- Design
- Multicentre randomised controlled trial, allocation-blinded sensory endpoints
- Population
- 91 adults with painful diabetic neuropathy
- Primary outcome
- Pain response (>=50% relief) and sensory improvement (>=3-point mTCNS fall) at 6 months
- Effect
- Sensory improvement 55.2% vs 25.0% (p=0.01); IENFD +0.58 vs -0.07 fibres/mm (p=0.03)
The PDN-Sensory randomised trial tested high-frequency 10-kHz spinal cord stimulation added to conventional medical management in painful diabetic neuropathy, and it was designed to answer the objection that has followed this device: that it treats the pain and leaves the neuropathy untouched.
Ninety-one participants were randomised, 41 to stimulation plus conventional management and 50 to conventional management alone. In a modified intention-to-treat worst-case analysis, 27 of 34 stimulation participants who underwent a temporary trial achieved at least 50% lower-limb pain relief, against 2 of 50 on conventional management (p<0.001). Sensory improvement — a fall of at least 3 points on the modified Toronto Clinical Neuropathy Score — occurred in 16 of 29 (55.2%) versus 12 of 48 (25.0%), p=0.01. Mean lower-calf intraepidermal nerve fibre density rose by 0.58 fibres/mm with stimulation and fell by 0.07 without, p=0.03. Eight of ten hierarchical secondary endpoints were met, including sleep and quality of life.
The nerve fibre density and sensory score assessments were allocation-blinded, which is what makes this more than another open-label pain trial: a patient who knows the device is on can report less pain, but cannot will their nerve fibres to grow. The authors put it no higher than consistent with a potential disease-modifying effect requiring longer confirmation, and that is the right level.
- 91 randomised; pain response 27 of 34 versus 2 of 50 (p<0.001).
- Sensory improvement in 55.2% versus 25.0% (p=0.01), on a blind-assessed score.
- Intraepidermal nerve fibre density +0.58 fibres/mm versus -0.07 (p=0.03).
- Eight of ten hierarchical secondary endpoints met, including sleep and quality of life.
Why it matters
Painful diabetic neuropathy is one of the few conditions where the honest answer has been that nothing available modifies the disease, only the symptom.
Don't overread it
Six months, 91 participants, and an unblindable device. The pain endpoint cannot be separated from knowing the stimulator is on; only the sensory score and fibre density were blind-assessed, and disease modification is a hypothesis here, not a finding.
The statistics, in plain English
The pain comparison, 27 of 34 against 2 of 50, is an unusually wide gap — but conventional management almost never produces a halving of pain, so the control rate is near the floor. The sensory and nerve fibre results are the ones to weigh, because the assessors did not know who had the device.
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