Objective evaluation of peripheral nerve function and pathology is essential for the early diagnosis and determination of clinical staging of diabetic polyneuropathy (DPN). To this end, we attempted to apply the photoacoustic imaging (PAI) to clinical diagnosis of DPN and characterization of background pathology. PAI is the imaging system for the dual ultrasound detection of the specific tissues or organs and released signals from the same tissues irradiated with laser light with specific wave length. For the application of PAI to DPN, we selected the median (MN) and sural nerves (SN) for the evaluation and applied laser light to these nerves for the detection of signals from hemoglobin. With this method, PAI enables depiction of nerve bundle cross sectional area (NA), and hemoglobin distribution, thereby blood volume (BV), vascular area (VA) or caliber at the arteriolar/venular levels. In this study, 12 healthy control subjects (C) and 54 diabetic patients (DM) with (n=30) or without DPN (n=24) were subjected to PAI examination. DPN was confirmed by Japanese study group criteria. Correlation analysis was also conducted between PAI data and clinical staging of DPN. We found significant increases of NA 14% in MN and 18% in SN in DM compared to C, and trends of increases in NA toward advanced DPN. There was also a trend of increase in VA in DM with advanced DPN although there was no significant difference between C and DM. Compared to C, BV in SN was increased 12% in DM, but it was decreased in DM with DPN compared to those without DPN. These findings indicated that expanded nerve bundle area with decreased BV was characteristic in DPN. Our results suggest that endoneurial edema of nerve bundles, epi- and perineurial fibrosis and congestion with endoneurial ischemia may contribute to the development of DPN. We consider that PAI is a new and valuable method for the clinical application to DPN.
S. Yagihashi: None.