Читать книгу Pediatric Ear Diseases - Y. Naito - Страница 9

The foundation for temporal bone imaging diagnosis lies in obtaining a thorough understanding of the ear’s normal anatomical structures and their three-dimensional relationship. Through repeated comparison and identification of the details of normal structures and the anatomical terms that describe them, one gradually forms a mental image of the temporal bone’s overall three-dimensional orientation. When one concurrently views clinical case images, one’s eyes are drawn naturally to those forms that differ from the norm, which can then be compared to various known disease findings to arrive at an accurate diagnosis. This process also applies to pediatric cases but, with the exception of minor ailments such as otitis media, encounters with infant diseases in everyday clinical practice are infrequent, and examples of imaging diagnosis even rarer. Consequently, pediatric images are usually interpreted with normal adult anatomy in mind. However, the temporal bone of infants in particular differs from that of an adult’s with respect to the sizes and relative ratios of each component, so caution is required in reading and interpreting findings.

This chapter displays a complete series of serial cross-section and descriptive images, without omission, of temporal bone CT axial sections and coronal sections from both infants and older children. By examining the images from infants and older children, first separately and then in comparison, we will be able to develop a mental image of the anatomy of the temporal bone and its postnatal development.

Infant

Older Child

Infant

Figure 1 shows the basic anatomy of the ear. All the anatomical components shown in this figure exist from birth; however their sizes and locations change with age. The inner ear and ossicles in an infant’s temporal bone are the same size as an adult, but the external auditory canal, internal auditory canal, and mastoid air cells are still small and grow with age. Roughly speaking, the cochlea, vestibule, semicircular canals, and tympanic cavity are at the center and change little, while the periphery expands anteroposteriorly, laterally, and vertically. Horizontal expansion, both laterally and front to back, can be observed through axial sections and vertical expansion through coronal sections. Of the various structures of the temporal bone, normal development of the mastoid air cells is suppressed by otitis media. Consequently when viewing pediatric temporal bone images, along with age, one must also take previous middle ear diseases into consideration.

In order to avoid surgical complications during ear surgery, it is necessary to have an accurate grasp of the positions of major anatomical structures within the temporal bone. However, an infant’s temporal bone is smaller and more delicate than an adult’s and its anatomical orientation during surgery is different. When performing temporal bone surgery under a microscope, even an error of 1 mm may result in injury to the facial nerve, the semicircular canals, or the stapes. Common preoperative checkpoints for most otological surgical procedures include: 1) degree of mastoid air cell development and the height of the base of the middle cranial fossa lateral to the epitympanum (attic); 2) lateromedial width and air cell development of the facial recess region; 3) distance between the sigmoid sinus and the posterior wall of the external auditory canal; 4) pneumatization (=air cell development) in the direction of the mastoid process; and 5) thickness of the cranial wall in the temporoparietal region. If any of these are narrower or smaller than normal, one must plan ahead to determine how to overcome the difficulties presented to secure sufficient surgical field visibility and achieve one’s objective.

The images shown are of a 4-month-old female infant who underwent CT examination for bilateral hearing loss. They are presented here as normal temporal bone CT images as no clear abnormal findings were discovered in them. The coronal section images were reconstructed from data taken in the axial section images, with no direct images taken from a supine hanging-head position. For display purposes, coronal section images have been magnified to approx. 1.7 times the axial section images. Also, the images are arranged from bottom to top (inferior to superior) for the axial sections and from front to back (anterior to posterior) for the coronal sections. Images of the same cross sections are arranged side by side, with the right image annotated to indicate each anatomical structure. (Scale shown in images indicates 1 cm)

The base line for the CT images was set based on the plane that includes bilateral OM lines, the line that passes through the outer canthus of the eye and the center of the external auditory canal.

Fig. 1. The anatomy of the ear. 2

Female, 4 months old: left axial section

1 OM line -2.91 mm

2 OM line -2.31 mm

3 OM line -1.71 mm

4 OM line -1.12 mm

5 OM line -0.52 mm

6 OM line +0.08 mm

7 OM line +0.68 mm

8 OM line +1.28 mm

9 OM line +1.88 mm

10 OM line +2.48 mm

11 OM line +3.08 mm

12 OM line +3.68 mm

13 OM line +4.28 mm

14 OM line +4.88 mm

b=basal turn of cochlea; p=promontory; mm=manubrium of malleus; su=subiculum of promontory; fr=facial recess

15 OM line +5.48 mm

b=basal turn of cochlea; p=promontory;mm=manubrium of malleus; le=lenticular process of incus;h=head of stapes; su=subiculum of promontory;ts=tympanic sinus; fr=facial recess

16 OM line +6.08 mm

b=basal turn of cochlea;o=osseous spiral lamina;p=promontory;n=neck of malleus;le=lenticular process of incus; =incudostapedial joint;h=head of stapes;ts=tympanic sinus;fr=facial recess

17 OM line +6.68 mm

18 OM line +7.28 mm

a=apical turn of cochlea; m=middle turn of cochlea; b=basal turn of cochlea; v=vestibule; s=singlar canal; h=head of malleus; ib=body of incus; il=long process of incus; is=short process of incus; ac=anterior crus of stapes; pc=posterior crus of stapes; ts=tympanic sinus

19 OM line +7.88 mm

a=apical turn of cochlea; m=middle turn of cochlea; b=basal turn of cochlea; v=vestibule; s=singlar canal; h=head of malleus; =malleoincudal joint; ib=body of incus; il=long process of incus; is=short process of incus; ac=anterior crus of stapes; pc=posterior crus of stapes; ts=tympanic sinus

20 OM line +8.48 mm

a=apical turn of cochlea; m=middle turn of cochlea; b=basal turn of cochlea; *=modiolus; f=footplate of stapes; v=vestibule; s=singlar canal; h=head of malleus; =malleoincudal joint; ib=body of incus

21 OM line +9.08 mm

a=apical turn of cochlea; m=middle turn of cochlea; b=basal turn of cochlea; *=modiolus; v=vestibule; sr=spherical recess; c=anterior attic bony plate (cog); h=head of malleus; =malleoincudal joint; ib=body of incus

22 OM line +9.68 mm

b=basal turn of cochlea; *=modiolus; v=vestibule; c=anterior attic bony plate (cog); h=head of malleus; =malleoincudal joint; ib=body of incus; ad=aditus ad antrum

23 OM line +10.28 mm

24 OM line +10.88 mm

b=basal turn of cochlea; =Bill’s bar; sv=superior vestibular nerve; v=vestibule; ad=aditus ad antrum

25 OM line +11.48 mm

26 OM line +12.08 mm

27 OM line +12.68 mm

28 OM line +13.28 mm

29 OM line +13.88 mm

30 OM line +14.48 mm

31 OM line +15.07 mm

32 OM line +15.67 mm

33 OM line +16.27 mm

34 OM line +16.87 mm

35 OM line +17.47 mm

36 OM line +18.07 mm

Female, 4 months old: left coronal section

1 +4.00 mm from center of external auditory canal

2 +3.35 mm from center of external auditory canal

3 +2.70 mm from center of external auditory canal

4 +2.04 mm from center of external auditory canal

5 +1.39 mm from center of external auditory canal

b=basal turn of cochlea; m=middle turn of cochlea; a=apical turn of cochlea; h=head of malleus

6 +0.74 mm from center of external auditory canal

7 +0.09 mm from center of external auditory canal

ft=tympanic segment of facial nerve; b=basal turn of cochlea; m=middle turn of cochlea; ib=body of incus; h=head of malleus; n=neck of malleus

8 -0.56 mm from center of external auditory canal

ft=tympanic segment of facial nerve; b=basal turn of cochlea; m=middle turn of cochlea; p=promontory; =transverse crest; ib=body of incus; mm=manubrium of malleus

9 -1.22 mm from center of external auditory canal

10 -1.87 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; b=basal turn of cochlea; p=promontory; =transverse crest; is=short process of incus; il=long process of incus; mm=manubrium of malleus; ac=anterior crus of stapes; f=footplate of stapes

11 -2.52 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; b=basal turn of cochlea; p=promontory; is=short process of incus; le=lenticular process of incus; =incudostapedial joint; h=head of stapes; f =footplate of stapes; mm=manubrium of malleus

12 -3.17 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; b=basal turn of cochlea; p=promontory; is=short process of incus; le=lenticular process of incus; h=head of stapes; pc=posterior crus of stapes; f =footplate of stapes

13 -3.82 mm from center of external auditory canal

14 -4.47 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; bh=basal turn of cochlea (hook portion); s=singlar canal; ad=aditus ad antrum; fr=facial recess; ts=tympanic sinus

15 -5.13 mm from center of external auditory canal

v=vestibule; ad=aditus ad antrum; fr=facial recess

16 -5.78 mm from center of external auditory canal

v=vestibule; ts=tympanic sinus; fr=facial recess

17 -6.43 mm from center of external auditory canal ts=tympanic sinus

18 -7.08 mm from center of external auditory canal ts=tympanic sinus

19 -7.73 mm from center of external auditory canal ts=tympanic sinus

20 -8.38 mm from center of external auditory canal ts=tympanic sinus

21 -9.04 mm from center of external auditory canal

22 -9.69 mm from center of external auditory canal

23 -10.34 mm from center of external auditory canal

24 -10.99 mm from center of external auditory canal

Older Child

Postnatal growth of the temporal bone is extremely rapid in the first three years, then continues at a gradually decreasing rate until at puberty it has just about reached adult size. The temporal bone of a child at puberty has almost completed growing and is basically no different from that of an adult.

Compared to the infant images, the temporal bone of the older child is larger overall and displays dramatic development and expansion of the air cells. The bone forming the external auditory canal has also developed and elongated. The internal auditory canal is also longer, but its internal diameter does not appear to have changed significantly. There is almost no change to the inner ear or tympanic cavity. The mastoid segment of the facial nerve is longer due to the growth of the mastoid process.

While infant temporal bone imaging is often conducted to scrutinize congenital abnormalities, in older children as a rule the diagnosis of congenital disease has already been established and imaging is used to test for acquired disease. In this volume as well, the majority of cases concerning congenital disease were diagnosed before five years old, whereas over half the cases of inflammatory disease are of children ten years or older.

In other words, in pediatric ear imaging diagnosis, inflammatory and infectious diseases or injuries become more common the older the child, and insufficient development of mastoid air cells, granulation and fluid retention due to inflammation, osteolytic lesions, and so on are subject to observation. By comparing the normal images shown here with the various cases cited later on in the chapter on inflammatory diseases in children, one may attain an understanding of how these diseases influence temporal bone development and which areas are vulnerable to harm.

The images shown are of a male, sixteen years, ten months old, who underwent CT examination for functional hearing loss. They are presented here as normal temporal bone CT images as no clear abnormal findings were discovered in them. The coronal section images were reconstructed from data taken in the axial section images. For display purposes, coronal section images have been magnified to approx. 1.7 times the axial section images. Also, the images are arranged from bottom to top (inferior to superior) for the axial sections and from front to back (anterior to posterior) for the coronal sections. Images of the same cross sections are arranged side by side, with the right image annotated to indicate each anatomical structure. (Scale shown in images indicates 1 cm)

Male, 16 years, 10 months old: left axial section

1 OM line +8.49 mm

2 OM line +9.12 mm

3 OM line +9.75 mm

4 OM line +10.38 mm

5 OM line +11.00 mm

6 OM line +11.62 mm

7 OM line +12.25 mm

8 OM line +12.88 mm

9 OM line +13.50 mm

10 OM line +14.13 mm

11 OM line +14.75 mm

12 OM line +15.38 mm

13 OM line +16.00 mm

14 OM line +16.62 mm p=promontory; ts=tympanic sinus

15 OM line +17.25 mm

16 OM line +17.88 mm

b=basal turn of cochlea; p=promontory; mm=manubrium of malleus; ts=tympanic sinus; fr=facial recess

17 OM line +18.50 mm

b=basal turn of cochlea ; p=promontory; mm=manubrium of malleus; le=lenticular process of incus; su=subiculum of promontory; ts=tympanic sinus; fr=facial recess

18 OM line +19.12 mm

b=basal turn of cochlea; o=osseous spiral lamina; p=promontory; n=neck of malleus; le=lenticular process of incus; =incudostapedial joint; h=head of stapes; su=subiculum of promontory; ts=tympanic sinus; fr=facial recess

19 OM line +19.75 mm

20 OM line +20.38 mm

21 OM line +21.00 mm

a=apical turn of cochlea; m=middle turn of cochlea; b=basal turn of cochlea; v=vestibule; h=head of malleus; =malleoincudal joint; ib=body of incus; il=long process of incus; is=short process of incus; ac=anterior crus of stapes; pc=posterior crus of stapes; p=posterior ampulla

22 OM line +21.63 mm

a=apical turn of cochlea; m=middle turn of cochlea; b=basal turn of cochlea; *=modiolus; v=vestibule; f=footplate of stapes; c=anterior attic bony plate (cog); h=head of malleus; =malleoincudal joint; ib=body of incus; is=short process of incus; s=singlar canal; p=posterior ampulla

23 OM line +22.25 mm

m=middle turn of cochlea; b=basal turn of cochlea; *=modiolus; v=vestibule; sr=spherical recess; c=anterior attic bony plate (cog); h=head of malleus; =malleoincudal joint; ib=body of incus

24 OM line +22.88 mm

m=middle turn of cochlea; b=basal turn of cochlea ; v=vestibule; sr=spherical recess; c=anterior attic bony plate (cog); h=head of malleus; =malleoincudal joint; ib=body of incus; ad=aditus ad antrum

25 OM line +23.50 mm

b=basal turn of cochlea; sv=superior vestibular nerve; v=vestibule; ad=aditus ad antrum

26 OM line +24.12 mm

b=basal turn of cochlea; =Bill’s bar; sv=superior vestibular nerve; v=vestibule; ad=aditus ad antrum

27 OM line +24.75 mm

28 OM line +25.38 mm

29 OM line +26.00 mm

30 OM line +26.62 mm

31 OM line +27.25 mm

32 OM line +27.88 mm

33 OM line +28.50 mm

34 OM line +29.13 mm

35 OM line +29.75 mm

36 OM line +30.38 mm

Male, 16 years, 10 months old: left coronal section

1 +10.39 mm from center of external auditory canal

2 +9.74 mm from center of external auditory canal

3 +9.09 mm from center of external auditory canal

4 +8.44 mm from center of external auditory canal

5 +7.79 mm from center of external auditory canal

6 +7.14 mm from center of external auditory canal

b=basal turn of cochlea; m=middle turn of cochlea; a=apical turn of cochlea; h=head of malleus

7 +6.48 mm from center of external auditory canal

b=basal turn of cochlea; m=middle turn of cochlea; a=apical turn of cochlea; p=promontory; =transverse crest; h=head of malleus

8 +5.83 mm from center of external auditory canal

b=basal turn of cochlea; m=middle turn of cochlea; p=promontory; =transverse crest; h=head of malleus; n=neck of malleus

9 +5.18 mm from center of external auditory canal

ft=tympanic segment of facial nerve; b=basal turn of cochlea; m=middle turn of cochlea; p=promontory; =transverse crest; ib=body of incus; h=head of malleus; n=neck of malleus

10 +4.53 mm from center of external auditory canal

11 +3.88 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; b=basal turn of cochlea; p=promontory; is=short process of incus; il=long process of incus; mm=manubrium of malleus; ac=anterior crus of stapes; f=footplate of stapes

12 +3.23 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; b=basal turn of cochlea; p=promontory; is=short process of incus; le=lenticular process of incus; h=head of stapes; f=footplate of stapes; mm=manubrium of malleus

13 +2.58 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; b=basal turn of cochlea; p=promontory; s=singlar canal; is=short process of incus; le=lenticular process of incus; =incudostapedial joint; h=head of stapes; f=footplate of stapes; mm=manubrium of malleus

14 +1.92 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; b=basal turn of cochlea; p=promontory; s=singlar canal; ad=aditus ad antrum; h=head of stapes; pc=posterior crus of stapes; fr=facial recess

15 +1.27 mm from center of external auditory canal

ft=tympanic segment of facial nerve; v=vestibule; bh=basal turn of cochlea (hook portion); s=singlar canal; ad=aditus ad antrum; fr=facial recess; ts=tympanic sinus

16 +0.62 mm from center of external auditory canal

17 -0.03 mm from center of external auditory canal

ft=tympanic segment of facial nerve; p=posterior ampulla; fr=facial recess; ts=tympanic sinus

18 -0.68 mm from center of external auditory canal

p=posterior ampulla; ts=tympanic sinus

19 -1.34 mm from center of external auditory canal

ts=tympanic sinus

20 -1.99 mm from center of external auditory canal

21 -2.64 mm from center of external auditory canal

22 -3.29 mm from center of external auditory canal

23 -3.94 mm from center of external auditory canal

24 -4.59 mm from center of external auditory canal