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

Cervical spinal cord stimulation exerts anti-epileptic effects in a rat model of epileptic seizure through the suppression of CCL2-mediated cascades

Epidural spinal cord stimulation (SCS) is indicated for the treatment of intractable pain and is widely used in clinical practice. In previous basic research, the therapeutic effects of SCS have been demonstrated for epileptic seizure. However, the mechanism has not yet been elucidated. In this study, we investigated the therapeutic effect of SCS and the influence of epileptic seizure. First, SCS in the cervical spine was performed. The rats were divided into four groups: control group and treatment groups with SCS conducted at 2, 50, and 300 Hz frequency. Two days later, convulsions were induced by the intraperitoneal administration of kainic acid, followed by video monitoring to assess seizures. We also evaluated glial cells in the hippocampus by fluorescent immunostaining, electroencephalogram measurements, and inflammatory cytokines such as C-C motif chemokine ligand 2 (CCL2) by quantitative real-time polymerase chain reaction. Seizure frequency and the number of glial cells were significantly lower in the 300 Hz group than in the control group. SCS at 300 Hz decreased gene expression level of CCL2, which induces monocyte migration. SCS has anti-seizure effects by inhibiting CCL2-mediated cascades. The suppression of CCL2 and glial cells may be associated with the suppression of epileptic seizure.

Investigation of the effects of high cervical spinal cord electrical stimulation on improving neurological dysfunction and its potential mechanism in rats with traumatic brain injury

To explore the effects of high cervical spinal cord electrical stimulation (cSCS) on the recovery of neurological function and its possible mechanism in rats with traumatic brain injury (TBI). 72 rats were randomly divided into: (1) a sham group; (2) a traumatic brain injury (TBI) group; (3) a TBI+cSCS group; (4) a LY294002+TBI+cSCS group. The degree of neurological dysfunction was evaluated by modified Neurological severity score (mNSS). The pathological changes of the brain tissue in the injured area were observed by HE staining, and the apoptosis of neuron cells were observed by TUNEL staining. The expressions of BDNF and VEGFmRNA were detected by polymerase chain reaction (PCR), and the expressions of p-AKT, AKT, Bcl-2, Bax and caspase-3 proteins were detected by western blot. Compared with that of the TBI and LY294002+TBI+cSCS groups, the mNSS of the TBI+cSCS group were significantly lower on day 3 and 7 ( P <0.05). Compared with that in the TBI and LY294002+TBI+cSCS groups, the apoptosis of neuron cells in the TBI+cSCS group decreased significantly ( P < 0.05). Compared with the TBI and LY294002+TBI+cSCS group, the expression of Bcl-2 protein increased and the expressions of Bax and Caspase-3 proteins decreased in the TBI+cSCS group ( P < 0.05). Compared with that in the TBI and LY294002+TBI+cSCS groups, the intensity of p-Akt/Akt in the TBI+cSCS group increased ( P < 0.05). We found that cSCS had a protective effect on neuron cells after craniocerebral injury and could improve neurological dysfunction in rats, the mechanism of which might be that cSCS made the PI3K/Akt pathway more active after TBI.

Intravitreal quantum dots for retinitis pigmentosa: a first-in-human safety study

Background: Studies indicate that electrical stimulation of retinitis pigmentosa (RP) retina is beneficial. Quantum dots (QDs) can convert light to electrical stimulus and therefore may have therapeutic potential for RP. Methods: This was an open-label, fellow eye-controlled, first-in-human safety study. Five adults with end-stage (arm A) and 15 with severe (arm B) RP received one or two intravitreal injections of 0.2 or 2μM cadmium/selenium 655 Alt QDs. Results: No adverse events were attributed to QDs. In arm A, median best corrected visual acuity was unchanged. In arm B, mean best corrected visual acuity improved from 6/398 to 6/177, versus 6/147 to 6/144 in the fellow eye. Conclusion: Intravitreal QDs can be safely administered to patients with RP. Vision appears to benefit and further validating studies are justified.

Enhancement of brain plasticity and recovery of locomotive function after lumbar spinal cord stimulation in combination with gait training with partial weight support in rats with cerebral ischemia

Lumbar spinal cord stimulation (LSCS) is reportedly effective for the recovery of locomotive intraspinal neural network, motor cortex and basal ganglia in animals with complete spinal cord injury and parkinsonism. We evaluated the effect of LSCS in combination with gait training on the recovery of locomotive function and brain plasticity using a rat model of brain ischemia. Adult male Sprague Dawley rats with ischemia were randomly assigned into one of four groups: sham treatment (group 1), LSCS only (group 2), LSCS with gait training and 50% (group 3) and 80% (group 4) of body weight support. Evaluations before randomization and 4weeks after intervention included motor scoring index, real-time PCR and Western blot. Motor scoring index was significantly improved after the intervention in groups 2 and 3. The ratio of phospho-protein kinase C (PKC) to PKC measured in the infarcted area tended to be higher in groups 3 and 4. Protein expression of mGluR2 and mRNA expression of mGluR1 measured in the contralateral cortex were lower in groups 3 and 4. The ratio of phospho-Akt to Akt and mRNA expression of vascular endothelial growth factor measured in the ischemic border zone were higher in group 2. The mRNA expression of MAP1b measured in the infarcted area was significantly higher in group 2. The findings suggest that LSCS and gait training with an adequate amount of body weight support may promote brain plasticity and facilitate the functional recovery.

Cerebral collaterals and collateral therapeutics for acute ischemic stroke

Cerebral collaterals are vascular redundancies in the cerebral circulation that can partially maintain blood flow to ischemic tissue when primary conduits are blocked. After occlusion of a cerebral artery, anastomoses connecting the distal segments of the MCA with distal branches of the ACA and PCA (known as leptomeningeal or pial collaterals) allow for partially maintained blood flow in the ischemic penumbra and delay or prevent cell death. However, collateral circulation varies dramatically between individuals, and collateral extent is significant predictor of stroke severity and recanalization rate. Collateral therapeutics attempt to harness these vascular redundancies by enhancing blood flow through pial collaterals to reduce ischemia and brain damage after cerebral arterial occlusion. While therapies to enhance collateral flow remain relatively nascent neuroprotective strategies, experimental therapies including inhaled NO, transient suprarenal aortic occlusion, and electrical stimulation of the parasympathetic sphenopalatine ganglion show promise as collateral therapeutics with the potential to improve treatment of acute ischemic stroke.

Spinal cord stimulation exerts neuroprotective effects against experimental Parkinson's disease

In clinical practice, deep brain stimulation (DBS) is effective for treatment of motor symptoms in Parkinson’s disease (PD). However, the mechanisms have not been understood completely. There are some reports that electrical stimulation exerts neuroprotective effects on the central nervous system diseases including cerebral ischemia, head trauma, epilepsy and PD, although there are a few reports on neuroprotective effects of spinal cord stimulation (SCS). We investigated the neuroprotective effects of high cervical SCS on PD model of rats. Adult female Sprague-Dawley rats received hour-long SCS (2, 50 or 200 Hz) with an epidural electrode at C1–2 level for 16 consecutive days. At 2 days after initial SCS, 6-hydroxydopamine (6-OHDA) was injected into the right striatum of rats. Behavioral evaluations of PD symptoms were employed, including cylinder test and amphetamine-induced rotation test performed at 1 and 2 weeks after 6-OHDA injection. Animals were subsequently euthanized for immunohistochemical investigations. In order to explore neurotrophic and growth factor upregulation induced by SCS, another cohort of rats that received 50 Hz SCS was euthanized at 1 and 2 weeks after lesion for protein assays. Behavioral tests revealed that the number of amphetamine-induced rotations decreased in SCS groups. Immunohistochemically, tyrosine hydroxylase (TH)-positive fibers in the striatum were significantly preserved in SCS groups. TH-positive neurons in the substantia nigra pars compacta were significantly preserved in 50 Hz SCS group. The level of vascular endothelial growth factor (VEGF) was upregulated by SCS at 1 week after the lesion. These results suggest that high cervical SCS exerts neuroprotection in PD model of rats, at least partially by upregulation of VEGF. SCS is supposed to suppress or delay PD progression and might become a less invasive option for PD patients, although further preclinical and clinical investigations are needed to confirm the effectiveness and safety.

Blood flow increase by cervical spinal cord stimulation in middle cerebral and common carotid arteries

The effect of spinal cord stimulation (SCS) on cerebral blood flow (CBF) has, in the past, been evaluated by semiquantitative techniques, but has not been used to treat CBF diseases. The aim of this study was to assess the effect of cervical SCS on regional blood flow by both semiquantitative and quantitative methods. Thirty-five patients with cervical SCS-implanted devices were enrolled. The following parameters were measured before and after cervical SCS: systolic and diastolic velocity (cm/s) in the middle cerebral artery (MCA) by transcranial Doppler (TCD) and volume blood flow quantification (ml/min) in the common carotid artery (CCA) by color Doppler. During cervical SCS there was a significant and bilateral increase in systolic (21%) and diastolic (26%) velocity in the MCA and in CCA blood flow (50%). We conclude that cervical SCS increases blood flow in the middle cerebral artery and common carotid artery. The consistent increase supports the potential usefulness of cervical SCS as an adjuvant treatment for cerebral blood flow diseases.

Effect of anesthesia and cerebral blood flow on neuronal injury in a rat middle cerebral artery occlusion (MCAO) model

Middle cerebral artery occlusion (MCAO) models have become well established as the most suitable way to simulate stroke in experimental studies. The high variability in the size of the resulting infarct due to filament composition, rodent strain and vessel anatomy makes the setup of such models very complex. Beside controllable variables of homeostasis, the choice of anesthetics and the grade of ischemia and reperfusion played a major role for extent of neurological injury. Transient MCAO was induced during either isoflurane or ketamine/xylazine (ket/xyl) anesthesia with simultaneously measurement of cerebral blood flow (CBF) in 60 male Wistar rats (380-420 g). Neurological injury was quantified after 24 h. Isoflurane compared with ket/xyl improved mortality 24 h after MCAO (10 vs. 50 %, p = 0.037) and predominantly led to striatal infarcts (78 vs. 18 %, p = 0.009) without involvement of the neocortex and medial caudoputamen. Independent of anesthesia type, cortical infarcts could be predicted with a sensitivity of 67 % and a specificity of 100 % if CBF did not exceed 35 % of the baseline value during ischemia. In all other cases, cortical infarcts developed if the reperfusion values remained below 50 %. Hyperemia during reperfusion significantly increased infarct and edema volumes. The cause of frequent striatal infarcts after isoflurane anesthesia might be attributed to an improved CBF during ischemia (46 ± 15 % vs. 35 ± 19 %, p = 0.04). S-100β release, edema volume and upregulation of IL-6 and IL-1β expression were impeded by isoflurane. Thus, anesthetic management as well as the grade of ischemia and reperfusion after transient MCAO demonstrated important effects on neurological injury.

Sphenopalatine ganglion stimulation for vasospasm after experimental subarachnoid hemorrhage

Object

Sphenopalatine ganglion stimulation activates perivascular vasodilatory nerves in the ipsilateral anterior circle of Willis. This experiment tested whether stimulation of the ganglion could reverse vasospasm and improve cerebral perfusion after subarachnoid hemorrhage (SAH) in monkeys.

Methods

Thirteen cynomolgus monkeys underwent baseline angiography followed by creation of SAH by placement of autologous blood against the right intradural internal carotid artery, the middle cerebral artery (MCA), and the anterior cerebral artery. Seven days later, angiography was repeated, and the right sphenopalatine ganglion was exposed microsurgically. Angiography was repeated 15 minutes after exposure of the ganglion. The ganglion was stimulated electrically 3 times, and angiography was repeated during and 15 and 30 minutes after stimulation. Cerebral blood flow (CBF) was monitored using laser Doppler flowmetry, and intracranial pressure (ICP) was measured throughout. The protocol was repeated again. Evans blue was injected and the animals were killed. The brains were removed for analysis of water and Evans blue content and histology.

Results

Subarachnoid hemorrhage was associated with significant vasospasm of the ipsilateral major cerebral arteries (23% ± 10% to 39% ± 4%; p < 0.05, paired t-tests). Exposure of the ganglion and sham stimulation had no significant effects on arterial diameters, ICP, or CBF (4 monkeys, ANOVA and paired t-tests). Sphenopalatine ganglion stimulation dilated the ipsilateral extracranial and intracranial internal carotid artery, MCA, and anterior cerebral artery compared with the contralateral arteries (9 monkeys, 7% ± 9% to 15% ± 19%; p < 0.05, ANOVA). There was a significant increase in ipsilateral CBF. Stimulation had no effect on ICP or brain histology. Brain water content did not increase but Evans blue content was significantly elevated in the MCA territory of the stimulated hemisphere.

Conclusions

Sphenopalatine ganglion stimulation decreased vasospasm and increased CBF after SAH in monkeys. This was associated with opening of the blood-brain barrier.

Amount but not pattern of protective sensory stimulation alters recovery after permanent middle cerebral artery occlusion

BACKGROUND AND PURPOSE

Using a rodent model of ischemia (permanent middle cerebral artery occlusion), our laboratory previously demonstrated that 4.27 minutes of patterned single-whisker stimulation delivered over 120 minutes can fully protect from impending damage when initiated within 2 hours of permanent middle cerebral artery occlusion ("early"). When initiated 3 hours postpermanent middle cerebral artery occlusion ("late"), stimulation resulted in irreversible damage. Here we investigate the effect of altering pattern, distribution, or amount of stimulation in this model.

METHODS

We assessed the cortex using functional imaging and histological analysis with altered stimulation treatment protocols. In 2 groups of animals we administered the same number of whisker deflections but in a random rather than patterned fashion distributed either over 120 minutes or condensed into 10 minutes postpermanent middle cerebral artery occlusion. We also tested increased (full-whisker array versus single-whisker) stimulation.

RESULTS

Early random whisker stimulation (condensed or dispersed) resulted in protection equivalent to early patterned stimulation. Early full-whisker array patterned stimulation also resulted in complete protection but promoted faster recovery. Late full-whisker array patterned stimulation, however, resulted in loss of evoked function and infarct volumes larger than those sustained by single-whisker counterparts.

CONCLUSIONS

When induced early on after ischemic insult, stimulus-evoked cortical activity, irrespective of the parameters of peripheral stimulation that induced it, seems to be the important variable for neuroprotection.

Striatal stimulation nurtures endogenous neurogenesis and angiogenesis in chronic-phase ischemic stroke rats

Deep brain stimulation (DBS) is used to treat a variety of neurological disorders including Parkinson's disease. In this study, we explored the effects of striatal stimulation (SS) in a rat model of chronic-phase ischemic stroke. The stimulation electrode was implanted into the ischemic penumbra at 1 month after middle cerebral artery occlusion (MCAO) and thereafter continuously delivered SS over a period of 1 week. Rats were evaluated behaviorally coupled with neuroradiological assessment of the infarct volumes using magnetic resonance imaging (MRI) at pre- and post-SS. The rats with SS showed significant behavioral recovery in the spontaneous activity and limb placement test compared to those without SS. MRI visualized that SS also significantly reduced the infarct volumes compared to that at pre-SS or without SS. Immunohistochemical analyses revealed a robust neurogenic response in rats that received SS characterized by a stream of proliferating cells from the subventricular zone migrating to and subsequently differentiating into neurons in the ischemic penumbra, which exhibited a significant GDNF upregulation. In tandem with this SS-mediated neurogenesis, enhanced angiogenesis was also recognized as revealed by a significant increase in VEGF levels in the penumbra. These results provide evidence that SS affords neurorestoration at the chronic phase of stroke by stimulating endogenous neurogenesis and angiogenesis.

Mild sensory stimulation completely protects the adult rodent cortex from ischemic stroke

Despite progress in reducing ischemic stroke damage, complete protection remains elusive. Here we demonstrate that, after permanent occlusion of a major cortical artery (middle cerebral artery; MCA), single whisker stimulation can induce complete protection of the adult rat cortex, but only if administered within a critical time window. Animals that receive early treatment are histologically and behaviorally equivalent to healthy controls and have normal neuronal function. Protection of the cortex clearly requires reperfusion to the ischemic area despite permanent occlusion. Using blood flow imaging and other techniques we found evidence of reversed blood flow into MCA branches from an alternate arterial source via collateral vessels (inter-arterial connections), a potential mechanism for reperfusion. These findings suggest that the cortex is capable of extensive blood flow reorganization and more importantly that mild sensory stimulation can provide complete protection from impending stroke given early intervention. Such non-invasive, non-pharmacological intervention has clear translational potential.

Angiogenesis and improved cerebral blood flow in the ischemic boundary area were detected after electroacupuncture treatment to rats with ischemic stroke

OBJECTIVES

Acupuncture has been known to be effective in cerebral ischemia, and promoting angiogenesis is considered as a potential therapy of ischemic stroke. Recent data have also shown that angiogenesis indeed brings benefit to cerebral circulation and behavior improvement. We examined the effect of electroacupuncture on vascular endothelial cell proliferation in the ischemic stroke model.

METHODS

A local ischemia was induced using the method of middle cerebral artery occlusion (MCAO) in rat. Rats were randomly divided into two groups: the control group (with MCAO) and the electroacupuncture group (with MCAO+electroacupuncture). The vascular endothelial cell (EC) proliferation were stained by double-immunofluorescence labeling method (Ki67 and vWF), region cerebral blood flow (rCBF) was measured using laser Doppler flowmeter (LDF), and the neurological scores was assessed. Electroacupuncture stimulation was applied to the acupoint GV26 (Shuigou) during the occlusion period.

RESULTS

In the control group, the EC proliferation started at 24 hours, was sustained for at least 7 days with a maximum induction at 3 days, decreased thereafter at 7 days, and was absent at 12 days after MCAO. However, EC proliferation started at 12 hours after MCAO in electroacupuncture group, and increased significantly in the number of cells at 1, 2, 3, and 7 days compared with control group (P<0.01). Electroacupuncture increased significantly the rCBF, and reduced markedly the neurological scores compared with control group (P<0.01).

CONCLUSION

This result suggests that the effect of electroacupuncture might be closely associated with promoting angiogenesis in the cerebral ischemic condition.

Electrical stimulation of the cerebral cortex exerts antiapoptotic, angiogenic, and anti-inflammatory effects in ischemic stroke rats through phosphoinositide 3-kinase/Akt signaling pathway

BACKGROUND AND PURPOSE

Neuroprotective effects of electric stimulation have been recently shown in ischemic stroke, but the underlying mechanisms remain poorly understood.

METHODS

Adult Wistar rats weighing 200 to 250 g received occlusion of the right middle cerebral artery for 90 minutes. At 1 hour after reperfusion, electrodes were implanted to rats on the right frontal epidural space. Electric stimulation, at preset current (0 to 200 microA) and frequency (0 to 50 Hz), was performed for 1 week. Stroke animals were subjected to behavioral tests at 3 days and 1 week postmiddle cerebral artery and then immediately euthanized for protein and immunohistochemical assays. After demonstration of behavioral and histological benefits, subsequent experiments pursued the mechanistic hypothesis that electric stimulation exerted antiapoptotic effects through the phosphoinositide 3-kinase-dependent pathway; thus, cortical stimulation was performed in the presence or absence of specific inhibitors of phosphoinositide 3-kinase (LY294002) in stroke rats.

RESULTS

Cortical stimulation abrogated the ischemia-associated increase in apoptotic cells in the injured cortex by activating antiapoptotic cascades, which was reversed by the phosphoinositide 3-kinase inhibitor LY294002 as reflected behaviorally and immunohistochemically. Furthermore, brain levels of neurotrophic factors (glial cell line-derived neurotrophic factor, brain-derived neurotrophic factor, vascular endothelial growth factor) were upregulated, which coincided with enhanced angiogenesis and suppressed proliferation of inflammatory cells in the ischemic cortex.

CONCLUSIONS

These results suggest that electric stimulation prevents apoptosis through the phosphoinositide 3-kinase pathway. Consequently, the ischemic brain might have been rendered as a nurturing microenvironment characterized by robust angiogenesis and diminished microglial/astrocytic proliferation, resulting in the reduction of infarct volumes and behavioral recovery. Electric stimulation is a novel and potent therapeutic tool for cerebral ischemia.

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.

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.

Spinal cord stimulation in the treatment of post-stroke patients: current state and future directions

A decrease in cerebral blood flow (CBF) and brain metabolic activity are well-known complications of stroke. Spinal cord stimulation (SCS) is successfully being used for the treatment of several low-perfusion syndromes. The aim of this chapter is to describe the data that support the effect of SCS on CBF and the use of SCS in the treatment of stroke and cerebral low perfusion syndromes. In addition, we present our relevant studies. Since April 1995, we have assessed 49 non-stroke patients. The following parameters were measured pre- and post-stroke: (1) CBF in healthy contralateral tissue by single photon emission computed tomography (SPECT), (2) systolic and diastolic velocity in the middle cerebral artery (MCA) by transcranial Doppler, (3) blood flow quantification in the common carotid artery (CCA) by color Doppler, and (4) glucose metabolism in healthy contralateral tissue by positron emission tomography (PET). Our results showed that during cervical SCS there was a significant (p < 0.001) increase in systolic (> or =21%) and diastolic (>26%) velocity in the MCA, and CCA blood flow (> or =51%) as well as glucose metabolism (44%). We concluded that cervical SCS (cSCS) can modify CBF and brain metabolism. Its potential role in the management of stroke and low-perfusion syndromes is further investigated by experimental studies and reports describing clinical experience. Appropriate clinical trials are warranted.

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.

Electrical forepaw stimulation during reversible forebrain ischemia decreases infarct volume

BACKGROUND AND PURPOSE

Functional stimulation is accompanied by increases in regional cerebral blood flow which exceed metabolic demands under normal circumstances, but it is unknown whether functional stimulation is beneficial or detrimental in the setting of acute ischemia. The aim of this study was to determine the effect of forepaw stimulation during temporary focal ischemia on neurological and tissue outcome in a rat model of reversible focal forebrain ischemia.

METHODS

Sprague-Dawley rats were prepared for temporary occlusion of the right middle cerebral artery (MCA) using the filament model. Cerebral blood flow in the MCA territory was continuously monitored with a laser-Doppler flowmeter. Subdermal electrodes were inserted into the dorsal forepaw to stimulate either the forepaw ipsilateral or contralateral to the occlusion starting 1 minute into ischemia and continuing throughout the ischemic period. A neurological evaluation was undertaken after 24 hours of reperfusion, and animals were then euthanized and brain slices stained with 2,3,5-triphenyltetrazolium chloride. Cortical and striatal damage was measured separately.

RESULTS

The cortical and striatal infarct volumes were both significantly reduced in the contralateral stimulated group compared with the ipsilateral stimulated group (48% total reduction). There were no statistically significant differences in the neurobehavioral scores between the 2 groups, or in the laser-Doppler flow measurements from the MCA core.

CONCLUSIONS

Functional stimulation of ischemic tissue may decrease tissue damage and improve outcome from stroke. Although the precise mechanism of this effect remains to be determined, functional stimulation could readily be translated to clinical practice.