Proximal neuropathic lesions in distal symmetric diabetic polyneuropathy: findings of high-resolution magnetic resonance neurography

Abstract

Objective: This study investigated high-resolution magnetic resonance neurography (MRN) in distal symmetric diabetic polyneuropathy (dPNP).

Research design and methods: MRN comprised high-resolution transaxial imaging of peripheral nerves of the lower limbs in 20 patients with type 2 diabetes (10 with dPNP, type 2/dPNP[+], and 10 without dPNP, type 2/dPNP[-]), seven patients with type 1 diabetes (two with dPNP, type 1/dPNP[+], five without dPNP, type 1/dPNP[-]), and 10 nondiabetic control subjects. Intraneural T2 lesions, as the main diagnostic criterion of MRN, were detected visually by two independent observers and quantitatively by analysis of T2 contrast ratios.

Results: Multifocal fascicular, symmetric intraneural T2 lesions occurred in the proximal trunks of sciatic nerves in four patients (three with type 2/dPNP[+] and one with type 1/dPNP[+]) but not in control subjects (type 2/dPNP[-], type 1/dPNP[-], nondiabetic control subjects), which was confirmed by quantitative analysis. Clinical severity was higher in patients with T2 lesions (neuropathy deficit score: 10 vs. 7.8; P = 0.05).

Conclusions: For the first time, proximal neuropathic lesions of dPNP are reported in vivo. This supports that accumulation of proximal, multifocal fascicular injury may be important in disease progression.

Figure 1

Multifocal fascicular symmetric lesions within proximal sciatic nerve trunks in type 1 and type 2 diabetic patients with distal symmetric polyneuropathy (two upper rows). Fascicular symmetric lesions of one type 1 diabetic patient with dPNP (type 1/dPNP[+]) (top row) and of one type 2 diabetic patient with dPNP (type 2/dPNP[+]) (second row from top). Diagnostic conspicuity by visual evaluation arises from pathologically increased T2-weighted hyperintense/bright contrast (left column, “Thigh sciatic nerve T2-w”) and is confirmed by quantitative lesion classification from contrast ratios (red overlay on T2-weighted images in right column, “Lesion classification”). In the three control groups, intraneural T2 lesions were not observed (type 1/dPNP[−], type 2/dPNP[−], and nondiabetic control subjects). One representative subject from each control group is shown (third to fifth row below white horizontal bar). Right and left sciatic nerves are denoted at the bottom. L, left; R, right; T2-w, T2 weighted. (A high-quality digital representation of this figure is available in the online issue.)