Effect and safety of spinal cord stimulation for treatment of chronic pain caused by diabetic neuropathy.

AIM: Spinal cord stimulation (SCS) has been shown effective as a therapy for different chronic painful conditions, but the effectiveness of this treatment for pain as a result of peripheral diabetic neuropathy is not well established. The primary objectives of this study were to evaluate the effect and safety of SCS for treatment of pain and the effects on microcirculatory blood flow in the affected areas in patients with refractory peripheral diabetic neuropathy. METHOD: The study was designed as a prospective, open-label study. Data were collected during screening, at implant and at regular intervals, after initiation of therapy. Eleven diabetic patients with chronic pain in their lower limbs and no response to conventional treatment were studied. The SCS electrode was implanted in the thoracic epidural space. Neuropathic pain relief was assessed by Visual Analogue Scale (VAS) and microcirculatory skin perfusion was measured with Laser Doppler flowmetry. RESULTS: Nine subjects had significant pain relief with the percutaneous electrical stimulator. Average pain score for all nine patients was 77 at baseline and 34 at 6 months after implantation. At the end of the study, eight of nine patients continued to experience significant pain relief and have been able to significantly reduce their pain medication. For six of them, the stimulator was the sole treatment for their neuropathic pain. No significant changes in microcirculatory perfusion were recorded. CONCLUSION: Spinal cord stimulation offers an effective and safe therapy for chronic diabetic neuropathic pain.

A randomized controlled trial of an implantable 2-channel peroneal nerve stimulator on walking speed and activity in poststroke hemiplegia.

OBJECTIVE: To determine the effect of a new implantable 2-channel peroneal nerve stimulator on walking speed and daily activities, in comparison with the usual treatment in chronic stroke survivors with a drop foot. DESIGN: Randomized controlled trial. SETTING: All subjects were measured 5 times in the gait laboratory. PARTICIPANTS: Twenty-nine stroke survivors with chronic hemiplegia with drop foot who fulfill the predefined inclusion and exclusion criteria were included in the study. INTERVENTION: The intervention group received an implantable 2-channel peroneal nerve stimulator for correction of their drop foot. The control group continued using their conventional walking device, consisting of an ankle-foot orthosis, orthopedic shoes, or no device. MAIN OUTCOME MEASURES: Walking speed, assessed both by a six-minute walk test (6MWT) and by using a 10-m walkway, was selected as primary outcome measure and activity monitoring data, consisting of percentage time spent on stepping, standing, and sitting/lying were selected as secondary outcome measure. RESULTS: Functional electric stimulation (FES) resulted in a 23% improvement of walking speed measured with the 6MWT, whereas the improvement in the control group was only 3% (P=.010). Comfortable walking speed measured on a 10-m walkway was also significantly improved in favor of FES (P=.038). The percentage time spent on stepping deteriorated with 3% in the intervention and 0.8% in control group, which was not statistically significant between both groups (P=.13). CONCLUSIONS: The present study shows a clinically relevant effect of the implantable 2-channel peroneal nerve stimulator on walking speed in the sample of stroke survivors included in our study.

Heart rate control via vagus nerve stimulation.

Objectives. There is ample and well-established evidence that direct electrical stimulation of the vagus nerve can change heart rate in animals and humans. Since tachyarrhythmias cannot always be controlled through medication, we sought, in this pilot study, to elucidate whether a clinical implantable lead system that is used in cervical vagus nerve stimulation therapy (VNS therapy) also can be used for control of heart rate, and tachycardia in particular. Materials and Methods. Experiments were carried out in three pigs (weight 21-26 kg) under general anesthesia. The right and left vagus nerves in the neck region were exposed by dissection, and bipolar, multiturn, helical, silicone leads were wrapped around the vagus nerves. Stimulation was applied by an external device with multivariable settings: frequency 10-100 Hz, pulse duration 100-700 µsec; delay 0-0.5 msec; current 0.5-14 mA. Measurements were performed under normal sinus rhythm (RR-interval 501 ± 30 msec) and during isoprenaline-induced tachycardia (RR-interval 284 ± 11 msec). Results. VNS, under optimal pacing conditions (100 Hz; 5 mA; 0.2 msec; 70 msec delay), in an electrocardiogram-triggered (ECG-triggered) pacing mode, increased RR-intervals by approximately 40%, irrespective of the duration of the RR-interval preceding VNS. The maximum effect on heart rate was established within approximately 5 sec after the onset of stimulation and was reversible and reproducible. No differences were found between stimulation of the right or left vagus nerve. Conclusion. VNS can be used effectively and rapidly to decrease heart rate, in acute settings, when connected to an external pacing system. Future devices that are fully implantable may be used for nonpharmacological treatment of illnesses in which tachycardia results in deterioration of cardiac function.

Laryngeal and vocal changes during vagus nerve stimulation in epileptic patients.

Left vagus nerve stimulation (VNS) by means of an implanted electrode has proven to reduce seizure frequency in epileptic patients with medically refractory seizures. This technique is now widely applied over the world. Voice changes appear to be one of the major side effects. The morphodynamic changes in the larynx and the acoustic impacts have been analyzed in detail in 7 implanted patients. Basic vagus stimulation is well tolerated. Extra stimulation induces an adductory spasm of either the ipsilateral vocal fold or the vestibular fold. The result, when the patient phonates, consists of a slight increase of F0 as well as a moderate increase of random period perturbation, but there is no evidence for the occurrence of "bifurcations." Further, as the glottic closure remains sufficient, there is no increase in turbulent noise. The lack of increase in turbulent noise and the lack of "bifurcations" appears to clearly differentiate a spasmodic contraction of the vocal cord from a unilateral vocal fold paralysis.