Auricular Vagus Nerve Stimulation Manages Refractory Sympathetic Hyperactivity Post-Hemorrhage

Managing Autonomic Instability After Acute Brain Injury

Acute neurological injuries, including intracerebral hemorrhage and traumatic brain injury, frequently disrupt the complex neurocircuitry responsible for homeostatic respiratory and autonomic control [1]. This disruption often manifests as a profound autonomic imbalance, characterized by a catecholamine surge and sympathetic overactivity that complicates the clinical course [2]. While traditional pharmacological interventions target these symptoms, the central role of the autonomic nervous system in driving these pathological states has led to increased interest in neuromodulation [3]. Peripheral nerve stimulation is rapidly evolving as a viable strategy to address functional neurological deficits by directly targeting these underlying neural circuits [4]. Specifically, modulating the vagus nerve has demonstrated potential in regulating cardiac dynamics and systemic inflammatory responses across a variety of clinical presentations [5]. A recent case report now examines how this non-invasive approach might address the specific challenges of paroxysmal sympathetic hyperactivity (a syndrome of cyclical, uninhibited sympathetic surges following severe brain injury) when standard medications fail.

Clinical Presentation and Limitations of Standard Pharmacotherapy

The study details the clinical course of a 63-year-old male who developed paroxysmal sympathetic hyperactivity following an intracerebral hemorrhage. This condition, which involves sudden and cyclical surges in sympathetic activity, manifested in this patient through a specific constellation of symptoms including tachypnea, tachycardia, hypertension, and increased muscle tone. These paroxysms represent a significant challenge in neurocritical care, as the resulting physiological stress can complicate the recovery process and increase the risk of secondary complications such as myocardial strain or skin breakdown. To manage these autonomic surges, clinicians initiated a 2-week regimen of combination pharmacotherapy consisting of the beta-blocker propranolol, the antispasmodic baclofen, and the anticonvulsant gabapentin. This multi-modal approach targeted different pathways of the sympathetic and motor systems to dampen the paroxysmal episodes. Following this initial 14-day period, the researchers observed that the patient's blood pressure, heart rate, and muscle tone improved. However, despite these gains in hemodynamic and motor stability, tachypnea remained inadequately controlled, persisting as a refractory symptom that hindered the patient's overall stabilization. The persistence of rapid breathing forced a difficult clinical trade-off regarding the use of more aggressive interventions. While the administration of sedative agents successfully alleviated the tachypnea, these medications simultaneously caused a decreased consciousness level. Because maintaining neurological engagement is critical for both clinical assessment and the rehabilitation process, the sedatives could not be continued. This impasse, where standard pharmacological interventions either failed to control respiratory symptoms or compromised the patient's neurological status, necessitated the exploration of adjunctive transcutaneous auricular vagus nerve stimulation (a method of delivering electrical pulses to the auricular branch of the vagus nerve via the skin of the ear) to bridge the therapeutic gap.

Adjunctive Neuromodulation and Early Response

To address the persistent respiratory symptoms without further compromising the patient's neurological status, the clinical team introduced transcutaneous auricular vagus nerve stimulation as an adjunctive treatment to the ongoing pharmacotherapy. This neuromodulation technique involves applying electrical stimulation to the auricular branch of the vagus nerve through the skin of the external ear, aiming to modulate autonomic tone by increasing parasympathetic activity to counterbalance sympathetic excess. By integrating this stimulation into the existing regimen of propranolol, baclofen, and gabapentin, the researchers sought to achieve a synergistic effect that could suppress the overactive sympathetic drive while avoiding the sedative side effects associated with traditional pharmacological escalations. The clinical response to this combined approach became evident during the first month of intervention. After 4 weeks of transcutaneous auricular vagus nerve stimulation treatment, the frequency of paroxysmal sympathetic hyperactivity episodes and the severity of tachypnea improved. This reduction in the number of autonomic surges suggested that the electrical stimulation provided a stabilizing effect on the patient's dysregulated autonomic nervous system. For the clinician, this improvement in respiratory rate is particularly significant, as refractory tachypnea often serves as a barrier to weaning from mechanical ventilation or progressing with physical therapy in the post-hemorrhage setting. Beyond the stabilization of autonomic parameters, the addition of neuromodulation appeared to facilitate neurological recovery. The patient’s consciousness level showed improvement after 4 weeks of treatment, a finding that contrasts with the previous decline in awareness observed when sedative agents were used to control respiratory symptoms. This gain in consciousness is a critical clinical milestone, as it allows for more active participation in rehabilitation and provides a clearer window for ongoing neurological assessment. The observation that autonomic control could be achieved alongside an improved level of arousal suggests that this technique may help restore a more physiological balance between the brainstem's autonomic centers and higher cortical functions.

Long-Term Stabilization and Reduced Medication Burden

The clinical utility of transcutaneous auricular vagus nerve stimulation was most evident in the significant reduction of the patient's pharmacological burden. Following 4 weeks of treatment, the clinical team successfully discontinued both baclofen and gabapentin, two agents previously required to manage muscle tone and sympathetic surges. Furthermore, the dosage of propranolol was reduced during this same period. For the practicing clinician, this reduction in polypharmacy is a vital outcome, as it minimizes the risk of drug-to-drug interactions, cognitive clouding, and metabolic strain in a patient already recovering from a major intracerebral hemorrhage. Sustained neuromodulation led to further clinical stabilization over the subsequent month. After 8 weeks of continued treatment, the patient exhibited only mild tachypnea that occurred occasionally under strong stimulation, such as during intensive nursing care or physical manipulation. Notably, no other sympathetic symptoms besides this mild tachypnea were observed at the 8-week mark, indicating a near-complete resolution of the paroxysmal sympathetic hyperactivity episodes that had previously proved refractory to standard care. Concurrently, the patient's consciousness level showed further improvement at the 8-week mark, suggesting that the continued reduction in autonomic instability and sedative medication allowed for greater neurological recovery. Based on these longitudinal observations, the researchers concluded that transcutaneous auricular vagus nerve stimulation may be a safe adjunctive intervention option for drug-refractory paroxysmal sympathetic hyperactivity. The non-invasive nature of the device, which targets the auricular branch of the vagus nerve without requiring surgical implantation, provides a low-risk method for modulating the autonomic nervous system in the intensive care or step-down setting. This case demonstrates that when traditional pharmacological strategies fail to control symptoms like tachypnea without causing excessive sedation, transcutaneous neuromodulation offers a viable pathway to achieve symptomatic control while facilitating the withdrawal of systemic medications.

References

1. Goldman M, Lucke‐Wold B, Katz J, Dawoud B, Dagra A. Respiratory Patterns in Neurological Injury, Pathophysiology, Ventilation Management, and Future Innovations: A Systematic Review. Exploratory Research and Hypothesis in Medicine. 2022. doi:10.14218/erhm.2022.00081

2. Wang Y, Qian Y, Smerin D, Zhang S, Zhao Q, Xiong X. Newly Detected Atrial Fibrillation after Acute Stroke: A Narrative Review of Causes and Implications. Cardiology. 2019. doi:10.1159/000502971

3. Vandenberk B, Haemers P, Morillo CA. The autonomic nervous system in atrial fibrillation—pathophysiology and non-invasive assessment. Frontiers in Cardiovascular Medicine. 2024. doi:10.3389/fcvm.2023.1327387

4. Latif U, Moghim R, Valimahomed A, et al. Consensus Guidelines for the Use of Peripheral Nerve Stimulation in the Treatment of Chronic Pain and Neurological Diseases: A Neuron Project from the American Society of Pain and Neuroscience. Journal of Pain Research. 2025. doi:10.2147/jpr.s537222

5. Elamin ABA, Forsat K, Senok SS, Goswami N. Vagus Nerve Stimulation and Its Cardioprotective Abilities: A Systematic Review. Journal of Clinical Medicine. 2023. doi:10.3390/jcm12051717