Quantitative MRI Assessment Using Variable Echo Time Imaging of Peripheral Nerve Injury in ATTRv Amyloidosis Patients

Early detection of peripheral nerve damage in patients with hereditary transthyretin amyloidosis (ATTRv) has become essential for the prompt initiation of effective, recently approved therapies. In our study, we propose a new variable echo time (vTE) MRI sequence as a non-invasive method to detect nerve injury in ATTRv patients and to establish a novel potential imaging marker of neuropathy that correlates with disease severity and abnormal results of NCS.

In this cohort study, twenty patients with clinically confirmed ATTRv polyneuropathy (PNP) and twenty-one healthy volunteers underwent 3 T MRI. vTE was performed on the right thigh to include the proximal tract of the sciatic nerve. The cross-sectional area of the whole sciatic nerve, inner epineurium, and endoneurial fascicles was segmented, and the corresponding pseudo-T2* was extrapolated from the two acquired echoes of the vTE.

Significantly higher fascicles pT2* (p = < 0.001), total cross-sectional area (CSA: p = 0.017) and fascicular area (p = < 0.001) were found in the ATTRv group compared to healthy controls. Fascicles pT2* also correlated with previously validated clinical outcome measures such as Polyneuropathy Disability Scoring System (PND score p = < 0. 001), Neuropathy Impairment Score (NIS p = 0.030) and NIS items related to the lower limbs, and with nerve conduction parameters, demonstrating the ability to discriminate ATTRv patients with different degrees of PNP from HC.

In conclusion, the vTE sequence provides novel and reliable imaging markers capable of detecting early nerve microstructural changes related to disease onset and severity.