Original articleMRI of the spinal cord in neuromyelitis optica and recurrent longitudinal extensive myelitisIRM de la moelle epinière dans la neuromyélite optique et la myélite longitudinale extensive récidivante
Introduction
Neuromyelitis optica (NMO), or Devic's disease, is a severe inflammatory and necrotizing disease that clinically affects the optic nerves and spinal cord in a relapsing course. Although NMO has a worldwide distribution, it frequently strikes nonwhite populations. It has been recently suggested that NMO is distinct from multiple sclerosis (MS) following the identification of a highly specific biomarker called NMO-IgG [1], which targets aquaporin-4, a water channel protein mainly expressed in astrocytic foot processes at the blood-brain barrier [2], [3]. NMO-IgG status has helped to define an NMO spectrum of disorders, including the Asian optic spinal form of MS, recurrent longitudinal extensive transverse myelitis (RLEM), recurrent optic neuritis and extensive myelitis or optic neuritis associated with autoimmune diseases [4].
Spinal cord and brain MRI have important diagnostic utility. Spinal cord MRI with signal abnormalities extending over greater or equal to three vertebral segments and brain MRI not meeting diagnostic criteria for MS are supportive criteria proposed by the Mayo Clinic in 1999 for the diagnosis of NMO [5]. However, studies focusing on the neuroradiological aspects of NMO are scarce. In addition, the evolution of MRI lesions has rarely been studied. The aim of this study is to familiarize radiologists with the baseline and follow-up MRI characteristics of NMO and RLEM.
Section snippets
Methods
We reviewed the MRI data of consecutive patients diagnosed with NMO or RLEM since 1998 at the hospital of Fort-de-France (Martinique, French West Indies). The Martinique population is mostly Afro-Caribbean (> 90%), with some interbreeding with the Caucasian population. The crude prevalence of NMO in Martinique was evaluated as 2.3/10,000 population as of 31 December 1999 [6]. Patients were included if they had undergone a spinal cord MRI either during two different cord attacks or at the acute
Patients
The study group consisted of 20 Afro-Caribbean patients (18 women/two men). Age ranged from 23 to 86 years (mean: 45 years). Their demographic, clinical and biological data are summarized in Table 1. Seventeen patients (16 women/one man) had NMO and the remaining three (two women/one man) had RLEM. Serum samples of all patients were tested for NMO-IgG using an indirect immunofluorescence technique (Neuroimmunology Unit of Lyon, France). NMO-IgG testing was positive in four NMO patients: two had
Discussion
In our series of NMO and RLEM cases, conventional MRI during medullary attacks revealed LEL in 67% of cases, SL in 25% cases and normal findings in 8% of cases. T1-weighted hypointensity signals associated with medullary widening and corresponding to reactive edema were present in the majority of attacks. On axial plane sequences, T2 hyperintensity signals involved predominantly the central regions. Contrast retention after gadolinium injection was present in 69% of the medullary attacks in our
Conclusion
The present study demonstrates the main MRI characteristics in NMO and RLEM patients in cases of cord attack, with analysis of the outcomes of signal abnormalities. Radiologists need to be aware of NMO and RLEM MRI patterns, as they require aggressive treatment to prevent relapses and to improve functional recovery.
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