TPE treatment in most patients.

Conclusion

The present study provides clinical support for the importance of TPE in refractory acute attack in NMO. However, with new diagnostic technologies and increasing clinical awareness, we may see a more improved ways of TPE in these patients in the future; hence, TPE is more effective modality of treatment as it also removed the antibodies.

Myointimal Hyperplasia in a Patient with Neuromyelitis Optica (Devic's Disease) after the Creation of an Arteriovenous Graft

Neuromyelitis optica, also known as Devic's disease, is an autoimmune disorder that leads to the inflammation and demyelination of nerves. Devic's disease primarily affects the optic nerve and spinal cord, but can lead to a significant loss of function throughout the body if not treated with steroid therapy or plasmapheresis. We recently saw a 62-year-old patient who received plasmapheresis for Devic's disease through a PTFE arteriovenous graft in her left arm. Her graft clotted without warning, and percutaneous thrombolysis was not successful. A new vascular access was achieved with the use of an immediate-cannulation PTFE graft, and the patient received plasmapheresis immediately after her operation. However, the patient returned within 2 weeks with a thrombosed graft. Extensive myointimal fibrosis was noted within the brachial artery and axillary vein during a graft thrombectomy. Subsequent placement of a new arteriovenous fistula in her contralateral arm was eventually successful. Myointimal fibrosis may be a sequela of symptomatic antibody-positive Devic's disease, and avoidance of synthetic materials may be indicated in this patient population to avoid exacerbation of an autoimmune response.

Pathogenic implications of cerebrospinal fluid barrier pathology in neuromyelitis optica

Pathogenic autoantibodies associated with neuromyelitis optica (NMO) induce disease by targeting aquaporin-4 (AQP4) water channels enriched on astrocytic endfeet at blood–brain interfaces. AQP4 is also expressed at cerebrospinal fluid (CSF)–brain interfaces, such as the pial glia limitans and the ependyma and at the choroid plexus blood–CSF barrier. However, little is known regarding pathology at these sites in NMO. Therefore, we evaluated AQP4 expression, microglial reactivity, and complement deposition at pial and ependymal surfaces and in the fourth ventricle choroid plexus in 23 autopsy cases with clinically and/or pathologically confirmed NMO or NMO spectrum disorder. These findings were compared to five cases with multiple sclerosis, five cases of choroid plexus papilloma, and five control cases without central nervous system disease. In the NMO cases, AQP4 immunoreactivity was reduced relative to control levels in the pia (91%; 21/23), ependyma (56%; 9/16), and choroid plexus epithelium (100%; 12/12). AQP4 immunoreactivity was normal in MS cases in these regions. Compared to MS, NMO cases also showed a focal pattern of pial and ependymal complement deposition and more pronounced microglial reactivity. In addition, AQP4 loss, microglial reactivity, and complement deposition colocalized along the pia and ependyma only in NMO cases. Within the choroid plexus, AQP4 loss was coincident with C9neo immunoreactivity on epithelial cell membranes only in NMO cases. These observations demonstrate that NMO immunopathology extends beyond perivascular astrocytic foot processes to include the pia, ependyma, and choroid plexus, suggesting that NMO IgG-induced pathological alterations at CSF–brain and blood–CSF interfaces may contribute to the occurrence of ventriculitis, leptomeningitis, and hydrocephalus observed among NMO patients. Moreover, disruption of the blood–CSF barrier induced by binding of NMO IgG to AQP4 on the basolateral surface of choroid plexus epithelial cells may provide a unique portal for entry of the pathogenic antibody into the central nervous system.

Role of low plasma volume treatment on clinical efficacy of plasmapheresis in neuromyelitis optica

BACKGROUND:

Neuromyelitis optica (NMO) is an autoimmune demyelinating disease preferentially targeting the optic nerves and spinal cord. Plasmapheresis (PP) is an effective adjunct therapy in severe NMO attacks. The recommended minimum plasma volume to be treated per session of PP is equivalent to total plasma volume (TPV) of the patient.

AIM:

To study the effect of lower plasma volume treated in patients with NMO on clinical efficacy of plasmapheresis in comparison to minimum recommended volume.

METHODS:

This retrospective study was done on acute NMO patients who were managed with PP at our center. Patients who had 5 sessions of PP, spread over 10 days, were included. Clinical outcome was defined as per predefined criteria.

RESULTS:

24 patients who underwent PP for acute NMO met our inclusion criteria. Females (age; mean (SD) 33.7 (11.2) years) were more common (n = 18). The minimum recommended plasma volume (PV) that was supposed to be treated per patient during entire acute therapeutic period was 195.5 (14.6) mL per kilogram-body-weight (kg-bw). We treated lower plasma volume (mean (SD) 112.7 (17.0) mL per kg-bw); the difference was significant (P < 0.05). The volume treated was same across the gender (P > 0.05). Significant clinical improvement was observed in 79% of patients (n = 19) after 6 months. There were no significant differences in volume of plasma treated, between patients who had moderate and marked improvement; also, who did, and did not have significant clinical improvement (P > 0.05; for both).

CONCLUSIONS:

Plasmapheresis is a safe and efficient add-on therapy in NMO, especially in steroid-resistant cases. Although the volumes of plasma treated during acute plasmapheresis were less than recommended minimum volumes, majority of patients had significant clinical improvement.

Treatment of neuromyelitis optica

PURPOSE OF REVIEW

Neuromyelitis optica (NMO) is an antibody-mediated inflammatory disease of the central nervous system with a predilection for the optic nerves, spinal cord and certain brain regions. It has a distinct pathogenesis relating to aquaporin-4 autoimmunity and complement-mediated injury. This knowledge has translated into targeted efforts to develop novel, disease-specific treatments. In this review, we discuss evidence supporting the use of currently available treatments for acute exacerbations and for long-term disease modification. We also discuss the risks and benefits of available and emerging immunotherapies.

RECENT FINDINGS

Early, accurate diagnosis of NMO with appropriate acute and long-term immunosuppressive treatment is of prime importance for the prevention of disability associated with this disease. Standard measures for the management of acute exacerbations include intravenous methylprednisolone and plasmapheresis. First-line, long-term immunotherapies for NMO include azathioprine, mycophenolate mofetil and rituximab. Three randomized controlled treatment trials evaluating these agents are currently being conducted. In addition, there are numerous emerging therapies that are based upon current understanding of the disease immunopathogenesis.

SUMMARY

NMO is an autoimmune disease that is separate from multiple sclerosis. Better understanding of its antibody and complement-dependent pathophysiology has proven to be critical for the formulation of current and future treatment strategies.

Discriminating long myelitis of neuromyelitis optica from sarcoidosis

OBJECTIVE

To compare longitudinally extensive myelitis in neuromyelitis optica spectrum disorders (NMOSD) and spinal cord sarcoidosis (SCS).

METHODS

We identified adult patients evaluated between 1996 and 2015 with SCS or NMOSD whose first myelitis episode was accompanied by a spinal cord lesion spanning ≥3 vertebral segments. All NMOSD patients were positive for aquaporin-4-immunoglobulin G, and all sarcoidosis cases were pathologically confirmed. Clinical characteristics were evaluated. Spine magnetic resonance imaging was reviewed by 2 neuroradiologists.

RESULTS

We studied 71 patients (NMOSD, 37; SCS, 34). Sixteen (47%) SCS cases were initially diagnosed as NMOSD or idiopathic transverse myelitis. Median delay to diagnosis was longer for SCS than NMOSD (5 vs 1.5 months, p < 0.01). NMOSD myelitis patients were more commonly women, had concurrent or prior optic neuritis or intractable vomiting episodes more frequently, had shorter time to maximum deficit, and had systemic autoimmunity more often than SCS (p < 0.05). SCS patients had constitutional symptoms, cerebrospinal fluid (CSF) pleocytosis, and hilar adenopathy more frequently than NMOSD (p < 0.05); CSF hypoglycorrhachia (11%, p = 0.25) and elevated angiotensin-converting enzyme (18%, p = 0.30) were exclusive to SCS. Dorsal cord subpial gadolinium enhancement extending ≥2 vertebral segments and persistent enhancement >2 months favored SCS, and ringlike enhancement favored NMOSD (p < 0.05). Maximum disability was similar in both disorders.

INTERPRETATION

SCS is an under-recognized cause of longitudinally extensive myelitis that commonly mimics NMOSD. We identified clinical, laboratory, systemic, and radiologic features that, taken together, help discriminate SCS from NMOSD.

Present and Future Therapies in Neuromyelitis Optica Spectrum Disorders

Neuromyelitis optica spectrum disorders (NMOSD) are important evolving entities, which have reached much attention in the recent years. NMOSD are characterized by inflammatory lesions in the optic nerves, spinal cord, and central parts of the brain, as well as an autoimmune process directed against aquaporin-4. As disability in NMOSD accumulates by inflammatory damage from attacks, both the treatment and prevention of attacks are decisive for the long-term outcome. NMOSD attacks are treated with high-dose intravenous corticosteroids and apheresis therapies, in particular therapeutic plasma exchange. In cases of incomplete remission, escalation of attack treatment is recommended. Preventive therapy is immunosuppressive and should by commenced as early as possible. Apart from classical immunosuppressants such as azathioprine and mycophenolate mofetil, repurposed biologicals are increasingly used. B-cell depletion with rituximab and other agents, inhibition of the interleukin-6 receptor with tocilizumab, and blockade of complement-mediated damage by eculizumab all are promising therapeutic strategies evaluated in randomized controlled trials. In this review, we will discuss present and future immunotherapies for NMOSD and also consider combination of treatments, plasma, cellular and other therapies. Current advances in immunopathological knowledge are translated into innovative concepts and begin a new era of NMOSD therapy.

Neuromyelitis optica: Evaluation of 871 attacks and 1,153 treatment courses

OBJECTIVE

Neuromyelitis optica (NMO) attacks often are severe, are difficult to treat, and leave residual deficits. Here, we analyzed the frequency, sequence, and efficacy of therapies used for NMO attacks.

METHODS

A retrospective review was made of patient records to assess demographic/diagnostic data, attack characteristics, therapies, and the short-term remission status (complete remission [CR], partial remission [PR], no remission [NR]). Inclusion criteria were NMO according to Wingerchuk's 2006 criteria or aquaporin-4 antibody-positive NMO spectrum disorder (NMOSD). Remission status was analyzed with generalized estimating equations (GEEs), a patient-based statistical approach.

RESULTS

A total of 871 attacks in 185 patients (142 NMO/43 NMOSD, 82% female) were analyzed. The 1,153 treatment courses comprised high-dose intravenous steroids (HD-S; n = 810), plasma exchange (PE; n = 192), immunoadsorption (IA; n = 38), other (n = 80), and unknown (n = 33) therapies. The first treatment course led to CR in 19.1%, PR in 64.5%, and NR in 16.4% of attacks. Second, third, fourth, and fifth treatment courses were given in 28.2%, 7.1%, 1.4%, and 0.5% of attacks, respectively. This escalation of attack therapy significantly improved outcome (p < 0.001, Bowker test). Remission rates were higher for isolated optic neuritis versus isolated myelitis (p < 0.001), and for unilateral versus bilateral optic neuritis (p = 0.020). Isolated myelitis responded better to PE/IA than to HD-S as first treatment course (p = 0.037). Predictors of CR in multivariate GEE analysis were age (odds ratio [OR] = 0.97, p = 0.011), presence of myelitis (OR = 0.38, p = 0.002), CR from previous attack (OR = 6.85, p < 0.001), and first-line PE/IA versus HD-S (OR = 4.38, p = 0.006).

INTERPRETATION

Particularly myelitis and bilateral optic neuritis have poor remission rates. Escalation of attack therapy improves outcome. PE/IA may increase recovery in isolated myelitis.

Plasma Exchange in a Patient with Tumefactive, Corticosteroid-Resistant Multiple Sclerosis

Tumefactive multiple sclerosis (MS) is an aggressive form of MS that can be difficult to treat with standard therapies. In severe MS relapses, plasma exchange (PLEX) has shown some benefit, but reports of its use in patients with tumefactive MS are limited. This article describes the successful use of PLEX in a patient with tumefactive MS. A 46-year-old right-handed woman with a recent diagnosis of MS presented with drowsiness, dysarthria, horizontal nystagmus, and quadriparesis. Her brain magnetic resonance images demonstrated multiple tumefactive demyelinating lesions in the medulla, bilateral periventricular white matter, and corona radiata white matter. She was initially treated with a 10-day course of intravenous methylprednisolone without benefit; therefore, PLEX was initiated. After the second exchange, the patient started to improve and was discharged initially to rehabilitation and then home. She was started on disease-modifying therapy with natalizumab and did not experience further relapses but had slow clinical decline during the next year, which led to discontinuation of natalizumab treatment. PLEX may be used as second-line treatment in corticosteroid-resistant MS relapses, but there are limited reports of its use in patients with tumefactive MS. This patient presented with aggressive disease with multiple tumefactive lesions and did not respond to standard treatment with corticosteroids. PLEX was successful in improving her symptoms, allowing her to return home, although the disease progressed during the next year.

Inventory of a Neurological Intensive Care Unit: Who Is Treated and How Long?

Purpose. To characterize indications, treatment, and length of stay in a stand-alone neurological intensive care unit with focus on comparison between ventilated and nonventilated patient. Methods. We performed a single-center retrospective cohort study of all treated patients in our neurological intensive care unit between October 2006 and December 2008. Results. Overall, 512 patients were treated in the surveyed period, of which 493 could be included in the analysis. Of these, 40.8% had invasive mechanical ventilation and 59.2% had not. Indications in both groups were predominantly cerebrovascular diseases. Length of stay was 16.5 days in mean for ventilated and 3.6 days for nonventilated patient. Conclusion. Most patients, ventilated or not, suffer from vascular diseases with further impairment of other organ systems or systemic complications. Data reflects close relationship and overlap of treatment on nICU with a standardized stroke unit treatment and suggests, regarding increasing therapeutic options, the high impact of acute high-level treatment to reduce consequential complications.

Outcomes after early administration of plasma exchange in pediatric central nervous system inflammatory demyelination

The use of plasma exchange has been described in steroid-refractory central nervous system inflammatory demyelination in adults, but less has been published regarding its use in children and adolescents. We describe 12 children treated with plasma exchange for acute severe central nervous system inflammatory demyelination. The clinical attack leading to plasma exchange included symptomatic spinal cord lesions in 10 and symptomatic brainstem lesions in 2 children. Diagnosis was acute transverse myelitis in 6, relapsing-remitting multiple sclerosis in 5, and acute disseminated encephalomyelitis in 1 child. Adverse events related to plasma exchange necessitating intervention were observed in 3 children. Median Expanded Disability Status Scale score at plasma exchange start was 7.5 (range 4-9.5). At 3 months, 7 children were ambulatory without aid (Expanded Disability Status Scale score of ≤4). This retrospective study suggests that plasma exchange can be effective in ameliorating symptoms in severe pediatric central nervous system inflammatory demyelination, although lack of randomization or control group limits the ability to attribute this outcome entirely to plasma exchange.

Treatment of acute relapses in neuromyelitis optica: Steroids alone versus steroids plus plasma exchange

BACKGROUND

Although adding plasma exchange (PLEX) to steroids in severe neuromyelitis optica (NMO) attacks is common practice in steroid-resistant cases, the benefit of this strategy has not been previously quantified.

OBJECTIVE

The objective of this paper is to compare the efficacy of high-dose intravenous methylprednisolone (IVMP) versus IVMP+PLEX in treatment of acute NMO relapses.

METHODS

We conducted a retrospective review of the last 83 NMO admissions to the Johns Hopkins Hospital treated with IVMP alone versus IVMP+PLEX (for steroid-resistant cases). Extended Disability Status Scale (EDSS) score was calculated at baseline, at presentation, at discharge, and on follow-up.

RESULTS

Eighteen NMO relapses (16 patients, 87% female, mean age at relapse: 33.9±23.8, median baseline EDSS 2.5) were treated with IVMP alone and 65 relapses (43 patients, 95% female, mean age at relapse: 43.8±15.7, median baseline EDSS 5.75) were treated with IVMP + PLEX. Sixty-five percent of IVMP + PLEX patients achieved an EDSS equal or below their baseline at follow-up while only 35% of the IVMP-only patients achieved their baseline EDSS on follow-up (odds ratio=3.36, 95% CI 1.0657 to 10.6004, p = 0.0386). PLEX was more effective in improving EDSS in patients on preventive immunosuppressive medications at time of relapse.

CONCLUSIONS

PLEX+IVMP are more likely to improve EDSS after NMO relapses compared to IVMP alone, especially in patients taking preventive medications.

Longitudinally extensive transverse myelitis

PURPOSE OF REVIEW

Longitudinally extensive transverse myelitis (LETM) is a frequently devastating clinical syndrome which has come into focus for its association with neuromyelitis optica (NMO). Recent advances in the diagnosis of NMO have led to very sensitive and specific tests and advances in therapy for this disorder. LETM is not pathognomonic of NMO, therefore it is important to investigate for other causes of myelopathy in these patients. This review aims to discuss recent advances in NMO diagnosis and treatment, and to discuss the differential diagnosis in patients presenting with LETM.

RECENT FINDINGS

Fluorescence-activated cell sorting and cell binding assays for NMO-IgG are the most sensitive for detecting NMO spectrum disorders. Patients who have a clinical presentation of NMO, who have been tested with older ELISA or immunofluorescence assay and been found to be negative, should be retested with a fluorescence-activated cell sorting assay when available, particularly in the presence of recurrent LETM. Novel therapeutic strategies for LETM in the context of NMO include eculizumab, which could be considered in patients with active disease who have failed azathioprine and rituximab. Thorough investigation of patients with LETM who are negative for NMO-IgG may lead to an alternate cause for myelopathy.

SUMMARY

LETM is a heterogeneous condition. Novel treatment strategies are available for NMO, but other causes need to be excluded in NMO-IgG-seronegative patients.

Potential therapeutic benefit of C1-esterase inhibitor in neuromyelitis optica evaluated in vitro and in an experimental rat model

Neuromyelitis optica (NMO) is an autoimmune demyelinating disease of the central nervous system in which binding of anti-aquaporin-4 (AQP4) autoantibodies (NMO-IgG) to astrocytes causes complement-dependent cytotoxicity (CDC) and inflammation resulting in oligodendrocyte and neuronal injury. There is compelling evidence for a central role of complement in NMO pathogenesis. Here, we evaluated the potential of C1-esterase inhibitor (C1-inh) for complement-targeted therapy of NMO. C1-inh is an anti-inflammatory plasma protein with serine protease inhibition activity that has a broad range of biological activities on the contact (kallikrein), coagulation, fibrinolytic and complement systems. C1-inh is approved for therapy of hereditary angioedema (HAE) and has been studied in a small safety trial in acute NMO relapses (NCT 01759602). In vitro assays of NMO-IgG-dependent CDC showed C1-inh inhibition of human and rat complement, but with predicted minimal complement inhibition activity at a dose of 2000 units in humans. Inhibition of complement by C1-inh was potentiated by ∼10-fold by polysulfated macromolecules including heparin and dextran sulfate. In rats, intravenous C1-inh at a dose 30-fold greater than that approved to treat HAE inhibited serum complement activity by <5%, even when supplemented with heparin. Also, high-dose C1-inh did not reduce pathology in a rat model of NMO produced by intracerebral injection of NMO-IgG. Therefore, although C1r and C1s are targets of C1-inh, our in vitro data with human serum and in vivo data in rats suggest that the complement inhibition activity of C1-inh in serum is too low to confer clinical benefit in NMO.

Neuromyelitis optica: clinical features, immunopathogenesis and treatment

The term 'neuromyelitis optica' ('Devic's syndrome', NMO) refers to a syndrome characterized by optic neuritis and myelitis. In recent years, the condition has raised enormous interest among scientists and clinical neurologists, fuelled by the detection of a specific serum immunoglobulin (Ig)G reactivity (NMO-IgG) in up to 80% of patients with NMO. These autoantibodies were later shown to target aquaporin-4 (AQP4), the most abundant water channel in the central nervous system (CNS). Here we give an up-to-date overview of the clinical and paraclinical features, immunopathogenesis and treatment of NMO. We discuss the widening clinical spectrum of AQP4-related autoimmunity, the role of magnetic resonance imaging (MRI) and new diagnostic means such as optical coherence tomography in the diagnosis of NMO, the role of NMO-IgG, T cells and granulocytes in the pathophysiology of NMO, and outline prospects for new and emerging therapies for this rare, but often devastating condition.

Aquaporin-4 antibodies (NMO-IgG) as a serological marker of neuromyelitis optica: a critical review of the literature

Antibodies to aquaporin-4 (called NMO-IgG or AQP4-Ab) constitute a sensitive and highly specific serum marker of neuromyelitis optica (NMO) that can facilitate the differential diagnosis of NMO and classic multiple sclerosis. NMO-IgG/AQP4-Ab seropositive status has also important prognostic and therapeutic implications in patients with isolated longitudinally extensive myelitis (LETM) or optic neuritis (ON). In this article, we comprehensively review and critically appraise the existing literature on NMO-IgG/AQP4-Ab testing. All available immunoassays-including tissue-based (IHC), cell-based (ICC, FACS) and protein-based (RIPA, FIPA, ELISA, Western blotting) assays-and their differential advantages and disadvantages are discussed. Estimates for sensitivity, specificity, and positive and negative likelihood ratios are calculated for all published studies and accuracies of the various immunoassay techniques compared. Subgroup analyses are provided for NMO, LETM and ON, for relapsing vs. monophasic disease, and for various control groups (eg, MS vs. other controls). Numerous aspects of NMO-IgG/AQP4-Ab testing relevant for clinicians (eg, impact of antibody titers and longitudinal testing, indications for repeat testing, relevance of CSF testing and subclass analysis, NMO-IgG/AQP4-Ab in patients with rheumatic diseases) as well as technical aspects (eg, AQP4-M1 vs. AQP4-M23-based assays, intact AQP4 vs. peptide substrates, effect of storage conditions and freeze/thaw cycles) and pitfalls are discussed. Finally, recommendations for the clinical application of NMO-IgG/AQP4-Ab serology are given.

Immunoadsorption therapy for neuromyelitis optica spectrum disorders long after the acute phase

Neuromyelitis optica (NMO) is a severe inflammatory demyelinating disease with exacerbations involving recurrent or bilateral optic neuritis and longitudinally extensive transverse myelitis. Pulse steroid therapy is recommended as the initial, acute-phase treatment for NMO. If ineffective, treatment with plasma exchange (PE) should commence. However, no evidence exists to support the effectiveness of PE long after the acute phase. Immunoadsorption therapy (IA) eliminates pathogenic antibodies while sparing other plasma proteins. With IA, side effects of PE resulting from protein substitution can be avoided. However, whether IA is effective for NMO remains unclear. We describe a patient with anti-aquaporin-4-positive myelitis who responded to IA using a tryptophan polyvinyl alcohol gel column that was begun 52 days after disease onset following the acute phase. Even long after the acute phase when symptoms appear to be stable, IA may be effective and should not be excluded as a treatment choice.

Immunopathogenesis of neuromyelitis optica

Neuromyelitis optica (NMO, Devic's syndrome) is a clinical syndrome characterized by optic neuritis and (mostly longitudinally extensive) myelitis. If untreated, NMO usually takes a relapsing course and often results in blindness and tetra- or paraparesis. The discovery of autoantibodies to aquaporin-4, the most abundant water channel in the CNS, in 70-80% of patients with NMO (termed NMO-IgG or AQP4-Ab) and subsequent investigations into the pathogenic impact of this new reactivity have led to the recognition of NMO as an autoimmune condition and as a disease entity in its own right, distinct from classic multiple sclerosis. Here, we comprehensively review the current knowledge on the role of NMO-IgG/AQP4-Ab, B cells, T cells, and the innate immune system in the pathogenesis of NMO.

Treating neuromyelitis optica with the interleukin-6 receptor antagonist tocilizumab

We present a 32-year-old female patient with fulminant neuromyelitis optica. After the initial treatment with the monoclonal antibody rituximab failed, therapy with the anti-IL-6 receptor antagonist tocilizumab was initiated. The patient experienced a clinically relevant improvement from severe tetraparesis to low-grade paresis, which is still maintained. On MRI of the spinal cord an almost complete restitution of a predescribed extensive myelopathy accompanied this clinical improvement. Meanwhile clinical stability was achieved for over 1 year without any side effects of the ongoing treatment with tocilizumab.

Experimental mouse model of optic neuritis with inflammatory demyelination produced by passive transfer of neuromyelitis optica-immunoglobulin G

Background

Although optic neuritis (ON) is a defining feature of neuromyelitis optica (NMO), appropriate animal models of NMO ON are lacking. Most NMO patients are seropositive for immunoglobulin G autoantibodies (NMO-IgG) against the astrocyte water channel aquaporin-4 (AQP4).

Methods

Several approaches were tested to develop a robust, passive-transfer mouse model of NMO ON, including NMO-IgG and complement delivery by: (i) retrobulbar infusion; (ii) intravitreal injection; (iii) a single intracranial injection near the optic chiasm; and (iv) 3-days continuous intracranial infusion near the optic chiasm.

Results

Little ON or retinal pathology was seen using approaches (i) to (iii). Using approach (iv), however, optic nerves showed characteristic NMO pathology, with loss of AQP4 and glial fibrillary acidic protein immunoreactivity, granulocyte and macrophage infiltration, deposition of activated complement, demyelination and axonal injury. Even more extensive pathology was created in mice lacking complement inhibitor protein CD59, or using a genetically modified NMO-IgG with enhanced complement effector function, including significant loss of retinal ganglion cells. In control studies, optic nerve pathology was absent in treated AQP4-deficient mice, or in wild-type mice receiving control (non-NMO) IgG and complement.

Conclusion

Passive transfer of NMO-IgG and complement by continuous infusion near the optic chiasm in mice is sufficient to produce ON with characteristic NMO pathology. The mouse model of NMO ON should be useful in further studies of NMO pathogenesis mechanisms and therapeutics.

Development, maintenance and disruption of the blood-brain barrier

The interface between the blood circulation and the neural tissue features unique characteristics that are encompassed by the term 'blood-brain barrier' (BBB). The main functions of this barrier, namely maintenance of brain homeostasis, regulation of influx and efflux transport, and protection from harm, are determined by its specialized multicellular structure. Every constituent cell type makes an indispensable contribution to the BBB's integrity. But if one member of the BBB fails, and as a result the barrier breaks down, there can be dramatic consequences and neuroinflammation and neurodegeneration can occur. In this Review, we highlight recently gained mechanistic insights into the development and maintenance of the BBB. We then discuss how BBB disruption can cause or contribute to neurological disease. Finally, we examine how this knowledge can be used to explore new possibilities for BBB repair.

Principles of separation: indications and therapeutic targets for plasma exchange

Extracorporeal "blood purification," mainly in the form of hemodialysis has been a major portion of the clinical activity of many nephrologists for the past 5 decades. A possibly older procedure, therapeutic plasma exchange, separates and then removes plasma as a method of removing pathogenic material from the patient. In contrast to hemodialysis, therapeutic plasma exchange preferentially removes biologic substances of high molecular weight such as autoantibodies or alloantibodies, antigen-antibody complexes, and Ig paraproteins. These molecular targets may be cleared through two alternative procedures: centrifugal separation and membrane separation. This review presents operational features of each procedure, with relevance to the nephrologist. Kinetics of removal of these plasma constituents are based on the principles of separation by the apheresis technique and by features specific to each molecular target, including their production and compartmentalization in the body. Molecular targets for common renal conditions requiring therapeutic plasma exchange are also discussed in detail.

Aquaporin-4 antibodies (NMO-IgG) as a serological marker of neuromyelitis optica: a critical review of the literature

Antibodies to aquaporin-4 (called NMO-IgG or AQP4-Ab) constitute a sensitive and highly specific serum marker of neuromyelitis optica (NMO) that can facilitate the differential diagnosis of NMO and classic multiple sclerosis. NMO-IgG/AQP4-Ab seropositive status has also important prognostic and therapeutic implications in patients with isolated longitudinally extensive myelitis (LETM) or optic neuritis (ON). In this article, we comprehensively review and critically appraise the existing literature on NMO-IgG/AQP4-Ab testing. All available immunoassays-including tissue-based (IHC), cell-based (ICC, FACS) and protein-based (RIPA, FIPA, ELISA, Western blotting) assays-and their differential advantages and disadvantages are discussed. Estimates for sensitivity, specificity, and positive and negative likelihood ratios are calculated for all published studies and accuracies of the various immunoassay techniques compared. Subgroup analyses are provided for NMO, LETM and ON, for relapsing vs. monophasic disease, and for various control groups (eg, MS vs. other controls). Numerous aspects of NMO-IgG/AQP4-Ab testing relevant for clinicians (eg, impact of antibody titers and longitudinal testing, indications for repeat testing, relevance of CSF testing and subclass analysis, NMO-IgG/AQP4-Ab in patients with rheumatic diseases) as well as technical aspects (eg, AQP4-M1 vs. AQP4-M23-based assays, intact AQP4 vs. peptide substrates, effect of storage conditions and freeze/thaw cycles) and pitfalls are discussed. Finally, recommendations for the clinical application of NMO-IgG/AQP4-Ab serology are given.

C1q-targeted monoclonal antibody prevents complement-dependent cytotoxicity and neuropathology in in vitro and mouse models of neuromyelitis optica

Neuromyelitis optica (NMO) is an autoimmune disorder with inflammatory demyelinating lesions in the central nervous system, particularly in the spinal cord and optic nerve. NMO pathogenesis is thought to involve binding of anti-aquaporin-4 (AQP4) autoantibodies to astrocytes, which causes complement-dependent cytotoxicity (CDC) and downstream inflammation leading to oligodendrocyte and neuronal injury. Vasculocentric deposition of activated complement is a prominent feature of NMO pathology. Here, we show that a neutralizing monoclonal antibody against the C1q protein in the classical complement pathway prevents AQP4 autoantibody-dependent CDC in cell cultures and NMO lesions in ex vivo spinal cord slice cultures and in mice. A monoclonal antibody against human C1q with 11 nM binding affinity prevented CDC caused by NMO patient serum in AQP4-transfected cells and primary astrocyte cultures, and prevented complement-dependent cell-mediated cytotoxicity (CDCC) produced by natural killer cells. The anti-C1q antibody prevented astrocyte damage and demyelination in mouse spinal cord slice cultures exposed to AQP4 autoantibody and human complement. In a mouse model of NMO produced by intracerebral injection of AQP4 autoantibody and human complement, the inflammatory demyelinating lesions were greatly reduced by intracerebral administration of the anti-C1q antibody. These results provide proof-of-concept for C1q-targeted monoclonal antibody therapy in NMO. Targeting of C1q inhibits the classical complement pathway directly and causes secondary inhibition of CDCC and the alternative complement pathway. As C1q-targeted therapy leaves the lectin complement activation pathway largely intact, its side-effect profile is predicted to differ from that of therapies targeting downstream complement proteins.

Therapeutic cleavage of anti-aquaporin-4 autoantibody in neuromyelitis optica by an IgG-selective proteinase

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system caused by binding of pathogenic IgG autoantibodies (NMO-IgG) to astrocyte water channel aquaporin-4 (AQP4). Astrocyte damage and downstream inflammation require NMO-IgG effector function to initiate complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC). Here, we evaluated the potential therapeutic utility of the bacterial enzyme IdeS (IgG-degrading enzyme of Streptococcus pyogenes), which selectively cleaves IgG antibodies to yield Fc and F(ab')(2) fragments. In AQP4-expressing cell cultures, IdeS treatment of monoclonal NMO-IgGs and NMO patient sera abolished CDC and ADCC, even when IdeS was added after NMO-IgG was bound to AQP4. Binding of NMO-IgG to AQP4 was similar to that of the NMO-F(ab')(2) generated by IdeS cleavage. NMO-F(ab')(2) competitively displaced pathogenic NMO-IgG, preventing cytotoxicity, and the Fc fragments generated by IdeS cleavage reduced CDC and ADCC. IdeS efficiently cleaved NMO-IgG in mice in vivo, and greatly reduced NMO lesions in mice administered NMO-IgG and human complement. IgG-selective cleavage by IdeS thus neutralizes NMO-IgG pathogenicity, and yields therapeutic F(ab')(2) and Fc fragments. IdeS treatment, by therapeutic apheresis or direct administration, may be beneficial in NMO.