Research Digest by Muhammed: Nerve Stimulation in Obstructive Sleep Apnoea
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Title: Bilateral hypoglossal nerve stimulation in treatment of adult obstructive sleep apnoea
Type: Original Article 
Journal: European Respiratory Journal


Obstructive sleep apnoea (OSA) is a disorder characterised by repeated episodes of absent (apnoeic) or decreased (hypopnoeic) inspiratory airflow during sleep. The main mechanism behind this is that during sleep the pharyngeal muscle loses tone and so the throats airspace narrows. The tongue also loses tone and while lying back in bed, can fall into the remaining airspace pulled by gravity causing complete or partial obstructions. This invariably leads to snoring, and indeed many patients that do snore may have undiagnosed OSA!






These apnoeic and hypopnoeic events lead to recurrent drops in oxygen saturation and this predisposes the individual to an array of serious health risks including hypertension, heart attacks and strokes, decreased vigilance and road traffic accidents, and a seriously decreased quality of life with mood disorders. These patients have a disrupted sleep-wake cycle and are excessively sleepy during the day which is frustrating and upsetting to them.


The 'gold standard treatment' for OSA is continuous positive airway pressure (CPAP). This is a continuous pressure of air, delivered via a mask overnight, which splints the airway open to prevent the occlusive events from occurring. However, patients have complained that this is often uncomfortable resulting in problems with adherence – an issue which remains challenging. 





Due to this, there is interest in developing alternative therapies for OSA. 'Hypoglossal nerve stimulation' is one of those emerging treatment options which show some promise. Stimulating the hypoglossal nerve leads to contraction of the genioglossus muscle (one of the tongue muscles). This leads to increases in the tone of the tongue which prevents it falling backwards while asleep and occluding the upper airway.

 

A study stimulating both hypoglossal nerves in the treatment of OSA was recently performed and it assessed the safety and efficacy of the GenioTM system. The investigators assessed changes in the apnoea-hypopnoea index (AHI), an index used to indicate the severity of OSA, along with device-related serious adverse events, measures of sleepiness and other parameters. Twenty two patients completed the trial, which they were a part of for 6 months. Significant improvements were found in all of the measures, and the device had no problems; although, 3 patients (of the original 27 that were implanted) needed the device removed due to infection around the surgical site.





The study did have some limitations; the main being that, by design, it was an observational study and therefore did not have a control group. This is problematic as there is nothing to compare the positive results to and it could be that the improvements, however unlikely, would have happened with time anyway.


It remains to be seen if this therapy would make headways in changing the management of OSA but this trial does provide hope for patients with OSA who have failed CPAP, and remain untreated.



Muhammed is a year 4 medical students at St George's. University of London, who is interested in academia. Dr Deeban Ratneswaran is a PhD student at King's College London who is currently investigating electrical stimulation as a treatment option in patients with OSA.

Image references:
https://www.oneidanydentist.com/library/7751/Snoring%26SleepApnea.html
https://en.wikipedia.org/wiki/Continuous_positive_airway_pressure
https://onlinelibrary.wiley.com/doi/full/10.1002/lio2.312

  

Originally published 14 March 2020 , updated 14/03/2020

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