Video-assisted thoracoscopic surgery retrieval of a migrated unilateral hypoglossal nerve stimulator sensor lead

Abstract

Obstructive sleep apnea is a common chronic condition typically treated with positive airway pressure. However, many patients have difficulty with adherence to this therapy, and for some, implantation of a hypoglossal nerve stimulator has become an option. Although device implantation is generally well-tolerated, a minority of patients will experience serious adverse events. Here we report the unusual complication of the sensor lead migrating to the costophrenic angle and invading the pleural space. Nine months after original implantation, the sensor lead malfunctioned and was found to be displaced. Initial explantation and reimplantation of a new device resulted in the inability to find a portion of the lead. Reimaging showed the missing lead at the costophrenic angle, and the patient underwent thoracoscopic removal. He resumed therapy with the new device without difficulty. This case demonstrates the ability of the lead to migrate far from the implantation site, which has rarely been reported.

Citation:

Rosen R, Padhya T, Daniel J, Sharma A. Video-assisted thoracoscopic surgery retrieval of a migrated unilateral hypoglossal nerve stimulator sensor lead. J Clin Sleep Med. 2024;20(11):1851–1855.

BRIEF SUMMARY

Current Knowledge/Study Rationale: The hypoglossal nerve stimulator is an implantable device that has been found to be a safe treatment for applicable patients with sleep apnea. At this time, few major complications have been reported.

Study Impact: This case report presents a case of the sensor lead migrating into the pleura far from implantation site. Although an uncommon complication, this case study should inform physicians to search further for the sensor lead if migration is expected.

INTRODUCTION

Obstructive sleep apnea (OSA) is a common chronic condition characterized by upper airway collapse during sleep. It affects an estimated 26% of individuals aged 30–70.¹ OSA is associated with multiple comorbidities such as cardiovascular disease and stroke, metabolic disorders, cognitive decline, depression, and premature death.^1–3 Although OSA has traditionally been treated first-line with weight loss and positive airway pressure, these therapies have had low rates of long-term adherence.^1,4

The unilateral hypoglossal nerve stimulator (HGNS) implant developed by Inspire Medical (Golden Valley, Minnesota) gained approval by the United States Food and Drug Association in 2014.^2,4 At this time, it is the only United States Food and Drug Association-approved HGNS implantable device.^4,5 The device selectively activates the protrusor branches of the hypoglossal nerve.^2,4–6 During the implantation, the battery and processor unit are implanted into the chest wall, and the sensing lead is tunneled between the external and internal intercostal muscles to initiate nerve stimulation upon the initiation of inhalation.^2,4 The original procedure required 3 incisions: a modified submandibular incision, an upper chest incision for the placement of the generator, and another chest incision between the fourth and fifth rib in the midaxillary line. In the last 2 years, the procedure has eliminated the lower chest incision.

Although adverse events are not common, one of the most feared complications is pleural injury resulting in pneumothorax. This can happen immediately at the time of surgery, but can also occur late, possibly due to lead migration. Recent studies on the United States Food and Drug Association’s Manufacturer and User Facility Device Experience database found 196 adverse events, with 13 pleural injuries with or without pneumothorax.⁷ However, 12 of these were intraoperative, and there is a dearth of reports on late pleural injuries. Here we present a case of the sensor lead penetrating into the pleural space requiring thoracoscopic retrieval.

REPORT OF CASE

A 64-year-old male with history of OSA and restless leg syndrome presented to clinic in December, 2021 for management of his OSA and other sleep disturbances. He had received an HGNS out of state 9 months prior to presentation, using the 3-incision approach, which was activated 1 month later. Three months after activation, he had a titration study in the sleep lab, which reported prolonged sleep latency, low total sleep time, and an apnea-hypopnea index of 15 events/h. In addition to OSA and restless leg syndrome, also reported waking up multiple times throughout the night to eat and therefore only would have the HGNS on 2–3 hours per night. He had no other complaints regarding the implant.

Repeat titration study with polysomnography at our institution was completed the following month. He reported no issues with device other than not using it enough, felt comfortable and was not awakened by the stimulation. However, during regular follow up the sense lead waveform revealed abnormal “noise,” which indicated a possible electrical leakage (Figure 1). Sense lead waveform is regularly obtained at each clinic visit to ensure that this portion of the device is still functioning. This is a standard requirement by the device manufacturer given the known late complication of lead tip fractures. A discussion with the device manufacturer led to a recommendation of further work up and inactivating the device until this work up was complete. Obtaining a computed tomography (CT) scan was recommended.

Figure 1. Normal waveforms (A) and patient’s waveforms (B).

CT of chest demonstrated displacement of the HGNS sense lead as it was abutting the pleura of the right lower hemithorax. As the patient remained comfortable with no symptoms related to the displacement of the sensor, consent for removal and replacement of the respiratory sensing lead of the HGNS system was obtained and the surgery was scheduled for September, 2022. Although the patient had no major symptoms, the significant displacement of the sense lead tip into the pleura was worrisome to both the patient and the operating surgeon given the unknown risk of future complications.

During the surgery, an incision was made at the midaxillary line in the right lower thorax through the prior implant scar and the old sense lead was identified and removed, however the metal tip was unable to be identified. The new HGNS was then implanted through a second incision in the right upper chest, also utilizing a scar from the prior implant. The new sense lead was inserted between the second and third intercostal space through this upper chest incision, and intraoperative and immediate postoperative testing showed proper functioning. The patient tolerated the procedure well and was discharged the same day.

The new HGNS was activated 2 weeks later and the device began being titrated to therapeutic level. Because of inability to locate part of lead during surgery, a CT chest was obtained in October, 2022, which showed again the original fractured lead abutting the pleura in the lower hemithorax. However, the new device continued to work well with no reported intolerance to the stimulation and a new polysomnography in December, 2022 showing a titration apnea-hypopnea index of 3 events/h.

As the patient continued to have concerns about the retained lead, he visited with thoracic surgery in January 2023, who reassured him that it was of no emergent risk and ordered a repeat CT to look for any movement since last study. Repeat CT shown in Figure 2, revealed that the sensor was now in the posterior costophrenic angle, fortunately with no associated lung trauma or pneumothorax. After reviewing the results, the thoracic surgeon recommended removal of the lead using video-assisted thoracoscopic surgery, which was scheduled for March. During the surgery, the broken lead was found with a small pleural attachment, as shown in Figure 3. The lead was removed without difficulty. After surgery, he was admitted to the intensive care unit for monitoring, and was discharged on postoperative day 4 after an uncomplicated hospital course. Since discharge, he has had no concerns.

Figure 2. CT chest in axial (A), coronal (B), and sagittal (C) planes.

Red arrows points to sensor lead. CT = computed tomography.

Figure 3. Thoracoscopic view of lead in pleura.

DISCUSSION

The HGNS has become a common option for treatment of OSA for patients who are intolerant of CPAP or other conventional therapies.^4,5 It has led to improved quality of life in these patients.^3,8,9 Despite being a more invasive treatment option, it is generally well-tolerated and has been found to be relatively safe, with few major adverse events.^3,4,6,7,9

Multiple studies have discussed common adverse events of the HGNS, beginning with the original Stimulation Therapy for Apnea Reduction trial and the Adherence and Outcome of Upper Airway Stimulation for OSA International Registry. The Stimulation Therapy for Apnea Reduction trial found that the most common adverse event was incision-related discomfort.⁴ It also found that the most common device-related adverse events were tongue discomfort and tongue weakness.^3,9 Adherence and Outcome of Upper Airway Stimulation for OSA International Registry found similar findings of mostly benign adverse events.^4,6 However, further studies into the Manufacturer and User Facility Device Experience database were conducted, finding 132 reports from May, 2014 to September, 2019 with 134 adverse events. These reports included 32 requiring revision surgery and 17 requiring explant. Among more serious events, they found 5 pneumothoraxes, 1 pleural effusion, and 1 lead migration into the pleura, although none of these led to long-term harm.⁴ A separate analysis of the Manufacturer and User Facility Device Experience database from January, 2000 to May, 2020 found 12 device migrations, 11 of which required reoperation, although the researchers did not differentiate between the sensor lead and other parts of the HGNS.⁷

A similar case was published by Lou et al describing the sensor lead migrating into the pleura.⁶ This patient began experiencing pruritis of the chest wall 3 years after implantation using the 3-incision approach, which led to frequent scratching of the sensor site. Two weeks later, he noticed a nontender and immobile superficial mass (coiling of the wire) but had no other symptoms. CT showed migration through the fifth intercostal space into the pleural space, with a superficial coiling of the wire. Similar to our patient, he initially underwent implantation via a traditional 3-incision approach, and, upon diagnosis of lead migration, had no pneumothorax or other lung trauma.

Lou et al proposed multiple possible mechanisms for migration of the sensor in their patient, including weakness and sarcopenia (muscle wasting) caused by multiple comorbidities, atrophy of the intercostals, or patient manipulation from repetitive scratching, also known as “twiddler’s syndrome.”⁶ With regard to twiddler’s syndrome, similar cases have been described of conscious or unconscious movements causing lead dislodgment or fractures in other implantable devices such as deep brain stimulators and implantable cardiac devices, as well as a 270-degree rotation of the implantable pulse generator of an HGNS.^10–12

The patient described in the current report was younger and without comorbidities that might lead to atrophy of the intercostal muscles. Although he did not report any pruritis or other discomfort at the implantation site, considering his history of restless leg syndrome and other sleep disturbances, unconscious movements may have played a role in the lead dislodgment and migration.

Two other possible factors to consider are the 3-incision approach and older-generation lead. With regard to the approach, the 2-incision approach has gained favor since its proposal in 2020 and United States Food and Drug Association approval in 2021.¹³ Although having the benefits of shorter operative time and less incision-related trauma, multiple studies have failed to show any differences in perioperative complication rate.^14,15 Although Sagalow et al found a significantly higher rate of surgical revision in the 3-incision approach, the authors did not provide the reasons for the revision surgeries. Average time to complication was 9.66 months. Given the 2-incision technique has been the mainstay for around 2 years, comparing the complication rates is premature.¹⁴ In addition, the respiratory sensing lead was updated in 2022 to replace the previous polyethylene insulation layer with a silicone insulation layer to reinforce the area of likely fracture.¹⁶ Time will tell if this prevents late complication of lead tip break as well.

Despite being common to remove a fractured or migrated sensor lead during reimplantation surgery, little information is included about this decision-making process in available literature. A reasonable question is whether revision and removal is even necessary in cases of lead fracture. Future studies will need to be conducted on this, as there is ample evidence in the literature of minimal issues with retained leads from other devices such as pacemakers. There may also be cases where the system continues to function despite a lead break. The effectiveness of the device and long-term outcomes in these cases is unknown given the limited number of cases at this point. However, as current magnetic resonance imaging guidelines with an HGNS implant only allow for magnetic resonance imaging in the case of an intact system, leaving behind a fractured lead would likely prohibit the patient from obtaining an magnetic resonance imaging in the future.¹⁶ When feasible it is advisable to remove the sensor lead during the revision surgery.

With any implantable device, it is important to use care during implantation to limit risk of major complications. Careful manipulation of the intercostal muscles, cautious positioning of sensor lead with attention to avoiding bending of the tip, adequate anchoring by avoiding acute angles where the wire and tip meet, and limited fascial pocket dissection during placement help avoid risk of pneumothorax or device migration of the HGNS.⁴ With this patient, due to lack of records from the outside hospital, the technique used for implantation is unknown.

This patient was fortunate to not have any major complications from lead migration and underwent both replacement of the sense lead in the second intercostal space and uncomplicated explantation of the migrated lead tip. During removal of the sense lead portion of the implant, it is imperative to carefully follow the wires to the leads, remove the anchoring stitches, and pull gently to remove the lead. This would not have made a difference in this case since the lead tip had broken off from the anchored portion, but it is an important point nonetheless. Any resistance should prompt a reevaluation and further distal dissection to loosen the lead from the surrounding tissue. Abnormal sense lead signals, such as the “noise” in the sense lead waveform of our patient, can be a sign of lead fracture or migration.⁶ The most current recommendations are to check the respiratory waveforms at each postoperative follow up visit to ensure the system is intact. As shown in Figure 1, an abnormal waveform can be an immediate indicator of sense lead issues. When abnormal signals are present, further investigation of the device should be initiated, and a CT scan of the chest is crucial to obtain as much information on the location of the lead prior to surgery. As HGNS becomes more popular as a treatment for OSA, it is important for clinicians involved in OSA care to understand both the perioperative and delayed adverse events of the device, especially the ones that require intervention.

DISCLOSURE STATEMENT

All authors have seen and approved the manuscript. Work was performed at Tampa General Hospital in Tampa, Florida. The authors report no conflicts of interest.

ABBREVIATIONS

CT

computed tomography

HGNS

hypoglossal nerve stimulator

OSA

obstructive sleep apnea