Pacinian corpuscle loss on routine forefoot MRI as an imaging biomarker for large-fiber sensory dysfunction in type 2 diabetic polyneuropathy.

objectivesTo evaluate the relationship between Pacinian corpuscle (PC) count on forefoot MRI in diabetic sensorimotor polyneuropathy (DSP) and large-fiber sensory dysfunction as quantified by nerve conduction studies (NCS). MATERIALS AND

methodsThirty-nine patients with type 2 diabetes and neurologically confirmed DSP (mean age 67.9 ± 13.5 years; 29 males) underwent forefoot MRI and NCS, including compound muscle and sensory nerve action potentials (cMAP, sNAP) and conduction velocities of tibial, peroneal, and sural nerves. PC counts were assessed in the subcutaneous and deep regions of each digit. Spearman's rank correlation analysis examined the relationship between total PC counts and sural sNAP amplitudes.

resultsBased on motor and sensory amplitudes and age-adjusted conduction velocities of NCS, 10 patients were classified as having mild-to-moderate DSP, and 29 as having severe DSP. Severe DSP was associated with sensory large-fiber impairment, with 86.1% of patients showing abolished sural sNAP amplitudes. Total PC counts were significantly lower in severe cases compared to mild-to-moderate polyneuropathy (54.1 ± 40.6 vs 146.1 ± 43.2; p < 0.001). Spearman's rank correlation analysis revealed a strong positive association between PC counts and sural sNAP amplitudes (ρ = 0.638, p < 0.001). Likewise, patients with severe DSP had substantially reduced or absent sural sNAP amplitudes (median [range]: 0.1 [0.1-1.7] µV) and lower PC counts, while those with mild-to-moderate DSP showed both higher sural sNAP amplitudes (median [range]: 2.3 [0.9-11.4] µV) and PC counts (p < 0.001).

conclusionForefoot MRI-detected PC counts closely correlate with large-fiber sensory function in DSP, supporting their potential as noninvasive imaging biomarkers of polyneuropathy severity. KEY POINTS: Question DSP is linked to loss of PC on forefoot MRI; however, it remains unclear whether the number of PC correlates with DSP severity. Findings Forefoot MRI showed lower PC counts in patients with severe DSP than in those with mild-to-moderate disease and indicated a strong association between PC loss and electrophysiological measures of large-fiber sensory dysfunction. Clinical relevance MRI-based PC quantification is a promising imaging biomarker for large-fiber sensory dysfunction in DSP, complementing established clinical and electrophysiological methods for diagnosing and assessing DSP severity.