Spinal cord stimulation for cerebral vasospasm as prophylaxis

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 proposed use of cervical spinal cord stimulation for the treatment and prevention of cognitive decline in dementias and neurodegenerative disorders

Cervical spinal cord stimulation is a well-established treatment for intractable neuropathic upper extremity pain. More than 20years ago it was demonstrated that cervical spinal cord stimulation could engender an increase in cerebral blood flow. Cerebral blood flow has been shown to be decreased in many patients with dementia and in various neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. Furthermore, there is evidence that reduced cerebral blood flow worsens neurodegenerative disease and may also predict which patients progress from mild cognitive impairment to full blown Alzheimer's disease. Thus, the identification of decreased cerebral blood flow in patients with early cognitive problems may offer clinicians a window of opportunity to intervene and prevent further brain damage. Further evidence that supports augmenting cerebral blood flow as an effective strategy for preventing and treating cognitive brain dysfunction comes from experimental studies with omental transposition. The author proposes cervical spinal cord stimulation as a titratable, programmable extracranial neuromodulation technique to increase cerebral blood flow for the purposes of improving cognitive function and preventing cognitive deterioration in patients with dementias and neurodegenerative disorders.

Electrical modulation of the sympathetic nervous system in order to augment cerebral blood flow: a protocol for an experimental study

Introduction Cerebral blood flow (CBF) is regulated by several mechanisms. Neurogenic control has been a matter of debate, even though several publications reported the effects of changes in sympathetic tone on CBF. Transcutaneous electrical nerve stimulation and spinal-cord stimulation have been shown to influence peripheral and cerebral blood flow through a sympathetic pathway. The authors hypothesise that certain pathological conditions result in a relative increase in the neurogenic regulation of CBF and that this regulation can be modulated electrically. Methods and analysis Patients with cerebral vasospasm after subarachnoid haemorrhage will be included. The experimental set-up measures several parameters that are involved in cerebral blood flow regulation in patients with cerebral vasospasm after subarachnoid haemorrhage. Measurements are taken at baseline and with stimulation in several frequencies. An ad hoc statistical analysis is used to evaluate different settings of the electrical stimulation. Autoregulation is evaluated with transfer function analysis and autoregulatory index calculations. Ethics and dissemination Ethical registration was granted by Medical Review Ethics Committee Groningen (ID METc 2010.123). All participants provide written informed consent on participation. Upon finishing a pilot study to investigate feasibility and effect, either future prospective (randomised) studies will be designed, or other modalities of electrical stimulation will be explored using the same set-up. Trial Registration Dutch Trial Registry: NTR2358.

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 beneficial effect of spinal cord stimulation in a patient with severe cerebral ischemia and upper extremity ischemic pain

Spinal cord stimulation (SCS) is used in the treatment of chronic pain, ischemia because of obstructive arterial disease, and anginal pain. Recently, a number of studies have described the effects of the high cervical SCS, including increased cerebral blood flow, although the underlying mechanisms are unknown. This case report describes a patient with a severe complex ischemic condition affecting both cerebral and upper limb blood flow with an associated complex regional pain syndrome in upper limb. While all previous clinical treatments proved ineffective, cervical SCS afforded satisfactory results. Possible mechanisms underlying the cervical SCS effect are discussed.

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.

Mechanisms of spinal cord stimulation in ischemia

OBJECT

The goal of this study was to assess the duration of neuroprotection after SCS. Nearly 40 years after the first description of spinal cord stimulation (SCS), the mechanisms underlying its physiological effects remain unclear. It is known that SCS affects activity in the nervous system on a broad scale. Local neurohumoral changes within the dorsal horn of the spinal cord have been described, as have changes in cortical activation in a number of brain regions. Spinal cord stimulation has even been found to have profound effects on sympathetic vascular tone, a discovery that has led to its use in ameliorating blood flow in the limbs, heart, and brain.

METHODS

In an effort to delineate the limits of neuroprotection offered by SCS, the authors have studied its use in an experimental model of permanent middle cerebral artery (MCA) occlusion in rats. The investigators applied SCS in a delayed fashion 3, 6, or 9 hours after MCA occlusion. The results are reported and mechanisms underlying the physiological effects of SCS are reviewed, with particular attention being paid to the effect of SCS on cerebral blood flow in the setting of cerebral ischemia.

CONCLUSIONS

The authors found that SCS applied as late as 6 hours postischemia significantly reduces stroke volumes, whereas SCS applied 9 hours after ischemia fails to reduce stroke injury.

Cervical spinal cord stimulation improves neurological dysfunction induced by cerebral vasospasm

The effect of cervical spinal cord stimulation on the cerebral blood flow has been investigated both experimentally and clinically since 1986. Although the effect of the spinal cord stimulation on cerebral ischemia induced by cerebral vasospasm after subarachnoid hemorrhage has been investigated widely, neurological dysfunction induced by cerebral vasospasm and the effect of the spinal cord stimulation on neurological dysfunction have not been investigated so far. The aim of this study is to investigate the neurological dysfunction induced by cerebral vasospasm after subarachnoid hemorrhage and whether the spinal cord stimulation improves this neurological dysfunction or not in New Zealand albino rabbits. The animals were divided into sham and experiment groups: Sham group. Motor evoked potentials were recorded before experimental procedure was performed in this group. Just after, intracisternal saline was injected and 3 days later a stimulation electrode was placed in the cervical epidural space. Motor evoked potentials were recorded but electrical stimulation was not applied. Experiment group. Firstly, motor evoked potentials had been recorded before experimental procedure was performed in also this group. After then a stimulation electrode was placed in the cervical epidural space of the animals in which subarachnoid hemorrhage procedure was performed 3 days ago. Motor evoked potentials were recorded both before and after spinal cord stimulation. Motor evoked potential latencies and amplitudes did not change in the sham operation group. But, motor evoked potential latencies extended and the amplitudes decreased in the experiment group before spinal cord stimulation. Spinal cord stimulation improved the changes occurring in latencies and amplitudes in the experiment group. Spinal cord stimulation improves the neurological dysfunction induced by cerebral vasospasm and motor evoked potentials recording is a reliable electrophysiological method to detect cerebral vasospasm and to assess the effects of different treatments in cerebral vasospasm.

Evidence for a central pathway in the cerebrovascular effects of spinal cord stimulation

OBJECTIVE

Cervical spinal cord stimulation (SCS) augments cerebral blood flow (CBF) in a number of animal models. The mechanisms underlying the cerebrovascular effects of SCS are not yet well delineated. In this study, we analyzed two alternative pathways in CBF alterations induced by SCS in rats, one involving direct modulation of sympathetic outflow and the other through central vasomotor influence.

METHODS

Resection of the superior cervical ganglion (SCG), SCS alone, or SCS after SCG removal was performed in adult male Sprague-Dawley rats. CBF was measured with (14)C-inosine monophosphate radiotracer studies. In another set of experiments, SCS was performed after spinalization at the cervicomedullary junction or after laminectomy alone.

RESULTS

Baseline CBF in the SCG removal group was 71 +/- 8 ml/100 g/min, similar to controls. SCS alone significantly increased blood flow to 100 +/- 10 ml/100 g/min (P < 0.05). Animals that underwent SCS after SCG removal demonstrated a similar robust augmentation in CBF. SCS-induced changes in CBF were completely attenuated by spinalization.

CONCLUSION

The profound effects of spinal cord transection on SCS-induced CBF augmentation, together with the lack of effect of surgical sympathectomy, suggest that the mechanisms underlying the effects of SCS involve central influences rather than cervical sympathetic outflow. These findings suggest a possible role for brainstem vasomotor centers in the cerebrovascular effects of SCS.

Sympathetic mechanisms in cerebral blood flow alterations induced by spinal cord stimulation

OBJECT

Cervical spinal cord stimulation (SCS) has been found to augment cerebral blood flow (CBF) in a number of animal models, although the mechanisms underlying the cerebrovascular effects of SCS are poorly described. In this study, the authors examined the role of sympathetic tone in CBF alterations induced by SCS in rats.

METHODS

Spinal cord stimulation was performed at three intervals while CBF was monitored with laser Doppler flowmetry (LDF). Either hexamethonium (5, 10, or 20 mg/kg), prazosin (0.25, 0.5, or 1 mg/kg), idazoxan (0.5, 1, or 2 mg/kg), propranolol (1, 2, or 4 mg/kg), or vehicle was administered intravenously before the second stimulation. Changes in LDF values due to SCS were recorded as the percentage of change from baseline values and were analyzed. In vehicle-treated animals, SCS increased LDF values by 60.5 +/- 1.8% over baseline, whereas both high-dose hexamethonium and prazosin completely abolished the SCS-induced increases in LDF values. On the other hand, LDF values increased by 50.9 +/- 4% and 61.4 +/- 4% after SCS in the presence of idazoxan or propranolol, respectively. Administration of sympathetic nervous system blockers resulted in a variable degree of systemic hypotension as well. Nevertheless, induced hypotension without sympathetic blockade had only a minimal effect on SCS-induced augmentation of LDF values (48 +/- 1.4% over baseline).

CONCLUSIONS

Sympathetic tone plays a major role in SCS-induced increases in CBF. This effect seems to be mediated primarily by alpha1-adrenergic receptors. Systemic hypotension alone cannot explain the effects of sympathetic blockade on the SCS response. Clinical use of SCS in the treatment of cerebral ischemia should take alpha1-adrenergic receptor sympathetic tone into account.

Therapeutic approaches to vasospasm in subarachnoid hemorrhage

Delayed vasospasm as a result of subarachnoid blood after rupture of a cerebral aneurysm is a major complication. It is seen in over half of patients and causes symptomatic ischemia in about one third. If left untreated, it leads to death or permanent deficits in over 20% of patients. The essential cause and the relative contribution of true muscle spasm and other changes in the vessel wall remain uncertain. The mainstays of treatment are careful maintenance of fluid balance, induced hypervolemia and hypertension, calcium antagonists, balloon or chemical angioplasty, and, in some centers, cisternal fibrinolytic drugs. Promising future lines of treatment include gene therapy, nitric oxide donors, magnesium, sustained release cisternal drugs, and several other drugs that are under experimental or clinical trial.