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Shyam Sunder Tummanapalli, Tushar Issar, Natalie Kwai, Ann Poyten, Arun Krishnan, Mark D P Willcox, Maria Markoulli; Assessment of corneal nerve structure and peripheral nerve function in detection of diabetic peripheral neuropathy. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1811. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To examine the ability of corneal nerve fibre assessment and axonal ion-channel function to diagnose diabetic peripheral neuropathy (DPN).
A total of 36 subjects with type 1 diabetes and 10 age-matched controls underwent confocal microscopy to assess corneal nerve fibre length, density area, width, branch density, and inferior whorl length. The presence and severity of DPN were assessed using the total neuropathy score (TNS). Participants with diabetes were stratified into those with neuropathy (DPN+; TNS > 1; n = 10) and those without neuropathy (DPN- ; TNS < 1; n = 26). Motor excitability studies were conducted on the median nerve to assess axonal ion-channel function in the nodal and internodal regions of the axonal membrane. Parameters obtained included stimulus-response behaviour, threshold electrotonus (depolarizing and hyperpolarizing), current-threshold relationship and recovery cycle. Areas under the receiver operating characteristic curves (AUCs) were calculated to obtain specificity and sensitivity of measures to diagnose DPN.
A significant reduction was found in fibre density (fibres/mm2; 28.31 ± 5.72 vs. 19.73 ± 4.06, P < 0.01), fibre length (mm/mm2; 16.90 ± 1.59 vs. 12.44 ± 1.07, P < 0.01), inferior whorl length (mm/mm2; 16.44 ± 6.02 vs. 9.31 ± 3.75, P < 0.01), and subexcitability (%; 13.40 ± 3.01 vs. 9.70 ± 3.04, P = 0.01) in DPN+ compared to controls. Depolarizing threshold electrotonus (under shoot) (-19.33 ± 3.37 vs. -17.05 ± 3.23, P = 0.04) and latency derived from the recovery cycle paradigm (ms; 6.44 ± 0.67 vs. 9.70 ± 3.04, P = 0.02) were significantly increased in DPN+ compared to controls. The tests that were best able to diagnose DPN were fibre length (0.97; P < 0.001; sensitivity 100%; specificity 90%), branch density (0.93; P < 0.001; sensitivity 90%; specificity 90%), fibre density (0.91; P < 0.001; sensitivity 100%; specificity 90%), inferior whorl length (0.90; P < 0.001; sensitivity 100%; specificity 90%) and measures of internodal sodium ion-channel function (subexcitability: 0.83; P < 0.001; sensitivity 80%; specificity 80%).
Nerve fibre length, density, branch density and inferior whorl length were able to diagnose DPN with higher sensitivity than measures of axonal ion-channel dysfunction in patients with type 1 diabetes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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