Sequential diffusion-weighted magnetic resonance imaging study of lysophosphatidyl choline-induced experimental demyelinating lesion: an animal model of multiple sclerosis.

Abstract

To differentiate the surrounding edema from the focal demyelinating lesion during the early phase of the lesion using an apparent diffusion coefficient (ADC), and to monitor the changes in ADCs during the complete progression of a lysophosphatidyl choline (LPC)-induced experimental demyelinating lesion, an animal model of multiple sclerosis (MS). Eighteen rats divided into two groups-demyelinating lesion (group I, N = 12) and vehicle group (saline injected; group II, N = 6)-were studied. A 0.2-microl quantity of 1% LPC solution in isotonic saline was injected in the rat brain internal capsule (IC) area to create the demyelinating lesion. Six rats were used exclusively for histology. Diffusion-weighted (DW) images were acquired at different diffusion weightings on the 3rd, 5th, 10th, 15th, and 20th days after LPC injection. ADC was measured from three regions of interest (ROIs) within the IC: focal demyelinating lesion (area A), surrounding area of the lesion (area B), and contralateral IC area (area C). Histology revealed demyelination of the IC area during the early phase of lesion progression up to day 10 and remyelination thereafter. Elevated ADCs were observed for the surrounding edematous area (area B), compared to the focal demyelinating lesion (area A) during the early phase of the demyelination process, while substantial reduction of ADCs was noticed during remyelination for both regions. Measurement of ADC showed clear differentiation of the surrounding edema from the LPC-induced focal demyelinating lesion in rats, especially during the early phase of the lesion progression.