Cause:
(1) congenital
(1a) malformation of the larynx and vocal cords
(1b) substernal thyroid gland
(1c) neurologic impairment (Arnold-Chiari malformation, etc.)
(2) acquired
(2a) trauma to the mouth or neck
(2b) surgery to mouth or neck, including thyroidectomy or neck dissection
(2c) psychogenic
(2d) myasthenia gravis
(2e) Guillain-Barre
(2f) multiple sclerosis
(2g) poliomyelitis
(2h) cancer in the head or neck
Presentation:
(1) Wheezing and shortness of breath, sometimes precipitated by exertion.
(2) Patients may have a feeling of tightness in the throat or upper airways.
(3) There is failure of symptoms to improve on maximal asthma therapy without evidence of noncompliance or malingering.
(4) Patients with dysphonia, voice fatigue or other glottic symptoms are easier to diagnose correctly.
(5) Patients usually are not awakened at night by symptoms. Patients may snore or have apnea during sleep.
Physical Examination:
(1) Wheezing maximal over the larynx. The wheezing may be limited to inspiration or during both inspiration and expiration.
(2) Laryngoscopy during a symptomatic episode may be diagnostic. It may show paralysis of the vocal cords, impaired abduction or paradoxical adduction. The examination may be negative if the patient is asymptomatic, depending on the cause and severity of the condition.
Respiratory Function and Laboratory Testing:
(1) Depressed tidal volume and peak flow.
(2) Failure to improve on bronchodilators.
(3) Flow-volume curves may show an impaired inspiratory cycle with normal expiratory cycle.
(4) Arterial blood gases may be normal during dyspneic episodes.
(5) The alveolar-arterial tension differences are usually normal.
Treatment:
(1) Nocturnal symptoms in some cases may improve on continuous positive airway pressure (CPAP).
(2) Psychogenic cases may benefit from psychosocial intervention and medication.
(3) Some patients may benefit from surgical intervention.
