Epidural spinal cord electrical stimulation in diabetic critical lower limb ischemia

Use of consecutive transcutaneous oxygen measurement when assessing the need for revascularization and association with the outcomes of ischemic diabetic ulcers

This study compared the ankle-brachial index (ABI) with transcutaneous oxygen pressure (TcPO2 ) in assessing peripheral vascular disease (PVD) prevalence in 100 diabetic foot ulcer (DFU) patients. Patients were categorized into vascular or nonvascular reconstruction groups and underwent both ABI and TcPO2 measurements four times over 6 months. Predictive validity for PVD diagnosis was analysed using the area under the receiver-operating characteristic curve (AUC). The study found TcPO2 to be a superior predictor of PVD than ABI. Among the DFU patients, 51 with abnormal TcPO2 values underwent vascular reconstruction. Only TcPO2 values showed significant pretreatment differences between the groups and increased post-reconstruction. These values declined over a 6-month follow-up, whereas ABI values rose. For those with end-stage renal disease (ESRD), TcPO2 values saw a sharp decrease within 3 months. Pre-reconstruction TcPO2 was notably lower in amputation patients versus limb salvage surgery patients. In conclusion, TcPO2 is more effective than ABI for evaluating ischemic limb perfusion and revascularization necessity. It should be prioritized as the primary follow-up tool, especially for ESRD patients.

Quantitative assessment of painful diabetic peripheral neuropathy after high-frequency spinal cord stimulation: a pilot study

OBJECTIVE

Randomized trials have demonstrated efficacy of spinal cord stimulation (SCS) for treatment of painful diabetic neuropathy (PDN). Preliminary data suggested that treatment of PDN with high-frequency SCS resulted in improvements on neurological examination. The purpose of the present study was to explore whether patients with PDN treated with high-frequency SCS would have improvements in lower-extremity peripheral nerve function.

DESIGN

Prospective cohort study in an outpatient clinical practice at a tertiary care center.

METHODS

Patients with PDN were treated with high-frequency SCS and followed up for 12 months after SCS implantation with clinical outcomes assessments of pain intensity, neuropathic symptoms, and neurological function. Small-fiber sudomotor function was assessed with the quantitative sudomotor axon reflex test (QSART), and large-fiber function was assessed with nerve conduction studies (NCS). Lower-extremity perfusion was assessed with laser Doppler flowmetry.

RESULTS

Nine patients completed 12-month follow-up visits and were observed to have improvements in lower-extremity pain, weakness, and positive sensory symptoms. Neuropathy impairment scores were improved, and 2 patients had recovery of sensory responses on NCS. A reduction in sweat volume on QSART was observed in the proximal leg but not at other sites. No significant differences were noted in lower-extremity perfusion or NCS as compared with baseline.

CONCLUSIONS

The improvement in pain relief was concordant with improvement in neuropathy symptoms. The findings from this study provide encouraging preliminary data in support of the hypothesis of a positive effect of SCS on peripheral neuropathy, but the findings are based on small numbers and require further evaluation.

TRIAL REGISTRATION

ClinicalTrials.gov ID NCT03769675.

Clinical Effect Analysis of Spinal Cord Electrical Stimulator Implantation for Diabetic Foot

OBJECTIVE

To investigate the clinical effect of spinal cord electrical stimulator implantation in the treatment of a diabetic foot (DF).

MATERIALS AND METHODS

We recruited 19 patients with DF who were admitted to Shengjing Hospital of China Medical University between January 2018 and May 2020. All the patients were treated with spinal cord electrical stimulator implantation. Skin temperature, degree of pain, quality of life (QOL) score, limb (toe) preservation, and nerve conduction velocity of the patients were compared pre- and postoperatively.

RESULTS

The diameter and peak velocity of multisegment arteries in the lower limbs had significantly increased post surgery. Foot skin temperature significantly increased in patients with good effect. The postoperative visual analog scale score of the patients was significantly lower than that noted preoperatively (p < 0.05). The conduction velocities of the lower limb sensory nerves (eg, superficial peroneal nerve and sural nerve) and motor nerves (eg, common peroneal nerve and tibial nerve) had improved post surgery. Moreover, patients' QOL score had significantly improved postoperatively (p < 0.05). The limb (toe) salvage rate was 94.74%.

CONCLUSION

The implantation of a spinal cord electrical stimulator for treating DF can effectively relieve pain and other associated symptoms. Additionally, this device can promote nerve function recovery and lower limb blood supply and reduce the risk of toe amputation; therefore, it is clinically effective and should be considered in the treatment of DF.

Spinal cord stimulation in experimental chronic painful diabetic polyneuropathy: Delayed effect of High-frequency stimulation

Background

Spinal cord stimulation (SCS) has been shown to provide pain relief in painful diabetic polyneuropathy (PDPN). As the vasculature system plays a great role in the pathophysiology of PDPN, a potential beneficial side‐effect of SCS is peripheral vasodilation, with high frequency (HF) SCS in particular. We hypothesize that HF‐SCS (500 Hz), compared with conventional (CON) or low frequency (LF)‐SCS will result in increased alleviation of mechanical hypersensitivity in chronic experimental PDPN.

Methods

Diabetes was induced in 8‐week‐old female Sprague–Dawley rats with an intraperitoneal injection of 65 mg/kg of streptozotocin (n = 44). Rats with a significant decrease in mechanical withdrawal response to von Frey filaments over a period of 20 weeks were implanted with SCS electrodes (n = 18). Rats were assigned to a cross‐over design with a random order of LF‐, CON‐, HF‐ and sham SCS and mechanical withdrawal thresholds were assessed with von Frey testing.

Results

Compared with sham treatment, the average 50% WT score for 5 Hz was 4.88 g higher during stimulation (p = 0.156), and 1.77 g higher post‐stimulation (p = 0.008). CON‐SCS resulted in 50% WT scores 5.7 g, and 2.51 g higher during (p = 0.064) and after stimulation (p < 0.004), respectively. HF‐SCS started out with an average difference in 50% WT score compared with sham of 1.87 g during stimulation (p = 0.279), and subsequently the steepest rise to a difference of 5.47 g post‐stimulation (p < 0.001).

Conclusions

We demonstrated a delayed effect of HF‐SCS on mechanical hypersensitivity in chronic PDPN animals compared with LF‐, or CON‐SCS.

Significance

This study evaluates the effect of SCS frequency (5–500 Hz) on mechanical hypersensitivity in the chronic phase of experimental PDPN. High frequency (500 Hz) – SCS resulted in a delayed effect‐ on pain‐related behavioural outcome in chronic PDPN.

Neurostimulation Methods in the Treatment of Chronic Pain

The main neuromodulatory methods using neurostimulation principles are described. It concerns peripheral nerve stimulation (PNS), spinal cord stimulation (SCS), deep brain stimulation (DBS), motor cortex stimulation (MSC), and repetitive transcranial magnetic stimulation (rTMS). For each method the history, pathophysiology, the principles for use and the associated diagnoses are mentioned. Special attention is focused on the most common neuromodulatory invasive methods like SCS and MCS and non-invasive methods such as rTMS. In addition to the positive effects, side effects and complications are described and discussed in detail. In conclusion, neuromodulatory (neurostimulatory) techniques are highly recommended for the treatment of different types of pharmacoresistant pain.

Activity-dependent plasticity in spinal cord injury

The adult mammalian central nervous system (CNS) is capable of considerable plasticity, both in health and disease. After spinal neurotrauma, the degrees and extent of neuroplasticity and recovery depend on multiple factors, including the level and extent of injury, postinjury medical and surgical care, and rehabilitative interventions. Rehabilitation strategies focus less on repairing lost connections and more on influencing CNS plasticity for regaining function. Current evidence indicates that strategies for rehabilitation, including passive exercise, active exercise with some voluntary control, and use of neuroprostheses, can enhance sensorimotor recovery after spinal cord injury (SCI) by promoting adaptive structural and functional plasticity while mitigating maladaptive changes at multiple levels of the neuraxis. In this review, we will discuss CNS plasticity that occurs both spontaneously after SCI and in response to rehabilitative therapies.

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.

Putative mechanisms behind effects of spinal cord stimulation on vascular diseases: a review of experimental studies

Spinal cord stimulation (SCS) is a widely used clinical technique to treat ischemic pain in peripheral, cardiac and cerebral vascular diseases. The use of this treatment advanced rapidly during the late 80's and 90's, particularly in Europe. Although the clinical benefits of SCS are clear and the success rate remains high, the mechanisms are not yet completely understood. SCS at lumbar spinal segments (L2-L3) produces vasodilation in the lower limbs and feet which is mediated by antidromic activation of sensory fibers and decreased sympathetic outflow. SCS at thoracic spinal segments (T1-T2) induces several benefits including pain relief, reduction in both frequency and severity of angina attacks, and reduced short-acting nitrate intake. The benefits to the heart are not likely due to an increase, or redistribution of local blood flow, rather, they are associated with SCS-induced myocardial protection and normalization of the intrinsic cardiac nervous system. At somewhat lower cervical levels (C3-C6), SCS induces increased blood flow in the upper extremities. SCS at the upper cervical spinal segments (C1-C2) increased cerebral blood flow, which is associated with a decrease in sympathetic activity, an increase in vasomotor center activity and a release of neurohumoral factors. This review will summarize the basic science studies that have contributed to our understanding about mechanisms through which SCS produces beneficial effects when used in the treatment of vascular diseases. Furthermore, this review will particularly focus on the antidromic mechanisms of SCS-induced vasodilation in the lower limbs and feet.

Spinal cord stimulation for ischemic heart disease and peripheral vascular disease

Ischemic disease (ID) is now an important indication for electrical neuromodulation (NM), particularly in chronic pain conditions. NM is defined as a therapeutic modality that aims to restore functions of the nervous system or modulate neural structures involved in the dysfunction of organ systems. One of the NM methods used is chronic electrical stimulation of the spinal cord (spinal cord stimulation: SCS). SCS in ID, as applied to ischemic heart disease (IHD) and peripheral vascular disease (PVD), started in Europe in the 1970s and 1980s, respectively. Patients with ID are eligible for SCS when they experience disabling pain, resulting from ischaemia. This pain should be considered therapeutically refractory to standard treatment intended to decrease metabolic demand or following revascularization procedures. Several studies have demonstrated the beneficial effect of SCS on IHD and PVD by improving the quality of life of this group of severely disabled patients, without adversely influencing mortality and morbidity. SCS used as additional treatment for IHD reduces angina pectoris (AP) in its frequency and intensity, increases exercise capacity, and does not seem to mask the warning signs of a myocardial infarction. Besides the analgesic effect, different studies have demonstrated an anti-ischemic effect, as expressed by different cardiac indices such as exercise duration, ambulatory ECG recording, coronary flow measurements, and PET scans. SCS can be considered as an alternative to open heart bypass grafting (CABG) for patients at high risk from surgical procedures. Moreover, SCS appears to be more efficacious than transcutaneous electrical nerve stimulation (TENS). The SCS implantation technique is relatively simple: implanting an epidural electrode under local anesthesia (supervised by the anesthesist) with the tip at T1, covering the painful area with paraesthesia by external stimulation (pulse width 210, rate 85 Hz), and connecting this electrode to a subcutaneously implanted pulse generator. In PVD the pain may manifest itself at rest or during walking (claudication), disabling the patient severely. Most of the patients suffer from atherosclerotic critical limb ischemia. All patients should be therapeutically refractory (medication and revascularization) to become eligible for SCS. Ulcers on the extremities should be minimal. In PVD the same implantation technique is used as in IHD except that the tip of the electrode is positioned at T10-11. In PVD the majority of the patients show significant reduction in pain and more than half of the patients show improvement of circulatory indices, as shown by Doppler, thermography, and oximetry studies. Limb salvage studies show variable results depending on the stage of the trophic changes. The underlying mechanisms of action of SCS in PVD require further elucidation.

Spinal cord stimulation reducing infarct volume in a model of focal cerebral ischemia in rats

OBJECT

The authors previously showed that spinal cord stimulation (SCS) increases cerebral blood flow in rats, indicating that this technique may be useful in the treatment of focal cerebral ischemia. In the present study, the neuroprotective potential of SCS in the setting of middle cerebral artery occlusion (MCAO) was investigated.

METHODS

The authors induced permanent, focal cerebral ischemia by using either suture-induced occlusion or direct division of the MCA in Sprague-Dawley rats. Electrical stimulation of the cervical spinal cord was performed during cerebral ischemia. Cerebral blood flow was assessed using both laser Doppler flowmetry (LDF) and quantitative radiotracer analysis. Stroke volumes were analyzed after 6 hours of ischemia. Spinal cord stimulation resulted in a 52.7 +/- 13.3% increase in LDF values (nine animals). Following MCAO, LDF values decreased by 64.1 +/- 3.6% from baseline values (10 animals). Spinal cord stimulation subsequently increased LDF values to 30.9 +/- 13.5% below original baseline values. These findings were corroborated using radiotracer studies. Spinal cord stimulation in the setting of transcranial MCAO significantly reduced stroke volumes as well (from 203 +/- 33 mm3 [control] to 32 +/- 8 mm3 [MCAO plus SCS], seven animals in each group, p < 0.001). Similarly, after suture-induced MCAO, SCS reduced stroke volumes (from 307 +/- 29 mm3 [control] to 78 +/- 22 mm3 [MCAO plus SCS], 10 animals in each group, p < 0.001).

CONCLUSIONS

A strategy of performing SCS for the prevention of critical ischemia is feasible and may have the potential for the treatment and prevention of stroke.

Plasma brain natriuretic peptide levels in normotensive Type 2 diabetic patients without cardiac disease and macroalbuminuria

To clarify the relationship of the plasma brain natriuretic peptide (BNP) levels to diabetic complications, we studied plasma BNP levels in 100 normotensive diabetic patients without clinical cardiac disease and macroalbuminuria. The values of plasma BNP levels were not significantly different between patients with microalbuminuria and those with normoalbuminuria (12.2 +/- 2.0 vs. 12.3 +/- 1.3 pg/ml, means +/- S.E.M.), and neither were the BNP levels of patients with and without retinopathy significantly different (15.7 +/- 3.4 vs. 11.4 +/- 1.0 pg/ml). BNP levels of the subjects with cerebral vascular disease (CVD) were not statistically different from those of subjects without CVD (17.5 +/- 5.5 vs. 11.7 +/- 1.0 pg/ml), although mean BNP value of subjects with CVD was higher than that of subjects without it. With regard to peripheral vascular disease (PVD), BNP levels of the subjects with PVD were not statistically different from those of subjects without PVD (13.5 +/- 2.3 vs. 12.1 +/- 1.2 pg/ml). We also studied radial arterial oxygen tension of 45 patients and compared these levels between those with and without diabetic complications. However, we could not find statistical differences between them. In conclusion, our study suggests that BNP and arterial oxygen tension levels will not be affected by retinopathy, microalbuminuria, CVD, and PVD in normotensive diabetic patients without clinical cardiac disease and macroalbuminuria. Therefore, when normotensive diabetic patients without macroalbuminuria show increased plasma level of BNP, we should examine their cardiac function in detail, considering subclinical cardiac disease.