Intra-Operative Detection of a Left-Sided Non-Recurrent Laryngeal Nerve During Vagus Nerve Stimulator Implantation
Total Page:16
File Type:pdf, Size:1020Kb
medicina Case Report Intra-Operative Detection of a Left-Sided Non-Recurrent Laryngeal Nerve during Vagus Nerve Stimulator Implantation Jason John Labuschagne 1,2,3,* and Niels Hammer 4,5,6,* 1 Netcare Unitas Hospital, Centurion 0140, South Africa 2 Department of Neurosurgery, University of Witwatersrand, Johannesburg 2193, South Africa 3 Department of Pediatric Neurosurgery, Nelson Mandela Children’s Hospital, Johannesburg 2193, South Africa 4 Department of Macroscopic and Clinical Anatomy, Medical University of Graz, 8010 Graz, Austria 5 Department of Trauma, Orthopedic and Plastic Surgery, University Hospital of Leipzig, 04109 Leipzig, Germany 6 Fraunhofer Institute for Machine Tools and Forming Technology, 01187 Dresden, Germany * Correspondence: [email protected] (J.J.L.); [email protected] or [email protected] (N.H.); Tel.: +43-316-38571100 (N.H.) Received: 22 August 2020; Accepted: 18 September 2020; Published: 23 September 2020 Abstract: Left sided non-recurrent laryngeal nerves (NRLN) are very rarely observed during surgery in the head and neck region. Arising directly from the cervical aspect of the vagus nerve, the NRLN lies in a vulnerable position distant from its normal location. NRLNs are normally associated with embryological branchial arch aberrations and subsequent vascular anomalies. The anomalous course of the NRLN makes it more susceptible to injury during surgery in the neck region. Knowledge of this anatomical variant will reduce the potential for injury and resultant vocal cord paralysis. During microsurgical dissection of the carotid sheath for the implantation of a vagus nerve stimulator in a 19-year-old female patient with refractory epilepsy, a moderate-sized branch of the main vagus nerve trunk was identified postero-medially within the carotid sheath. Intra-operative stimulation of this nerve resulted in a compound muscle evoked potential from the left vocal cord. Thus, this branch was confirmed to be a left-sided NRLN. The patient had no associated vascular anomalies. This is first reported case of a left-sided NRLN found during VNS insertion. Awareness of the possibility of an NRLN is imperative to prevent iatrogenic injury. A medial location of the vagus nerve within the carotid sheath should alert the surgeon to the possible presence of an NRLN. The absence of fourth branchial arch remnant anomalies is not a guarantee as to the absence of a left-sided NRLN. The addition of intra-operative nerve monitoring for vagus nerve stimulator (VNS) implantation procedures should be strongly considered to help avoid iatrogenic injury. Keywords: nerve stimulation; non-recurrent laryngeal nerve; seizure treatment; vagus nerve; vagal trunk; variational anatomy 1. Introduction Left sided non-recurrent laryngeal nerves (NRLN) are very rarely observed during surgery in the head and neck region. In “non-anomalous” cases, the right recurrent laryngeal nerve (RLN) arises from the right vagus nerve anterior to the first part of the subclavian artery, it then hooks around the right subclavian artery and ascends towards the tracheo-oesophageal groove before entering the larynx [1]. On the left side, the RLN is given off by vagus at the inferior border of the arch of the aorta, it then passes inferior to the arch of the aorta, immediately lateral to the ligamentum arteriosum, Medicina 2020, 56, 489; doi:10.3390/medicina56100489 www.mdpi.com/journal/medicina Medicina 2020, 56, x FOR PEER REVIEW 2 of 5 it then passes inferior to the arch of the aorta, immediately lateral to the ligamentum arteriosum, and Medicina 2020, 56, 489 2 of 6 ascends in the tracheo-oesophageal groove to the larynx [1]. Non-recurrent laryngeal nerves arise directly from the cervical aspect of the vagus nerve to enter the larynx directly without first descendingand ascends to in the the thoracic tracheo-oesophageal level. NRLNs groove have tobeen the reported larynx [1 ].in Non-recurrentonly 0.3–0.8% laryngeal[2] of the nervespopulation arise ondirectly the right from side, the cervical and they aspect are extremely of the vagus rare nerve on th toe enterleft side, the larynxwith a directly reported without incidence first of descending less than 0.004%to the thoracic [2]. Indeed, level. to NRLNsour knowledge, have been only reported four ca inses only of left-sided 0.3–0.8% NRLNs [2] of the have population been reported on the [3]. right side,The and anomalous they are extremely course of rare the onNRLN the leftmakes side, it withmore a susceptible reported incidence to injury of during less than surgery 0.004% in the [2]. neckIndeed, region. to our Knowledge knowledge, of only both four the cases normal of left-sided anatomy NRLNs and anatomical have been reportedvariants [of3]. the recurrent laryngealThe anomalous nerve should course serve of to the reduce NRLN iatrogenic makes itmore injury susceptible to the nerve. to injury We report during a case surgery of a inleft the NRLN neck discoveredregion. Knowledge during vagus of both nerve the st normalimulator anatomy implantation and anatomical (VNS). variants of the recurrent laryngeal nerve should serve to reduce iatrogenic injury to the nerve. We report a case of a left NRLN discovered 2.during Case vagusReport nerve stimulator implantation (VNS). 2. CaseA 19-year-old Report female patient with drug-resistant epilepsy, who was not considered a suitable candidate for resective epilepsy surgery, was offered vagal nerve stimulation for seizure control. SurgeryA 19-year-old was performed female patient under with general drug-resistant anaesthesia epilepsy, after whothe administration was not considered of intravenous a suitable antibioticscandidate forand resective under strict epilepsy aseptic surgery, protocol. was o Theffered patient vagal nervewas placed stimulation supine for with seizure the control.head in the midlineSurgery and a wasslightly performed extended under position. general A horizontal anaesthesia neck afterincision the was administration made at the level of intravenous of the mid larynx,antibiotics halfway and under between strict asepticthe clavicle protocol. and Themastoi patientd process. was placed The supinesternocleidomastoid with the head in muscle the midline was dissectedand a slightly along extended its anterior position. aspect A horizontaland retracted neck posteriorly. incision was A made combination at the level of ofsharp the midand larynx, blunt dissectionhalfway between was used the to clavicle expose and a 4-cm mastoid long process. segmen Thet of the sternocleidomastoid carotid sheath. The muscle fibrous was connective dissected tissuealong itsof the anterior sheath aspect was opened and retracted with atraumatic posteriorly. forceps A combination by splitting of the sharp fibres and of blunt the sheath dissection medially was andused laterally to expose to a reveal 4-cm longthe contents segment of the carotidcarotid sheath.sheath. TheFurther fibrous dissection connective was tissue performed of the sheathunder wasmicroscopic opened withvisualisation. atraumatic (Zeiss, forceps Kinevo by splitting 900, Carl the Zeiss fibres AG, of the Oberkochen, sheath medially Germany). and laterally to reveal the contentsDuring ofdissection the carotid of the sheath. carotid Further sheath, dissection a moderat wase-sized performed branch under of the microscopic main vagus visualisation. nerve trunk (Zeiss,was identified Kinevo postero-medially 900, Carl Zeiss AG, wi Oberkochen,thin the carotid Germany). sheath (Figure 1). Vessel loops were placed around the proximalDuringdissection and distal ofends the of carotid the main sheath, vagal amoderate-sized trunk and around branch the proximal of the main portion vagus of nerve the medial trunk wasbranch. identified Intra-operative postero-medially stimulation within (0.3 themA carotid monopolar sheath stimulation) (Figure1). Vesselwas delivered loops were by a placed commercially around availablethe proximal neurostimu and distallator ends (Medtronic of the main NIM vagal® Eclipse, trunk Minneapolis, and around the MN, proximal USA) to portion the vagus ofthe trunk medial and tobranch. the medial Intra-operative branch. The stimulation vocal cord (0.3 responses mA monopolar were stimulation)recorded by wasa commercially delivered by available a commercially EMG ® embeddedavailable neurostimulator endotracheal tube (Medtronic device used NIM to deEclipse,tect vocal Minneapolis, cord responses MN, USA)(Medtronic to the NIM vagus® Flex, trunk EMG and Tube,to the Minneapolis, medial branch. MN, The USA). vocal Stimulation cord responses of the werecommon recorded trunk by and a commerciallymedial branch available both elicited EMG a ® compoundembedded endotrachealmuscle evoked tube potential device from used the to left detect vocal vocal cord. cord A similar responses latency (Medtronic period of NIM 6 ms Flex,was detectedEMG Tube, following Minneapolis, stimulation MN, USA). of both Stimulation the trunk of and the the common medial trunk branch; and however, medial branch the amplitude both elicited of thea compound compound muscle muscle evoked potential potential was approximately from the left vocal halfcord. when A the similar vagal latency trunk periodwas stimulated of 6 ms was as opposeddetected followingto the medial stimulation branch stimulation. of both the trunk and the medial branch; however, the amplitude of the compoundThe VNS muscle coils potentialof the VNS was Stimulator approximately (AspireSR, half when model the 106, vagal Cyberonics trunk was Inc. stimulated Houston,