Quantitative sensory testing in type 1 diabetic patients with painful and painless diabetic neuropathy
The mechanism underlying the development of painful diabetic neuropathy (DN) is unknown. The aim of this study was to compare quantitative sensory testing (QST) characteristics of patients with painful and painless DN and to correlate QST measures with DN pain. 50 type 1 diabetic patients with DN (30 with painful DN and 20 with painless DN) and 32 age-matched non-diabetic controls were included in this study. For all patients and controls, a detailed assessment of DN was performed which comprised McGill visual analog scale (McGill VAS) for pain, neuropathy symptom profile and neuropathy disability score, QST in form of cold thresholds (CT), warm thresholds (WT), and vibration perception thresholds (VPT), nerve conduction studies (NCS), deep-breathing hear rate variability (DB-HRV), and Neuropad staining scores. Measures of QST, NCS, and DB-HRV were correlated with McGill VAS for pain. Apart from NCS, there were no significant differences in CT, WT, and VPT, DB-HRV and Neuropad scores between patients with painful and painless DN. Cold threshold (r = −0.57, P = 0.005), warm threshold (r = 0.47, P = 0.026), and DB-HRV (r = 0.50, P = 0.023), however, correlated significantly with McGill VAS scores of pain. In conclusion, QST is a helpful tool to identify small nerve fibers damage of DN, correlates with pain intensity but cannot differentiate between painful and painless DN. Both central and peripheral neural injury could be implicated in the genesis of DN pain.