© Springer-Verlag Italia 2015Angelo Sghirlanzoni, Giuseppe Lauria and Luisa Chiapparini (eds.)Prognosis of Neurological Diseases10.1007/978-88-470-5755-5_12
12. Myelin Disorders: Devic’s Syndrome
Scientific Direction, Fondazione Istituto Neurologico Carlo Besta, Milano, Italy
KeywordsAquaporin-4 autoantibodiesDevic syndromeLongitudinally extensive transverse myelitisMyelin oligodendrocyte glycoproteinNeuromyelitis opticaOptic neuritis
Terminology and definition – Neuromyelitis optica is an immune-mediated condition of the CNS that preferentially involves the spinal cord and the optic nerves.
Clinical features – Severe episodes of recurrent optic neuritis and myelitis. Brain involvement is present in most cases.
Blood – Serum autoantibodies targeting aquaporin-4.
CSF – Oligoclonal bands or elevated IgG index in 10–20 % of patients.
MRI – Spinal cord lesions longer than three spinal segments and primarily involving the central part of the spinal cord, optic nerve neuritis.
Neurophysiology – Reduced amplitudes and/or prolonged latencies of VEP.
Top differential diagnoses – MS; myelitis and/or optic neuritis of various origins (e.g., systemic lupus erythematosus, Sjögren’s syndrome, sarcoidosis, vasculitis).
Principle of treatment – Corticosteroids; plasma exchange; long-term immunosuppression; symptomatic treatments.
Disability – Most patients with AQP4-IgG positive NMO/NMOSD have a severe, relapsing course. Within 5 years from onset, more than 50 % of patients with relapsing NMO are blind in one or both eyes or need assistance to walk or are confined to wheelchair. Patients with negative AQP4-IgG NMO or NMOSD often have a less severe course.
AQP4-IgG, Aquaporin-4 autoantibodies; CNS, Central nervous system; CSF, Cerebrospinal fluid; LETM, Longitudinally extensive transverse myelitis; NMOSD(s), NMO spectrum disorder(s); GFAP, Glial fibrillary acid protein; MOG, Myelin oligodendrocyte glycoprotein; MRI, Magnetic resonance imaging; MS, Multiple Sclerosis; NMO, Neuromyelitis Optica; ON, Optic neuritis; SLE, Systemic lupus erythematosus; VEP, Visual evoked potential
Neuromyelitis optica NMO (synonyms: Devic’s syndrome, NMO spectrum disorders (NMOSDs); optic neuritis (ON); longitudinally extensive transverse myelitis (LETM); opticospinal syndrome) is an immune-mediated inflammatory disorder of the central nervous system (CNS) that preferentially involves the spinal cord and the optic nerves. It is characterized by primary damage to astrocytes caused by aquaporin-4 (AQP4-IgG) autoantibodies leading to secondary demyelination and axonal injury. Detection of AQP4 in serum has prompted recognition of a heterogeneous spectrum of clinical disorders (NMOSD) that previously would not have met diagnostic criteria for NMO.
NMO is a rare condition; knowledge regarding its epidemiology is limited. Its incidence is 0.53–4/1,000,000 population; prevalence is 5.2–40.4/1,000,000 in Europe and North America. Clinical symptoms more often occur between 35 and 45 years of age, but NMO may also occur in children and the elderly. AQP4 antibodies are more frequent in women.
NMO is sporadic, though 3 % of familial cases have been reported. African-Americans with demyelinating disease commonly have an aggressive optic-spinal syndrome.
12.3 Clinical Features
In most cases (80–90 %) NMO is a relapsing condition with severe attacks of LETM or unilateral or bilateral optic neuritis (ON), often causing loss of vision with incomplete recovery. A monophasic course is less frequent (10–20 % of cases) and is more often associated with simultaneous optic neuritis and myelitis. Brain involvement, as initial event or at relapse , is recognized and included among the diagnostic criteria for NMO/NMOSD . Brain damage is present in more than 60 % of patients; hypothalamus, medulla, and brainstem are most frequently involved . Syndromes of inappropriate antidiuretic hormone secretion (SIADH) or cognitive impairment have been reported .
NMO is diagnosed according to the revised criteria for “definite” NMO , which recommend the presence of optic neuritis, acute myelitis, and at least two of three diagnostic tests, i.e., a contiguous spinal cord MRI lesion at least three segments in length, brain MRI at onset “non-diagnostic” for MS, or anti-AQP4-IgG seropositivity. AQP4-IgG positive LETM is classified as neuromyelitis optica spectrum disorder (NMOSD) [1, 2].
Serum – Autoantibodies against aquaporin-4 (AQP4-IgG) have specificity for NMO/NMOSD greater than 90 %, but sensitivity ranges from 50 to 70 %. Assays detecting IgG binding to cells expressing recombinant AQP4 with quantitative flow cytometry or visual observation are more sensitive than ELISA and immunoprecipitation . More than half of the patients with NMOSD are AQP4-IgG positive. A proportion of 10–30 % of NMOSD patients remains AQP4-IgG antibody-negative during acute attacks. Retesting is warranted in high-risk patients.
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