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ENT and Speech Disorders in Children With Down's Syndrome: an Overview of Pathophysiology, Clinical Features, Treatments, and Current Management

Posted on: Friday, 17 December 2004, 03:00 CST

Summary:Down's syndrome is the most commonly occurring genetic abnormality, involving about 1 in 600 births. The increasing life expectancy of individuals with Down's syndrome has revealed the presence of several unexpected pathological processes. Among these, ENT disorders hold an important place because of their high incidence and severity. Accurate knowledge of the pathophysiology underlying ENT disorders (facial dysmorphism, ear abnormalities, upper airway abnormalities, and immunodeficiency) allow an understanding of the reasons for the development of the upper airway obstruction, obstructive sleep apnea syndrome, subglottic stenosis, deafness, speech delay, and ENT infections that occur frequently in these children. Early screening and specific treatment may allow some of the long-term sequelae to be avoided, or at least their prognosis to be improved. In order to help health care professionals in their daily practice, this review makes a series of recommendations to allow them to develop a master plan for the ENT management of children with Down's syndrome. In children with Down's syndrome, ENT disorders occur frequently and are often severe They develop owing to craniofacial, functional, and immune system abnormalities. Early screening and treatment allow improvements in long-term outcomes. Clin Pediatr. 2004;43:783-791

Introduction

Down's syndrome (OMIM #190685) is one of the most common genetic abnormalities, involving 1 in 600 to 700 births. The phenotype of children with Down's syndrome encompasses several abnormalities, including cardiac and intestinal malformations and immune disorders that can be fatal. Early screening and treatment for these serious disorders have been provided to children with Down's syndrome for some time. Progress in the management of such fatal abnormalities has led to an increase in the life expectancy of these children. Owing to this increase in life expectancy other problems have emerged. Among these, the high prevalence of ENT disease frequently causes an increase in Down's syndrome-related handicap. Speech and hearing impairment, upper airway obstruction, and ENT infections are frequently observed in these children, mostly linked to functional and structural abnormalities of the ear, nose, throat, and immune system. However, appropriate screening may allow effective treatment of these diseases and improve both quality and length of life. Moreover, correct management of associated communication disorders can improve the social integration of children with Down's syndrome.

In order to better understand the mechanisms involved in the development of otolaryngological disorders in children with Down's syndrome, we first describe the functional and morphologic abnormalities that cause them. We then discuss the methods used to diagnose and treat ENT disease in these children. Using this information we finally suggest a protocol for the investigation and management of these children from birth to adulthood.

Functional and Structural Abnormalities are the Underlying Cause of ENT Disorders

Facial Dysmorphism and Down 's Syndrome

Before its genetic characterization Down's syndrome was recognised by specific phenotypic features, first described by the British physician John Langdon Down in 1866. Among these are craniofacial dysmorphism and associated skeletal and soft tissue abnormalities.

The primary skeletal abnormalities affecting the craniofacial features in Down's syndrome include brachycephaly with a structurally normal brain and midface deficiency, leading to a flattened facial profile.1 The nose is short with a flat nasal bridge, and the oral cavity is relatively small, with a tendency to protrude the tongue.2 There can be atlantoaxial instability of the cervical spine, which can lead to spinal cord compression with neck trauma, and this should be evaluated with flexion-extension spinal radiographs by at least age 3 years. In addition, the paranasal sinuses may be small and their ostia obstructed by hypertrophic mucosa.3

The abnormalities of the soft tissues consist of upsloping palpebral fissures, inner epicanthic folds, Brushfield spots on the iris, and hypoplastic, low-set ears. The hard palate in children with Down's syndrome appears narrow and vaulted,3 causing, when associated with macroglossia and tongue hyperprotrusion, a decrease in the volume of the oral cavity, impairing both mastication and speech.

Otologic Abnormalities

Abnormalities can involve all parts of the auditory system. External ear canals may be stenotic in 40-50% of cases, especially in their medial part, and become obstructed by earwax and skin debris,4-8 causing hearing impairment and making examination of the tympanic membrane difficult or impossible.

In the middle ear, the eardrum may lie in an oblique position,6 and reduced mobility or malformation of the ossicular chain (in 25% of cases)9 can lead to a conductive hearing loss.6,10-12 Sound conduction can also be impaired by persistence of mesenchymal tissue within the tympanic cavity (75% of cases).9

Finally, anomalies such as Mondini or Sheibe dysplasia can affect the inner ear, causing endolymphatic hydrops (the most common feature) in a shortened cochlea.9,13,14 Very occasionally a cochleosaccular dysplasia is found.15 The only abnormalities of the vestibular system observed are malformations of the semicircular canals.9,16 There also appears to be a reduction in the number of spiral ganglion neurons found in the temporal bones of Down's patients as compared with normal temporal bones.13 Some authors propose that the degeneration of the auditory nerve could be due to progressive compression in the internal auditory meatus.17 Sometimes a bony dehiscence of the facial canal is noted.9,13 Although these anomalies of the inner ear have been frequently observed (in 36.6% to 71% of cases),9,13 there has been no direct correlation between hearing loss and these malformations.9

Pharyngolaryngeal Anomalies

The main feature of the pharyngolaryngeal abnormalities is a reduced airway. This reduced size is due to several factors: a narrow nasopharynx, adenotonsillar hypertrophy, hyperplasia, and hypotonia of the soft palate caused by dysfunction of the upper airway muscles.18,19 Furthermore, this hypotonia leads to a collapse of the openings of the Eustachian tubes in the nasopharynx, which are also shorter in children with Down's syndrome.4,5,7

The larynx is short and located more cranially than is usual. Laryngo- and tracheobronchomalacia are frequent consequences of associated hypotonia and laryngotracheal cartilaginous hypoplasia.20 More rarely found are subglottic stenosis (mainly posterior) and tracheal stenosis, but their incidence is higher in children with Down's (4% of pediatric subglottic stenosis)21 than in the general child population.2,19,22,23

Immune Deficiency in Children with Down's Syndrome

The reasons for the high infection rate found in 2% of children with Down's syndrome are unclear.8 Down's syndrome is associated with early thymic dysfunction involving T lymphocytes.24 Although the total number of T lymphocytes is normal, the ratio of suppressor cytotoxic T8 lymphocytes is increased. The activity of the natural killer cells and the level of interleukin-2 are decreased, contributing to T-cell dysfunction. Furthermore, neutrophil function is altered, causing a reduction in immune function.25 Rarely, the number of eosinophils is decreased.

The level of production of immunoglobulins is normal; however, the ratios between subtypes are modified. Levels of immunoglobulin G2 (IgG2) and 4 are lower and IgG1 and 3 are greater than usually observed. The decrease of the IgG subtype 4 is correlated with an increase in the level of bacterial infection. The mechanisms underlying this increase in infection are not known, but it is established that the pulmonary immune response depends on this IgG subtype.24-26

The Diagnosis and Treatment of ENT Disorders in Children with Down's Syndrome

Hearing Disorders

Deafness is the most common of the ENT pathologies observed in children with Down's syndrome. Early management is necessary to minimize communication and social impairments. Between 38% and 78% of children with Down's syndrome4,27-31 have a conductive hearing loss; 90% of these are caused by otitis media with effusion.32 The other 10% are related to impacted earwax, skin debris, stenotic ear canals, and ossicular chain abnormalities.

In order to diagnose a hearing impairment, all the authors propose evaluation with a clinical examination and pure tone or behavioral audiometry (behavioral observation audiometry, distraction audiometry, or conditioned play audiometry) according to the age and the developmental stage of the child.8,30,310-33 Shott et al8 systematically refer patients for auditory brainstem response (ABR) evaluation, whereas others prefer to use it only with patients who are difficult to assess. Actually, this examination is more frequently proposed since these children are classified in the group of neonates at high risk of hearing impairment. Tympanometry was performed after clinical examination by Rattan et al,30 Maroudias et al,31 and lino et al.33The purpose of this examination was to detect a middle ear effusion or ossicular abnormalities. Tympanometry was abnormal in 36% to 56% of cases,6,31 whereas audiometry assessment revealed a conductive hearing loss in 46.1% to 50% of cases and a sensorineural hearing loss in 4% to 11.4%. Tympanometry seems to be a good way to screen for conductive hearing loss in children with Down's syndrome, as it is quick and fairly sensitive. lino et al33 are the only ones to recommend computed tomography (CT) scan evaluation. However, CT scan evaluation was not able to predict any auditory threshold, and the only purpose of this examination was to detect middle or inner ear abnormalities. The small number of cases involved in this study does not permit an accurate evaluation of the usefulness of CT scanning in Down's syndrome. Hassman et al6 tried to assess the effectiveness of distortion product otoacoustic emissions (DPOAE) to evaluate audiologic disorders in children with Down's syndrome. The results of DPOAE studies are difficult to analyze. In many of these patients tympanometric abnormalities hampered the performance of DPOAE. In fact, the correlation between hearing loss and DPOAE results are known only in an adult Down's syndrome population. Given that adults with Down's syndrome suffer from early presbycusis,17,34 the place of DPOAE is not well defined.

Anatomical and functional abnormalities such as chronic nasal obstruction, adenotonsillar hypertrophy, collapse of the Eustachian tubes, and recurrent acute otitis media increase the prevalence of chronic otitis media with effusion. This can lead to sclerosis of the mastoid air cells.35 The treatment of otitis media in children with Down's syndrome is currently being debated. Because of the poor efficacy of medical treatment and the high recurrence rate of otitis media in these children, close follow-up and "aggressive" treatment are required. Adenoidectomy may be indicated in some, but this simple surgical treatment is not without problems. Adenoidectomy may cause velar insufficiency and hypernasal speech owing to imbalance of the upper airway muscles.36 Otitis media with effusion may require the insertion of ventilation tubes (grommets). Shott et al8 clearly showed that early grommet insertion (from 11 months onward) achieved normal hearing in 98% of cases with otitis media with effusion. However, efficacy is short-lived because of extrusion of the tubes as demonstrated by lino et al.33 As long as these children have middle ear and Eustachian tube dysfunction, they will need regular grommet replacement. Unfortunately, it is known that repeated replacement may lead to undesirable sequelae such as perforation of the eardrum (in 16%).31 It may be that the placement of longer term "T" tubes at the outset could decrease the rate of such complications. However, note that hearing thresholds with a grommet inserted can be lower than expected because of ossicular abnormalities. Other complications such as cholesteatoma are also more frequently observed.33,37

The etiology of sensorineural deafness in children with Down's syndrome is unclear. Even if the cochlear abnormalities seen are correlated to the severity of the deafness,9 thresholds should not generally exceed 40-50 clBHL.30,31,38 A severe (70 to 90 dBHL thresholds) or profound (more than 90 dBHL) hearing loss must lead to the search for another etiology such as a mutation of the GJB2 gene (connexin 26).38 In the adult population of patients with Down's syndrome, mild sensorineural deafness is a common feature, owing mostly to early presbycusis.17,24 The treatment of sensorineural deafness in children with Down's is the same as with all children, that is, with hearing aids, cochlear implants, and speech therapy. However, the practitioner has to keep in mind that mental handicap and specific language troubles may interfere with treatment and require a particular approach by the speech therapist. Good rehabilitation, including a combined approach utilizing the teaching of sign language, may help to improve the language development of these children.

Speech Disorders

Speech is a complex function involving normal hearing, phonadon, and central nervous system function. Hearing loss greater than 15 dBHL affects normal learning, speech, and cognitive development.27,37,39,40 Even if hearing is normal, speech and cognitive development are altered in children with Down's syndrome (see Chapman41 for references). During the first year of life, delay in babbling is observed. Nonverbal requests are fewer in these children than in controls. Single words and 2-word combinations appear at the expected stages of development, but overall expressive language quality is impaired both in vocabulary and syntax. In contrast, the understanding of language is correlated with the developmental stage and the communication mode is total, using oral communication aided by gestures.41 In childhood, deficiencies in verbal short-term memory, limiting the development of grammar and the understanding of the meaning of words, are detected.42 Alteration of the audiophonatory loop'13 leads to phonological errors and reduced intelligibility. Interestingly, skill levels in language comprehension are better than would be expected when compared to the language production level.44,45 In adolescence, expressive language syntax and vocabulary continue to be delayed relative to language understanding. Intelligibility is a decisive factor in understanding the speech of children with Down's syndrome48 and depends on their age and hearing status.

A study carried out in 1993 by Hamilton47 looking at the speech difficulties experienced by children with Down's syndrome confirmed a hypothesis put forward in 1976. By use of electropalatography, it was shown that the muscular control of the tongue, the coordination between lips and tongue, and the planning of motor sequences were all impaired.21,48,49 These difficulties lead to dysphasia, dyspraxia, dysarthria, and articulation problems.47

The main features of the voicedisorders occurring in children with Down's syndrome are harshness, hoarseness, and gruffness.50 A "singing voice" is not possible for the majority.50 Study of the voice disorder (dysphonia) with laryngeal electromyography coupled with a computerized profile of voice analysis (Spoken Dialog System, SDS) by Pryce50 showed that these disorders were due to muscular fatigue caused by the excessive effort required to move the hypotonie laryngeal muscles. It has been shown too that other factors such as dehydration increase the vocal disability.50

The treatment of communication disorders is one of the parts of an educational project in which people with Down's syndrome have to learn to read simple information, to write their name and common words, to speak with an intelligible voice, and to count money (in order to be independent in the everyday life). This treatment has to begin early to be successful.37 Early education to sound must be begun from 3 months, and then speech therapy treatment has to be continued until adulthood. This therapy is based on 3 main strands. First, therapy promotes voice production, sometimes using a feedback system.50 Then, an improvement of buccofacial movement must be achieved to increase intelligibility.47 Finally, strategies using visual and gestural techniques must be taught to supplement spoken language. Thus, from 2 years to 6 years or more the learning of sign language, using both visual and gestural techniques, can improve language fluency and global word analysis and recognition. Treatment of the hearing impairment is a priority. The type and severity of the hearing impairment will dictate the type of device that is appropriate (hearing aids, soundfield amplification, etc) to develop communication through the auditory channel.37,51 Note that language learning may continue during adulthood in patients with Down's syndrome so that long-term speech therapy may be appropriate. Screening for communication disorders must therefore be one of the main concerns of the treating practitioner because of their high incidence and wide social impact.

Breathing Disorders

The incidence of upper airway obstruction in children with Down's syndrome is 14%. Among them, 39.5% suffer from obstructive sleep apnea syndrome (OSAS),19 characterized by hypoventilation and nocturnal oxygen desaturation.19,52 In these patients, chronic hypoxia can cause pulmonary artery hypertension and provoke heart failure in children with cardiac anomalies. OSAS is often underdiagnosed; 68% of the children with Down's syndrome in the study by Marcus et al52 had OSAS that was not clinically suspected. Clinical features are noisy breathing, snoring, disturbed sleep, sitting sleep position, daytime sleepiness, and behavioral changes. The etiology of OSAS is the same as in the adult population, but the causes are multiple in 38% of cases.19 Pharyngeal obstruction (macroglossia, high vaulted palate, micrognathia, tonsillar hypertrophy), functional problems (velar hypotonia, mucosal dryness, obesity), and nasal obstruction (narrow nasal airway, adenoid hypertrophy, rhinosinusitis) contribute to the severity of OSAS.

Other causes of upper airway obstruction include pharyngomalacia, laryngomalacia, tracheobronchomalacia, and subglottic stenosis.23,53 In contrast to OSAS, this diagnosis is usually made early (30 months,19 24.7 months53), especially if heart anomalies were associated with the Down's syndrome. In the study by Jacobs et al,19 with 518 patients, among the 71 suffering from upper airway obstruction, 48% had laryngotracheal abnormalities and 86% pharyngeal abnormalities. Thirty-nine of them underwent endoscopy. Of those with laryngotracheal abnormalities, the findings were reported as follows: 28% had laryngomalacia, 59% tracheobronchomalacia, 23% subglottic stenosis, and 5% tracheal stenosis. Boseley et al2 and de Jong e\t al53 observed that gastrooesophageal reflux disease (GORD) and repeated intubations were the main risk factors for subglottic stenosis. Unfortunately, in this group of patients, intubations were frequent because of the high incidence of cardiac and digestive disorders requiring surgery.

The treatment of obstructive sleep apnea syndrome (OSAS) consists of the correction of the various causes of upper airway obstruction. Oxygen and C-PAP (continuous positive airway pressure) are useful before surgery, or in cases of incomplete relief of the symptoms after surgery or if surgery itself is contraindicated. Blowing the nose and nasal douching, with antibiotic treatment during acute periods of infection, are required to treat nasal obstruction. Adenoideclomy or : adenotonsillectomy can improve nasal and pharyngeal obstruction. With this treatment, symptoms were improved in a third of cases.19,52 However, macroglossia was corrected by adenotonsillectomy only if associated with significant nasal obstruction.36 Results of uvulopalatopharyngoplasty are less impressive. Upper airway obstruction was improved in only 25% of cases. This is probably related to associated muscular hypotonia. In contrast, plication of the tonsillar pillars at the time of tonsillectomy reduced upper airway obstruction in all the patients without soft palate anomalies operated on in the group described by Jacobs et al.19 In the same study, patients who underwent tongue reduction or tongue-hyoid suspension were less likely to experience symptom relief (70% failure rate).

While laryngomalacia can frequently be treated conservatively, subglottic stenosis often requires surgical treatment, including L- stage laryngotracheoplasty or laryngotracheoplasty following lracheostomy; 94% of patients undergoing surgery for subglottic stenosis required tracheostomy, with its associated morbidity.2 Boseley et al2 reported 16 cases of patients with Down's syndrome aged from 2 months to 11 years who underwent laryngeal expansion for subglottis stenosis; 31% of them required more than 1 procedure to correct the stenosis, though 71% were eventually decannulated. These rates are similar to the general pediatric population with subglottic stenosis. Complications arising after surgery were lower airway tract infections and recurrence of the stenosis. Recurrences were correlated with the original severity of the lesion and GORD.22 Prevention of recurrence in these children was helped by using an endotracheal tube smaller than that normally used in children of equal weight during subsequent surgery.

When all surgical procedures are taken into account, breathing was improved in 76% of the children and pulmonary artery hypertension reduced in 97%.19 The failures were found when the cause of upper airway obstruction was multifactorial, involving morphologic features, functional features, or immune system deficiency. In addition to the procedures mentioned, Bell et al54 proposed maxillary-mandibular advancement osteotomies to treat children with severe OSAS and micrognathia in whom other treatments were insufficient. In this group 50% were decannulated without major complications. However, these results involved only 8 patients.

Infectious Disorders

As discussed previously, immune system deficiency involves about 2% of children with Down's syndrome8 who are therefore more susceptible to infectious disease. The most common infectious diseases affect the skin, mucous membranes, digestive system, and airways.24 In an attempt to prevent them, clinical examination should be performed every 3 to 4 months. In cases of IgG type 4 deficiency, immunoglobulins can be given intravenously to avoid recurrent bacterial infection.24,26

Table 1

RECOMMENDATIONS FOR THE ENT SCREENING OF CHILDREN WITH DOWN'S SYNDROME

Laryngitis with croup seems to be more frequently observed,55 as are bronchiolitis and pneumonia. Chronic rhinitis and sinusitis may lead to acute and chronic otitis media. Other infections of the ear such as otitis externa are mainly caused by ear canal stenosis with obstruction, and infected otorrhoea with Ps. aeruginosa and methicillin-resistant Staph. aureus in children with grommets.33

The Practical Management of ENT Disorders in Children with Down's Syndrome

Hearing disorders are of primary concern because of their high prevalence and their importance in causing communication handicap. Most authors suggest screening children with Down's syndrome in the early stages of the neonatal period to improve later learning and speech development.8,56 We endorse the recommendations made by the English National Deaf Children's Society57 regarding neonatal screening. They consider that babies with Down's syndrome should be included as a high-risk group in targeted neonatal screening programs in the same way as premature neonates. Nevertheless, note that the setting up of the universal neonatal screening could permit reduction of the number of children with Down's syndrome who won't be referred for this examination. ABR examination is the best method for neonatal hearing screening in these neonates for 2 reasons. The first is the high sensitivity of this technique and the second is the poor number of studies assessing the DPOAE efficiency in these children. ABR evaluation should be performed in the first month, preferably with the child asleep (Table 1). However, deafness can appear later, so follow-up must be close. From 3 months to 5 years of age, every child with Down's syndrome should undergo clinical examination with otoscopy, tympanometry, and behavioral audiometry every 6 months at least58 (Table 1). Results of the audiometric evaluation should be compared with the developmental stage of the child and not with the chronological age, as demonstrated by Flexer et al.59,60 If this is not done, deafness may be overestimated. If the child is not willing to cooperate, the examination must be performed under anesthetic. From 5 years to adolescence, an annual complete evaluation is required, substituting pure-tone audiometry for behavioral audiometry, depending on the assessment of developmental delay58 (Table 1). Finally, remember that familial and genetic evaluation may be required in cases of severe to profound sensorineural deafness38 (Table 2). The purpose of the otological follow-up is to detect and rapidly treat the causes of hearing impairment, such as earwax or otitis media with effusion, which are often otherwise asymptomatic.

Upper airway endoscopy must be performed if upper airway obstruction or OSAS is suspected.19 This endoscopy, like intubation, must be done carefully because of the neurologic risks caused by the frequently occurring atlantoaxial instability. The nasal airway and the pharynx should be examined each clinical occasion if the child is cooperative. However, it may be possible to inspect the upper airway during anesthesia carried out for other reasons (Table 2), allowing early diagnosis. The parents should be aware of the risks of OSAS, and a detailed history should be taken to detect any symptoms, however soft, of OSAS.

Table 2

ADDITIONAL SCREENING DEPENDING ON CLINICAL FEATURES

Finally, every child with Down's syndrome will benefit from speech therapy assessment to evaluate and treat speech delays and deficits in phonation and articulation.37 If evaluation can be performed early, treatment depends on the developmental skills and the cooperation of the child. Early treatment, begun as soon as 3 months old, may allow improvement of language learning skills in children with Down's syndrome (Table 1). The parents and specialist teachers have to take part in the educational project and must be aware that the use of hearing aids and methods such as sound-field amplification can improve the listening skills of the children.51 Special care should be provided for hearing aid users because of an increased risk of malfunction due to earwax and physical damage to the instrument. If spoken language is poor, sign language can be a useful adjunct to reaching fuller communication.

Surprisingly, we found no reports of balance impairment in children with Down's syndrome and cannot therefore assess the incidence of such problems in this population. People with Down's syndrome are known to have motor delays and fine motor skills impairment, and it may be that balance impairment is hidden behind these features. Thus we can speculate that balance impairment may be underdiagnosed. Moreover, this type of impairment could worsen the motor skills disorder. It may sometimes be appropriate to screen these children for balance impairment, with videonystagmography and posturography evaluations (Table 2), first to evaluate its prevalence, and then to improve motor rehabilitation.

Conclusion

In the past, mental handicap was the only feature characterizing people with Down's syndrome, leaving them dependent on others and on the fringes of society. Since then the strenuous efforts made by families, teachers, and patients themselves have allowed social integration to become much more achievable. Children with Down's syndrome have specific health needs that must be identified to help their particular problems in hearing, communication, and breathing. The roles of ENT specialists, audiologists, pediatricians, obstetricians, geneticists, general practitioners, speech therapists, and specialized teachers are to prevent, to screen for, and to treat such problems. This multidisciplinary management requires a good knowledge of the ENT disorders related to Down's syndrome by each member of the team. People with Down's syndrome can now live to be much older than they could in the past and most wish to reach their maximum potential. This can be made possible by improving their quality of life and increasing their autonomy and social integration achieved by, among other things, the appropriate management of their ENT problems.

Preconception screening to reduce theoccurrence of Down's syndrome is at present not possible, which is why all efforts are geared around prenatal diagnosis and early screening. Although we cannot cure children of their chromosomal abnormality, we can relieve many of their ENT disorders if diagnosed early. Recommendations suggested in this review will, we hope, help healthcare professionals determine a master plan for the management of ENT disorders in children with Down's syndrome in their care during their daily practice.

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Frdric Venail, MD1

Quentin Gardiner, MD2

Michel Mondain, MD, PhD1

1 Paediatric ENT Department, CHU Gui de Chauliac, Montpellier, France; 2 Department of Otolaryngology, Ninewells Hospital and Medical School, Dundee, UK.

Reprint requests and correspondence to: Michel Mondain, MD, PhD, Service ORL B-CHU Gui de Chauliac, 34925 Montpellier, France.

2004 Westminster Publications, Inc., 708 Glen Cove Avenue, Glen Head, NY 11545, U.S.A.

Copyright Westminster Publications, Inc. Nov/Dec 2004

Source: Clinical Pediatrics

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