Diagnostic significance of sensory nerve action potential amplitude in early-stage diabetic neuropathy / 中华神经科杂志

ABSTRACT

Objective To investigate the diagnostic significance of sensory nerve action protential (SNAP) on diabetic neuropathy (DN), through measuring amplitude and amplitude ratio. Methods There were 91 patients with type 2 diabetes involing 51 cases without neurologic symptom/sign as subgroup Ⅰ, 30 cases with mild neuropathy as subgroup Ⅱ and 10 cases with severe neuropathy as subgroup Ⅲ, according to Toronto clinical scoring system (TCSS). Thirty-nine healthy volunteers with age- and gender-matched were served as controls. SNAP were antidromically recorded using surface electrodes. The observed parameters were as follows conduction velocity and amplitude of median, radial and sural nerve, shorten for Vine, Vra and Vsu and Ame, Ara and Asu, respectively; sural/radial nerve amplitude ratio (SRAR) and median/ radial nerve amplitude ratio (MRAR). Results (1) As compared with the controls (P<0.05),conduction velocity (m/s, Vine 46. 2 ±7.3, Vra 45.8±6. 9, Vsu 30. 3±9. 5) and amplitude (μV, Am 15.4±10.5, Ar 16.6±9.8, As 5.9±6. 3)decreased significantly in subgroup Ⅲ; Vsu (46.2± 4. 7) significantly slowed in subgroup Ⅱ (P = 0. 002) ; both Ame (34. 5 ± 10. 2, 33. 0 ± 14. 6) and Asu (13.8± 5.6, 10.7 ± 5.5) decreased significantly in both subgroup Ⅰ and Ⅱ respectively, with Asu decreasing more significantly in subgroup Ⅱ (Z=- 3.22, P = 0. 001) ; SRAR (0. 432± 0. 112) was significantly smaller only in subgroup Ⅰ , both SRAR (0. 330 ±0. 102) and MRAR (1. 008 ± 0. 225) were significantly smaller in subgroup Ⅱ. SRAR decreased more significantly in subgroup Ⅱ (t = - 3. 86, P = 0. 003). (2) The abnormal rate of Ame was the highest in subgroup Ⅰ (26. 0%), and Asu in subgroup Ⅱ (41.4%) ; while that of combination of Asu and SRAR (68.9%) was significantly higher than that of Asu alone (x2 = 9. 212, P = 0. 003). (3) TCSS scores were negatively related to Van (r = - 0. 583), Ame (r=-0. 406), Asu (r=-0.620) and SRAR (r=-0.527, all P<0.05), and there was no significant correlation of TCSS scores with MRAR in subgroup Ⅱ; both SRAR (r = -0.435) and MRAR (r = - 0. 319) were negatively related to the diabetic duration (both P < 0. 05). Conclusions In mild or early DN, SNAP amplitude is more sensitive than conduction velocity, combination of SRAR and Vsu may be serve as a useful indication for early diagnosis. In the DN patient, diabetic duration has more influence on the measurement of sensory NCS, and SRAR is related to the severity of neuropathy.