High-Frequency (10 kHz) Electrical Stimulation of Peripheral Nerves for Treating Chronic Pain: A Double-Blind Trial of Presence vs Absence of Stimulation

Objectives The study objectives were to perform a clinical audit of patients implanted with 10 kHz spinal cord (SCS) and peripheral nerve (PNS) stimulators for treating chronic pain and to investigate the effect of 10 kHz PNS on pain and other sensory modalities in a double-blind cross-over trial. Methods Pain, disability, and medication status were audited for 12 months after stimulator implantation in 58 SCS patients and in 11 PNS patients with an electrode positioned along a branch of the occipital or trigeminal nerve (four patients), a limb nerve trunk (four patients), or the S1 nerve root, genito-femoral nerve or ileo-inguinal nerve (one patient each). In PNS patients, pain and other sensory modalities were also assessed double-blind before and after the stimulator was switched either ON or OFF for two hours (protocol 1) or four hours (protocol 2). Results Decreases in pain and disability after stimulator implantation were maintained in both groups at 3-6 months, but these decreases were greater in PNS than SCS patients. In PNS trial patients, pain increased after the system had been turned OFF overnight for at least 12 hours before testing. Pain did not change after two hours of PNS but had decreased significantly after four hours. Other sensory modalities were minimally affected either by two or four hours of stimulation. Conclusions These findings suggest that PNS at 10 kHz decreases pain when conducted for at least four hours. Stimulation analgesia does not appear to be due to sensory conduction block.