Recurrent Intraoperative Asystole Induced by Tumor Manipulation in a Cervical Vagal Schwannoma: A Case Report

Technical Summary: Recurrent Intraoperative Asystole Induced by Tumor Manipulation in a Cervical Vagal Schwannoma

Problem Statement
Vagal schwannomas are rare, benign tumors arising from the Schwann cells of the vagus nerve (cranial nerve X). While surgical resection is the primary treatment, it presents significant risks, specifically intraoperative hemodynamic instability caused by vagal nerve manipulation. Excessive traction or stimulation of the vagus nerve can trigger severe bradyarrhythmias, including complete cardiac asystole. Additionally, preserving postoperative nerve function (preventing hoarseness, dysphagia, or Horner's syndrome) remains a critical challenge, particularly when balancing complete tumor removal against nerve preservation. The management of transient intraoperative asystole often involves prophylactic pharmacological intervention (e.g., atropine) or temporary pacing, though the necessity of these measures in brief, self-limiting episodes is not fully standardized.

Methodology
This case report details the management of a 37-year-old male with an incidentally discovered right-sided cervical vagal schwannoma.

• Preoperative Assessment: Diagnosis was established via contrast-enhanced MRI, revealing a 6.8 cm "string-of-beads" lesion located between the right common carotid artery and internal jugular vein.
• Surgical Procedure: The patient underwent complete microsurgical excision under general anesthesia. The approach involved a 7-cm incision along the anterior border of the sternocleidomastoid muscle, followed by careful blunt dissection to open the carotid sheath.
• Intraoperative Management: Dissection was performed under microscopic visualization. Crucially, intraoperative neuromonitoring (IONM) was not available. The surgical team relied on visual identification of the nerve-tumor interface and real-time electrocardiogram (ECG) monitoring.
• Response to Complications: During tumor manipulation, three distinct episodes of complete cardiac asystole occurred. The management protocol for these events was the immediate cessation of traction on the tumor, allowing for spontaneous recovery of sinus rhythm without the administration of atropine, vasopressors, or temporary cardiac pacing.
• Postoperative Evaluation: The patient was monitored for neurological deficits (hoarseness, dysphagia, Horner's syndrome) and discharged on postoperative day 4. Pathological confirmation was achieved via histopathological examination (H&E and S-100 immunostaining).

Key Results

• Hemodynamic Events: Three episodes of complete cardiac asystole were induced by tumor traction. Each episode lasted approximately 3–4 seconds and resolved spontaneously within seconds of releasing the traction. No pharmacological or pacing intervention was required.
• Surgical Outcome: The tumor was completely excised en bloc. The gross appearance confirmed the "string-of-beads" morphology seen on MRI.
• Pathological Findings: Histology revealed typical schwannoma features, including hypercellular Antoni A areas with Verocay bodies and hypocellular Antoni B areas. Immunohistochemistry was strongly positive for S-100 protein, confirming the diagnosis.
• Neurological Outcome: The patient exhibited no postoperative hoarseness, dysphagia, or Horner's syndrome, indicating intact vagal and sympathetic nerve function. At one-month follow-up, the patient remained asymptomatic with no evidence of recurrence.

Significance and Claims
The authors claim that this case provides several clinical insights regarding the management of cervical vagal schwannomas:

1. Conservative Management of Asystole: The case demonstrates that brief (3–4 seconds), self-limiting episodes of intraoperative asystole can be managed safely with a "wait-and-see" approach involving immediate cessation of manipulation, rather than automatic pharmacological or pacemaker intervention.
2. Physiological Neuromonitoring: In the absence of IONM, the occurrence of traction-induced bradycardia or asystole served as a "physiological neuromonitoring" signal. This indicated the presence of functional vagal fibers, guiding the surgeon to adjust dissection strategies to preserve nerve integrity.
3. Microsurgical Technique: The successful preservation of nerve function without IONM underscores the value of meticulous microsurgical technique, including sharp microdissection and precise identification of the nerve-tumor interface, as a cornerstone of nerve-sparing surgery.
4. Surgical Strategy: The case supports the feasibility of complete extracapsular resection with nerve preservation, potentially facilitated by the tumor's specific "string-of-beads" anatomical morphology which may provide natural cleavage planes.

The authors acknowledge limitations, noting that as a single case report, findings may not be generalizable, and the lack of IONM precluded objective intraoperative nerve function data. However, they conclude that vigilant intraoperative monitoring and refined surgical technique can yield excellent outcomes even in resource-limited settings.