Upper Airway (Hypoglossal Nerve) Stimulation for Treatment of Obstructive Sleep Apnea

Key points

  • Obstructive sleep apnea is a multilevel process consisting of physiologic and anatomic obstructive patterns leading to partial or complete collapse of the upper airway and resulting comorbidities.

  • Studies have shown apnea-hypopnea index (AHI) response rate of 75% (AHI less than 20 events per hour and overall >50% reduction) and improvement in quality of life in patients treated with upper airway stimulation (UAS).

  • UAS is indicated in patients with positive airway pressure failure, who are 22 years of age or older, with AHI 15 to 65, with body mass index less than or equal to 32 and anatomy amenable to implantation and likelihood of high success.

  • Drug-induced sleep endoscopy is an essential evaluation step to exclude patients with retropalatal concentric collapse.

  • Preparation of cranial nerve XII and determination of functional breakpoint to exclude the lateral XII branches and include the medial XII branches are critical to optimize surgical success.

Introduction

OSA is characterized by repeated partial or complete collapse of the upper airway during sleep. Cessation of breathing leads to nocturnal hypoxemia and arousals resulting in increase in mortality and comorbidities, such as hypertension, stroke, myocardial infarction, and diabetes. OSA has emerged as a serious medical condition with considerable health and social ramifications. Positive airway pressure (PAP) is the first-line medical management of OSA with high efficacy of successful treatment. Compliance with PAP therapy remains low, however, approximately 50% to 60%, resulting in many untreated patients with OSA. Patients with OSA who are intolerant of PAP can be treated by other interventions, such as oral appliance therapy and upper airway surgical options.

A detailed perioperative assessment of patients with OSA, including clinical examination, drug-induced sleep endoscopy (DISE), and radiographic analysis, is critical to ensure selection of the most effective surgical treatment option depending on the level of airway obstruction. Patients with multilevel obstruction may be treated with traditional Stanford protocol phase 1, consisting of nasal, palatal, and tongue base surgery; maxillomandibular advancement (MMA); or upper airway stimulation (UAS). The treatment selection depends on the severity of OSA and likelihood of surgical success.

Upper airway therapy through the neuromuscular stimulation of the hypoglossal nerve and genioglossus muscle has emerged as an effective treatment option and must be included in the surgeon’s armamentarium for treatment of OSA. This therapy utilizes an implantable device with a stimulation electrode placed around the protrusive branches of the hypoglossal nerve and a sensor lead placed in the intercostal space to detect inspiration. The patient-specific programmable device stimulates the hypoglossal nerve during timed inspiration to alleviate the airway obstruction in patients with moderate or severe OSA.

UAS has been shown to affect the retroglossal and retropalatal areas be increasing the airway in an anterior-posterior direction. By stimulating the hypoglossal nerve, the tongue base protrudes due to genioglossus muscle activation, resulting in opening of the airway in the retroglossal region. The exact mechanism of the effects on the retropalatal areas is not entirely known; however, a concentric palatal collapse is a contraindication to UAS therapy. Various UAS devices have been developed over the years, with the technology subsequently modified. Most recently, Inspire Medical Systems (Maple Grove, Minnesota) has obtained Food and Drug Administration approval for a UAS device, and a 5-year Stimulation Therapy for Apnea Reduction (STAR) outcome study showed improvement in sleepiness (Epworth Sleepiness Scale [ESS]) and quality of life (Functional Outcomes of Sleep Questionnaire [FOSQ]), with normalization of scores increasing from 33% to 78% and 15% to 67%, respectively, and showed an apnea-hypopnea index (AHI) response rate of 75% (AHI <20 events per hour and overall >50% reduction).

Surgeons need to have thorough understanding of the preoperative and surgical protocols to optimize postoperative outcomes. This article describes the steps required for preoperative assessment, diagnostic work-up, performance of implantation of the UAS device, and postoperative management.

Surgical technique

Diagnostic work-up

A baseline polysomnography (PSG) or home sleep study is obtained to first diagnose the severity of OSA. After confirmation of OSA, comprehensive clinical, radiographic, and endoscopic diagnostic work-up is performed to determine the appropriate selection of sleep surgical options. The clinical examination consists of evaluation of the nasal passages, oropharyngeal space, and retroglossal area. DISE is performed to characterize airway collapse pattern. The pattern and degree of collapse is scored according to the velum, oropharyngeal, tongue base, and epiglottis classification.

UAS indications:

  • 1.

    PAP failure

  • 2.

    22 years of age or older

  • 3.

    AHI 15 to 65

  • 4.

    Body mass index (BMI) ≤32

  • 5.

    Anatomy amenable to implantation and likelihood of high success

UAS contraindications:

  • 1.

    Sleep study showing greater than 25% central or mixed apneas

  • 2.

    Concentric palatal collapse seen on DISE

  • 3.

    Unable to operate the therapy

  • 4.

    Pregnancy

  • 5.

    Preexisting anatomic alterations or neurologic disorders

  • 6.

    Patients who require MRI

    • a.

      Inspire Model 3024: MRI is contraindicated because it may cause tissue damage and/or damage to the UAS device.

    • b.

      Inspire Model 3028: if certain conditions are met, patients may undergo an MRI scan on head and extremities.

UAS precautions:

  • 1.

    BMI greater than 32 may be associated with decreased likelihood of surgical success.

  • 2.

    Diathermy (primarily used in physical therapy): do not use shortwave diathermy, microwave diathermy, or therapeutic ultrasound diathermy on patients with a neurostimulation system.

  • 3.

    Electromagnetic compatibility and interference, electrocautery, irradiation, lithotripsy, radiofrequency ablation, radiograph, fluoroscopy, ultrasonics, defibrillation, or radition can adversely affect the UAS system.

Preparation and patient positioning

  • 1.

    The patient is taken to the operating room and is placed in the supine position, and short-acting muscle relaxers are used prior to intubating orally or nasally.

  • 2.

    Patient is given dexamethasone and preoperative antibiotics, such as IV cefazolin, within 60 minutes of first incision.

  • 3.

    Nerve Monitoring System (NIM) (Medtronic, Minneapolis, Minnesota) monitors the tongue response by utilizing sensor leads (Xomed 82273049) and bipolar simulating probe (Xomed 8225401).

    • a.

      Inclusion: NIM blue electrode is placed using a Debakey forceps right of the midline and in the floor of the mouth by plunging into the genioglossus muscle (avoid frenulum and salivary duct). This ensures inclusion of the protrusive muscles (genioglossus oblique [GGo] and genioglossus horizontal [GGh]) and of the tongue narrowing/flattening muscles (transverse and vertical [T/V]), which are innervated by the medial branches of XII.

    • b.

      Exclusion: NIM red electrode is placed using a Debakey 5 cm from the tip of the tongue and inserted into the ventrolateral and submucosal surface of the tongue. This ensures exclusion of the retractor muscles (styloglossus [SG] and hyoglossus [HG]), which are innervated by the lateral branches of XII.

  • 4.

    Bite block is placed to hold the mouth open to visualize the tongue during device testing at the end of the case.

  • 5.

    Shoulder roll and jelly donut used to extend the head to the left for optimal surgical access. Keep the arm on the implant side free of IV, pulse oximetry, and blood pressure cuff and loosely tuck.

  • 6.

    The 3 surgical sites are then marked at the stimulation lead incision (neck), implantable pulse generator (IPG) pocket incision (superior chest), and sense lead incision (inferolateral chest).

    • a.

      Stimulation lead incision: 4-cm to 6-cm incision is marked midway along the length of the right mandible and midway between the hyoid and mandible while staying 1 cm from the midline.

    • b.

      IPG pocket incision: 5.5-cm incision is marked 5 cm inferior to clavicle and midway between the sternum and deltopectoral groove.

    • c.

      Sense lead incision: palpate the 5th (±1) rib using inferolateral margin of pectoralis major as a landmark; 4-cm to 6-cm incision marked following the curvature of the rib approximately 5 cm lateral from a line straight down from the nipple.

  • 7.

    The face, neck, and chest are then prepped with betadine. Sterile towels are secured with staples to isolate surgical sites. Adhesive drape (Ioban [3M, St. Paul, Minnesota]) is placed over exposed skin to maintain aseptic technique at all 3 surgical sites. A transparent drape (1012 [3M]) is then placed across the loban to cover the oral cavity while ensuring visual access to the tongue. A split sheet is then secured over the drapes.

Surgical procedure

  • 1.

    Neck incision is carried through the skin, platysma, and superficial layer of the deep cervical fascia while avoiding the marginal mandibular branch of the facial nerve. The submandibular gland is located, carefully dissected at the inferior and anterior aspect away from the mylohyoid muscle, and retracted posteriorly.

  • 2.

    Identify the anterior belly of digastric muscles and trace back to the digastric tendon. Tunnel under the digastric tendon toward the mylohyoid muscle to provide a path for the stimulating lead. Place a vessel loop around the digastric tendon and retract inferiorly. Free the posterior margin of the mylohyoid muscle and retract the muscle anteriorly.

  • 3.

    By retracting the submandibular gland posteriorly, the mylohyoid muscle anteriorly, and the digastric tendon inferiorly, the hypoglossal nerve (cranial nerve [CN] XII) can be visualized, which lies superficial to the HG muscle and deep to the mylohyoid muscle. Surgeons must be careful not to injure important structures in the field, such as the lingual nerve and submandibular duct. Once the hypoglossal nerve is identified, the ranine vein may need to be ligated and divided because it often lies over the nerve.

  • 4.

    Identify the hypoglossal nerve (CN XII) and the functional breakpoint using stimulation and NIM monitoring. The goal is to separate the branches of XII that produce a uniform protrusive and stiffened tongue motion from the branches of XII that cause tongue retraction. Surgeons should work counterclockwise along the hypoglossal nerve from inferior to posterior (geniohyoid [GH], GGh, GGo, T/V, HG, and SG) and stimulate the individual branches within the main trunk to exclude the lateral XII branches (HG and SG) and include the medial XII branches (GGh, GGo, and T/V) and, when possible, the C1 branch from XII to the GH muscle ( Fig. 1 ).

Jan 19, 2020 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Upper Airway (Hypoglossal Nerve) Stimulation for Treatment of Obstructive Sleep Apnea
Premium Wordpress Themes by UFO Themes