Saturday, 16 September 2017

Imaging nerve connections

Grussu F, Schneider T, Tur C, Yates RL, Tachrount M, IanuĊŸ A, Yiannakas MC, Newcombe J, Zhang H, Alexander DC, DeLuca GC, Gandini Wheeler-Kingshott CAM. Neurite dispersion: a new marker of multiple sclerosis spinal cord pathology? Ann Clin Transl Neurol. 2017 Aug 15;4(9):663-679.

OBJECTIVE:

Conventional magnetic resonance imaging (MRI) of the multiple sclerosis spinal cord is limited by low specificity regarding the underlying pathological processes, and new MRI metrics assessing microscopic damage are required. We aim to show for the first time that neurite orientation dispersion (i.e., variability in axon/dendrite orientations) is a new biomarker that uncovers previously undetected layers of complexity of multiple sclerosis spinal cord pathology. Also, we validate against histology a clinically viable MRI technique for dispersion measurement (neurite orientation dispersion and density imaging, NODDI), to demonstrate the strong potential of the new marker.

METHODS:

We related quantitative metrics from histology and MRI in four post mortem spinal cord specimens (two controls; two progressive multiple sclerosis cases). The samples were scanned at high field, obtaining maps of neurite density and orientation dispersion from NODDI and routine diffusion tensor imaging (DTI) indices. Histological procedures provided markers of astrocyte, microglia, myelin and neurofilament density, as well as neurite dispersion.

RESULTS:

We report from both NODDI and histology a trend toward lower neurite dispersion in demyelinated lesions, indicative of reduced neurite architecture complexity. Also, we provide unequivocal evidence that NODDI-derived dispersion matches its histological counterpart (P < 0.001), while DTI metrics are less specific and influenced by several biophysical substrates.

INTERPRETATION:

Neurite orientation dispersion detects a previously undescribed and potentially relevant layer of microstructural complexity of multiple sclerosis spinal cord pathology. Clinically feasible techniques such as NODDI may play a key role in clinical trial and practice settings, as they provide histologically meaningful dispersion indices.

Neurites are bits of nerve sprouts that allow nerves to communicate and so allows the exchange of information among neurons. There is evidence to believe that changes of their architecture can impact directly on neural function. Alteration of dendrite morphology could account per se for impairment beyond mere neuronal death. neurite orientation dispersion, namely the variability of neurite orientations, is a new sensitive and specific biomarker of multiple sclerosis spinal cord pathology. I was going to review this but when I read it online, it went over my head maybe DrK can decipher it. He speaks MRI ...I don't. However there is a problem of nerve connections in the spinal cord. watch this space.

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