Factors Affecting Vagus Nerve Stimulation Outcomes in Epilepsy

Epilepsy as a common neurological disease is mostly managed effectively with antiepileptic medications. One-third of patients do not respond to medical treatments requiring alternative therapies. Vagus nerve stimulation (VNS) has been used in the last decades for the treatment of medically resistant epilepsy. Despite the extensive use of VNS in these patients, factors associated with clinical outcomes of VNS remain to be elucidated. In this study, we evaluated factors affecting VNS outcomes in epileptic patients to have a better understanding of patients who are better candidates for VNS therapy. Several databases including PubMed, Scopus, and Google Scholar were searched through June 2020 for relevant articles. The following factors were assessed in this review: previous surgical history, age at implantation and gender, types of epilepsy, duration of epilepsy, age at epilepsy onset, frequency of attacks, antiepileptic drugs, VNS parameters, EEG findings, MRI findings, and biomarkers. Literature data show that nonresponder rates range between 25% and 65%. Given the complexity and diversity of factors associated with response to VNS, more clinical studies are needed to establish better paradigm for selection of patients for VNS therapy.

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Implant- and anesthesia-related factors affecting threshold intensities for vagus nerve stimulation

10.1101/2021.01.22.427329 ◽

2021 ◽

Author(s):

Umair Ahmed ◽

Yao-Chuan Chang ◽

Maria F. Lopez ◽

Jason Wong ◽

Timir Datta-Chaudhuri ◽

...

Keyword(s):

Vagus Nerve ◽

Nerve Stimulation ◽

Vagus Nerve Stimulation ◽

Pearson Correlation ◽

Physiological Responses ◽

Fiber Types ◽

Electrode Impedance ◽

Related Factors ◽

Factors Affecting

AbstractVagus nerve stimulation (VNS) is used as therapy in epilepsy and depression and is tested as a potential treatment for several chronic disorders. Typically, VNS is delivered at increasing stimulus intensity until a response is observed (threshold intensity). Factors that affect threshold intensities for engagement of different fiber types and concomitant physiological responses have not been studied. We determined neural and physiological responses to increasing stimulus intensities of VNS in anesthetized and awake animals, and examined the effect of implant- and anesthesia-related factors on threshold intensities in a rodent model of VNS. In acute and long-term cervical vagus nerve implants (53 and 14 rats, respectively) VNS was delivered under isoflurane, ketamine-xylazine, or awake at different intensities. Stimulus-evoked compound action potentials (eCAPs) were recorded, elicited physiological responses were registered, including changes heart rate (HR), breathing, and blood pressure (BP), and threshold intensities were determined. The intensity that elicits eCAPs (“neural threshold”) is significantly lower than what elicits a physiological response (“physiological threshold”, PT) (25 μA ±1.8 vs. 70 μA ±5.2, respectively; Mean ±SEM). Changes in BP occur at the lowest stimulus intensities (80 μA ±7), followed by changes in HR (105 μA ±8.4) and finally in breathing (310 μA ±32.5). PT is lower with than without electrode insulation (60 μA ±12, vs. 700 μA ±123). PT and electrode impedance are correlated in long-term (r=0.47; p<0.001) but not in acute implants (r=-0.34; p NS); both PT and impedance increase with implant age (Pearson correlation r=0.44; p<0.001 and r=0.64; p<0.001, respectively). PT is lowest when animals are awake (210 μA ±33; Mean ±SEM), followed by ketamine-xylazine (630 μA ±154), and isoflurane (1075 μA ±131). The sequence of physiological responses with increasing VNS intensity is similar in both anesthetized and awake states. Implant age, electrical impedance and the type of anesthesia affect VNS threshold and should be accounted for when determining stimulation dose.

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Efficacy of vagus nerve stimulation in posttraumatic versus nontraumatic epilepsy

Journal of Neurosurgery ◽

10.3171/2012.8.jns122 ◽

2012 ◽

Vol 117 (5) ◽

pp. 970-977 ◽

Cited By ~ 28

Author(s):

Dario J. Englot ◽

John D. Rolston ◽

Doris D. Wang ◽

Kevin H. Hassnain ◽

Charles M. Gordon ◽

...

Keyword(s):

Vagus Nerve ◽

Seizure Frequency ◽

Nerve Stimulation ◽

Vagus Nerve Stimulation ◽

Prospective Trial ◽

Treatment Strategies ◽

Adjunctive Treatment ◽

Posttraumatic Epilepsy ◽

Improved Outcomes ◽

Antiepileptic Medications

Object In the US, approximately 500,000 individuals are hospitalized yearly for traumatic brain injury (TBI), and posttraumatic epilepsy (PTE) is a common sequela of TBI. Improved treatment strategies for PTE are critically needed, as patients with the disorder are often resistant to antiepileptic medications and are poor candidates for definitive resection. Vagus nerve stimulation (VNS) is an adjunctive treatment for medically refractory epilepsy that results in a ≥ 50% reduction in seizure frequency in approximately 50% of patients after 1 year of therapy. The role of VNS in PTE has been poorly studied. The aim of this study was to determine whether patients with PTE attain more favorable seizure outcomes than individuals with nontraumatic epilepsy etiologies. Methods Using a case-control study design, the authors retrospectively compared seizure outcomes after VNS therapy in patients with PTE versus those with nontraumatic epilepsy (non-PTE) who were part of a large prospectively collected patient registry. Results After VNS therapy, patients with PTE demonstrated a greater reduction in seizure frequency (50% fewer seizures at the 3-month follow-up; 73% fewer seizures at 24 months) than patients with non-PTE (46% fewer seizures at 3 months; 57% fewer seizures at 24 months). Overall, patients with PTE had a 78% rate of clinical response to VNS therapy at 24 months (that is, ≥ 50% reduction in seizure frequency) as compared with a 61% response rate among patients with non-PTE (OR 1.32, 95% CI 1.07–1.61), leading to improved outcomes according to the Engel classification (p < 0.0001, Cochran-Mantel-Haenszel statistic). Conclusions Vagus nerve stimulation should be considered in patients with medically refractory PTE who are not good candidates for resection. A controlled prospective trial is necessary to further examine seizure outcomes as well as neuropsychological outcomes after VNS therapy in patients with intractable PTE.

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Implant- and anesthesia-related factors affecting cardiopulmonary threshold intensities for vagus nerve stimulation

Journal of Neural Engineering ◽

10.1088/1741-2552/ac048a ◽

2021 ◽

Author(s):

Umair Ahmed ◽

Yao-Chuan Chang ◽

Maria F Lopez ◽

Jason Wong ◽

Timir Datta-Chaudhuri ◽

...

Keyword(s):

Vagus Nerve ◽

Nerve Stimulation ◽

Vagus Nerve Stimulation ◽

Related Factors ◽

Factors Affecting

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Long-term outcome after callosotomy or vagus nerve stimulation in consecutive prospective cohorts of children with Lennox–Gastaut or Lennox-like syndrome and non-specific MRI findings

Seizure ◽

10.1016/j.seizure.2013.02.009 ◽

2013 ◽

Vol 22 (5) ◽

pp. 396-400 ◽

Cited By ~ 25

Author(s):

Arthur Cukiert ◽

Cristine M. Cukiert ◽

Jose A. Burattini ◽

Alessandra M. Lima ◽

Cassio R. Forster ◽

...

Keyword(s):

Vagus Nerve ◽

Nerve Stimulation ◽

Vagus Nerve Stimulation ◽

Mri Findings ◽

Term Outcome ◽

Long Term Outcome ◽

Prospective Cohorts

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Effect of Transcutaneous Vagus Nerve Stimulation in Dysphagia After Lateral Medullary Infarction: A Case Report

American Journal of Speech-Language Pathology ◽

10.1044/2019_ajslp-18-0262 ◽

2019 ◽

Vol 28 (4) ◽

pp. 1381-1387

Author(s):

Ying Yuan ◽

Jie Wang ◽

Dongyu Wu ◽

Dahua Zhang ◽

Weiqun Song

Keyword(s):

Vagus Nerve ◽

Nerve Stimulation ◽

Vagus Nerve Stimulation ◽

Rating Scale ◽

Tube Feeding ◽

Nasogastric Feeding ◽

Lateral Medullary Infarction ◽

Severe Dysphagia ◽

Transcutaneous Vagus Nerve Stimulation ◽

Medullary Infarction

Purpose Severe dysphagia with weak pharyngeal peristalsis after dorsal lateral medullary infarction (LMI) requires long-term tube feeding. However, no study is currently available on therapeutic effectiveness in severe dysphagia caused by nuclear damage of vagus nerve after dorsal LMI. The purpose of the present investigation was to explore the potential of transcutaneous vagus nerve stimulation (tVNS) to improve severe dysphagia with weak pharyngeal peristalsis after dorsal LMI. Method We assessed the efficacy of 6-week tVNS in a 28-year-old woman presented with persisting severe dysphagia after dorsal LMI who had been on nasogastric feeding for 6 months. tVNS was applied for 20 min twice a day, 5 days a week, for 6 weeks. The outcome measures included saliva spitted, Swallow Function Scoring System, Functional Oral Intake Scale, Clinical Assessment of Dysphagia With Wallenberg Syndrome, Yale Pharyngeal Residue Severity Rating Scale, and upper esophagus X-ray examination. Results After tVNS, the patient was advanced to a full oral diet without head rotation or spitting. No saliva residue was found in the valleculae and pyriform sinuses. Contrast medium freely passed through the upper esophageal sphincter. Conclusion Our findings suggest that tVNS might provide a useful means for recovery of severe dysphagia with weak pharyngeal peristalsis after dorsal LMI. Supplemental Material https://doi.org/10.23641/asha.9755438

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