Cervical spinal cord stimulation increases cerebral cortical blood flow in an experimental cerebral vasospasm model

Cervical spinal cord stimulation for prevention and treatment of cerebral vasospasm after aneurysmal subarachnoid hemorrhage: clinical and radiographic outcomes of a prospective single-center clinical pilot study

BACKGROUND

Cerebral vasospasm induced by aneurysmal subarachnoid hemorrhage (aSAH) is a major cause of high morbidity and mortality, for which there is no consistently effective treatment. Cervical spinal cord stimulation (cSCS) has been shown to induce vasodilatation and improve peripheral and cerebral blood flow in both animal and human studies. This pilot study was performed to assess the clinical effect and long-term results of cSCS treatment in aSAH patients.

METHODS

This was the first IRB- and US FDA-approved prospective non-randomized non-controlled study comprising of 12 aSAH patients (8 women, 4 men, age range 34-62 years) treated between May and November 2008. All patients underwent up to 2 weeks of cSCS with a single percutaneously implanted 8-contact electrode. Neurological outcomes at discharge and follow-up of up to 13 years and mortality/complications rates were analyzed.

RESULTS

All 12 aSAH patients underwent cSCS electrode implantation immediately after securing the aneurysm. Patients were stimulated for 10-14 consecutive days starting within 3 days of aneurysm rupture. Angiographic vasospasm occurred in six patients; two patients developed new vasospasm-related neurological symptoms; both recovered completely by discharge time. One patient died from unrelated multi-system failure; the rest were followed up clinically (average, 7.5 years; range, 12-151 months) and angiographically (average, 6.5 years; range, 36-125 months). No delayed ischemic neurological deficits/strokes and no cSCS-related adverse effects were observed.

CONCLUSIONS

Our short- and long-term data suggest that cSCS is feasible and safe for patients in the acute aSAH settings. Small size of the patient cohort and lack of control do not allow us to conclude whether cSCS is able to prevent cerebral vasospasm, decrease its severity, and improve clinical outcomes in aSAH patients. However, our findings support further clinical trials and development of cSCS as a new concept to prevent and treat cerebral vasospasm.

TRIAL REGISTRATION

CLINICALTRIALS

gov NCT00766844, posted on 10/06/2008.

The Potential Role of Neuromodulation in Subarachnoid Hemorrhage

OBJECTIVES

Aneurysmal subarachnoid hemorrhage (SAH) continues to be a difficult cerebrovascular disease with limited pharmacologic treatment options. Cerebral vasospasm (CV) and delayed cerebral ischemia (DCI) are leading causes of morbidity and mortality after SAH. Despite the advances in the understanding of its pathophysiology and tremendous efforts to date, nimodipine is currently the sole Food and Drug Administration-approved treatment for patients with SAH, with benefits that are marginal at best. The neuromodulation therapies are promising, especially those that target CV and DCI to improve functional outcomes. The aim of this review is therefore to summarize the available evidence for each type of neuromodulation for CV and DCI, with a special focus on its pathophysiological mechanisms, in addition to their clinical utility and drawbacks, which we hope will lead to future translational therapy options after SAH.

MATERIALS AND METHODS

We conducted a comprehensive review of preclinical and clinical studies demonstrating the use of neuromodulation for SAH. The literature search was performed using PubMed, Embase, and ClinicalTrials.gov. A total of 21 articles published from 1992 to 2021 and eight clinical trials were chosen.

RESULTS

The studies reviewed provide a compelling demonstration that neuromodulation is a potentially useful strategy to target multiple mechanisms of DCI and thus to potentially improve functional outcomes from SAH. There are several types of neuromodulation that have been tested to treat CV and DCI, including the trigeminal/vagus/facial nerve stimulation, sphenopalatine ganglion and spinal cord stimulation, transcranial direct electrical stimulation, transcutaneous electrical neurostimulation, and electroacupuncture. Most of them are in the preclinical or early phases of clinical application; however, they show promising results.

CONCLUSIONS

DCI has a complex pathogenesis, making the unique anatomical distribution and pleiotropic capabilities of various types of neuromodulation a promising field of study. We may be at the cusp of a breakthrough in the use of these techniques for the treatment of this stubbornly difficult disease.

The influence of neuromuscular electrical stimulation on the heart rate variability in healthy subjects

[Purpose] The purpose of this study was to examine the effect of neuromuscular electrical stimulation (NMES) on heart rate variability (HRV). [Subjects and Methods] Ten healthy subjects participated in the study. All subjects received NMES with a pulse duration of 300 us and frequency of 30 Hz at the vastus lateralis and vastus medialis for 15 minutes. The stimulation intensity was adjusted in the range of 20 to 30 mA. HRV using a pulse oximeter was measured in the sitting position before and after NMES. [Results] After the NMES, all HRV data slightly increased, but there was no significance between before and after data. [Conclusion] We suggest that strengthening exercises using NMES may be undertaken safely.

Effect of cervical spinal cord electrical stimulation on nitric oxide levels in brain and dermal tissues: an evaluation using by real-time nitric oxide measurement

OBJECTIVE

Nitric oxide synthesized from L: -arginine via the nitric oxide synthase enzyme family is the main regulatory molecule in many physiological systems. The level of nitric oxide can now be measured in tissues by a direct real-time amperometric method. The effect of electrical stimulation of the upper cervical spine on the arteries that supply the brain and upper extremities has been established by experimental studies, and thus it has begun to be used in clinical practice to increase blood flow in the brain and the peripheral vascular system. The mechanism of this effect is still a subject of research. This is the first report of real-time nitric oxide measurement in living brain and dermal tissue during electrical stimulation of the upper cervical spine.

METHODS

Using the amperometric method, nitric oxide levels in frontal subcortical and front foot skin were measured before, during and after electrical stimulation of the upper cervical spine in three groups of rabbits that received infusions of saline solution, 7-aminoguanidine or atropine.

RESULTS

By electrical stimulation, tissue nitric oxide levels increased significantly and remained increased during stimulation in the brain and skin. The nitric oxide levels dropped back to normal value 1 min after stimulation was turned off.

CONCLUSION

The results we obtained have showed that real-time nitric oxide could also be measured by an amperometric method in living tissues like brain. The effect of stimulation on nitric oxide levels of living tissues disappears immediately when the stimulation is turned off.

Use of Cervical Spinal Cord Stimulation in Treatment and Prevention of Arterial Vasospasm after Aneurysmal Subarachnoid Hemorrhage

Based on past laboratory and anecdotal clinical experience, we hypothesized that prolonged cervical spinal cord stimulation (SCS) in the acute settings of aneurysmal subarachnoid hemorrhage (aSAH) would be both safe and feasible, and that 2-week stimulation will reduce incidence of cerebral arterial vasospasm. The goal of our clinical study was to establish feasibility and safety of cervical SCS in a small group of selected aSAH patients. Single-arm non-randomized prospective study of cSCS in aSAH patients involved percutaneous implantation of 8-contact electrode in 12 consecutive aSAH patients that satisfied strict inclusion criteria. The electrode insertion was performed immediately upon surgical or endovascular securing of the ruptured aneurysm while the patient was still under general anesthesia. Patients were stimulated for 14 consecutive days or until discharge. There were no complications related to the electrode insertion or to SCS during the study and no long-term side effects of SCS during 1-year follow-up. There was 1 unrelated death and two electrode pullouts. This article summarizes technical details of SCS electrode insertion and the stimulation parameters used in the research study. Our study of SCS for prevention of vasospasm after aSAH conclusively shows both safety and feasibility of this promising treatment approach. Despite high level of acuity in aSAH patients, impaired level of consciousness, frequent patient repositioning, need in multiple tests and variety of monitors, SCS electrodes may be safely implanted and maintained for the two-week period. Long-term follow up shows no adverse effects of cervical SCS in this patient category.

The influence of transcutaneous electrical neurostimulation (TENS) on human cerebral blood flow velocities

BACKGROUND

It has been shown that transcutaneous electrical neurostimulation (TENS) reduces sympathetic tone. Spinal cord stimulation (SCS) has proven qualities to improve coronary, peripheral, and cerebral blood circulation. Therefore, we postulate that TENS and SCS affect the autonomic nervous system in analogous ways. In this line of thought, cervical application of TENS might be a useful and simple adjunct in the treatment of cerebrovascular disease by improving cerebral blood flow. Experiments were performed in order to assess whether cervical TENS is safe and whether an effect on cerebral blood flow velocity (CBFV) can be shown in healthy subjects.

METHOD

A controlled, non-randomized, phase 1 study was performed with 20 healthy volunteers. Cervical TENS was applied in several frequencies, with and without hyperventilation. Continuous registration of blood pressure, pulse, CBFV (estimated by transcranial Doppler sonography) and end-tidal carbon dioxide concentration was performed.

FINDINGS

Cervical TENS was well-tolerated by all subjects. Despite small effects on heart rate (HR) and mean arterial blood pressure (MAP), a significant effect on middle cerebral artery (MCA) blood flow velocity was not demonstrated. No effect of age, gender, current or session order on MCA, HR, or MAP was found. TENS did not influence the effect of hyperventilation.

CONCLUSIONS

In these experiments, application of cervical TENS is proven to be a safe procedure. However, no effects on cerebral blood flow velocity could be detected, perhaps due to the intact cerebral autoregulation in the healthy volunteers.

Assessment of the outcomes of cerebral blood flow measurements after electrical stimulation of upper right incisor tooth in rabbits

The cerebral vessels are innervated by sympathetic, parasympathetic, and sensory nerves. A sensory innervation of the cerebral vessels originating in the trigeminal ganglion has been described in a number of species by several investigations. It has been shown that the electrical stimulation of the trigeminal ganglion causes an increase of cerebral cortical blood flow (CCoBF). The aim of the present study was to determine the effects of dental electrical stimulation the CCoBF in rabbits. A stimulating electrode was located in the upper right incisor tooth of rabbits and trigeminal ganglion was stimulated orthodromically via the infraorbital nerve. Variations in the cortical CCoBF were evaluated by laser-Doppler flowmetry. In experiment group, CCoBF increased together with the beginning of electrical stimulation (5 V, 0.5-ms impulse duration, square-shaped, 10-Hz frequency). The right and left hemisphere CCoBF values of stimulation period at 15s, 30s, 45s, 60s, 75s, and 90s were significantly higher than those of baseline and 105 and 120s (p < 0.05). The maximum increase in right and left CCoBF was 15.6% and 15.1% respectively. In post-stimulation period, the right CCoBF decreased gradually and returned to the baseline values at 120 s. In experiment groups, the CCoBF values of right hemisphere were comparable that of left hemisphereL (p > 0.05). This study demonstrated that the electrical stimulation of the trigeminal nerve's infraorbital branch via dental pulp increases the cortical right and left CCoBF under physiological conditions.

Effect of electrical stimulation of the cervical spinal cord on blood flow following subarachnoid hemorrhage

Object

Cervical spinal cord stimulation (SCS) increases global cerebral blood flow (CBF) and ameliorates cerebral ischemia according to a number of experimental models as well as some anecdotal reports in humans. Nonetheless, such stimulation has not been systematically applied for use in cerebral vasospasm. In the present study the authors examined the effect of cervical SCS on cerebral vasoconstriction in a double-hemorrhage model in rats.

Methods

Subarachnoid hemorrhage (SAH) was induced with 2 blood injections through an indwelling catheter in the cisterna magna. Spinal cord stimulation was applied 90 minutes after induction of the second SAH (Day 0) or on Day 5 post-SAH. Measurements of the basilar artery (BA) diameter and cross-sectional area and regional CBF (using laser Doppler flowmetry and 14C-radiolabeled N-isopropyl-p-iodoamphetamine hydrochloride) were obtained and compared between SAH and sham-operated control rats that did not receive SCS.

Results

At Day 0 after SAH, there were slight nonsignificant decreases in BA diameter and cross-sectional area (89 ± 3% and 81 ± 4%, respectively, of that in controls) in no-SCS rats. At this time point, BA diameter and crosssectional area were slightly increased (116 ± 6% and 132 ± 9%, respectively, compared with controls, p < 0.001) in SCS-treated rats. On Day 5 after SAH, no-SCS rats had marked decreases in BA diameter and cross-sectional area (64 ± 3% and 39 ± 4%, respectively, compared with controls, p < 0.001) and corrugation of the vessel wall. These changes were reversed in rats that had received SCS (diameter, 110 ± 9% of controls; area, 106 ± 4% of controls; p < 0.001). Subarachnoid hemorrhage reduced CBF at Days 0 and 5 post-SAH, and SCS increased flows at both time points, particularly in regions supplied by the middle cerebral artery.

Conclusions

Data in this study showed that SCS can reverse BA constriction and improve global CBF in this SAH model. Spinal cord stimulation may represent a useful adjunct in the treatment of vasospasm.

Roles of dorsal column pathway and transient receptor potential vanilloid type 1 in augmentation of cerebral blood flow by upper cervical spinal cord stimulation in rats

Clinical and basic studies have indicated that upper cervical spinal cord stimulation (cSCS) significantly increases cerebral blood flow (CBF), but the mechanisms are incompletely understood. This investigation was conducted to differentiate between stimulation of dorsal column fibers and upper cervical spinal cord cell bodies in cSCS-induced increases in CBF and decreases in cerebrovascular resistance (CVR). cSCS (50 Hz, 0.2 ms, 1 min) was applied on the left C1-C2 dorsal column of pentobarbital anesthetized, ventilated and paralyzed male rats. Laser Doppler flowmetry probes were placed bilaterally over the parietal cortex, and arterial pressure was monitored. cSCS at 30%, 60%, and 90% of motor threshold (MT) produced vasodilation bilaterally in cerebral cortices. Subsequently, cSCS was applied at 90% MT, and ipsilateral responses were recorded. Ibotenic acid (0.3 mg/ml, 0.1 ml) placed on dorsal surface of C1-C2 (n=7) to suppress cell body activity, did not affect cSCS-induced %DeltaCBF (42.5+/-8.1% vs. 36.8+/-7.1%, P>0.05) and %DeltaCVR (-19.4+/-4.2% vs. -15.2+/-5.6%, P>0.05). However, bilateral transection of the dorsal column at rostral C1 (n=8) abolished cSCS-induced changes in CBF and CVR. Also, rostral C1 transection (n=7) abolished cSCS-induced changes in CBF and CVR. Resinferatoxin (RTX), an ultrapotent transient receptor potential vanilloid type 1 (TRPV1) agonist, was used to inactivate TRPV1 containing nerve fibers/cell bodies. RTX (2 microg/ml, 0.1 ml) placed on the C1-C2 spinal cord (n=7) did not affect cSCS-induced %DeltaCBF (60.2+/-8.1% vs. 46.3+/-7.7%, P>0.05) and %DeltaCVR (-25.5+/-3.5% vs. -21.4+/-8.9%, P>0.05). However, i.v. RTX (2 microg/kg, n=9) decreased cSCS-induced %DeltaCBF from 65.0+/-9.5% to 27.4+/-7.2% (P<0.05) and %DeltaCVR from -28.0+/-7.6% to -14.8+/-4.2% (P<0.05). These results indicated that cSCS-increases in CBF and decreases in CVR occurred via rostral spinal dorsal column fibers and did not depend upon C1-C2 cell bodies. Also, our results suggested that cerebral but not spinal TRPV1 was involved in cSCS-induced cerebral vasodilation.

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.

Cervical spinal cord stimulation in cerebral ischemia

Spinal cord stimulation (SCS) is a well established therapy in the treatment for chronic pain. SCS has also been shown to increase peripheral blood flow and is now an accepted treatment in the management of ischemic limb pain and angina. There is a growing body of evidence that cervical spinal cord stimulation also increases cerebral blood flow (CBF) in both animal and human models. SCS could potentially impact on the treatment of cerebral vasospasm and stroke by an increase in CBEF The utility of SCS is also being explored in novel applications such as adjunctive tumor therapy, where resistance to therapy conferred by tissue hypoxia may be ameliorated by CBF augmentation.