Aquaporins, anti-aquaporin-4 autoantibodies and neuromyelitis optica

Recent Advances in Neuromyelitis Optica Spectrum Disorder: Pathogenesis, Mechanisms and Potential Treatments

Neuromyelitis optica spectrum disorder (NMOSD) is an acute or subacute demyelinating disease that affects mainly the optic nerve and spinal cord. A major proportion of NMOSD cases have a relationship with autoimmunity to aquaporin 4 (AQP4) found on the central nervous system. NMOSD can occur repeatedly, causing symptoms such as decreased vision and weakness of limbs. The main goal of current therapy is to relieve acute symptoms and prevent recurrence of the disease. Without timely and appropriate treatment, the recurrence and disability rates are high. In the present work, we review recent advances in the diagnosis and treatment of patients with NMOSD, as well as the pathogenesis and mechanisms of AQP4-IgG-seropositive NMOSD.

Normal-Appearing Cerebellar Damage in Neuromyelitis Optica Spectrum Disorder

BACKGROUND AND PURPOSE

The cerebellum plays an important role in motor and cognitive functions. However, whether and how the normal-appearing cerebellum is impaired in patients with neuromyelitis optica spectrum disorders remain unknown. We aimed to identify the occult structural damage of the cerebellum in neuromyelitis optica spectrum disorder and its possible causes at the level of substructures.

MATERIALS AND METHODS

Normal-appearing gray matter volume of the cerebellar lobules and nuclei and normal-appearing white matter volume of the cerebellar peduncles were compared between patients with neuromyelitis optica spectrum disorder and healthy controls.

RESULTS

The cerebellar damage of patients with neuromyelitis optica spectrum disorder in the hemispheric lobule VI, vermis lobule VI, and all cerebellar nuclei and peduncles was related only to spinal lesions; and cerebellar damage in the hemispheric lobules VIII and X was related only to the aquaporin-4 antibody. The mixed cerebellar damage in the hemispheric lobules V and IX and vermis lobule Crus I was related mainly to spinal lesions; and mixed cerebellar damage in the hemispheric lobule VIIb was related mainly to the aquaporin-4 antibody. Other cerebellar substructures showed no significant cerebellar damage.

CONCLUSIONS

We have shown that the damage in cerebellar normal-appearing white matter and normal-appearing gray matter is associated with aquaporin-4-mediated primary damage or axonal degeneration secondary to spinal lesions or both. The etiologic classifications of substructure-specific occult cerebellar damage may facilitate developing neuroimaging markers for assessing the severity and the results of therapy of neuromyelitis optica spectrum disorder occult cerebellar damage.

Optic neuritis with radiological longitudinal spinal cord involvement and seronegative anti-aquaporin antibody: Evidence from a case study

In recent years, not only the incidence of brain demyelinating disease has increased, but also it seems that the world is facing new forms of autoimmune diseases of the brain. Distinguishing these diseases from each other is very important, since each requires a different treatment. The new criteria that were put forward in 2015 were meant to pave the way for better diagnosis of these diseases called neuromyelitis optica spectrum disease (NMOSD). However, too much emphasis on the criteria based on the convergence and association of radiological findings with the clinical symptoms actually causes confusion in the diagnosis. Here, the case of a 16-year-old child suffering from optic neuritis has been discussed. Her cervical magnetic resonance imaging (MRI) revealed longitudinal extensive transverse myelitis (LETM); however, the patient had no symptoms of the spinal cord's involvement. According to the 2015 criterion, the diagnosis of NMOSD cannot be accepted for this patient. Therefore, this case report emphasizes on the modification of the existing criterion.

Epidemiological, clinical, and immunological characteristics of neuromyelitis optica: A review

The aim of this study was to review the epidemiological and clinical characteristics of neuromyelitis optica (NMO) and the immunopathological mechanisms involved in the neuronal damage. NMO is an inflammatory demyelinating autoimmune disease of the central nervous system that most commonly affects the optic nerves and spinal cord. NMO is thought to be more prevalent among non-Caucasians and where multiple sclerosis (MS) prevalence is low. NMO follows a relapsing course in more than 80-90% of cases, which is more commonly in women. It is a complex disease with an interaction between host genetic and environmental factors and the main immunological feature is the presence of anti-aquaporin 4 (AQP4) antibodies in a subset of patients. NMO is frequently associated with multiple other autoantibodies and there is a strong association between NMO with other systemic autoimmune diseases. AQP4-IgG can cause antibody-dependent cellular cytotoxicity (ADCC) when effector cells are present and complement-dependent cytotoxicity (CDC) when complement is present. Acute therapies, including corticosteroids and plasma exchange, are designed to minimize injury and accelerate recovery. Several aspects of NMO pathogenesis remain unclear. More advances in the understanding of NMO disease mechanisms are needed in order to identify more specific biomarkers to NMO diagnosis.

Monitoring neuromyelitis optica activity

Neuromyelitis optica (NMO) is a demyelinating and inflammatory disease essentially restricted to the spinal cord and the optic nerves. Emerging evidence indicates that serum antiaquaporin-4 (AQP4) antibodies have a critical role in its pathogenesis. NMO courses with multiple relapses, often leading to severe disability. Management of NMO focuses on the effective treatment of acute attacks and the prevention of relapses. The latter is currently attempted with immunosuppressive drugs. Although several factors have been associated with disease activity, especially serum levels of anti-AQP4 IgG, no single one of them has been proved clinically useful for guiding treatment. New drugs that target specifically AQP4 antibodies and complement activation are being developed; they may prove to be more efficient with fewer side effects.