Gadofluorine M-enhanced magnetic resonance nerve imaging: comparison between acute inflammatory and chronic degenerative demyelination in rats.

Nerve imaging by magnetic resonance imaging (MRI) is an emerging tool for the diagnostic work-up of patients with PNS disorders. We have recently shown that the experimental MR contrast agent gadofluorine M (Gf, Bayer Schering Pharma AG, Berlin) accumulates in nerves undergoing Wallerian degeneration and in areas of acute focal demyelination allowing in-vivo assessment of nerve pathology. The exact pathomechanism underlying Gf accumulation in peripheral nerve disorders is unknown so far. In the present study we compared nerve signal alterations on T2-w and Gf-enhanced T1-w MRI in two different models of acute inflammatory and chronic degenerative demyelination: experimental autoimmune neuritis (EAN) induced by immunization with PNS myelin and experimental Charcot-Marie-Tooth (CMT) disease in rats overexpressing the myelin protein PMP22. During the acute stage of inflammation and demyelination, strong Gf enhancement on T1-w MRI was seen in nerve roots and peripheral nerves in EAN, which resolved with completed remyelination. Similarly, Gf accumulation was seen in CMT rats during early stages with active demyelination at 6 weeks while at chronic stages (9 months) Gf enhancement decreased despite numerous demyelinated axons and onion bulb formation. At all disease stages no signal alterations were seen on T2-w MRI. In conclusion, our data show that the novel MR contrast agent Gf, but not Gadolinium (Gd)-DTPA, facilitates detection of ongoing demyelination by MR neurography independent from the underlying pathology. It appears that the extent of Gf enhancement depends on the acuity of demyelination and is probably related to a transient disturbance of the blood-nerve barrier. Clinical development of Gf may help to further improve the sensitivity of nerve lesion assessment by MRI in patients with peripheral neuropathies.