A 57-year-old man comes to the office due to unrefreshing sleep. He feels tired during the day and occasionally has to nap during his lunch hours. According to his wife, the patient snores loudly during sleep and frequently gasps for breath. He also has severe claustrophobia. Past medical history is significant for hypertension. The patient takes no sedative medications and is a lifetime nonsmoker. Blood pressure is 156/94 mm Hg and BMI is 30 kg/m2. Physical examination is significant for a bulky tongue and crowded, narrow oropharynx. Electrical stimulation of which of the following nerves may improve the pathophysiologic cause of this patient's symptoms?
Show Explanatory Sources
Obstructive sleep apnea (OSA) is characterized by recurrent episodes of upper airway collapse during sleep. Anatomical and neuromuscular mechanisms have been implicated in OSA. Neuromuscular weakness as a pathogenic mechanism in OSA is supported by the fact that apneas occur only during sleep, a time of muscle relaxation. The upper airway dilator muscles weaken during the transition from wake to sleep, leading to airway narrowing and ultimately collapse in individuals with OSA.
Stimulation of the hypoglossal nerve using an implantable nerve stimulator causes the tongue to move forward slightly, increasing the anteroposterior diameter of the airway. Studies with these devices have shown a reduction in the number of obstructive events during sleep.
(Choices B and C) The lingual nerve arises from the mandibular division of the trigeminal nerve and supplies sensory innervation to the tongue. The maxillary division of the trigeminal nerve provides sensation to the mid-face area. Neither of these nerves provides motor innervation to the oropharyngeal muscles involved in OSA.
(Choice D) The phrenic nerve supplies the diaphragm. Although diaphragmatic paralysis can cause sleep apnea, OSA with loud snoring and gasping respirations is due to oropharyngeal rather than diaphragmatic dysfunction.
(Choice E) The vocal cords are innervated by the recurrent laryngeal nerve, but sleep apnea is primarily a problem of the pharynx, not larynx.
Educational objective:
Neuromuscular weakness of the oropharynx is involved in the pathophysiology of obstructive sleep apnea. Electrical stimulation of the hypoglossal nerve increases the diameter of the oropharyngeal airway and decreases the frequency of apneic events.