Trigeminal Nerve Stimulation Improves Cerebral Macrocirculation and Microcirculation After Subarachnoid Hemorrhage: An Exploratory Study

Three Pillars of Recovery After Aneurysmal Subarachnoid Hemorrhage: A Narrative Review

Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating neurologic disease with high mortality and disability. There have been global improvements in survival, which has contributed to the prevalence of patients living with long-term sequelae related to this disease. The focus of active research has traditionally centered on acute treatment to reduce mortality, but now there is a great need to study the course of short- and long-term recovery in these patients. In this narrative review, we aim to describe the core pillars in the preservation of cerebral function, prevention of complications, the recent literature studying neuroplasticity, and future directions for research to enhance recovery outcomes following aSAH.

Intra-arterial lidocaine administration of lidocaine in middle meningeal artery for short-term treatment of subarachnoid hemorrhage-related headaches

BACKGROUND AND PURPOSE

We report short- and intermediate-term effects on headaches with intra-arterial injection of lidocaine in the middle meningeal artery in patients with severe headaches associated with subarachnoid hemorrhage.

METHODS

We treated seven patients with intra-arterial lidocaine in doses up to 50 mg in each middle meningeal artery via a microcatheter bilaterally (except in one patient). We recorded the maximum intensity of headache (graded by 11-point numeric rating scale) prior to procedure and every day for the next 10 days or discharge, whichever came first. We identified changes in the middle meningeal artery pre- and post-intra-arterial lidocaine administration and quantified from Grade 0 (no change) to Grade 5 (severe narrowing or near occlusion of anterior and posterior dural branches or proximal middle meningeal artery that precludes adequate imaging of distal branches).

RESULTS

We observed improvement in severity of headaches of headache in all seven subarachnoid hemorrhage patients. The resolution of headache was immediate and complete in four patients, unilateral immediate resolution in one patient, and delayed complete resolution in patient. Two patients met the definition of severe headache (defined as 2 or more days with maximum pain scores of 8 or greater or need for 3 or more different analgesics for 2 or more days) post-lidocaine treatment. One of these patients had are lapse in headache with the severity matching pretreatment severity and required a second treatment. On analysis of angiographic data, there was consistent narrowing of middle meningeal arteries after administration of intra-arterial lidocaine and was graded as 5 in 2 arteries, 4 in 10 arteries, and 3 in 2 arteries.

CONCLUSIONS

We found that intra-arterial injection of lidocaine can result in consistent amelioration of headache in patients with subarachnoid hemorrhage. The therapeutic benefit may be related to vasoconstriction (reversal of vasodilation) in the middle meningeal arteries after administration of lidocaine.

Bimodal functions of calcitonin gene-related peptide in the brain

AIMS

Calcitonin gene-related peptide (CGRP) is a pluripotent neuropeptide crucial for maintaining vascular homeostasis, yet its full therapeutic potential remains incompletely exploited. Within the brain, CGRP demonstrates a distinct bimodal effect, contributing to neuroprotection in ischemic conditions while inducing neuronal sensitization and inflammation in non-ischemic settings. Despite extensive research on CGRP, the absence of a definitive determinant for this observed dichotomy has limited its potential for therapeutic applications in the brain. This review examines the effects of CGRP in both physiological and pathological conditions, aiming to identify a unifying factor that could enhance its therapeutic applicability.

MATERIALS AND METHODS

This comprehensive literature review analyzes the molecular pathways associated with CGRP and the specific cellular responses observed in these contexts. Additionally, the review investigates the psychological implications of CGRP in relation to cerebral perfusion levels, aiming to elucidate its underlying factors.

KEY FINDINGS

Reviewing the literature reveals that, elevated levels of CGRP in non-ischemic conditions exert detrimental effects on brain function, while they confer protective effects in the context of ischemia. These encompass anti-oxidative, anti-inflammatory, anti-apoptotic, and angiogenic properties, along with behavioral normalization. Current findings indicate promising therapeutic avenues for CGRP beyond the acute phases of cerebral injury, extending to neurodegenerative and psychological disorders associated with cerebral hypoperfusion, as well as chronic recovery following acute cerebral injuries.

SIGNIFICANCE

Improved understanding of CGRP's bimodal properties, alongside advancements in CGRP delivery methodologies and brain ischemia detection technologies, paves the way for realizing its untapped potential and broad therapeutic benefits in diverse pathological conditions.

Neurobehavioral Impairments Predict Specific Cerebral Damage in Rat Model of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a severe form of stroke that can cause unpredictable and diffuse cerebral damage, which is difficult to detect until it becomes irreversible. Therefore, there is a need for a reliable method to identify dysfunctional regions and initiate treatment before permanent damage occurs. Neurobehavioral assessments have been suggested as a possible tool to detect and approximately localize dysfunctional cerebral regions. In this study, we hypothesized that a neurobehavioral assessment battery could be a sensitive and specific method for detecting damage in discrete cerebral regions following SAH. To test this hypothesis, a behavioral battery was employed at multiple time points after SAH induced via an endovascular perforation, and brain damage was confirmed via postmortem histopathological analysis. Our results demonstrate that impairment of sensorimotor function accurately predict damage in the cerebral cortex (AUC 0.905; sensitivity 81.8%; specificity 90.9%) and striatum (AUC 0.913; sensitivity 90.1%; specificity 100%), while impaired novel object recognition is a more accurate indicator of damage to the hippocampus (AUC 0.902; sensitivity 74.1%; specificity 83.3%) than impaired reference memory (AUC 0.746; sensitivity 72.2%; specificity 58.0%). Tests for anxiety-like and depression-like behaviors predict damage to the amygdala (AUC 0.900; sensitivity 77.0%; specificity 81.7%) and thalamus (AUC 0.963; sensitivity 86.3%; specificity 87.8%), respectively. This study suggests that recurring behavioral testing can accurately predict damage in specific brain regions, which could be developed into a clinical battery for early detection of SAH damage in humans, potentially improving early treatment and outcomes.

CGRP as a potential mediator for the sexually dimorphic responses to traumatic brain injury

BACKGROUND

The outcomes of traumatic brain injury (TBI) exhibit variance contingent upon biological sex. Although female sex hormones exert neuroprotective effects, the administration of estrogen and progesterone has not yielded conclusive results. Hence, it is conceivable that additional mediators, distinct from female sex hormones, merit consideration due to their potential differential impact on TBI outcomes. Calcitonin gene-related peptide (CGRP) exhibits sexually dimorphic expression and demonstrates neuroprotective effects in acute brain injuries. In this study, we aimed to examine sex-based variations in TBI structural and functional outcomes with respect to CGRP expression.

METHODS

Male and female Sprague Dawley rats were exposed to controlled cortical impact to induce severe TBI, followed by interventions with and without CGRP inhibition. In the acute phase of TBI, the study centered on elucidating the influence of CGRP on oxidative stress, nuclear factor erythroid 2-related factor 2 (Nrf2) and endothelial nitric oxide synthase (eNOS) signaling in the peri-impact tissue. Subsequently, during the chronic phase of TBI, the investigation expanded to evaluate CGRP expression in relation to lesion volume, microvascular dysfunction, and white matter injury, as well as working and spatial memory, anxiety-like, and depression-like behaviors in subjects of both sexes.

RESULTS

Female rats exhibited elevated levels of CGRP in the peri-impact brain tissue during both baseline conditions and in the acute and chronic phases of TBI, in comparison to age-matched male counterparts. Enhanced CGRP levels in specific brain sub-regions among female rats correlated with superior structural and functional outcomes following TBI compared to their male counterparts. CGRP inhibition induced heightened oxidative stress and a reduction in the expression of Nrf2 and eNOS in both male and female rats, with the observed alteration being more pronounced in females than in males.

CONCLUSIONS

This study marks the inaugural identification of CGRP as a downstream mediator contributing to the sexually dimorphic response observed in TBI outcomes.

Trigeminal nerve stimulation: a current state-of-the-art review

Nearly 5 decades ago, the effect of trigeminal nerve stimulation (TNS) on cerebral blood flow was observed for the first time. This implication directly led to further investigations and TNS' success as a therapeutic intervention. Possessing unique connections with key brain and brainstem regions, TNS has been observed to modulate cerebral vasodilation, brain metabolism, cerebral autoregulation, cerebral and systemic inflammation, and the autonomic nervous system. The unique range of effects make it a prime therapeutic modality and have led to its clinical usage in chronic conditions such as migraine, prolonged disorders of consciousness, and depression. This review aims to present a comprehensive overview of TNS research and its broader therapeutic potentialities. For the purpose of this review, PubMed and Google Scholar were searched from inception to August 28, 2023 to identify a total of 89 relevant studies, both clinical and pre-clinical. TNS harnesses the release of vasoactive neuropeptides, modulation of neurotransmission, and direct action upon the autonomic nervous system to generate a suite of powerful multitarget therapeutic effects. While TNS has been applied clinically to chronic pathological conditions, these powerful effects have recently shown great potential in a number of acute/traumatic pathologies. However, there are still key mechanistic and methodologic knowledge gaps to be solved to make TNS a viable therapeutic option in wider clinical settings. These include bimodal or paradoxical effects and mechanisms, questions regarding its safety in acute/traumatic conditions, the development of more selective stimulation methods to avoid potential maladaptive effects, and its connection to the diving reflex, a trigeminally-mediated protective endogenous reflex. The address of these questions could overcome the current limitations and allow TNS to be applied therapeutically to an innumerable number of pathologies, such that it now stands at the precipice of becoming a ground-breaking therapeutic modality.

Clinical changes of serum melatonin and ICAM-1 levels in patients with basal ganglia hypertensive intracerebral hemorrhage

Objective

To investigate the clinical changes of serum melatonin and intercellular adhesion molecule-1 (ICAM-1) levels in patients with basal ganglia hypertensive intracerebral hemorrhage (HICH).

Methods

In this retrospective observational study, patients with HICH in Suzhou Hospital of Traditional Chinese and Western Medicine from January 2020 to January 2021 were included as the observation group (n=120), and 120 healthy volunteers who underwent physical examination were included as the control group. According to the Glasgow Coma Scale (GCS), the observation group was divided into four subgroups: normal group (n=27), mild group (n=51), moderate group (n=24), and severe group (n=18). Differences in serum melatonin and ICAM-1 were compared between the observation group and the control group, and between the subgroups. Logistic regression was used to analyze the risk factors of poor prognosis, and the ROC curve was used to analyze the influence of melatonin and ICAM-1 levels on patient prognosis.

Results

Serum melatonin levels were lower in the observation group compared to the control group, while ICAM-1 levels were higher (P<0.05). With the aggravation of brain injury, serum melatonin decreased and ICAM increased (P<0.05). Decreased serum melatonin and increased ICAM-1 were independent risk factors for poor prognosis in patients with HICH. The combined AUC of serum melatonin and ICAM-1 for the detection of poor prognosis in patients with HICH was 0.860, which was higher than that of the two alone (P<0.05).

Conclusions

Low serum melatonin levels and high ICAM-1 levels are associated with poor prognosis in patients with HICH and can be used as predictors of patients' prognosis.

Nonpharmacological modulation of cortical spreading depolarization

AIMS

Cortical spreading depolarization (CSD) is a wave of pathologic neuronal dysfunction that spreads through cerebral gray matter, causing neurologic disturbance in migraine and promoting lesion development in acute brain injury. Pharmacologic interventions have been found to be effective in migraine with aura, but their efficacy in acutely injured brains may be limited. This necessitates the assessment of possible adjunctive treatments, such as nonpharmacologic methods. This review aims to summarize currently available nonpharmacological techniques for modulating CSDs, present their mechanisms of action, and provide insight and future directions for CSD treatment.

MAIN METHODS

A systematic literature review was performed, generating 22 articles across 3 decades. Relevant data is broken down according to method of treatment.

KEY FINDINGS

Both pharmacologic and nonpharmacologic interventions can mitigate the pathological impact of CSDs via shared molecular mechanisms, including modulating K⁺/Ca²⁺/Na⁺/Cl^- ion channels and NMDA, GABA_A, serotonin, and CGRP ligand-based receptors and decreasing microglial activation. Preclinical evidence suggests that nonpharmacologic interventions, including neuromodulation, physical exercise, therapeutic hypothermia, and lifestyle changes can also target unique mechanisms, such as increasing adrenergic tone and myelination and modulating membrane fluidity, which may lend broader modulatory effects. Collectively, these mechanisms increase the electrical initiation threshold, increase CSD latency, slow CSD velocity, and decrease CSD amplitude and duration.

SIGNIFICANCE

Given the harmful consequences of CSDs, limitations of current pharmacological interventions to inhibit CSDs in acutely injured brains, and translational potentials of nonpharmacologic interventions to modulate CSDs, further assessment of nonpharmacologic modalities and their mechanisms to mitigate CSD-related neurologic dysfunction is warranted.

Neurobehavioral impairments predict specific cerebral damage in rat model of subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a severe form of stroke that can cause unpredictable and diffuse cerebral damage, which is difficult to detect until it becomes irreversible. Therefore, there is a need for a reliable method to identify dysfunctional regions and initiate treatment before permanent damage occurs. Neurobehavioral assessments have been suggested as a possible tool to detect and approximately localize dysfunctional cerebral regions. In this study, we hypothesized that a neurobehavioral assessment battery could be a sensitive and specific early warning for damage in discrete cerebral regions following SAH. To test this hypothesis, a behavioral battery was employed at multiple time points after SAH induced via an endovascular perforation, and brain damage was confirmed via postmortem histopathological analysis. Our results demonstrate that impairment of sensorimotor function accurately predict damage in the cerebral cortex (AUC: 0.905; sensitivity: 81.8%; specificity: 90.9%) and striatum (AUC: 0.913; sensitivity: 90.1%; specificity: 100%), while impaired novel object recognition is a more accurate indicator of damage to the hippocampus (AUC: 0.902; sensitivity: 74.1%; specificity: 83.3%) than impaired reference memory (AUC: 0.746; sensitivity: 72.2%; specificity: 58.0%). Tests for anxiety-like and depression-like behaviors predict damage to the amygdala (AUC: 0.900; sensitivity: 77.0%; specificity: 81.7%) and thalamus (AUC: 0.963; sensitivity: 86.3%; specificity: 87.8%), respectively. This study suggests that recurring behavioral testing can accurately predict damage in specific brain regions, which could be developed into a clinical battery for early detection of SAH damage in humans, potentially improving early treatment and outcomes.

Evaluation of External Trigeminal Nerve Stimulation to Prevent Cerebral Vasospasm after Subarachnoid Hemorrhage Due to Aneurysmal Rupture: A Randomized, Double-Blind Proof-of-Concept Pilot Trial (TRIVASOSTIM Study)

Cerebral vasospasm remains the most frequent and devastating complication after subarachnoid aneurysmal hemorrhage because of secondary cerebral ischemia and its sequelae. The underlying pathophysiology involves vasodilator peptide release (such as CGRP) and nitric oxide depletion at the level of the precapillary sphincters of the cerebral (internal carotid artery network) and dural (external carotid artery network) arteries, which are both innervated by craniofacial autonomic afferents and tightly connected to the trigeminal nerve and trigemino-cervical nucleus complex. We hypothesized that trigeminal nerve modulation could influence the cerebral flow of this vascular network through a sympatholytic effect and decrease the occurrence of vasospasm and its consequences. We conducted a prospective double-blind, randomized controlled pilot trial to compare the effect of 10 days of transcutaneous electrical trigeminal nerve stimulation vs. sham stimulation on cerebral infarction occurrence at 3 months. Sixty patients treated for aneurysmal SAH (World Federation of Neurosurgical Societies scale between 1 and 4) were included. We compared the radiological incidence of delayed cerebral ischemia (DCI) on magnetic resonance imaging (MRI) at 3 months in moderate and severe vasospasm patients receiving trigeminal nerve stimulation (TNS group) vs. sham stimulation (sham group). Our primary endpoint (the infarction rate at the 3-month follow-up) did not significantly differ between the two groups (p = 0.99). Vasospasm-related infarctions were present in seven patients (23%) in the TNS group and eight patients (27%) in the sham group. Ultimately, we were not able to show that TNS can decrease the rate of cerebral infarction secondary to vasospasm occurrence. As a result, it would be premature to promote trigeminal system neurostimulation in this context. This concept should be the subject of further research.

Trigeminal nerve stimulation for prolonged disorders of consciousness: A randomized double-blind sham-controlled study

BACKGROUND

Trigeminal nerve stimulation (TNS) has been proposed as a promising intervention for coma awakening. However, the effect of TNS on patients with prolonged disorders of consciousness (pDoC) is still unclear.

OBJECTIVE

This study aimed to investigate the therapeutic effects of TNS in pDoC caused by stroke, trauma, and anoxia.

METHODS

A total of 60 patients (male =25, female =35) aged over 18 who were in a vegetative state or minimally conscious state were randomly assigned to the TNS (N = 30) or sham TNS (N = 30) groups. 4 weeks of intervention and a followed up for 8 weeks were performed. The Glasgow Coma Scale (GCS) and Coma Recovery Scale-Revised (CRS-R) scores as primary outcomes were assessed at baseline and at 2, 4, 8, and 12 weeks.

RESULTS

The score changes in the TNS group over time for CRS-R (2-week: mean difference = 0.9, 95% CI = [0.3, 1.5], P = 0.006; 4-week: 1.6, 95% CI = [0.8, 2.5], P < 0.001; 8-week: mean difference = 2.4, 95% CI = [1.3, 3.5], P < 0.001; 12-week: mean difference = 2.3, 95% CI = [1.1, 3.4], P < 0.001) and GCS (4-week: mean difference = 0.7, 95% CI = [0.3, 1.2], P = 0.002; 8-week: mean difference = 1.1, 95% CI = [0.6, 1.7], P < 0.001; 12-week: 1.1, 95% CI = [0.5, 1.7], P = 0.003) were higher than those in the sham group. 18-Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) revealed that the metabolism of the right parahippocampal cortex, right precuneus, and bilateral middle cingulate cortex was significantly increased in TNS group.

CONCLUSION

The results of this study indicate that TNS could increase local brain metabolism and may promote functional recovery in patients with prolonged disorders of consciousness.

REGISTRATION INFORMATION

Name of the registry: Chinese Clinical Trial Registry.

REGISTRATION NUMBER

ChiCTR1900025573. The date that the study was submitted to a registry: 2019-09-01. The date when the first patient was enrolled was 2021-01-20.

Neurocognitive Sequelae and Rehabilitation after Subarachnoid Hemorrhage: Optimizing Outcomes

Subarachnoid hemorrhage (SAH) is a medical emergency that requires immediate intervention. The etiology varies between cases; however, rupture of an intracranial aneurysm accounts for 80% of medical emergencies. Early intervention and treatment are essential to prevent long-term complications. Over the years, treatment of SAH has drastically improved, which is responsible for the rapid rise in SAH survivors. Post-SAH, a significant number of patients exhibit impairments in memory and executive function and report high rates of depression and anxiety that ultimately affect daily living, return to work, and quality of life. Given the rise in SAH survivors, rehabilitation post-SAH to optimize patient outcomes becomes crucial. The review addresses the current rehabilitative strategies to combat the neurocognitive and behavioral issues that may arise following SAH.

Microclots in subarachnoid hemorrhage: an underestimated factor in delayed cerebral ischemia?

Subarachnoid hemorrhage has a poor prognosis due to the wide array of associated complications such as vasospasm, early brain injury, cortical spreading depression, oxidative stress, inflammation, and apoptosis. Each of these complications increases the risk of delayed cerebral ischemia (DCI), but recent research has suggested microclots play a substantial role in DCI incidence. This review will focus on the underlying inflammatory and coagulative mechanisms of microthrombosis while also outlining the current literature relating microclot burden to DCI. With a better understanding DCI pathophysiology as it relates to microthrombosis, more effective therapies can be developed in the future to improve clinical outcomes of SAH.