Wednesday, 26 September 2012

Research: cortical lesions are less in NMO than MS

EPUB: Calabrese et al. No MRI evidence of cortical lesions in neuromyelitis optica. Neurology. 2012 Sep 19. 

BACKGROUND: Neuromyelitis optica (NMO) is a severe inflammatory demyelinating disease of the CNS in which a pathogenic role of anti-aquaporin-4 (AQP4) antibodies has been suggested. Although AQP4 is expressed in human cortex, recent histologic studies have failed to find any evidence of cortical demyelination in NMO.

OBJECTIVE: To evaluate, in vivo, the occurrence of focal and diffuse cortical pathology in NMO.

METHODS: We studied 30 patients with NMO, 30 patients with relapsing-remitting multiple sclerosis (RRMS), and 30 normal controls (NC). RRMS and NC were age- and gender-matched to NMO. The presence of cortical lesions (CLs) was evaluated on double inversion recovery sequence and cortical thickness (CTh) by the application of Freesurfer on 3 volumetric fast field echo T1-weighted images.

RESULTS: No CL was observed in NC or in NMO, while 83 CLs were identified in 20/30 (66.7%) patients with RRMS. Although NMO did not differ from NC in the global CTh, a mild thinning was observed in some cortical areas (postcentral [p = 0.018], precentral [p = 0.009], and calcarine [p = 0.015] gyri) and in the thalamus (p = 0.036). Global and regional cortical thickness was significantly decreased in RRMS compared to both NMO and NC.

DISCUSSION: Our in vivo data further suggest that the immune-mediated pathologic process occurring in NMO spares the most of the cortex. NMO differs from multiple sclerosis, where CLs and atrophy are frequently found, even in early disease phases. Thus, MRI analysis of the cortex may be a potential diagnostic tool, especially in ambiguous cases.

NMO is characterised by lesions in the spinal cord and optic nerve and fewer in the brain. This study suggests that there are no cortical lesions in NMO using an certain MRI technique, where as there cortical lesions (grey matter lesions on the outer layer of the brain) in about 70% of MSer. 

In EAE in rodents lesions are often in the spinal cord and optic nerve despite the fact that the target antigens are in the brain. Some think it is the type of T cell reaction that determines this.

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