Eustachian Tube: Structure, Function, and Role in Middle-Ear Disease, 2e

By Charles D. Bluestone, MD

When Charles Bluestone began his practice over 50 years ago, very little was known about middle-ear disease, in spite of its being the most common disease that clinicians in his field encounter. It has now been 40 years since he and Jack L. Paradise conducted their first investigation into the prevalence of otitis media in infants with cleft palate. Since then, Dr. Bluestone has devoted a major share of his professional career to understanding this disease and its impact on the health care of patients.

This second edition of Eustachian Tube: Structure, Function, and Role in Middle-Ear Disease includes a focus not only on the structure and function of the Eustachian tube (ET) and its role in the pathogenesis of middle-ear disease and related conditions, but also how this impacts the clinician’s management of middle-ear disease. Presented in this one source is the current state of knowledge about the ET within its “system” (the nasal cavities, nasopharynx, and palate at its proximal end and the middle ear and mastoid gas cells at its distal end). Dr. Bluestone also presents his hypotheses when definitive answers or consensus are not currently available. This volume contains a comprehensive review of all the research over the past 150 years along with updates covering the very latest research studies.

It is the hope of the author that this 2nd edition will stimulate more studies and help clinicians better understand ET function to provide the best possible health care to patients with middle-ear disease.

• Language: English
• Publisher: PMPH USA, Ltd.
• Release date: Oct 1, 2016
• ISBN: 9781607959441

Book preview

CHAPTER 1

INTRODUCTION AND OVERVIEW

All otitis media is middle-ear disease, but middle-ear disease includes more than otitis media, such as Eustachian tube (ET) dysfunction, myringosclerosis, tympanosclerosis, ossicular congenital and acquired disorders, otosclerosis, and congenital and acquired cholesteatoma.

The chapter includes

•Key advances in the study of the ET in the past 11 years.

•Glossary of terms.

•Historical perspective, including contributions of Eusthachius, Valsalva, Toynbee, Politzer, Rich, Perlman, and Ingelstedt.

•Other etiologic and pathogenic factors in the pathogenesis of middle-ear diseases.

Knowledge of the structure and function of the Eustachian tube (ET) system is necessary to understand the pathogenesis of otitis media, which will result in rational management decisions. The contents of this book have been divided into chapters that relate to the structure, function, and dysfunction of the ET system (i.e., the nasal cavities, nasopharynx, and palate, proximal to the ET, and middle ear cavity and mastoid gas cells distally); its role in the pathogenesis and management of middle-ear disease; and related diseases and disorders. Also presented are contributing factors other than the ET in the etiology and pathogenesis of otitis media, including infection owing to viruses and bacteria, the immunology of the host, the role of allergy, and social and environmental factors. This perspective is important at the outset so that the reader does not think that the only factor in the pathogenesis of middle-ear disease is dysfunction of the ET.

New to This Edition

This edition includes the many advances in the study of the ET over the past 11 years and contributions from several colleagues. (The first edition was solely written by Charles Bluestone.) Each chapter has been updated with important peer-reviewed articles published from 2004 to 2016.

Key New Advances

•Impact of human evolution on the structure and function of the ET, as well as pathogenesis and epidemiology of otitis media. Chapter 6: Pathogenesis

•An apparently unique case of alternobaric vertigo, not from the usual activities of scuba diving and airplane flying, but at ground level due to nasal obstruction, ET dysfunction, and a unilaterally functioning tympanostomy tube, which created a Toynbee phenomenon. Chapter 6: Pathogensis

•Pressure chamber evaluation of ET function. Chapter 8: Diagnosis and Tests of Function

•Balloon dilation of the ET. Chapter 9: Role in Management

Glossary of Terms

Some differences remain among health care professionals regarding the meanings of these terms. No organized professional body has agreed on the definitions used, but we have used these terms in our current texts on otitis media¹–⁵ and to some extent at the International Symposia on Recent Advances in Otitis Media,⁶,⁷ with the most recent being the 18th symposium held in June 7–11, 2015.

Middle-ear disease is a term that not only includes otitis media and its related conditions but also ET dysfunction, traumatic and infectious perforation of the tympanic membrane, tympanosclerosis, myringosclerosis, congenital and acquired disorders of the ossicules, congenital and acquired cholesteatoma, otosclerosis, and benign and malignant tumors.

Otitis media is an inflammation of the middle ear, without reference to etiology or pathogenesis. (NOTE: All otitis media is middle-ear disease but not all middle-ear disease is otitis media.

Acute otitis media is the rapid onset of signs and symptoms of acute infection in the middle ear.

Otitis media with effusion is an inflammation of the middle ear in which a collection of liquid is present in the middle-ear space and the tympanic membrane is intact.

Middle-ear effusion is the liquid resulting from otitis media or from ET dysfunction. The effusion may be

•Serous—thin, watery liquid

•Mucoid—thick, viscid, mucus-like liquid

•Purulent—pus-like liquid

Persistent middle-ear effusion is an effusion that persists in the middle ear after an episode of acute otitis media.

Eustachian tube dysfunction is an abnormal function of the ET but does not imply the type of dysfunction. The type of dysfunction must be specified because there are several ways in which the tube functions abnormally; it can be obstructed (too closed) or patulous (too open).

Atelectasis of the tympanic membrane–middle ear is the collapse or retraction of the tympanic membrane. Negative middle-ear pressure may or may not be present. It may be generalized or localized, the latter usually being a retraction pocket.

Retraction pocket is a localized area of atelectasis of the tympanic membrane.

Otorrhea is a discharge from the ear that can emanate from the external auditory canal, middle ear, mastoid, or brain. Discharge can be blood or cerebral spinal fluid. The consistency can be described as

•Serous—thin, watery liquid

•Mucoid—thick, viscid, mucus-like liquid

•Purulent—pus-like liquid

Chronic suppurative otitis media is a stage of ear disease in which there is chronic inflammation of the middle ear and mastoid gas cells and in which a nonintact tympanic membrane (perforation or tympanostomy tube) and otorrhea are present. Chronic otitis media is an incorrect term as chronic suppurative otitis media is preferred.

Cholesteatoma is keratinizing stratified squamous epithelium and an accumulation of desquamating epithelium of keratin within the middle ear or other pneumatized portions of the temporal bone, but it may also occur in other portions the skull. Chronic suppurative otitis media may or may not be present. Cholesteatoma that is associated with middle-ear disease and disorders and related conditions is acquired as opposed to congenital.

Eustachian tube (ET) is an organ consisting of a lumen with its mucosa, cartilage, surrounding soft tissue, peritubal muscles (tensor veli palatini, levator veli palatini, salpingopharyngeus, and tensor tympani), and its superior bony support, the sphenoid sulcus.

Eustachian tube system is contiguous organs, including the nose, palate, nasopharynx, ET, middle ear, and mastoid gas cells (see Figure 1–1).

FIGURE 1–1.

FIGURE 1–1. The ET as part of a system in which the pharynx, palate, and nasal cavities are at its proximal end, and the middle ear and mastoid gas cells are at its distal end.

Auditory tube is synonymous with ET, but the latter is correct.

Pharyngotympanic tube is synonymous with ET. This is a new term proposed by the International Federation of Anatomists to replace ET.

Pressure regulation is the physiologic function of the ET to regulate atmospheric pressure and gas pressure between the nasopharynx and the middle ear.

Ventilation is used synonymously with the physiologic function of pressure regulation, which is the more correct term for this function of the ET.

Protection is the physiologic function of the ET in which unwanted nasopharyngeal secretions and sound pressures are prevented from entering the middle ear by the unique structural and functional aspects of the tubal system.

Clearance is the physiologic function of the ET in which liquid is drained toward the nasopharynx by the mucociliary system of the tubal lumen and the pumping action of the tube during passive closing.

Drainage is used synonymously with clearance, but clearance is the more precise term.

Prograde is the flow of liquid down the ET tube and is synonymous with clearance.

Opening pressure is the pressure at which the ET opens to applied positive pressure.

Forced-opening pressure is used synonymously with opening pressure.

Closing pressure is the pressure that remaining in the middle ear following forced opening.

Residual pressure is the pressure remaining in the middle ear following applied positive or negative pressure and after swallowing.

Forced-response test is a test of ET function in which the middle ear is inflated with a constant airflow rate until the tube is opened.

Passive resistance is the resistance of the ET to airflow when active opening (i.e., dilation) of the tubal lumen is absent.

Active resistance is the resistance of the ET to airflow during active opening (i.e., dilation) of the tubal lumen.

Sonotubometry is a test of the ET opening during swallowing in which a sound generated within the nose and nasopharynx is recorded in the external auditory canal.

Compliance is the quality of yielding to pressure or force without disruption. When related to the ET as an organ, it is the distensibility of the walls of the lumen of the tube. The reciprocal of compliance is stiffness of the tube. We have used the expression floppy to describe increased compliance of the tube (decreased stiffness).

Failure of the opening mechanism is used to describe the pathophysiologic condition in which the ET does not actively open during swallowing activity owing to contraction of the tensor veli palatini muscle.

Functional obstruction is due to failure of the opening mechanism of the ET as opposed to anatomic (mechanical) obstruction.

Anatomic obstruction refers to obstruction of the ET, which can be intraluminal, intramural, or extramural.

Mechanical obstruction is used synonymously with anatomic obstruction.

Intrinsic obstruction is synonymous with intraluminal or intramural anatomic obstruction of the ET.

Extrinsic obstruction is synonymous with extramural anatomic obstruction of the ET.

Patulous Eustachian tube is a tube in which the lumen is too open, usually at rest, when the normal tubal lumen should be collapsed.

Semipatulous Eustachian tube is open at intervals at rest or is almost patulous and has abnormally low opening pressures on tests of function.

Valsalva’s maneuver is a method to force air into the ET and inflate the middle ear by applying positive pressure to the nasopharyngeal end of the tube by a forced expiration with the nose closed (autoinflation). This normally results in positive middle-ear pressure.

Valsalva’s test is a test of patency of the ET that normally should result in positive middle-ear pressure. It is not a test of ET function.

Politzer’s test is similar to Valsalva’s maneuver, but a bag filled with air is used to apply positive pressure to the nose, nasopharynx, and ET.

Politzerization is the method of Politzer to inflate the ET and middle ear either for testing tubal function or for treating middle-ear diseases and disorders.

Toynbee maneuver is swallowing with both nares held closed by the thumb and fore finger.

Toynbee test is used to assess ET function in which the subject swallows with the nose obstructed by pinching off the ala (nostrils) of the nose with the finger and thumb; the pressures in the middle ear are evaluated following the test. Compared with the other classic tests and maneuvers, this is a better, albeit crude, test of function.

Toynbee phenomenon (first introduced by Charles Bluestone) describes the effect on the ET system when there is nasal or postnasal obstruction and swallowing occurs.

Aspiration is the indrawing of fluid (i.e., gas or liquid) from the nasopharynx into the ET and middle ear owing to negative middle-ear pressure (under pressure).

Insufflation is forcing fluid (i.e., gas or liquid) into the ET–middle ear by the application of positive pressure into the nasopharynx; it occurs when the nose or nasopharynx is obstructed during a Valsalva maneuver, Toynbee test or phenomenon, or when blowing the nose.

Reflux is backward flow that, in the context of the pathophysiology of the ET, is abnormal flow of liquid (secretions) from the nasopharynx through the tube into the middle ear.

Retrograde is abnormal backward flow of liquid into the ET–middle ear and is synonymous with reflux.

Reflux otitis media refers to middle-ear disease caused by the reflux of nasopharyngeal secretions through the ET into the middle ear.

Historical Perspective

We stand on the shoulders of those who came before us.

—Sir Joseph Lister (1827–1912),

in acknowledgment of the contributions of

Ignaz Philipp Semmelweis (1818–1865) toward

our understanding of infection

Many historical figures have made invaluable contributions to our understanding of the ET. The most notable are Eustachius, Valsalva, Toynbee, Politzer, Rich, Perlman, and Ingelstedt (see "Encomium"). During the approximately 2400 years since Alcmaeon of Sparta first mentioned the tube, which was later definitively described by Bartolomeus Eustachius as the auditory tube and now bears his name, much has been written on its anatomy, function, and dysfunction. Alcmaeon thought that the tube that connected the nasal airway and the ear enabled goats to breathe through their ears and through their noses. The existence of the tube from the nasopharynx to the middle ear was vaguely known to the ancients (e.g., Aristotle, Celsus, and even Vesalius) during the Renaissance, but Alcmaeon and other contemporaries of Eustachius paid little attention to it.

The Discoverers: Eustachius, Valsalva, Toynbee, and Politzer

Bartolomeus Eustachius

Bartolomeus Eustachius was born somewhere in Italy circa 1510 and died in 1574; there is no agreement on his date or place of birth (Figure 1–2). He was relatively unrecognized in his time because his fine collection of anatomic plates, although completed in 1552, remained unprinted and forgotten in the Vatican library until discovered in the early 1700s and presented by Pope Clement XI to his physician, Giovanni Maria Lancisi, who later published them. Eustachius not only discovered the tube but also described the cochlea, pharyngeal musculature, optic nerves, thoracic duct, adrenal glands, and abducens nerve and gave the first accurate description of the uterus. Many think that he would have been as recognized for his achievements in describing the anatomy of the human body as Andreas Vesalius, who is considered the pioneer in the science of anatomy, had his works had been known during his day. Eustachius was a contemporary of Vesalius but an outspoken critic of some of his discoveries and theories related to the ear.⁸

FIGURE 1–2.

FIGURE 1–2. Bartolomeus Eustachius (1510–1574).

Eustachius published the first detailed description of the auditory (Eustachian) tube in 1562 in his thesis Epistola de auditus organis.⁹ He wrote:

From the cavity of the petrous bone, there in which the auditory passage called concha such a passage toward the nasal cavity is perforated. Others would perhaps think that this passage, about which this dissertation is being written, ends in that place; this is not so, however, for it is augmented by a substance of different nature and is carried on between two muscles of the pharynx and it ends in either cavity of the nose near the internal part of the root of the apophysis of the bone that is shaped like the wings of the bat, and is inserted in a thick revestment of the palate near the root of the uvula. Its substance, where it touches the extremity of the fissure which is common to the temporal and wedge-shaped bones, is cartilaginous, and quite thick; but the substance of the opposite part is not exactly cartilaginous, but is somewhat membranous and becomes thinner gradually; but the internal end of the passage facing the middle of the nasal cavity has a strong cartilage which is very thick and is covered by the mucous membranes of the nares, and is seen at the end of the same meatus as if it were a guardian. It is not round, but is somewhat depressed and makes two angles. It is as large as a writing cane, but is twice as large at the end as at the beginning, which is equally invested by a mucous membrane, which is, however, thinner.⁹

According to Politzer, Eustachius compared the tube to a writing pen and wrote:

It originates at the anterior course of the base of the skull, and takes an anterior course toward the pterygoid process of the sphenoid bone. It consists of two parts: the first solidly connected with the temporal bone, close to the tympanic cavity; the second soft, partly ligamentous, partly cartilaginous, directed toward the nasopharynx. Cross sections of the tube are not perfectly round and the inner part is twice as wide as the outer. Also, the inner part adjacent to the nasopharynx is lined with mucous membrane and seems to possess a sphincter at its end. The mucous lining is continuous with the nasal mucosa.⁸

Eustachius described not only the anatomy of the tube but also the physiologic and therapeutic importance of this discovery; however, it was not until the eighteenth century that his discovery of the structure and function of the tube began being appreciated.

Antonio Maria Valsalva

A century later, Antonio Maria Valsalva (1666–1723) (Figure 1–3) was born in Imola, Italy. He became notable for his description of the aortic sinus of Valsalva, but he is even more famous for his Treatise on the Human Ear. His description of the ET is classic, in which he detailed the cartilaginous, membranous, and osseous parts of the tube (Figures 1–4 and 1–5). He discovered and named the dilator tubae of the tensor veli palatini muscle and made note of the insertion of some fibers of the tensor tympani into the membranous portion of the tube (see Chapter 3). He recorded his thoughts on the acoustic functions of the ET and supported the concept of drainage of purulent material from the middle ear.⁸

His observations on the function of the ET resulted in the Valsalva’s maneuver, which he used in clinical practice and which has persisted to this day. In addition to the treatment of middle-ear effusion and negative pressure, the maneuver is used as an inflation test for the patency of the Eustachian tube (see the Glossary of Terms). Most likely, the maneuver was described much earlier, such as by Arab physicians of the eleventh century and some of the early Italian anatomists.¹⁰

FIGURE 1–3.

FIGURE 1–3. Antonio Maria Valsalva (1666–1723).

FIGURE 1–4.

FIGURE 1–4. Valsalva’s drawings of the external and middle ear and ET with the tensor veli palatini muscle. Reproduced with permission from Canalis RF.⁹

FIGURE 1–5.

FIGURE 1–5. Valsalva’s drawings of the right and left external, middle, and inner ears, including the ET and the tensor veli palatini muscle. Reproduced with permission from Canalis RF.⁹

Joseph Toynbee

During the nineteenth century, otologists continued the work of Eustachius. Joseph Toynbee (1815–1866) was an early English clinician who published a textbook on otologic diseases.¹¹ He was a pioneer in the field of aural pathology and described a method for removing temporal bones from cadavers; he performed over 2000 dissections of the ear. Among his contributions, he studied the muscles that open the ET.¹² He is credited with the eponymous test, Toynbee test (see the Glossary of Terms). His son Arnold Toynbee (1852–1883) was the famous economist and social reformer on behalf of the English working class and is considered to be the originator of the term industrial revolution.

Adam Politzer

The most famous otologist of the nineteenth century was Adam Politzer (1835–1920) (Figure 1–6), who is universally acknowledged as the father of modern otology.¹³ Politzer will be remembered for, among other important contributions, his method of inflating the ET–middle ear for treatment of middle-ear diseases (see the Glossary of Terms).¹⁴ Related to the role of the ET in the pathogenesis of middle-ear effusion, his hydrops ex vacuo theory is still considered to be a valid explanation. He wrote: It is beyond doubt that sometimes in excessive swelling of the tubal mucous membrane and impermeability of the ET there occurs in consequence of the consecutive rarefaction of the air in the tympanum, a transudation of serous fluid (see Chapter 6).¹⁵ His method of politzerization was recommended to restore normal middle-ear pressure (see Chapter 9).

FIGURE 1–6.

FIGURE 1–6. Adam Politzer (1835–1920).

Not only was this Viennese clinician a pioneer in otology, he was also a scholar who could speak many languages. Related to the ET, he translated ancient Egyptian writings that may have been some of the earliest descriptions of the auditory tube. In one such text, the following was stated: Man has two vessel-strands leading to the right ear, filled with Pneuma, ‘breath of life’; two similar strands leading to the left ear conduct the ‘breath of death.’⁸ However, Politzer made no conclusion from these passages that the Egyptians preceded Eustachius in describing the auditory tube. Adam Politzer remains a giant among the clinicians and investigators who have helped us understand the role that the ET plays in middle-ear disease.

The Pioneers: Rich, Perlman, and Ingelstedt

Arnold Rice Rich

During the first half of the twentieth century, Arnold Rice Rich (1893–1968), a professor of pathology at Johns Hopkins Medical School, distinguished himself by performing elegant physiologic experiments in which he assessed the function of the muscles of the ET and surrounding structures, such as the tensor veli palatini, tensor tympani, levator veli palatini, and salpingopharyngeus.¹⁶ He was the first investigator to attribute the sole active dilator function of the ET to contraction of the tensor veli palatini muscle. Although contested for over 60 years, his conclusions concerning the tensor veli palatini muscle have been confirmed in our laboratory¹⁷ and in Japan (see Chapter 3).¹⁸

Henry B. Perlman

In the midportion of the twentieth century, Henry B. Perlman, a professor of otolaryngology at the University of Chicago, made notable contributions to the understanding of the patulous ET, which could be caused by the denervation of the tensor veli palatini muscle.¹⁹,²⁰ (See Encomium: Sven Ingelstedt.)

Other Etiologic and Pathogenic Factors in the Pathogenesis of Otitis Media and Related Conditions

The etiology and pathogenesis of middle-ear disease are multifactorial, which includes factors other than the ET system, such as infection (usually viral and bacterial), immunologic status, environment, and even social and environmental factors (Figure 1–7). Probably the most important factor related to the increased incidence of otitis media in infants and young children is that they not only have an ET tube that is functionally and structurally immature, they also have an immune system that is immature. When they are exposed to upper respiratory tract infections, otitis media is a common complication (see Chapter 6).

The pathogenesis of acute otitis media is likely to occur with the following pattern in most individuals, especially children: the patient has an antecedent event (owing to infection or possibly allergy) that results in congestion of the respiratory mucosa of the upper respiratory tract, including the nasopharynx and the ET. Congestion of the mucosa in the ET results in the obstruction of the narrowest portion of the tube—the isthmus—and negative middle-ear pressure develops. If prolonged, it is followed by the aspiration of pathogens (viruses and bacteria) from the nasopharynx into the middle ear. Because the tube is obstructed, drainage and clearance of the middle-ear effusion, owing to the infection, accumulate in the middle ear. Microbial pathogens proliferate in the secretions, resulting in a suppurative and symptomatic acute otitis media.

FIGURE 1–7.

FIGURE 1–7. The etiology and pathogenesis of otitis media are multifactorial, in which the dysfunction of the ET plays a major role. Reproduced with permission from Bluestone CD and Klein JO.³

The acute onset of otitis media with effusion, although relatively asymptomatic in most children and adults, most likely has a similar sequence of events, but prolonged negative pressure in the middle ear can cause a sterile middle-ear effusion. For children with recurrent episodes of acute otitis media or otitis media with effusion, anatomic or pathophysiologic abnormalities of the ET appear to be an important, if not the most important, factor. A patient with such an underlying abnormality of the tube may be subject to recurrent episodes of otitis media or persistent fluid, or both, in the middle ear.

Abnormal function of the ET appears to be the most important factor in the pathogenesis of middle-ear disease. This hypothesis was first suggested more than 100 years ago by Politzer²¹; however, later studies suggested that otitis media was a disease primarily of the middle-ear mucous membrane and was caused by infection or allergic reactions in this tissue rather than by dysfunction of the ET.²²–²⁵ Related to this hypothesis is the concept that nasopharyngeal infection spreads up the mucosa of the ET, a hypothesis which was contradicted by our research team. Studies conducted at the Children’s Hospital of Pittsburgh, which involved humans as well as animals, have shown that the hydrops ex vacuo theory originally proposed by Adam Politzer over a century ago is most likely the primary pathogenic mechanism.²⁶–³¹

The vast majority of patients with otitis media and related conditions have (or have had in the past) abnormal function of the ET that may cause secondary mucosal disease of the middle ear, such as inflammation.³¹ Infection results from reflux, aspiration, or insufflation of nasopharyngeal viruses and bacteria through the ET and into the middle ear.³² Inflammation owing to infection or allergy may also cause partial intrinsic mechanical obstruction of the tube.²⁷,²⁸,³³–³⁸ A much smaller number of patients may have primary mucosal disease of the middle ear as a result of allergy or, more rarely, an abnormality of the cilia, such as in Kartagener’s syndrome.³⁸–⁴¹

Other factors in the etiology and pathogenesis of middle-ear disease in addition to those cited earlier (immunologic status and inflammation owing to infection or allergy) are as follows:

•Nasal obstruction owing to congenital or acquired diseases and disorders

•Adenoids

•Craniofacial malformations, such as Down syndrome

•Palatal, nasopharyngeal, and base of skull malformations; tumors; trauma; and surgical alterations

•Barotrauma

•Intranasal-nasopharyngeal foreign objects, such as nasogastric or endotracheal tubes

•Diseases and disorders of the tensor veli palatini muscle or its innervation

•Disruption of the continuity of the middle ear and mastoid gas cells (perforation of the tympanic membrane [see Chapters 5 and 6]).

In conclusion, even though factors other than ET dysfunction may cause middle-ear disease, abnormality of the tube is the most common because many of the factors listed previously can adversely affect the ET (see Chapter 2).

REFERENCES

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35.Friedman RA, Doyle WJ, Casselbrant ML, et al. Immunologic-mediated Eustachian tube obstruction: a double-blind crossover study. J Allergy Clin Immunol 1983;71:442–7.

36.Ackerman MN, Friedman RA, Doyle WJ, et al. Antigen-induced Eustachian tube obstruction: an intranasal provocative challenge test. J Allergy Clin Immunol 1984;73:604–9.

37.McBride TP, Doyle WJ, Hayden FG, Gwaltney JM. Alterations of the Eustachian tube, middle ear, and nose in rhinovirus infection. Arch Otolaryngol 1989;115:1054–9.

38.Buchman CA, Doyle WJ, Piltcher O, et al. Nasal and otologic effects of experimental respiratory syncytial infection in adults. Am J Otolaryngol 2002;23:70–5.

39.Miglets A. The experimental production of allergic middle-ear effusions. Laryngoscope 1973;83:1355–84.

40.Doyle WJ, Takahara T, Fireman P. The role of allergy in the pathogenesis of otitis media with effusion. Arch Otolaryngol 1985;111:502–6.

41.Fischer R, McAdams JA, Entis GN, et al. Middle ear ciliary defect in Kartagener’s syndrome. Pediatrics 1978;62:443–5.

CHAPTER 2

EPIDEMIOLOGY

Status of the function of the ET is an important factor in the epidemiology of middle-ear disease.

The chapter includes

•The importance of otitis media as a major public health problem, which, in turn, stresses the need to understand the role played by the ET in the pathogenesis of this disease.

•The risk factors associated with otitis media that have been identified and are related to the ET in the pathogenesis of the disease, such as young age.

•The impact of otitis media on our healthcare budget and at the personal level for patients and their families.

The currently available data on the epidemiology of middle-ear disease is important to review since the Eustachian tube (ET) is involved in the pathogenesis of this disease and its complications and sequelae and therefore affects the prevalence, incidence, and natural history in specific age groups and differing populations. The epidemiology of middle-ear disease (e.g., acute otitis media, persistent middle-ear effusion, and otitis media with effusion), chronic suppurative otitis media, and cholesteatoma is presented in this context.

Middle-Ear Disease

Middle-ear disease is a common cause of outpatient visits in the United States. In 2010, of the 132 million pediatric office visits, otitis media and ET disorders were the most common diagnosis, second only to routine infant or child health checkups.¹,² Infants and young children are most affected by this disease around the world.³–⁵ A recent study from Denmark (2014) reported two-thirds of preschool children had otitis media, despite reduction of known risk factors.⁶,⁷ The high prevalence of otitis media in infants emphasizes the importance in understanding the role that the ET plays in the pathogenesis of the disease in this highly susceptible age group. Studies revealed there was a dramatic increase in otitis media in children from the 1970s to the 1990s when the number of children in day-care facilities was on the rise.⁸–¹³ A study of Finnish children showed similar results, reporting increased rates of recurrent otitis media between 1978–1979 and 1994–1995, which paralleled a rise in the number of children in day-care facilities.³,¹⁰–¹³ A more recent study from Denmark reported in 2014, the rate of tympanostomy tube placement in children increased from 1997 to 2010, so that 3 in 10 children born in 2010 will undergo at least one insertion by their fifth birthday.¹⁴ Because exposure to upper respiratory tract infections increases with the number of contacts that infants and young children encounter¹³ and because their immune systems and the structure and function of their ET are immature, otitis media is now an all-too-frequent event (see Chapter 6, Pathogenesis).

There has been a recent impact of the pneumococcal conjugate vaccine in reducing the incidence of this most common pathogenic otic bacterium. As reported from Israel in 2015, PCV7 and PCV13 implementation was associated with rapid reduction of severe pneumococcal acute otitis media attacks.¹⁵ Another study from Spain by Ochoa-Gondar and colleagues (2015) also found that PCV7/13 had an aggregate effectiveness against vaccine-type pneumococcal infections was 72%.¹⁶ Although less common than in infants and young children, acute otitis media remains a health-care problem in older children, adolescents, and adults.¹⁰,¹⁷

Acute otitis media has been defined as the presence of a middle-ear effusion in which the signs and symptoms of acute infection are present, such as fever, irritability, and otalgia. Otitis media with effusion is characterized by the presence of relatively asymptomatic middle-ear effusion; however, some degree of hearing loss is usually present in both conditions. One study of 877 Boston children who were followed prospectively soon after birth found that 62% of them had acute otitis media by their first birthday and 17% had had more than three episodes. By age 3 years, 83% had had more than one episode and 46% had had more than three episodes.¹⁸ The incidence and prevalence of otitis media with effusion have also been found to be high in children. Of 103 children 2 to 6 years of age who were observed monthly over a 2-year period by otoscopy and tympanometry in a Pittsburgh day-care center, 53% had at least one episode of otitis media with effusion during the first year of the study and 61% during the second year; 30% had recurrent bouts, but 80% cleared within 2 months.¹⁹ In a similar study of 126 Pittsburgh schoolchildren 5 to 12 years of age, the incidence of otitis media with effusion was found to be much lower in children 6 years of age and older (Figure 2–1).²⁰ Maturation of the structure (e.g., length) and function (i.e., active opening mechanism) of the ET and maturation of the immune system by age 6 years may be associated with the observed decrease in otitis media. Otitis media is also commonly diagnosed in adults. Finkelstein and colleagues reported on 167 consecutive adults who had otitis media with effusion in Israel between 1987 and 1990 and attributed most of these middle-ear effusions to the association of sinusitis.²¹

FIGURE 2–1.

FIGURE 2–1. The incidence of otitis media with effusion appears to decrease after the age of 6 years. Group average of the normalized ear score—based on an arbitrary scoring system to summarize the child’s experience with otitis media and high negative middle-ear pressure over a 1-year period of time—in two studies of children in Pittsburgh. Adapted from Casselbrant ML et al.²⁰

Risk Factors Related to the ET

The risk factors that are considered to be associated with otitis media may be related to ET dysfunction. Table 2–1 lists the factors that have been shown to be related to increased risk and others that are thought to be associated. Of the 17 possible risk factors listed, a case can be made for most of them being related, at least to some degree, to dysfunction of the tube (see Chapter 5, Pathophysiology). Recently Casselbrant and colleagues (2015) reported that comorbidities, such atopy, asthma, gastroesophageal reflux disease, and upper respiratory tract infections, and others, collected by history predicted the occurrence of chronic otitis media with effusion.²²

Infants

Infants have a high rate of otitis media because the ET is shorter in infants than in older children and adults,²³,²⁴ they have difficulty in the active opening of the tube by swallowing,²⁵–²⁷ and they have immature immunity. Some infants who are otitis prone may have subtle evidence of a defect in immunity.²⁸,²⁹ Because the tube is short, aspiration, insufflation, or reflux nasopharyngeal secretions into the middle ear could be enhanced. Also, preterm infants have otitis media, and the lower the gestational age the higher the frequency, which is statistically significant in a report from 2014.³⁰ Failure of the opening mechanism may lead to middle-ear underpressures with subsequent aspiration of organisms from the nasopharynx into the middle ear. As noted clinically during otoscopy and tympanometry, infants insufflate their middle ears during crying (related to the short floppy tube), which is most likely a physiologic compensatory mechanism to maintain middle-ear pressure. Even though proof is lacking, nasopharyngeal secretions are probably also insufflated into the middle ear during crying, especially when an upper respiratory tract infection occurs, which then results in otitis media.

TABLE 2–1.Risk Factors for Otitis Media Related to ET Dysfunction

TABLE 2–1

An early age at onset has been associated with frequently recurrent disease in infants. In a study from Boston, Teele and colleagues reported that the peak incidence for first episodes of acute otitis media occurred at 6 months of age.¹⁸ Age at the first episode of acute otitis media was significantly and inversely associated with the risk of one or more or two or more episodes of acute otitis media in the 12 months after initial diagnosis. In a study from Norway, an association with allergy in the family appeared to be a predisposing factor for early onset.³¹ Universal infant hearing screening in The Netherlands identified risk factors using a parental questionnaire for selecting infants diagnosed or suspected of otitis media.³²

Genetic Predisposition and Ethnic Groups

Now that data are available from two studies in twins that have demonstrated a genetic predisposition for the occurrence of otitis media, the hereditary defect could be related to structural or functional abnormalities of the ET (or immunity or both) in possibly all populations.³¹,³³ Many patients are encountered in whom siblings, parents, and grandparents are affected. In a very comprehensive study, Casselbrant and colleagues recruited 168 like-sex twins and seven sets of triplets at birth in Pittsburgh and, for their first 2 years of life, followed them prospectively every month and whenever an upper respiratory tract infection intervened.³³ The investigators, who were validated for the presence or absence of middle-ear effusion using otoscopy, clinically evaluated the subjects at each visit. Home visits were made when the children could not be brought to the clinical site (Children’s Hospital of Pittsburgh Otitis Media Research Center). Of the 143 sets of twins and triplets in whom the zygosity was known, 67 were dizygotic and 76 were monozygotic. Figure 2–2 shows the rate of otitis media in the dizygotic and monozygotic twins. An estimate of heritability for the average proportion of time with middle-ear effusion by 24 months of age was 75%. In a follow-up of these children, Casselbrant and colleagues reported that from ages 2 to 5 years, the cumulative effect remained significant for the entire first 5 years of life.³⁴ The investigators concluded that a genetically determined predisposition for development of otitis media is likely.

In the other study, Kvaerner and colleagues gathered data from 2750 pairs of twins born in Norway between 1967 and 1974 by obtaining questionnaires related to lifetime prevalence of self-reported recurrent otitis media.³¹ They evaluated the rates in monozygotic and dizygotic twin pairs and the relative contribution of genes and environment to the variability in the predisposition to develop otitis media. Kvaerner and colleagues estimated additive genetic and dominance factors for otitis media at 74% in women, with the remaining 26% explained by environmental factors. For men, 45% was attributed to genetic factors and the remaining 55% about equally to either common familial or individual environmental factors.

FIGURE 2–2.

FIGURE 2–2. Rate of otitis media in dizygotic and monozygotic twins in the Pittsburgh prospective study of the influence of genetic factors. Adapted from Casselbrant ML et al.³³

Even though the study by Kvaerner and colleagues was neither prospective nor clinically assessed like the one by Casselbrant and colleagues,³⁴ together these two reports provide convincing data to support our clinical impression that there is a strong influence of heredity in the susceptibility for otitis media. In a more recent longitudinal study of 1373 same-sex English twin pairs, Rovers and colleagues further confirmed the genetic predisposition for otitis media.³⁵

In another, possibly related study, Todd and Todd reported on their evaluation of 115 nonsyndromic patients, aged 5 to 20 years, who had cardiac anomalies and reported a twofold higher prevalence of middle-ear pathology in individuals who had conotruncal cardiac malformations (transposition of the great vessels, tetralogy of Fallot, aortic stenosis) when compared with those patients with nonconotruncal anomalies (atrial septal defect, tricuspid atresia, atrioventricular canal).³⁶ The investigators concluded that individuals who have conotruncal cardiac anomalies are otitis prone, and this may be related to a neural crest–determined branchial field defect, which may be related to a deletion in chromosome 22q11. Even though the methodology of this study has been criticized, the findings, if confirmed by a study that prospectively evaluates infants who have cardiac anomalies for the occurrence of otitis media, may be important in localizing a genetic defect related to ET dysfunction.³⁷

High-Risk Populations

Certain ethnic groups, such as Native Americans,³⁸ North American Inuits,³⁹ and Australian Aborigines,⁴⁰,⁴¹ have an extraordinarily high rate of middle-ear disease that progresses to chronic suppurative otitis media. Despite the lack of proof of a genetic predisposition in these high-risk populations, it is likely that heredity is an important factor in the pathogenesis, and at least one study found differences in the bony anatomy of the ET between certain racial populations.⁴² Another study found abnormal ET function in members of a Native American tribe (see High-Risk Populations in the Cholesteatoma section).⁴³

FIGURE 2–3.

FIGURE 2–3. Cumulative incidence of the first episode of acute otitis media and middle-ear effusion (all episodes of acute otitis media and otitis media with effusion) in black and white children during their first 2 years of life. Adapted from Casselbrant ML et al.⁴⁶

Black Versus White Children in the United States

In the past, it has been assumed that black children in the United States have a lower incidence of otitis media than white children. This assumption was based on several studies, such as the prevalence study by Kessner and colleagues, in which they reported evidence of middle-ear pathology in 35.6% of 112 white children and 19% of black children in Washington, DC.⁴⁴ Another study from Cleveland by Marchant and colleagues reported that the incidence of otitis media was 62% in young black infants compared with 86% in white infants (p = .017).⁴⁵ The report from the US Division of Health Care Statistics found that the number of visits for otitis media between 1975 and 1990 made by black children was lower than for white children⁶; however, two reports in two different populations from Pittsburgh contradict these earlier findings. In the study reported by Casselbrant and colleagues, black infants have the same incidence of otitis media as white infants (Figure 2–3).⁴⁶ In the other study from Pittsburgh, Paradise and colleagues prospectively followed 2253 infants from soon after birth until age 2 years and reported that one or more episodes of middle-ear effusion occurred in 48% by age 2 months and 91% by 24 months of age and that black infants were affected to the same or a greater degree as white infants, especially among infants of a lower socioeconomic status (Table 2–2).³ A recent study by Fleming-Dutra and colleagues (2014) in the United States of race and otitis media reported the percentage of all visits resulting in a diagnosis of otitis media was 30% lower in black children compared with those who were nonblack.⁴⁷

TABLE 2–2.Selected Measures of the Occurrence and Treatment of Otitis Media During the First 2 Years of Life in 2,253 Pittsburgh Infants

Adapted from Paradise JL et al.³ MEE = middle-ear effusion.

Craniofacial Abnormalities

Infants and children with craniofacial malformations, such as those with cleft palate and Down syndrome, have a high rate of otitis media that is attributed to abnormalities of ET function.⁴⁸–⁵¹

Risk Factors for Inflammation

Risk factors for inflammation most likely adversely affect ET function. Infection secondary to the common cold can result in tubal obstruction, which has an increased frequency when infants and young children are in child day care, have older siblings, or are in the lower socioeconomic strata.³ The winter and spring seasons are associated with a higher rate of viral respiratory tract infections than the fall and winter months, which increases the risk of high negative middle-ear pressures and otitis media (Figure 2–4).¹⁹,⁵²,⁵³ Early onset of otitis media (in the first few months of life) as a risk factor for recurrent and chronic disease⁴⁹ could be related to a genetic predisposition or environmental factors, such as increased exposure to upper respiratory infections, or both. Also, inflammation owing to upper respiratory allergy has been shown to cause tubal obstruction.⁵⁴–⁵⁶

FIGURE 2–4

FIGURE 2–4. Monthly distribution of children according to the middle-ear status of their worst ear. Adapted from Casselbrant ML et al.¹⁹

Passive Smoking and Ambient Air Pollution

Even though conclusive data are lacking, exposure to smoke in the household has been shown to be a risk factor, which, like smoke from wood-burning stoves, could interfere with normal ET function (clearance and immune defense). Smoke exposure can result in goblet cell hyperplasia and mucus hypersecretion in the