Age-Related Morphologic Changes in the Human Tympanic Membrane A
Light and Electron Microscopic Study
Carlos B. Ruah, MD; Patricia A. Schachern; Daniel Zelterman, PhD; Michael M. Paparella, MD; Tae H. Yoon, MD
\s=b\ To our knowledge, the normal changes that occur in the tympanic membrane after birth have not been described, despite several reports that their otoscopic appearance in healthy, full-term infants is different from that in adults. To provide such a description, the tympanic membranes of 54 temporal bones that had no pathologic evidence of otologic diseases, from patients aged 33 weeks' gestation to 91 years, were examined with light or electron microscopy. The changes encountered in thickness, cellularity, vascularity, collagen, and elastin indicated that the eardrum continues to change beyond the first year of life and into old age. (Arch Otolaryngol Head Neck Surg. 1991;
117:627-634)
Accepted for publication December 3,1990. From the University of Minnesota Otitis Media Research Center, Department of Otolaryngology, University of Minnesota Medical School and the Minnesota Ear, Head, and Neck Clinic, P.A., Minneapolis (Drs Ruah, Paparella, and Yoon and Ms Schachern); and the Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis (Dr Zelterman). Reprint requests to Room 122 Research East, 2630 University Avenue SE, Minneapolis, MN 55414 (Ms Schachern).
Althoughdisease diagnosis initially
of middleon is based the appearance and mobility of the tympanic membrane, findings in the eardrum may not always reflect patho¬ logic conditions in the middle-ear cleft. In silent otitis media, extensive inflam¬ matory disease may exist beneath an intact tympanic membrane that shows minimal otoscopie signs.1 Conversely, changes in color, reflexive reaction to light, translucency, and mobility of the eardrum have been found in healthy, full-term infants from birth to beyond 4 months of age.2"4 Due to the observa¬ tion that the middle ear continues to change after birth,5 several causes have been suggested for the otoscopie changes seen in these infants. These changes include persistence of mesenchymal tissue in the middle-ear cleft, presence of amniotic fluid, and changes in the tympanic membrane. Mesenchymal tissue usually is found in the normal middle ear in consider¬ able amounts but nearly disappears by 1 year of age.6 It may persist beyond 2 years of age when any form of persis¬ tent otitis media is present,1 and it may the
ear
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remain beyond 3 years in the presence of congenital anomalies of the ear.7 Amniotic fluid in the middle ear may trigger a transient foreign-body reac¬ tion that can result in otitis media or may disappear spontaneously as early as 2 days of age or may persist beyond 10 weeks of age.2A8
There have been several reports on the gross anatomic and light micro¬ scopic structure of the normal tympan¬ ic membrane as well as on its em¬ bryogenesis.5,9"11 Detailed electron mi¬ croscopic descriptions of the human tympanic membrane have given a bet¬ ter understanding of its function, heal¬ ing processes, and response to the pathogenesis and pathology of otitis media.12"14 The changes that normally occur in the tympanic membrane after birth remain unclear.2"5 For this rea¬ son, we monitored the normal develop¬ ment of the eardrum to 91 years of age. MATERIALS AND METHODS Light Microscopic Examination
Forty-six normal human temporal bones from subjects ranging in age from 2 days to 91
years were harvested at autopsy, fixed in 10% buffered formaldehyde solution, decalci¬
fied in trichloroacetic acid, dehydrated in a graded series of ethanol, and embedded in celloidin. Sections were cut from superiorly to inferiorly at a thickness of 20 µ , and every 10th section was retained for staining with hematoxylin-eosin. Adjacent sections were stained with Gomori's trichrome strain for collagen and with Verhoeffs stain for elastin.
Morphometric Examination The thickness of the tympanic membrane determined at six different levels: (1) in the midlevel of Shrapnell's membrane within the lateral malleolar ligament; (2) in the posterosuperior quadrant below the level of the lateral process of the malleus where the pars tensa acquires its anatomic characteristics (presence of a fibrous layer and attachment to a groove of bone); (3) in the anterosuperior quadrant adjacent to level 2; (4) in the posteroinferior quadrant just below the level of the umbo; (5) in the anteroinferior quadrant ad¬ jacent to level 4; and (6) at the level of the umbo, defined as the last section retained that still includes the manubrium. Measure¬ ments of the pars flaccida were made at a magnification of 40 and of the pars tensa at 100 with a calibrated eyepiece-micro¬ meter. Due to irregularity in the thickness of the tympanic membrane, on average three measurements of thickness were obtained: at one third, at one half, and at two thirds of its total length at each level. These measure¬ ments were then plotted against age, and, where a statistically significant relationship existed (P
Light and Electron Microscopic Study
Carlos B. Ruah, MD; Patricia A. Schachern; Daniel Zelterman, PhD; Michael M. Paparella, MD; Tae H. Yoon, MD
\s=b\ To our knowledge, the normal changes that occur in the tympanic membrane after birth have not been described, despite several reports that their otoscopic appearance in healthy, full-term infants is different from that in adults. To provide such a description, the tympanic membranes of 54 temporal bones that had no pathologic evidence of otologic diseases, from patients aged 33 weeks' gestation to 91 years, were examined with light or electron microscopy. The changes encountered in thickness, cellularity, vascularity, collagen, and elastin indicated that the eardrum continues to change beyond the first year of life and into old age. (Arch Otolaryngol Head Neck Surg. 1991;
117:627-634)
Accepted for publication December 3,1990. From the University of Minnesota Otitis Media Research Center, Department of Otolaryngology, University of Minnesota Medical School and the Minnesota Ear, Head, and Neck Clinic, P.A., Minneapolis (Drs Ruah, Paparella, and Yoon and Ms Schachern); and the Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis (Dr Zelterman). Reprint requests to Room 122 Research East, 2630 University Avenue SE, Minneapolis, MN 55414 (Ms Schachern).
Althoughdisease diagnosis initially
of middleon is based the appearance and mobility of the tympanic membrane, findings in the eardrum may not always reflect patho¬ logic conditions in the middle-ear cleft. In silent otitis media, extensive inflam¬ matory disease may exist beneath an intact tympanic membrane that shows minimal otoscopie signs.1 Conversely, changes in color, reflexive reaction to light, translucency, and mobility of the eardrum have been found in healthy, full-term infants from birth to beyond 4 months of age.2"4 Due to the observa¬ tion that the middle ear continues to change after birth,5 several causes have been suggested for the otoscopie changes seen in these infants. These changes include persistence of mesenchymal tissue in the middle-ear cleft, presence of amniotic fluid, and changes in the tympanic membrane. Mesenchymal tissue usually is found in the normal middle ear in consider¬ able amounts but nearly disappears by 1 year of age.6 It may persist beyond 2 years of age when any form of persis¬ tent otitis media is present,1 and it may the
ear
Downloaded From: http://archotol.jamanetwork.com/ by a Universite Laval User on 09/16/2015
remain beyond 3 years in the presence of congenital anomalies of the ear.7 Amniotic fluid in the middle ear may trigger a transient foreign-body reac¬ tion that can result in otitis media or may disappear spontaneously as early as 2 days of age or may persist beyond 10 weeks of age.2A8
There have been several reports on the gross anatomic and light micro¬ scopic structure of the normal tympan¬ ic membrane as well as on its em¬ bryogenesis.5,9"11 Detailed electron mi¬ croscopic descriptions of the human tympanic membrane have given a bet¬ ter understanding of its function, heal¬ ing processes, and response to the pathogenesis and pathology of otitis media.12"14 The changes that normally occur in the tympanic membrane after birth remain unclear.2"5 For this rea¬ son, we monitored the normal develop¬ ment of the eardrum to 91 years of age. MATERIALS AND METHODS Light Microscopic Examination
Forty-six normal human temporal bones from subjects ranging in age from 2 days to 91
years were harvested at autopsy, fixed in 10% buffered formaldehyde solution, decalci¬
fied in trichloroacetic acid, dehydrated in a graded series of ethanol, and embedded in celloidin. Sections were cut from superiorly to inferiorly at a thickness of 20 µ , and every 10th section was retained for staining with hematoxylin-eosin. Adjacent sections were stained with Gomori's trichrome strain for collagen and with Verhoeffs stain for elastin.
Morphometric Examination The thickness of the tympanic membrane determined at six different levels: (1) in the midlevel of Shrapnell's membrane within the lateral malleolar ligament; (2) in the posterosuperior quadrant below the level of the lateral process of the malleus where the pars tensa acquires its anatomic characteristics (presence of a fibrous layer and attachment to a groove of bone); (3) in the anterosuperior quadrant adjacent to level 2; (4) in the posteroinferior quadrant just below the level of the umbo; (5) in the anteroinferior quadrant ad¬ jacent to level 4; and (6) at the level of the umbo, defined as the last section retained that still includes the manubrium. Measure¬ ments of the pars flaccida were made at a magnification of 40 and of the pars tensa at 100 with a calibrated eyepiece-micro¬ meter. Due to irregularity in the thickness of the tympanic membrane, on average three measurements of thickness were obtained: at one third, at one half, and at two thirds of its total length at each level. These measure¬ ments were then plotted against age, and, where a statistically significant relationship existed (P
