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Pulsed radiofrequency treatment of the anterior ethmoidal nerve under nasal endoscopic guidance for the treatment of postherpetic neuralgia

A 20-year-old female patient presented for elective stabilisation of her right shoulder. She was known to have refractory epilepsy and had a vagal nerve stimulator implanted in her left subclavicular fossa. Shortly after an uneventful induction of anaesthesia and insertion of laryngeal mask airway the patient started to have intermittent periods of stridor. The episodes occurred with absolute regularity lasting for 15 s, resolving for exactly 30 s and then recurring. We increased the depth of anaesthesia (to 1.5 MAC)but this had no effect on the stridor. We assumed that in stimulating the vagus nerve, the vagal nerve stimulator was causing stimulation of the recurrent and superior laryngeal nerves causing repeated partial airway obstruction. We confirmed our assumption using fibreoptic bronchoscopy that, during an episode of stridor, clearly showed the left arytenoid cartilage being pulled across the midline, almost completely obstructing the glottic opening. As the patient was otherwise stable, we allowed the procedure to continue as planned with the episodes of stridor recurring with absolute precision every 30 s for the remaining time of the procedure. Postoperatively the patient confirmed that the vagal nerve stimulator was set to fire every 30 s and that she has noticed that her voice becomes hoarse for a few seconds every time the stimulator fires. However, she denied any breathing problems associated with its firing. Vagal nerve stimulators are used in the treatment of refractory epilepsy in adults and children and the use of this therapy is increasingly common in the UK. We were unaware of the potential for them to cause stridor under anaesthesia and a literature search led us to find only one case report [1]. Other concerns have been raised over other safety aspects of the device, with several accounts of intermittent asystole being related to firing of the vagal nerve stimulator [2]. We would therefore like to make our colleagues aware of the potential for an implanted vagal nerve stimulator to cause stridor or even asystole during anaesthesia.