Spinal cord lesions in patients with neuromyelitis optica: a retrospective long-term MRI follow-up study

Neuromyelitis optica: not a multiple sclerosis variant

PURPOSE OF REVIEW

The discovery of neuromyelitis optica (NMO)-immunoglobulin (Ig)G and its target antigen aquaporin 4 (AQP4) redefined NMO, historically considered a multiple sclerosis (MS) variant, as a specific disease entity. NMO and MS have divergent responses to immunotherapy and it is important to distinguish the conditions at disease onset. In this article, we review new pathological, imaging and clinical trial data pertaining to NMO, and discuss emerging concepts of molecular immunopathogenesis in NMO that can inform the development of targeted therapies.

RECENT FINDINGS

Recent studies illustrate the range of brain lesions associated with NMO, and the importance of diagnostic biomarkers in patients with atypical or limited presentations. Neuropathological studies showing perivascular astrocyte destruction and preserved myelin in early NMO lesions indicate a pathogenesis distinct from MS. Characterisation of NMO-IgG binding to AQP4 isoforms and the development of novel disease models have elucidated complement-mediated and cell-mediated mechanisms of astrocyte injury.

SUMMARY

NMO-IgG positive NMO is not an MS variant. Further work is required to delineate the pathogenesis of NMO syndromes without antibodies to AQP4. Methodological flaws inherent to small, open label trials of current NMO therapies limit extrapolation to clinical practice. In the coming years, NMO will be treated with targeted therapies that are emerging from an enhanced understanding of the molecular immunopathogenesis of the disease.

Diagnostic approach of patients with longitudinally extensive transverse myelitis

The aim of this study is to present a diagnostic and therapeutic approach in patients with LETM. In a period between June 2008 and June 2010, all patients who fulfilled criteria for LETM were included in the study. All patients underwent a standardized protocol of investigations presented in this paper. Ten patients were included (5 male, 5 female, with the age distribution from 24 to 70 years). Four patients were diagnosed with NMO/spatially limited NMO spectrum disorder, three patients were diagnosed with spinal cord ADEM, two multiple sclerosis (MS) and one patient with copper deficiency myelopathy. Laboratory support for the diagnosis of NMO was positive NMO-IgG antibody; for the diagnosis of ADEM signs of peripheral nervous system involvement on electromyoneurography; and for the diagnosis of MS brain MRI lesions typical for MS, as well as positive oligoclonal bands (OCB) in the cerebrospinal fluid (CSF). All cases with inflammatory myelopathy were treated either with steroids or plasma exchange and copper replacement was started in the case of copper deficiency. The mean time from the first symptom until the final diagnosis was 16.3 months (range 1 month to 7 years). As each of idiopathic inflammatory demyelinating diseases that can present with LETM have specific therapy, the postponement in making the correct diagnosis can lead to a poor recovery. In patients with LETM, a standardized diagnostic approach can result in a correct diagnosis and appropriate treatment.

Increased radial diffusivity in spinal cord lesions in neuromyelitis optica compared with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) and neuromyelitis optica (NMO) both affect spinal cord with notable differences in pathology.

OBJECTIVE

Determine the utility of diffusion tensor imaging (DTI) to differentiate the spinal cord lesions of NMO from MS within and outside T2 lesions.

METHODS

Subjects greater than or equal to 12 months from a clinical episode of transverse myelitis underwent a novel transaxial cervical spinal cord DTI sequence. Ten subjects with NMO, 10 with MS and 10 healthy controls were included.

RESULTS

Within T2 affected white matter regions, radial diffusivity was increased in both NMO and MS compared with healthy controls (p<0.001, respectively), and to a greater extent in NMO than MS (p<0.001). Axial diffusivity was decreased in T2 lesions in both NMO and MS compared with controls (p<0.001, p=0.001), but did not differ between the two diseases. Radial diffusivity and fractional anisotropy within white matter regions upstream and downstream of T2 lesions were different from controls in each disease.

CONCLUSIONS

Higher radial diffusivity within spinal cord white matter tracts derived from diffusion tensor imaging were appreciated in NMO compared with MS, consistent with the known greater tissue destruction seen in NMO. DTI also detected tissue alterations outside T2 lesions and may be a surrogate of anterograde and retrograde degeneration.

Spinal cord tumor versus transverse myelitis

BACKGROUND CONTEXT

Longitudinally extensive transverse myelitis (LETM) is one of the defining features of neuromyelitis optica (NMO). Despite the well-established criteria, clinical and paraclinical features, the disease is often misdiagnosed and erroneously treated.

PURPOSE

We report on a case of LETM in a patient with spatially limited NMO spectrum disorder that was misdiagnosed as spinal cord tumor and underwent spinal cord biopsy.

STUDY DESIGN

A 43-year-old female patient is described.

METHODS

The patient developed spastic tetraparesis over 1 week. Spinal cord magnetic resonance imaging (MRI) revealed LETM, and she was treated with steroids and recovered. Nine months later, her condition worsened and repeat spinal cord MRI was interpreted as a large intramedullary tumor in the cervical region with irregular postcontrast enhancement. Biopsy revealed demyelination. Cerebrospinal fluid (CSF) analysis revealed positive oligoclonal IgG bands, and serum was positive for NMO-IgG antibody.

RESULTS

The patient was diagnosed with spatially limited NMO spectrum disorder, treated with plasma exchange, high-dose corticosteroids, and cyclophosphamide, and with good recovery.

CONCLUSIONS

The factors favoring inflammatory LETM are acute or subacute onset of clinical symptoms, positive oligoclonal bands in the CSF, positive NMO-IgG or other antibodies, and brain MRI showing demyelinating lesions. Postcontrast axial MRI sequences of the spinal cord can also be helpful. In doubtful situations, a trial of therapy and follow-up MRI a month later might be a more prudent approach if the patient is not rapidly deteriorating.

Longitudinal extensive transverse myelitis--it's not all neuromyelitis optica

Longitudinal extensive transverse myelitis (LETM) is defined as a spinal cord lesion that extends over three or more vertebrae, as seen on MRI of the spine. The clinical presentation of a patient with LETM is often dramatic and can consist of paraparesis or tetraparesis, sensory disturbances, and gait, bladder, bowel and/or sexual dysfunction. LETM is a characteristic feature of neuromyelitis optica, but such spinal lesions can also occur in various other autoimmune and inflammatory diseases that involve the CNS--such as multiple sclerosis, sarcoidosis or Sjögren syndrome--or in infectious diseases with CNS involvement. Patients with a neoplastic disorder or traumatic spinal cord injury can also present with longitudinal spinal lesions. In this Review, the signs and symptoms that suggest various etiologies and differential diagnoses of LETM are described, and illustrated by educational case studies. The best therapeutic options for patients with each diagnosis are also discussed.

A population-based study of neuromyelitis optica in Caucasians

BACKGROUND

Epidemiologic studies have suggested different prevalence of neuromyelitis optica (NMO) in different ethnic groups. However, data on the incidence and prevalence of NMO in Caucasians are scarce.

OBJECTIVE

To estimate the incidence and prevalence of NMO in a predominantly Caucasian population based on the Wingerchuk 2006 criteria.

METHODS

The study was a population-based retrospective case series with longitudinal follow-up. Patients with multiple sclerosis (MS), optic neuritis (ON), acute transverse myelitis (TM), and NMO from the 4 neurology and 3 ophthalmology departments in the Region of Southern Denmark having been diagnosed between 1998 and 2008 were investigated. Patients were included based on 1) episodes of ON or TM and 2) an initial brain MRI not diagnostic for MS. An immunofluorescence assay was used to determine aquaporin-4 (AQP-4) antibodies.

RESULTS

A total of 477 patients with MS, TM, or ON were evaluated: 163 fulfilled the inclusion criteria, 42 (26%) qualified for the diagnosis of NMO, 26 (62.0%) of these were AQP4 antibody positive. All except one were Caucasian, the female:male ratio was 2.8:1, and mean age at onset was 35.6 years (range 15-64 years). The clinical presentation was heterogeneous including TM, longitudinally extensive TM, ON, and brainstem syndromes. The yearly incidence rate of NMO in the population was estimated to be 0.4 per 10(5) person-years (95% confidence interval [CI] 0.30-0.54) and the prevalence was 4.4 per 10(5) (95% CI 3.1-5.7).

CONCLUSIONS

Despite being a rare disease, NMO is more common in a Caucasian population than earlier believed.

The differential diagnosis of longitudinally extensive transverse myelitis

Longitudinally extensive transverse myelitis refers to florid and widespread inflammation of the spinal cord causing T2 hyperintensity on spinal magnetic resonance imaging that is seen to extend over three or more vertebral segments. Whilst rare, longitudinally extensive transverse myelitis is clinically important as it can lead to catastrophic morbidity, and a group of these patients are at risk of further attacks. Early identification and establishment of the underlying aetiology is vital in order to initiate appropriate therapy and optimize outcomes. Whilst longitudinally extensive transverse myelitis is classically associated with neuromyelitis optica, there are many other causes. These include other inflammatory aetiologies, infection, malignancy and metabolic disturbance. Some of these are readily treatable. Laboratory and radiological investigations can help to differentiate these causes. Treatment of longitudinally extensive transverse myelitis hinges on distinguishing inflammatory and non-inflammatory aetiologies and identifying patients who are at high risk of a recurrent course.

High resolution spectral domain optical coherence tomography (SD-OCT) in multiple sclerosis: the first follow up study over two years

BACKGROUND

"Non-invasive, faster and less expensive than MRI" and "the eye is a window to the brain" are recent slogans promoting optical coherence tomography (OCT) as a new surrogate marker in multiple sclerosis (MS). Indeed, OCT allows for the first time a non-invasive visualization of axons of the central nervous system (CNS). Reduction of retina nerve fibre layer (RNFL) thickness was suggested to correlate with disease activity and duration. However, several issues are unclear: Do a few million axons, which build up both optic nerves, really resemble billions of CNS neurons? Does global CNS damage really result in global RNFL reduction? And if so, does global RNFL reduction really exist in all MS patients, and follow a slowly but steadily ongoing pattern? How can these (hypothesized) subtle global RNFL changes be reliably measured and separated from the rather gross RNFL changes caused by optic neuritis? Before generally being accepted, this interpretation needs further critical and objective validation.

METHODOLOGY

We prospectively studied 37 MS patients with relapsing remitting (n = 27) and secondary progressive (n = 10) course on two occasions with a median interval of 22.4±0.5 months [range 19-27]. We used the high resolution spectral domain (SD-)OCT with the Spectralis 3.5 mm circle scan protocol with locked reference images and eye tracking mode. Patients with an attack of optic neuritis within 12 months prior to the onset of the study were excluded.

PRINCIPAL FINDINGS

Although the disease was highly active over the observation period in more than half of the included relapsing remitting MS patients (19 patients/32 relapses) and the initial RNFL pattern showed a broad range, from normal to markedly reduced thickness, no significant changes between baseline and follow-up examinations could be detected.

CONCLUSIONS

These results show that caution is required when using OCT for monitoring disease activity and global axonal injury in MS.

[Neurological catastrophes in demyelinating diseases]

Demyelinating diseases may cause neurological catastrophes in several ways. Rapidly progressing disease or severe acute bouts may seriously threaten the patient's life. Diagnostic procedures, errors in identifying the clinical picture and even treatments themselves may result in a catastrophe. This article reviews the most frequent catastrophic scenarios.

Heterogeneous pattern of retinal nerve fiber layer in multiple sclerosis. High resolution optical coherence tomography: potential and limitations

Background

Recently the reduction of the retinal nerve fibre layer (RNFL) was suggested to be associated with diffuse axonal damage in the whole CNS of multiple sclerosis (MS) patients. However, several points are still under discussion. (1) Is high resolution optical coherence tomography (OCT) required to detect the partly very subtle RNFL changes seen in MS patients? (2) Can a reduction of RNFL be detected in all MS patients, even in early disease courses and in all MS subtypes? (3) Does an optic neuritis (ON) or focal lesions along the visual pathways, which are both very common in MS, limit the predication of diffuse axonal degeneration in the whole CNS? The purpose of our study was to determine the baseline characteristics of clinical definite relapsing-remitting (RRMS) and secondary progressive (SPMS) MS patients with high resolution OCT technique.

Methodology

Forty-two RRMS and 17 SPMS patients with and without history of uni- or bilateral ON, and 59 age- and sex-matched healthy controls were analysed prospectively with the high resolution spectral-domain OCT device (SD-OCT) using the Spectralis 3.5mm circle scan protocol with locked reference images and eye tracking mode. Furthermore we performed tests for visual and contrast acuity and sensitivity (ETDRS, Sloan and Pelli-Robson-charts), for color vision (Lanthony D-15), the Humphrey visual field and visual evoked potential testing (VEP).

Principal Findings

All 4 groups (RRMS and SPMS with or without ON) showed significantly reduced RNFL globally, or at least in one of the peripapillary sectors compared to age-/sex-matched healthy controls. In patients with previous ON additional RNFL reduction was found. However, in many RRMS patients the RNFL was found within normal range. We found no correlation between RNFL reduction and disease duration (range 9–540 months).

Conclusions

RNFL baseline characteristics of RRMS and SPMS are heterogeneous (range from normal to markedly reduced levels).

EFNS guidelines on diagnosis and management of neuromyelitis optica

BACKGROUND AND PURPOSE

Neuromyelitis optica (NMO) or Devic's disease is a rare inflammatory and demyelinating autoimmune disorder of the central nervous system (CNS) characterized by recurrent attacks of optic neuritis (ON) and longitudinally extensive transverse myelitis (LETM), which is distinct from multiple sclerosis (MS). The guidelines are designed to provide guidance for best clinical practice based on the current state of clinical and scientific knowledge.

SEARCH STRATEGY

Evidence for this guideline was collected by searches for original articles, case reports and meta-analyses in the MEDLINE and Cochrane databases. In addition, clinical practice guidelines of professional neurological and rheumatological organizations were studied.

RESULTS

Different diagnostic criteria for NMO diagnosis [Wingerchuk et al. Revised NMO criteria, 2006 and Miller et al. National Multiple Sclerosis Society (NMSS) task force criteria, 2008] and features potentially indicative of NMO facilitate the diagnosis. In addition, guidance for the work-up and diagnosis of spatially limited NMO spectrum disorders is provided by the task force. Due to lack of studies fulfilling requirement for the highest levels of evidence, the task force suggests concepts for treatment of acute exacerbations and attack prevention based on expert opinion.

CONCLUSIONS

Studies on diagnosis and management of NMO fulfilling requirements for the highest levels of evidence (class I-III rating) are limited, and diagnostic and therapeutic concepts based on expert opinion and consensus of the task force members were assembled for this guideline.

Neuromyelitis optica - an update: 2007-2009

Neuromyelitis optica is an inflammatory demyelinating disorder of the central nervous system. The discovery of a specific antibody (NMO IgG /aquaporin-4 antibody) in patients with this condition has led to a marked revival of research on the disease. This article summarizes the major advances in neuromyelitis optica, particularly in the last 2 years, and supplements the previous review published in this Journal in 2007. Important among these developments are: the epidemiological studies, which have provided estimates of incidence and prevalence; identification of mutations in the aquaporin-4 gene; improved understanding of the effects of anti-aquaporin-4 antibody on astrocytes; roles of excitatory amino acid transporter type 2 and glutamate; requirement of aquaporin-4 to be in orthogonal arrays to be antigenic; recognition of the presence of aquaporin-4 antibody in patients with cancer and posterior reversible encephalopathy syndrome; possibility of monitoring the disease using the antibody, and the effectiveness of rituximab and mycophenolate in preventing relapses.

Diffuse white matter damage is absent in neuromyelitis optica

BACKGROUND AND PURPOSE

Neuromyelitis optica (NMO) is an idiopathic mostly relapsing inflammatory disease with attacks on the optic nerves and spinal cord. Whether NMO is a separate disease or a subtype of classic multiple sclerosis (MS) is unclear. Clinically, CSF and MR imaging parameters and histopathologic data suggest that the normal-appearing white matter (NAWM) may be affected in MS but not in patients with NMO. Therefore, we hypothesized that the NAWM in NMO is normal.

MATERIAL AND METHODS

We studied prospectively 8 patients with clinically definitive NMO or remitting longitudinal extensive transverse myelitis (LETM) and 8 healthy controls. Ratios of N-acetylaspartate to creatine (Cr) and choline to Cr and the absolute concentrations of the metabolites were measured by chemical shift imaging with a (1)H-MR spectroscopy operating at 3T. All patients with clinically definitive NMO and LETM were found to be positive for NMO-immunoglobin G with a commercially available test.

RESULTS

The metabolic pattern of the NAWM of patients with NMO showed no difference compared with age- and sex-matched healthy controls.

CONCLUSIONS

Diffuse white matter damage is absent in NMO.