Improvement in lung function following medialisation thyroplasty in a postbilateral lung transplant patient

Abstract

A 59-year-old man underwent external medialisation thyroplasty for his left unilateral vocal cord paralysis (UVCP) secondary to recent thoracic surgery. The patient had undergone bilateral lung transplant for idiopathic pulmonary fibrosis and was referred to the ear, nose and throat surgical team with new-onset voice hoarseness. Examination confirmed left UVCP, and after failing conservative management a decision was made to perform external medialisation thyroplasty. Following an uneventful procedure, the patient’s phonation returned to normal, and remarkably on spirometry there was evidence of significant improvement in lung function. Despite case series demonstrating subjective improvement in respiration, this is the first documented case, to our knowledge, of significant improvement in spirometry following this procedure.

Background

This case represents an unexpected outcome following a routine surgery for unilateral vocal cord paralysis (UVCP). Despite small case series demonstrating subjective improvements in respiration after medialisation thyroplasty, there is minimal literature exhibiting objective improvement in lung function following this procedure.

Case presentation

A 59-year-old man was referred to the ear, nose and throat (ENT) team during his hospital admission with new-onset hoarseness. The patient had undergone bilateral lung transplant for idiopathic pulmonary fibrosis 2 weeks earlier and was otherwise recovering well. Examination revealed hoarseness and associated soft breathy voice. There was no obvious oropharyngeal/oral cavity abnormality and no palpable neck masses or lymphadenopathy. On flexible nasoendoscopy the left vocal cord was fixed in the paramedian position with a normal mobile right cord. The patient was deemed suitable for conservative management initially of his left UVCP, and so was referred for speech pathology and outpatient ENT follow-up. Speech assessment demonstrated moderate-severe hyperfunctional dysphonia characterised by moderate breathiness, mild roughness and impaired breath support. There was a large glottic gap present on nasoendoscopy. The patient scored 17 out of 40 on the Voice Handicap Index-10 (VHI-10) questionnaire, indicative of an abnormal voice.^{1 2}

Despite overall moderate improvement in lung function following his transplant, the patient’s phonation did not recover after 18 months of regular therapy, so the decision was made to proceed with external medialisation thyroplasty. The patient underwent preoperative spirometry (see figures 1–3) as part of his routine transplant follow-up and his medialisation surgery occurred in late 2017. Surgery demonstrated a lateralised left vocal cord, and after placement of a stent an improvement in phonation was noted intraoperatively. He recovered well and was discharged the following day with follow-up organised.

Figure 1.

Spirometry readings presurgery and postsurgery (August and December). BD,bronchodilator; FET, forced expiratory time; FEV, forced expiratory volume; FIVC, forced inspiratory vital capacity; FVC, forced vital capacity; MFEF, maximum forced expiratory flow; NHANES, National Health and Nutrition Examination Survey; PEF, peak expiratory flow.

Figure 2.

Flow volume curves presurgery and postsurgery (August and December).

Figure 3.

Graphical representation of improvement in forced expiratory volume (FEV), forced vital capacity (FVC) and forced inspiratory vital capacity (FIVC) presurgery and postsurgery.

Investigations

See figures 1–3.

Outcome and follow-up

The patient’s phonation improved remarkably with a VHI-10 score of 6 out of 40 postoperatively compared with 17 out of 40 preoperatively. The patient described some limitation with regard to volume of his voice, however overall was satisfied that his voice had returned essentially to normal. Of interest however was improvement in the patient’s respiration. Postoperative spirometry occurred 2 months later, and remarkably there was significant improvement in his forced expiratory volume (FEV), forced vital capacity (FVC), forced inspiratory vital capacity (FIVC) and FEV/FVC ratio (see figures 1–3).

Discussion

Medialisation thyroplasty is a well-established therapy for UVCP to improve phonation and swallowing.³ Few studies have assessed the effects of thyroplasty on pulmonary function testing, with non-significant results demonstrated in the majority of these. The aetiology of respiratory impairment is also only hypothesised, but publications have suggested the paralytic vocal fold may be drawn into the airflow tract of the respiratory system during inspiration.^{4 5} Consequently, there is narrowing of the airway and subjective respiratory compromise. Objective data, although limited, highlight that these patients have altered spirometry, and the parameter most commonly affected is peak inspiratory flow.^{6 7}

Following external medialisation surgery however, evidence of objective changes in respiration in the literature is scarce.

In 2015, Asik et al⁸ assessed airway and respiratory parameters prospectively in patients undergoing laryngeal medialisation (either by injection laryngoplasty or thyroplasty for UVCP). Of the 11 patients who underwent thyroplasty, there was improvement in subjective airway measures; however, there was no significant improvement in spirometry (peak inspiratory and expiratory flow, FEV and FVC).⁸ Schneider et al⁹ conducted a similar study examining aerodynamic measurements in medialisation thyroplasty. Thirty patients underwent medialisation thyroplasty with a titanium implant, with preoperative and postoperative lung function testing recorded and analysed. Similar to Asik et al’s⁸ study, there was no significant improvement in any of the parameters except for airway resistance; however, subjective improvement in respiration during speaking, laughing, coughing and physical activity was noted by all participants.⁹ Interestingly in 1999, Janas et al¹⁰ conducted a similar study with 15 patients undergoing external medialisation surgery. All participants underwent preoperative and postoperative lung function testing, but in contrast to the previous two studies the ratio of forced expiratory flow to forced inspiratory flow for 12 of the 15 patients actually worsened. Despite this result, only two of these patients were symptomatic with regard to this objective measure of airflow obstruction.

The degree of airflow limitation and respiratory difficulty because of UVCP in this patient is difficult to interpret given his background of idiopathic pulmonary fibrosis and bilateral lung transplantation, and this is a notable confounding factor in this case presentation. At 2 months post-thyroplasty, there was a significant increase in FEV, FVC, FIVC and FEV/FVC, indicative of improved airflow both in the inspiratory and expiratory phases. The mechanism for the improvement in lung function is unclear; however, we hypothesise that a contributing factor may be the reacquirement of intrinsic positive end expiratory pressure (PEEP). Intrinsic PEEP is thought to be impaired in patients with UVCP due to inadequate glottic closure, although this has yet to be investigated in the literature to date. Following a procedure such as external medialisation thyroplasty whereby glottic closure is improved (through enhanced phonation), the ability to generate intrinsic PEEP may also be augmented. Gorham et al¹¹ explored laryngeal recovery after thyroplasty surgery demonstrating improvement in glottic closure for a majority of patients, although the effect on respiratory function in this study was not investigated. The advantages of PEEP include reduced airway resistance, reduced work of breathing and reduced alveolar collapse, which may all be contributing factors towards this patient’s improvement in lung function. Further studies exploring the respiratory parameters in patients undergoing medialisation surgery would be beneficial in generating a better understanding of the physiology behind this. There are certainly several other factors that likely contribute to the ultimate improvement in lung function as seen in this case.

Learning points.

• External medialisation thyroplasty is proven to enhance phonation in patients suffering from unilateral vocal cord paralysis (UVCP).

• The effects on respiration following thyroplasty are less clear, with the literature suggesting subjective symptomatic benefit without objective gains in pulmonary function.

• We have presented the case of a 57-year-old man with UVCP likely secondary to thoracic surgery who demonstrated notable improvement in phonation and respiration postexternal medialisation thyroplasty.

• To our knowledge this is the first documented case of significant improvement in spirometry following this procedure; the exact mechanism of this is unclear, although we hypothesise that through the reacquirement of natural positive end expiratory pressure through increased glottic closure, this may contribute to enhanced lung function likely among several other factors yet to be explored.