Focal dystonia

Key words: plethysmography; pulmonary function tests; spirometry; vocal cords

Abbreviations: Gaw = airway conductance; MVV = maximal voluntary ventilation; Palv = alveolar pressure; Pbox = plethysmographic box pressure; Raw = airway resistance; Vaw = airway flow; VCD = vocal cord dysfunction

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Herein we present a patient with dyspnea and dysphonia, who had previously received a diagnosis of asthma and was treated for asthma, but the final diagnosis of vocal cord dysfunction (VCD) was established, in part, with pulmonary function testing.

CASE REPORT

A 55-year-old man presented with a 5-year history of worsening dyspnea and associated dysphonia. His initial presentation of acute severe choking and stridor was attributed to asthma, and symptoms resolved in days after therapy with inhaled bronchodilators. Over the ensuing years, his symptoms were episodic and characterized mostly by stridor. Laryngeal polyps were noted during direct laryngoscopy 1 to 2 years later. Symptom frequency and severity worsened 1 year prior to evaluation at our institution, at which time there was persistent dysphonia, hoarseness, and multiple daily episodes of both inspiratory and expiratory limitation to breathing. His symptoms infrequently awoke him at night, were aggravated by emotional anxiety, and only mildly improved after therapy with low-dose lorazepam, taken 3 to 4 times a day.

The patient's medical history was significant for type II diabetes mellitus, hypertension, gastroesophageal reflux, and obesity. A review of symptoms revealed no focal or generalized dystonias, change in balance, bowel, or bladder habits, or focal neurologic deficit.

The physical examination revealed the following: temperature, 37.2[degrees]C; BP, 140/80 mm Hg; regular heart rate, 92 beats/min; and body mass index, 36.2. Tachypnea and stridorous respirations were noted with otherwise normal cardiovascular, upper and lower respiratory, and neurologic examinations. The results of standard blood chemistry tests, electrolyte measurements, urinalysis, thyroid-stimulating hormone measurement, and CT scans of the chest and neck were normal. Pulmonary function tests were ordered.

On presentation to the pulmonary function laboratory, the patient's expiratory flows were mildly reduced during the FVC maneuver (FE[V.sub.1], 2.82 L [78% predicted]; FVC, 3.71 L [81% predicted]). Note that the FE[V.sub.1] is reduced in proportion to the reduction in FVC, implying a restrictive rather than an obstructive pattern. The maximal voluntary ventilation (MVV) was 43 L/min, which was severely reduced (ie, 30% predicted) and was out of proportion to the FE[V.sub.1], giving an MVV/FE[V.sub.1] ratio of 15 (normal ratio, > 35). The diffusing capacity of the lung for carbon monoxide adjusted for hemoglobin (26.5) and oxygen saturation at rest and with exercise were normal.

The patient had difficulty performing reproducible maximal flow-volume curves. The best expiratory and inspiratory flow-volume maneuvers are shown in Figure 1. Both loops are characterized by "notching" that is not attributable to cough. In addition, the inspiratory loop showed a plateau that was reproducible with repeat maneuvers. The mid-vital capacity value of the expiratory/inspiratory flow ratio was > 2.

[FIGURE 1 OMITTED]

Airway resistance (Raw) studies were performed in a body plethysmograph (1) using panting to create airway flow (Vaw) vs alveolar pressure (Palv) graph loops. During normal panting maneuvers the Vaw vs Palv graph revealed a dramatic plateau in the inspiratory flow (Fig 2). Raw, calculated in a linear region spanning zero flow, was significantly elevated and measured 18.8 em [H.sub.2]O/s (405% predicted). Based on these test findings, the diagnosis of a variable, extrathoracic, large-airway obstruction was made, and an otorhinolaryngology evaluation was obtained.

[FIGURE 2 OMITTED]

Evaluation via direct laryngoscopy revealed intermittent paradoxical movement of the vocal cords, that is, adduction of the cords during inspiration and early expiration (Fig 3, top). At rest between inspiration and expiration, both arytenoid cartilages and the supraglottic laryngeal structures spontaneously moved and completely occluded the glottis (Fig 3, bottom). Immediately after closure of the glottis, there was reopening, and then the process was repeated.

[FIGURE 3 OMITTED]

As a result of these findings, and further neurologic evaluation, the diagnosis of idiopathic segmental dystonia, which is characterized by predominant laryngeal dysfunction and mild blepharospasm, was made. The patient was treated with botulinum toxin injection, 3 U into each thyroarytenoid muscle. The patient observed some mild relief of symptoms but required further injections 4 months later, again with some improvement but with no resolution of his symptoms.

DISCUSSION

VCD is a relatively uncommon disorder, but increasing numbers of publications have served to better outline its incidence and natural history. Retrospective case series (2,3) have shown that VCD is diagnosed predominantly in women who are 30 to 50 years old and who commonly have an increased body mass index and a history of psychiatric illness. As a result, nonorganic and psychogenic causes have been proposed as the predominant etiology of VCD. However, a greater emphasis on associated organic causes is now evolving and includes gastroesophageal reflux disease and neurologically based dystonias. Canine models (4) of gastroesophageal reflux disease have suggested that a pH of [less than or equal to] 2.5 induces laryngeal spasm through vagally mediated mechanisms and the sensitization of mucosal chemoreceptors. It is hypothesized, therefore, that laryngeal hyperreponsiveness may be the underlying cause for VCD. This state is thought to be induced by inflammatory insults and subsequently has been maintained by altered autonomic balance and repeated local stimuli. (5) In addition, neurologic dysfunction must be ruled out, requiring specialty consultation. As this case illustrates, a thorough neurologic evaluation revealed an idiopathic segmental dystonia underlying this patient's symptomatology.

Typically, VCD mimics asthma, and as a result it often remains undiagnosed for 5 to 10 years. (2,3) Patients usually present with episodic "attacks" that begin and end abruptly and are characterized by throat tightness, dysphonia, and inspiratory difficulty. However, stridor occurs in < 20% of cases. (2) In contrast to patients with asthma, VCD patients often are able to hold their breath during attacks and have their symptoms temporarily abated by distraction. (6) Often, asthma therapy is escalated because of "poor response," resulting in patients receiving large doses (ie, > 20 mg/d) of systemic steroid medications, and they are often incorrectly considered as having steroid-resistant asthma. (7) Newman et al (2) has reported that 55% of patients may have concurrent asthma that responds to therapy. However, the diagnosis of asthma in these patients is challenging because the accurate interpretation of a response to either methacholine challenge or bronchodilator challenge can be confounded by variable reproducibility in the patients' performance of pulmonary function testing.

The treatment of patients with VCD is difficult and requires a multidisciplinary approach addressing a combination of pharmacologic, behavioral, and psychiatric modalities. (8) Speech therapy plays an important role in long-term management by providing respiratory retraining to deemphasize laryngeal breathing. For acute presentations with severe symptoms, endotracheal intubation and/or tracheostomy can be avoided by the administration of helium/oxygen (70%/30%) with or without noninvasive positive-pressure ventilation. (8,9) Additionally, success has been reported with direct vocal cord injection of botulinum toxin A. The response to such therapy might help differentiate a dystonic from a psychogenic etiology. (10)

Pulmonary function testing may suggest, if not establish, the diagnosis of large airway obstruction. In our patient, spirometry revealed a near-normal FE[V.sub.1] in the setting of a decreased MVV and elevated Raw, which by itself is an unusual pattern. Our patient also exhibited a flattening of the inspiratory flow-volume loop at a mean flow of 2 L/s (Fig 1), which is highly suggestive of large airway obstruction. (11) Prior studies (2,12) have reported the diagnostic utility of "truncation" of the inspiratory flow-volume loop. Newman and colleagues (2) reported this finding in 23% of their patients with VCD, making it a common finding, but not a sensitive indicator of VCD. Kryger et al (11) also highlighted the utility of the mid-VC values of the expiratory/inspiratory flow ratio to differentiate extrathoracic from intrathoracic variable obstruction. (11) In healthy patients, this ratio is approximately 0.9, with a ratio of > 2 indicating extrathoracic obstruction and a ratio of < 0.5 indicating intrathoracic obstruction. In our patient, the ratio was 5.9, indicating the extrathoracic origin of the variable large airway obstruction. Newman et al (2) reported a statistically significant elevation in this ratio compared with asthmatic control subjects, but the actual number was not reported. Thomas and colleagues (7) reported that in seven patients with pseudosteroid-resistant asthma the presence of normal Raw may be a defining feature of VCD. This, however, proved not to be the case for the patient reported herein.

[FIGURE 1 OMITTED]

In 1956, DuBois et al (1) described a technique utilizing body plethysmography to determine Raw. In this technique, the patient pants in the plethysmograph box with the spirometry valve open and closed, thus generating two graphs (Vaw vs plethysmographic box pressure [Pbox], followed by Pbox vs Palv). Multiplying the slopes of the two eliminates Pbox to give the Vaw/Palv ratio, which equals airway conductance, the reciprocal of which is Raw. The change in slope of this graph has been used to identify various pulmonary abnormalities including airflow limitation. (13) However, this case highlights the visual representation of the Vaw vs Pbox loops, which is diagnostically helpful also. In this patient, the graph showed a pronounced flattening in the inspiratory portion (Fig 2), suggesting more significant flow limitation on inspiration compared to expiration. This finding is not commonly appreciated in cases of extrathoracic airway obstruction and highlights the utility of body plethysmography in establishing or further confirming this diagnosis. To the best of our knowledge, this is the first description of body plethysmography as a diagnostic tool for VCD.

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In summary, this case demonstrates two important clinical points. The first is the utility of pulmonary function testing in evaluating and diagnosing cases of central airway abnormalities including VCD. Specifically, the case highlights all the pulmonary function tools, including plethysmography, that are available for establishing such a diagnosis. The second point is the typical presentation of VCD and its initial misdiagnosis as asthma. The patient presented with a confusing constellation of symptoms that had not been adequately diagnosed and treated in the past. Pulmonary function testing was instrumental in establishing the diagnosis of variable extrathoracic large airway obstruction, which was definitively demonstrated with direct laryngoscopy (Fig 3).

[FIGURE 3 OMITTED]

ACKNOWLEDGMENT: The authors thank L.L. Oeltjenbruns for assisting with the manuscript preparation.

REFERENCES

(1) DuBois AB, Botelho SY, Comroe JH. A new method for measuring airway resistance in man using a body plethysmograph: values in normal subjects and inpatients with respiratory disease. J Clin Invest 1956; 35:327-335

(2) Newman KB, Mason UG III, Schmaling KB. Clinical features of vocal cord dysfunction. Am J Respir Crit Care Med 1995; 152:1382-1386

(3) Andranopoulos MV, Gallivan GJ, Gallivan KH. PVCM, PVCD, EPL, and irritable larynx syndrome: what are we talking about and how do we treat it? J Voice 2000; 14:607-618

(4) Loughlin CJ, Koufman JA, Averill DB, et al. Acid-induced laryngospasm in a canine model. Laryngoscope 1996; 106: 1506-1509

(5) Ayers JG, Gabbott PL. Vocal cord dysfunction and laryngeal hyperresponsiveness: a function of altered autonomic balance? Thorax 2002; 57:284-285

(6) Wood RP II, Milgrom H. Vocal cord dysfunction. J Allergy Clin Immunol 1996; 98:481-485

(7) Thomas PS, Geddes DM, Barnes PJ. Pseudo-steroid resistant asthma. Thorax 1999; 54:352-356

(8) Patterson DL, O'Connell EJ. Vocal cord dysfunction: what have we learned in 150 years? Insights Allergy 1994; 9:2-12

(9) Maillard I, Schweizer V, Broccard A, et al. Use of botulinum toxin type A to avoid tracheal intubation or tracheostomy in severe paradoxical vocal cord movement. Chest 2000; 118: 874-876

(10) Gallivan GJ. Paradoxical vocal cord movement. Chest 2001; 119:1619-1620

(11) Kryger M, Bode F, Antic R, et al. Diagnosis of obstruction of the upper and central airways. Am J Med 1976; 61:85-93

(12) Gallivan GJ, Hoffman L, Gallivan KH. Episodic paroxysmal laryngospasm: voice and pulmonary function assessment and management. J Voice 1996; 10:93-105

(13) DuBois AB. Significance of measurement of airway resistance: international symposium on body plethysmography. Progr Respir Res 1968; 4:109-115

* From the Department of Internal Medicine (Drs. Vlahakis, Patel, and Beck), Division of Pulmonary & Critical Care Medicine, and the Department of Otorhinolaryngology (Dr. Maragos), Mayo Clinic and Foundation, Rochester, MN.

Manuscript received January 24, 2002; revision accepted June 26, 2002.

Correspondence to: Nicholas E. Vlahakis, MD, Stabile Building, Room 8-62, Mayo Clinic, 200 First St SW, Rochester, MN 55905; e-mail: vlahakis.nicholas@mayo.edu

COPYRIGHT 2002 American College of Chest Physicians
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