Introduction
Laryngomalacia is the most common cause of neonatal stridor and accounts for 50–75 per cent of noisy breathing in this age group.Reference Olney, Greinwald, Smith and Bauman1 It classically presents within weeks of birth and resolves at 12–18 months of age.Reference Sivan, Ben-Ari, Soferman and DeRowe2 Only 10 per cent of cases require surgical intervention. The pathophysiology is thought to be due to anatomical abnormality or neuromuscular immaturity or dysfunction.
A group of children have been identified who do not have stridor normally but who develop it at night or during exercise. These children appear normal on flexible nasopharyngolaryngoscopy when awake, but have classical laryngomalacic movement of the larynx on induction of anaesthesia. These cases have been described as ‘state-dependent laryngomalacia’.Reference Amin and Isaacson3, Reference Smith, Sweeney, Smallman and Mortelliti4
We report an unusual case of state-dependent laryngomalacia in a 12-year-old girl, which worsened after anaesthesia with a laryngeal mask. Nine previous cases of state-dependent laryngomalacia have been reported, all of which involved children of four years or younger.Reference Amin and Isaacson3, Reference Smith, Sweeney, Smallman and Mortelliti4 There are no previous reports of laryngeal mask usage causing laryngomalacia.
Search strategy
Articles with the key words ‘laryngomalacia’, ‘state-induced’, ‘state-dependent’, ‘neurological variant’, ‘neurologic laryngomalacia’, ‘hypotonia’, ‘laryngeal mask’, ‘airway damage’, ‘airway injury’, ‘congenital stridor’ and ‘anaesthesia’ were reviewed, as identified by searching the Medline (1996 onwards), Embase (1996 onwards) and CINAHL (1982 onwards) databases. Articles sourced were cross-referenced for further related publications.
Case report
A 12-year-old girl presented with nasal obstruction and noisy breathing at night. She had been born following a normal pregnancy but had a complicated birth involving vacuum delivery after meconium aspiration. She had a history of laryngomalacia from the age of one month, which was often noted to be more pronounced at night. Despite improvement of these symptoms at a young age, the patient had presented repeatedly between the ages of six and nine years with a history of breathlessness on exertion and occasional noisy breathing at night. An adenoidectomy at seven years had failed to improve symptoms, but a laryngobronchoscopy at this stage revealed no abnormality.
The patient was listed for adenoidectomy and submucosal diathermy to the inferior turbinates. At operation, a moderate amount of adenoid tissue was curetted. During the anaesthetic, the airway was maintained with a reinforced laryngeal mask airway. No airway problems were identified during the procedure or in the immediate post-operative period. The child did complain of a sore throat immediately after the operation, but no respiratory distress was noted. She was therefore discharged as a day case.
Throughout the night following the operation, the child's mother noted much noisier breathing than normal, with frequent apnoeic periods. Subsequent flexible endoscope examination revealed no airway damage and normal vocal fold movement. Despite normal examinations, the child suffered intermittent hoarseness and breathlessness for the following three months.
Microlaryngoscopy was therefore performed. This showed laryngomalacic type movement on induction of anaesthesia, with redundant mucosa over the arytenoids prolapsing into the airway on inspiration (Figures 1 and 2). The child was treated with supraglottoplasty involving division of the aryepiglottic folds (Figure 3) and resection of redundant mucosa over the arytenoids with CO2 laser (Figure 4).
Initial microlaryngoscopic view of the larynx.
Microlaryngoscopic view of the larynx on inspiration, showing arytenoid tissue prolapsing into the airway.
Microlaryngoscopic view of the larynx showing laser division of the aryepiglottic folds.
Microlaryngoscopic view of the larynx showing resection of redundant mucosa over the arytenoids.
Good symptomatic improvement was observed post-operatively and at four month follow up. Long term follow up will be required to ensure that this is sustained.
Discussion
The cause of laryngomalacia is widely debated. Both anatomical and neurogenic theories have been suggested. The anatomical theory states that there is abnormal cartilaginous laxity which allows collapse of supraglottic structures on respiration. The neurogenic theory proposes a lack of neuromuscular control of the supraglottic structures. Much has been published to support each theory.
Multiple classification systems exist to describe the findings in cases of laryngomalacia.Reference McSwiney, Cavanagh and Languth5–Reference Shah and Wetmore7 A 1999 review by Olney et al. surveyed the reported literature and described three types of laryngomalacia:Reference Olney, Greinwald, Smith and Bauman1 type one, consisting of prolapse of the mucosa overlying the arytenoid cartilages; type two, caused by foreshortened aryepiglottic folds; and type three, consisting of posterior displacement of the epiglottis. If required, surgical treatment differs for each of these types. Some authors suggest that the pathophysiology of each of these types differs.
In the two previous reports of state-induced laryngomalacia, nine separate cases were identified. Amin and Isaacson described five children aged between seven weeks and eight months, and Smith et al. described four children aged between three and four years.Reference Amin and Isaacson3, Reference Smith, Sweeney, Smallman and Mortelliti4 All these children were reported by their parents to have intermittent stridor. In the older group, this was particularly noted at night. Fibre-optic nasopharyngolaryngoscopy in the clinic revealed no abnormality. However, on induction of anaesthesia, abnormality was noted. Different types of movement were seen. Four children had type one laryngomalacia, three had type two and two had type three. In Amin and Isaacson's group, no child required surgical intervention and symptoms resolved spontaneously. In Smith and colleagues' group of older children, three were treated by laser resection of prolapsing mucosa over the arytenoids, and one by division of the aryepiglottic fold.
Amin and Isaacson suggested that these cases gave further support for a neurogenic theory of laryngomalacia, as in their patients the abnormality only became apparent with depression of the central nervous system, in sleep or sedation. Smith et al. agreed that laryngomalacia has a neuromuscular origin, as findings were only observed in hypotonic states.
A further group of children have been observed with so-called ‘neurologic variant’ laryngomalacia. Apley identified 16 children as having ‘mental retardation’ in his 1953 series of stridulous children.Reference Apley8 However, it is difficult to discern whether all of these children were believed to have laryngomalacia. Much later, Belmont and Grundfast studied a series of 30 children with laryngomalacia, and reported that 13 per cent had hypotonia and 10 per cent had central sleep apnoea.Reference Belmont and Grundfast9 They hypothesised that these abnormalities shared an underlying dysfunction of neuromuscular control. Prescott studied 40 children receiving surgical management for laryngomalacia, and described 12 as having neuromuscular disorders.Reference Prescott10 This author also observed that three of these children had poor post-operative outcomes requiring permanent tracheostomy. All of these children had cerebral palsy.
Further support is given to the neurological theory of laryngomalacia causation by reports of acquired laryngomalacia in adults. New onset of laryngomalacia has been described after severe head injury and cerebrovascular accident.Reference Wiggs and DiNardo11, Reference Archer12 It has also been noted that, in the head injury population, neurological recovery may be coupled with improvement (if not total resolution) of laryngomalacia.
Although laryngeal injury post-intubation is widely reported, only one report of laryngeal injury following laryngeal mask use was found in the literature.Reference Rosenberg, Rontal, Rontal and Leben-Mansour13 In this case, a hoarse voice was noted post-operatively, and examination revealed anteromedial dislocation of the right arytenoid cartilage. This was treated with reduction and botulinum toxin to achieve splintage.
• Laryngomalacia commonly occurs in the neonatal period but can be seen in children up to four years old
• Both anatomical and neurogenic theories have been suggested to explain the cause of laryngomalacia
• Some children have laryngomalacic type movement only when asleep or during exercise; this has been labelled ‘state-dependent’ laryngomalacia
• In the presented case, a small airway injury led to state-dependent laryngomalacia in a patient with a past history of the condition
• This case may support a multifactorial aetiology for laryngomalacia, including both neurological control and structure of the larynx
It seems likely that our patient had an underlying neurological abnormality that predisposed her to intermittent laryngomalacic movement throughout childhood, as is generally presumed in children with state-induced laryngomalacia. In our patient's case, we hypothesise that insertion of the laryngeal mask airway caused a subtle injury to the larynx. More specifically, this could have comprised oedema and sustained swelling over the arytenoids or, possibly but less likely, dislocation of the corniculate or cuneiform cartilages. With such a change in the anatomical state of the larynx following injury, plus an underlying neurological predisposition, laryngomalacic movement developed.
Conclusion
Our patient's case seems to support a more complex, multifactorial aetiology for laryngomalacia which includes both the neurological control of the larynx as well as its structure.
