Magnetic resonance imaging of dorsal root ganglion in a pre-symptomatic subject with familial amyloid polyneuropathy transthyretin E61K.

We recently reported evidence of transthyretin (TTR) familial amyloid polyneuropathy (TTR FAP) associated with TTR E61K, which is characterized by late-onset sensory dominant polyneuropathy, autonomic disturbances, and cardiomyopathy. In those TTR FAP patients, no amyloid deposits were observed in the endoneurium of examined sural nerves. Furthermore, the amyloidogenicity of E61K TTR was similar to that of wild-type TTR in vitro. Thus, we speculated that dorsal root ganglia (DRGs) may be the initial sites for the lesions in amyloid neuropathy because there is no blood-nerve barrier. In the present study, lumbar magnetic resonance imaging was performed to evaluate the DRGs in pre-symptomatic TTR E61K and V30M subjects. Magnetic resonance imaging (3 T) was used for three-dimensional T2-weighted imaging (coronal sections; slice thickness, 2 mm), and the DRG volumes were measured. The mean volumes of the bilateral L3, L4, and S1 DRGs in the pre-symptomatic TTR E61K subject were larger than those for the pre-symptomatic TTR V30M subject and five control patients. The mean volumes of the bilateral L4 to S1 DRGs in the pre-symptomatic TTR V30M subject were similar to those in control patients. A number of lumbar DRGs were enlarged in the pre-asymptomatic TTR E61K subject, suggesting that DRGs may be the sites of the initial lesions in the peripheral nervous system of this FAP.