Intra-Operative Detection of a Left-Sided Non-Recurrent Laryngeal Nerve during Vagus Nerve Stimulator Implantation

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.

Variant Anatomy and Its Terminology

“…There exist several other less common variations of the aortic arch branches [ 83 ], which are presented by Moore as normal variations. However, one of these, the arteria subclavia aberrans retrooesophagea (obsoletely called “ arteria lusoria ”) arising as the last branch from the arcus aortae and passing posterior to the trachea and oesophagus, is present in 0.5–2% of cases [ 84 ] and is often combined with the non-recurrent laryngeal nerve [ 85 , 86 , 87 ]. Moore considered it to be an abnormal variation, meaning “not within the normal range of variation and, therefore, a congenital malformation” [ 5 ].…”

The dual effect of vagus nerve stimulation in pediatric patients with drug- resistant epilepsy: Is there more than seizure control?

“…An average cognitive score was plotted for each child in each group at baseline and 12month follow-up for the BMT group and at pre-implantation and 12-month post-implantation in the VNS group. The median overall cognitive score at baseline for BMT group was 7.5 (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) and for the VNS group was 11 (10)(11)(12)(13)(14)(15). At 12 months for the BMT it was 10 (5-19) and for for the VNS group it was 21 (15-26)..…”

“…Ten (62.5%) were males and six (37.5%) were females. The median age on presentation and the median age of onset of seizures was 9.5 (7)(8)(9)(10)(11)(12) and 0.75 (0-2) years in the BMT group and 10.5 (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) and 0.75 (0.25-11) years in the VNS group, respectively. The median age at VNS implantation was 10 (4-12) years.…”

“…Pre-operative preparations: According to our unit protocol, all the patients who were eligible for VNS implantation underwent preoperative evaluation which included detailed analysis of the seizure semiology, long-term video EEG monitoring, brain MRI examination, and agreement by the multidisciplinary epilepsy team of pediatric neurologists and neurosurgeons. They will also undergo full laboratory workup, echocardiography, and neck ultrasound to exclude any structural neck anomalies or aberrant vasculature [12]. All patients will receive prophylactic double (anti-Gram + ve and anti-Gram -ve ) antibiotics as per our hospital protocol (Ampicillinsulbactam 50 mg/kg), Ceftriaxone 50 mg/Kg).…”

The dual effect of vagus nerve stimulation in pediatric patients with drug-resistant epilepsy: Is there more than seizure control?

“…All patients who were eligible for VNS implantation underwent preoperative evaluation which included detailed analysis of the seizure semiology, long-term video Electroencephalography (EEG) monitoring, and brain Magnetic Resonance Imaging (MRI) examination. Also, full laboratory workup, echocardiography, and neck ultrasound to exclude any structural neck anomalies or aberrant vasculature were performed [12] . All children received prophylactic double antibiotics (anti-Gram + ve and anti-Gram −ve) as per our hospital protocol (Ampicillin-sulbactam 50 mg/kg and Ceftriaxone 50 mg/kg).…”