Epidemiology

Pediatric PVFM is not common. That being said, accurate diagnosis often takes months and sometimes years due to lack of familiarity with the disorder among medical professionals and misdiagnosis as asthma. The exact incidence and prevalence of PVFM in the general population are unknown, though systematic literature reviews suggest that roughly a third of cases affect the pediatric population. The average age of onset in children is 14 years, but it has been described in infants as young as 1-week-old [1–3].

In terms of demographics, multiple studies report that there is a 2:1–3:1 female-to-male predominance regardless of age. PVFM has also been associated with significant social stressors. In a case series of 22 juvenile patients, Powell et al. [4] found that 55% either participated in competitive organized sports or were heavily involved in other extracurricular activities. In another prospective survey study, Liao et al. [5] found that out of 39 subjects between 12 and 17 years of age, many were regularly involved in competitive activities such as track (30%), swimming (17%), and cheerleading or dancing (15%). Additionally, the majority of study participants were high-achieving students, either making straight-A’s (46.2%) or A’s and B’s (41%).

Pathophysiology

Theoretically, PVFM is often classified along a continuum of disorders that fall under what is called irritable larynx syndrome (ILS; [6]), with chronic throat clearing as the most mild and laryngospasm as the most severe on the continuum of disorders. ILS is believed to develop secondary to irritation to the laryngeal structure that is often multifactorial in nature. Given that all individuals experience some postnasal drip, reflux, and cough, it is only when a threshold of tolerance is passed that laryngeal stridor may occur. The ILS theoretical construct hypothesized that central neuroplastic changes to the laryngeal afferent receptor pathways occur secondary to repeated upper airway exposure or a single overwhelming upper airway exposure to an irritant(s). This hypothesis is supported by the work of Eric Kandel, who received a Nobel Prize for his work in a sea slug model demonstrating the neuroplasticity of the respiratory gill to repeated exposure to noxious agents, with eventual respiratory gill response to agents that the slug did not initially perceive as noxious. Given that the biological role of the larynx is to protect the lower airway, laryngeal adductory behavior in response to repeated or overwhelming exposure to laryngeal irritants is reasonable.

The primary etiology for the development of paradoxical vocal fold motion behavior is described by Mathers-Schmidt [7] as following into one of three primary groups: upper airway sensitivity to irritants (extraesophageal reflux or allergens), neurological, or psychological conditions. For the infant and very young child, it would be unlikely that a psychological condition could trigger the events; therefore the child should be carefully evaluated for probable environmental irritants, allergies, and reflux. Neurological conditions of which PVFM may be a clinical sign or symptom, for example, cerebral palsy or brainstem compression, should be ruled out. The neurological variation of paradoxical vocal fold motion behavior is distinct in its clinical presentation as will be described below.

Presentation

Infants and children with PVFM that is not due to a neurologic etiology will present with discrete, sudden-onset breathing attacks characterized by a primary difficulty with inhalation. In some children difficulty exhaling may accompany the inspiratory stridor. Not all children produce laryngeal stridor, and this symptom is not required to achieve an accurate diagnosis of PVFM. The predominance of inspiratory difficulty is one distinction of PVFM from asthma. There is not typically any loss of voice during a PVFM attack, making this clinical presentation distinct from laryngeal edema secondary to allergy which can also arise suddenly. Children will not experience oxygen desaturation during a breathing attack, and if the child loses consciousness as the PVFM attack progresses, the child’s larynx should relax open and a patent airway will be reestablished.

PVFM attacks can occur during the day with or without activity and can also occur at night. Pediatric PVFM events that occur at night will generally occur around the same time of the night with a sudden wakening with difficulty inhaling. Nocturnal PVFM events are often attributed to extraesophageal reflux events that occur at night. Daytime attacks can occur at any time of the day and may be directly related to mealtimes, exposure to certain allergens, odors, or cigarette smoke.

The neurological version of this behavior is very rare and is distinct from typical PVFM attacks in that these children will experience persistent difficulty with inhalation during their waking hours and will have no inspiratory difficulty during sleeping. The neurologic variant is not characterized by sudden, episodic difficulty with inhalation. The neurologic variant of PVFM has been attributed to four primary etiologies as described by Maschka et al. [8]: brainstem compression, cortical or upper motor neuron injury, nuclear or lower motor neuron injury, and movement disorder. Persistent difficulty with inspiration during waking hours that is secondary to any of the conditions just listed will not be amenable to behavioral intervention, and these children should be referred to the appropriate medical specialist for medical management.

Differential Diagnoses

The differential diagnosis for paradoxical vocal fold motion requires the consideration of many other clinical presentations that are not amenable to behavioral intervention and may warrant medical or surgical management. Paradoxical vocal fold behavior secondary to a neurological etiology is not typically helped by behavioral intervention, and these patients should be referred for medical management [8].

Speech-Language Pathologist Approach

The role of the SLP in the evaluation and treatment of PVFM differs in many ways from pediatric voice disorders in general. For the infant or child with PVFM, voice is typically not affected; therefore the usual voice acoustic, aerodynamic, and perceptual assessments that are often used for baseline and outcomes evidence are not employed with this population. Laryngeal visualization is paramount to rule out extrathoracic obstruction and other airway conditions for which behavioral intervention is contraindicated. The role of the SLP is sometimes questioned in the treatment of this disorder that does not fit within the well-recognized scope of communication and swallowing disorders. The SLP is the most appropriate professional for treatment delivery in this population given the extensive knowledge of the anatomy and physiology of the laryngeal and respiratory systems. Additionally, the SLP is best trained to determine the extent to which a swallowing impairment may be involved and to develop a behavioral treatment plan that both trains and generalizes the breathing recovery method.

The assessment process from the point of view of the SLP relies more heavily on the medical history in general and a highly detailed description of the nature of the problem. The degree to which the SLP and the medical team can obtain a detailed account of the presenting problem will play directly into development of a patient-specific approach for medical and behavioral intervention. Failure to attend to the patient-specific aspects of this disorder will likely result in reduced ability to resolve the symptoms in a timely fashion. Given that this disorder causes the perception of air hunger with associated fear and anxiety for both the patient and caregivers, it is paramount that an accurate diagnosis be made quickly and behavioral/medical intervention be conducted expeditiously.

History

The case history of the infant or child will require a detailed account of birth history, developmental history (gross and fine motor, speech, language, and cognition), breathing and feeding development from birth, and any medical conditions for which the child has been assessed and treated. Given the most probable triggers for PVFM in the pediatric population, it is vital that the child be assessed and treated for all of the following prior to referral to the SLP: extrathoracic obstruction, pulmonary function, allergies, and extraesophageal reflux. It can be frustrating for the SLP when a child is referred for assessment and treatment for PVFM, and the requisite medical assessments have not been completed prior to referral. Failure to do due diligence to rule in or out the likely differential diagnoses (Table 28.2) can delay appropriate diagnoses and treatment for those children for whom behavioral intervention is not appropriate. Case history questions that are useful are included in Table 28.3.

Table 28.3

Pediatric case history questions

Behavioral	Is the primary difficulty breathing in, breathing out, or both?
	Is there a noise when the breathing attack happens?
	Where does the noise come from? The chest or the throat?
	Is there any tightness when the breathing attack happens? Where is the tightness, in the chest or the throat?
	Does anything help the breathing problem?
	Does anything make the breathing attack worse?
	How often do the attacks occur?
	How long does the attack last?
	If the attack resolves, is it likely to come back?
	Is there a voice change or loss of voice when the attacks happen?
	Are there known triggers for the breathing attacks?
Environmental	Does the child live with animals in the house?
	Was the child exposed to any new environments or new construction at the time of onset of the breathing problem?
	Does change in the weather or movement from one environment to another, e.g., going from hot outdoor environment to air conditioned space, trigger the breathing problem?
Medical	Has the child been diagnosed with
	Allergies by an allergist? Any history of laryngeal edema secondary to food or environmental allergies?
	Asthma by a pulmonologist? If asthma medications have been prescribed, is the medication being taken as prescribed?
	Reflux? If reflux medication was prescribed previously, what was the dosing schedule?

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