Severe aquaporin-4 IgG-positive neuromyelitis optica spectrum disorder with short myelitis lesion and favourable outcome

Neuromyelitis optica spectrum disorders (NMOSD) refer to limited forms of neuromyelitis optica (NMO) including recurrent or simultaneous bilateral optic neuritis (ON) or longitudinally extensive transverse myelitis (LETM), extending three or more vertebral segments, unified by the seropositivity for anti-aquaporin-4 (AQP4) antibody [1]. Myelitis extending less than three vertebral segments in NMOSD has recently been recognized as a rare variant with not well-established clinical outcome. We here report a case of severe AQP4-IgG-positive NMOSD with short myelitis lesion and favourable outcome. A 24-year-old woman experienced in May 2011 sudden visual loss and ocular pain in left eye showing visual acuity \1/10 and significant P100 amplitude decrease and latency prolongation. Apart visual loss, neurological examination was unremarkable. Brain and orbits magnetic resonance imaging (MRI) revealed only an inflammatory injury to the left optic nerve. Left retrobulbar ON was diagnosed and treated with high-dose intravenous methylprednisolone (IVMP) for 5 days resulting in complete recovery of the visual acuity in several months. In October 2011, she presented with paresthesias affecting upper limbs, in the absence of any sensory level and motor impairment, and brain MRI showed three gadolinium-enhancing lesions located at left frontal horn periventricular white matter, genu of corpus callosum and within the cervical spinal cord C2–C3 (Fig. 1a, b). Cerebrospinal fluid analysis revealed no alterations including the absence of oligoclonal bands. Search for serum anti-AQP4 IgG with a commercial indirect immunofluorescence transfected cell-based assay, showing reliable sensitivity [1, 2, supplementary file], was positive. In May 2012, internuclear ophthalmoplegia (INO) and severe vertigo occurred, and brain MRI documented a slight FLAIR hyperintensity adjacent to the fourth ventricle floor (Fig. 1c, d). The clinical features reversed after an IVMP 5-day course. In July 2012, the patient experienced numbness and progressive weakness at both legs. Neurological examination revealed paraparesis with walking difficulty, rapidly evolving to paraplegia, as well as sensory loss below D5 thoracic level and urinary retention. TM was diagnosed, and spinal cord MRI showed a gadolinium-enhancing short lesion longitudinally extending only over two vertebral segments (Fig. 2a), as well as brain MRI revealed a large FLAIR hyperintensity adjacent to the fourth ventricle floor (Fig. 1e). The diagnosis of NMOSD was therefore supported [1]. Acute-phase treatment consisted of IVMP (1 g/day for 5 days) followed by two cycles of IV immunoglobulin (0.4 g/kg/day for 5 days) over 2 months. Motor, sensory and bladder dysfunctions greatly improved: at the end of August 2012, she was able to walk with bilateral assistance and, in October 2012, after an intensive physical rehabilitation, she was able to walk without aid. As maintenance therapy, oral azathioprine Electronic supplementary material The online version of this article (doi:10.1007/s10072-015-2277-z) contains supplementary material, which is available to authorized users.