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Home , Anotia, Antihelix, Antitragus, Auricle (anatomy), Cryptotia, Helix (ear)

97 Aman Deep1, Martin M. Mortazavi2 and Nimer Adeeb1 1Children’s of Alabama, Birmingham, Alabama, USA 2University of Washington School of Medicine, Seattle, Washington, USA

Anatomical observations are very important for determining grades of dysplasia. Grade I anomalies entail minor variations the shape, position, and variations of the ear. An anatomical that do not warrant the use of skin and cartilage to repair the variation can be an isolated anomaly or part of a syndrome and structural defect. The category includes , anomalies of its effect can range from no defect to complex loss. The the pinna (protruding ear, , Darwin’s tubercle, satyr ear has a very complex structure and careful observations can ear, Stahl ear, shell ear, Mozart ear, and lop ear), absent helical help in the diagnosis of anomalies and syndromes. The purpose cleft, and anomalies of the lobule and . Grade II dyspla- of this chapter is to describe anatomical variations of the ear. sia or second‐degree includes anomalies where some normal ear features are detectable and reconstruction requires the use of additional skin and cartilage. This grade covers Variations of the external ear severely deformed cup ear and mini ear. In Grade III dysplasia, no normal ear features are detectable and complete reconstruc- Various classifications are used in the literature to describe tion is required. This category includes microtia (unilateral or anomalies of the external ear. Recently, Hunter and Yotsuyanagi bilateral) with external acoustic meatus atresia, and or (2005) published a classification modified from the Weerda ­complete absence of the ear. classification (Table 97.1). They divided the anomalies into three Microtia Microtia is a congenital anomaly where the pinna is underde-

Table 97.1 Classification of anomalies of external ear. Adapted from Hunter veloped (Luquetti et al. 2012). It ranges from mild structural and Yotsuyanagi (2005). abnormality to absence of the ear/anotia (Fig. 97.1). Terminol- ogies ranging from “microtia”/“microtia/anotia” to “microtia‐ Grade of dysplasia Types anotia” are used in the literature. It can occur as an isolated anatomical anomaly or as part of a syndrome. Sufferers are pre- Grade I 1. Enlarged ear dominantly male. Microtia is unilateral in 77–93% of cases with 2. Anomalies of pinna: cryptotia, protruding ear, satyr ear, Stahl ear, Darwin’s tubercle, Shell 60% involvement of the right ear. The incidence is 0.8–2.4 per ear, Mozart ear, lop ear 10,000 live births. Hispanics and Asians have a higher preva- Lop ear is divided into mild and moderate lence than African Americans and Europeans. The highest inci- malformation: dence of 8.3 per 10,000 live births has been reported in Navajo 1. Mild anomalies: helical folding lies above Indians (Luquetti et al. 2012). the Darwin tubercle: (a) hiding ; and (b) Various risk factors have been reported including mater- constricted helix type IV A 2. Moderate anomalies: helical folding lies nal diabetes mellitus, low birth weight, advanced maternal above the Darwin tubercle: (a) absence of age, exposure to thalidomide, retinoic acid derivatives, and helix or cleft in helix; (b) anomalies of lobule; mycophenolate mofetil. There is some association of microtia and (c) anomalies of tragus with autosomal trisomies (18, 21, and 22) and trisomy 13 and Grade II 1. Cup ear 18 mosaicism. Single‐gene disorders, for example SIX1 and 2. Mini ear EYA1 and chromosomal translocation 6p24, are also reported to Grade III 1. Microtia (unilateral or bilateral) with external be associated with microtia. canal atresia Herman Marx (1926) proposed the first and most frequently 2. Anotia used classification system for the condition. He divided microtia

Bergman’s Comprehensive Encyclopedia of Human Anatomic Variation, First Edition. Edited by R. Shane Tubbs, Mohammadali M. Shoja and Marios Loukas. © 2016 John Wiley & Sons, Inc. Published 2016 by John Wiley & Sons, Inc.

1167 1168 Bergman’s Comprehensive Encyclopedia of Human Anatomic Variation

Figure 97.1 Variations of microtia: (a) typical ear; (b–d) first‐degree dysplasia; (e) second‐degree dysplasia; and (f–i) third‐degree dysplasia.

Source: Luquetti et al. (2012). Reproduced with permission from John Wiley & Sons. into three grades based on identification of auricular land- classification was based on embryological variations and surgi- marks. Rogers (1968) added grade IV microtia (anotia) to the cal classification as well as other external ear deformities and existing Marx classification. Tanger (1978) published a surgi- minor anomalies. Hunter and Yotsuyanagi (2009) recently pub- cal approach‐based classification system, and Weerda (1988) lished a classification to standardize the terminologies referring modified both of these systems and developed a new one. His to the external ear (Table 97.2).

Table 97.2 Classifications of microtia. Adapted from Luquetti et al. (2012).

Grade/type Description Grade/degree Description

Herman Marx Classification Weerda Classification Grade I is abnormal but all Grade I Macrotia, prominent ear, and cryptotia; landmarks are identifiable First‐degree Malformations Scaphoid ear, transverse cleft(coloboma), Stahl ear; Satyr ear; Darwin tubercle, defromed tragus and , helix crus absence; Lobular deformities: aplastic, hypoplastic and hyperplastic lobe, lobular fixation and lobular cleft; Deformity of cup ear I, IIa, IIb. Grade II Auricle is abnormal and few Grade II Deformity of cup ear III; landmarks are identifiable Second‐degree malformations Microtia: hypopastic upper pinna, hypoplastic middle pinna, and hyoplastic or aplastic lower pinna Grade III Anotia Grade III Grade III unilateral or bilateral microtia; Third‐degree Malformations Anotia

Tanger Classification Hunter Classification Type I Complete absence of ear Microtia All normal ear components are present and the (anotia) First‐degree median longitudinal length of ear is greater than two standard deviations below the mean Type II Complete hypoplasia of ear Microtia Presence of few normal ear components and median with and without external Second‐degree longitudinal length of ear is greater than two acoustic meatus atresia standard deviations below the mean (microtia) Type III Hypoplastic middle third of Microtia Some auricular structures are present but these auricle Second‐degree structures do not conform to recognized ear component Type IV Hypoplastic superior third of Anotia Ear is completely absent auricle, cup and lop ear and cryptotia Type V Prominent ear Chapter 97: Ear 1169

Figure 97.3 Protruding ear.

Source: Hunter and Yotsuyanagi (2005). Reproduced with permission from Figure 97.2 Macrotia. John Wiley & Sons. Source: Bauer (1997). Reproduced with permission from Elsevier.

assess protrusion is to measure the gap between the rim of the Macrotia helix and a point on the mastoid perpendicular to the helix rim. Macrotia is an abnormal enlargement of the pinna (Fig. 97.2): Any variation in shape or position of the mastoid can influence an ear with length for age measurement above the 97th percen- the measurement; this is the biggest drawback of the method. tile. An adult ear has a width range of 3–4.5 cm and length range Another widely used method is to measure the auriculocephalic of 5.5–7 cm, and the term macrotia is used when the ear meas- angle. If this is greater than 30–40 degrees, various authors ures more than these values. Feingold and Bossert (1974) pro- regard it as indicating protrusion. In the auriculocephalic angle posed a gold standard measurement. The curves were based on method any variation of temporal convexity or soft tissue the measurements they made of Caucasian children in Boston. above the bone can change the measurement, so it is not fool- According to Feingold and Bossert, the ear grows about 10% proof. Smith (1978) described the protruding ear as a result of a of its length and 40% of its height between the ages of 6 and developmental defect in the posterior auricular muscle. One role 14 years. The ear can be divided into three parts: of the posterior auricular muscle is to draw the pinna towards 1. Upper third: the part of the ear above inferior crus, which the , and dysfunction of this muscle causes the pinna to comprises 33% of the total height of the ear. protrude. According to the author, the protruding pinna should 2. Middle third: inferior crus to incisura, which comprises 43% be considered a part of the neuromuscular defect and not artic- of the height of the ear. ular cartilage dysmorphogenesis. Association of protruding 3. Lower third: incisura to the tip, which comprises 23% of the with myotonic dystrophy and congenital muscular dystrophy total height. has been frequently reported in the literature. Anencephaly, tri- In true macrotia, the upper third of the ear is most commonly somy 8 syndromes, 18p syndrome, 4p syndrome, and Langer‐ enlarged. Giedion syndrome are also associated with protruding ears.

Protruding ear Cryptotia Protruding ear is one of the most common anatomical varia- In cryptotia, the upper pole of helix cartilage is buried under tions. It is defined as an ear with a >40 degree angle in relation the fold of the skin which results in loss of the auriculoce- to the mastoid bone (Fig. 97.3). According to Carey (1993), the phalic sulcus (Fig. 97.4). This is more common in the Japanese gap between the mastoid bone and the helix in protruding ear is than the Caucasian population; its incidence in the former is greater than 2 cm. Driessen et al. (2011) found a sex difference about 1 in 400 births. The term cryptotia was introduced by in protrusion of the ear. In males, for an ear to be prominent, Sercer (1934). Altmann (1955) used the phrase “pocket ear” the protrusion should be greater than 21.5 mm for the upper for this anomaly. Gosserez and Piers (1959) called it “congen- or 20.0 mm for the lower part of the ear. In females, the protru- ital invagination” of external ear. There is no clear pathology sion in the upper ear should exceed 17.5 mm and the lower ear underpinning it, although various hypotheses have been pub- 15.5 mm. The auricular length is greater in males and correlates lished. Wreden (1879) reported this anomaly and proposed with age in both sexes. The most commonly used method to that abnormal insertion of the superior auricular muscle into 1170 Bergman’s Comprehensive Encyclopedia of Human Anatomic Variation

Figure 97.4 Cryptotia.

Source: Hunter and Yotsuyanagi (2005). Reproduced with permission from Figure 97.5 Stahl ear: (a) typical Stahl ear and (b) variant of Stahl ear. John Wiley & Sons. Source: Hunter and Yotsuyanagi (2005). Reproduced with permission from John Wiley & Sons. the upper part of the helix instead of the eminentia triangularis antihelicis trifurcate. There are various hypotheses regarding is the cause. Marx (1926) described this anomaly as a result the development of this variation but the most widely held is an of pressure from the umbilical cord over the auricle/vascular error in embryonic development during the third month when changes in the auricle. Sercer (1934) attributed it to a cartilage the helix and scaphoid are formed (Aki et al. 2000). developmental defect. Gosserez and Piers (1959) reported a series of 21 cases. Hirose et al. (1985) conjectured that the cause Shell ear was a defect in the intrinsic musculature. Hayashi et al. (1993) In Shell ear the superior crus is absent (Fig. 97.6). The described familial cases of cryptotia and described its X‐linked inferior crus is horizontal and wider. “Snail ear” and “shell ear” inheritance. They also suggested neuromuscular abnormality are other names used in the literature (Hunter and Yotsuyanagi as a cause of cryptoptia. 2005).

Stahl ear Question mark ear In Stahl’s ear, there is an abnormal cartilage fold extension to the In cases of question mark ear, the lower third of the ear is helix margin from the crus anthelix through the scaphoid affected (Fig. 97.7). It involves the cleft between the helix and (Fig. 97.5). This abnormality predominantly involves the supe- rior crus of the antihelix. There is also helix narrowing, scaphoid broadening, and superior crus antihelix hypoplasia or absence. In Stahl’s ear, some cases present as an abnormal inferior crus position while in others there is an extra crus, sometimes called a “third crus.” Yamada and Fukuda (1980) published a case series of 38 patients (21 males and 17 females) and classified this anomaly into four subdivisions: 1. Posteriosuperior extension of the third crus from the crura antihelix. The shape of the ridge is sharp. 2. Posteriorosuperior extension of the third crus from the crura antihelix with rounded ridge. 3. Posteriorosuperior extension of the third crus, which is wider and has two ridges. 4. Posterioinferior extension of the third crus from the crura antihelix. In the nineteenth century, Stahl divided auricular variations/ malformations into three subtypes: helix transversus spleni- Figure 97.6 Shell ear. formis; crus antihelicis trifurcata; and crus superius turgidum. Source: Hunter and Yotsuyanagi (2005). Reproduced with permission from Stahl’s ear comes under the second classification, that is, crus John Wiley & Sons. Chapter 97: Ear 1171

condition. Abnormal migration of neural crest cells (NCC) has been reported as the potential cause. It can occur as an isolated anomaly or a part of a syndrome complex. Its association with Brachmann‐de Lange syndrome, Treacher‐Collins syndrome and Goldenhar syndrome has been reported in the literature. Lammer (1991) proposed that retinoic acid embryopathy (RAE) is responsible for abnormal migration of NCC. In a retrospec- tive study, he described a case series in which patients exposed to retinoic acid during pregnancy had newborns with external ear defects including partial duplication of the ears.

Mozart ear In Mozart ear, the anterosuperior auricular margin has a bulg- ing appearance. The cavum conchae protrudes convexly and the external auditory meatus has a slit‐like opening (Fig. 97.9). In other words, the superior pinna margin bulges because of the two‐crura fusion of the antihelix and crus helix. The other char- acteristics of this anomaly are a smaller tragus, absent or poorly developed ear lobe, cavum cochae and crus helicus fusion, Figure 97.7 Question mark ear. non‐prominent antihelix lower half, crus helicus with hori- Source: Pan et al. (2010). Reproduced with permission from Elsevier. zontal ridge, and absence of the antitragus. In the literature the terms “lower conchal stria” or “convex conchae” are also used. Paton et al. (1986) published an article on Mozart ears. They the lobe of the ear. It can also present with a shallow dimple on carried out surveys among the patients attending ENT clinics the skin involving the posterior ear, absence or prominence of in Birmingham (1185 patients) and medical clinics in London the upper helix or ear lobe, and antitragus transposition. It can (1092 patients) and found only two cases. Yamashita et al. (2011) occur as an isolated anomaly or as part of a syndrome. In this reported a case of a female patient with Mozart ears. anomaly the scapha is absent and the ear protrudes from the affected site. It is a male‐predominant anomaly with a 2:1 sex Lop ears ratio and can present as a unilateral or bilateral defect. Its asso- Lop ear is an anomaly of the superior one‐third of the pinna ciation with auriculo‐condylar syndrome (ACS) and its autoso- (Fig. 97.10). It involves over‐folding of the scapha and helix, mal dominant inheritance have been reported. Pan et al. (2010) absence or smaller size of antihelix superior crus, smaller published a 32‐case series which included 30 sporadic cases and scapha, and an auricle that is shorter in vertical height. In Cau- two of familial origin. They divided the ear defect into moderate casian, African‐descent and Japanese populations the reported and severe types depending on the anatomical characteristics. incidences are 2–5%, 10–15%, and 38%, respectively. Lop ear In the moderate type the lobule and inferior part of the helix can occur as an isolated anomaly or as part of an autosomal presented with a cleft, and in the severe type the lobule and infe- dominant inherited disorder such as familial blepharophimo- rior part of the helix were absent. Question mark ear involves sis, scalp‐ear‐nipple syndrome, oto‐facio‐cervical, tricho‐rhino the first and second arches. Auriculo‐condylar syndrome phalangeal, brachio‐oto‐renal and lacrimal‐auricular‐dental‐ (ACS), Townes‐Brocks syndrome, Treacher‐Collins syndrome, digital syndromes, Kabuki syndrome, and Townes‐Brock syn- and oculoauriculo‐vertebral spectrum also involve the first and drome. It can also occur in association with Fraser and Mengel second arches. Question mark ear is closely associated with syndrome which exhibits autosomal recessive inheritance, and ACS, which is characterized by the presence of auricular clefts, also in Trisomy 21 and 4q deletion syndrome (Carey et al. 2006). microstomia, hypoplasia of the mandibular condyle, microg- Davis (1987) described hillock 3 hypoplasia as a major fac- nathia, temporomandibular joint abnormalities, and round tor in the pathogenesis of lop ears. According to him, hillock face with prominent cheeks. Masotti et al. (2008) conducted a 3 hypoplasia results in forward displacement of the helix to genome‐wide search and linked ACS to the 1p21.1–q23.3 gene. bridge the gap and the resultant pull causes the superior one‐ Due to the occurrence of question mark ear in ACS and its sim- third of the pinna to over‐fold. Karmody and Annino (1995) ilar inheritance mode, allelism could be plausible. described lop ear as an anomaly of the cartilage. Manigila and Maniglia (1981) ascribed it to failure of unfolding of the helix Mirror ear/polyotia during the 12–16th weeks of intrauterine life. Carey et al. (2006) Polyotia or mirror ear is characterized by presence of an acces- reported the cause of transient lop ear to be pressure on the fetal sory ear (Fig. 97.8). It has a comparable size and can be con- auricle from the brim of the maternal pelvis. Interestingly, in the sidered an extra auricle. There is no clear‐cut etiology of this Japanese population the incidence of lop ear at birth is 38% and 1172 Bergman’s Comprehensive Encyclopedia of Human Anatomic Variation

Figure 97.8 Polyotia.

Source: Gore et al. (2006). Reproduced with permission from Elsevier.

Figure 97.9 Mozart ear. Figure 97.10 Lop ear: (a) milder; and (b) severe form.

Source: Paton et al. (1986). Reproduced with permission from BMJ Publishing Source: Hunter and Yotsuyanagi (2005). Reproduced with permission from Group. John Wiley & Sons. Chapter 97: Ear 1173 at 1 year of age has decreased to only 6%. This could indicate correction of a transient lop ear initially caused by intrauterine compression. Hunter and Yotsuyanagi (2005) subclassified lop ear into a milder form and a moderate form. The milder form includes an anomaly limited to helix folding above Darwin’s tubercle. In the moderate form of lop ear, the folding of the helix extends below Darwin’s tubercle.

Upper auricular detachment In upper auricular detachment, there is no attachment between the crus helix and the anterior or ascending helix. The root of the helix and the distant lower end are also detached. The only site of attachment is to the mastoid area. In the literature, congenital amniotic bands and absence of mesenchymal fusion among the mandibular and hyoid arch hillocks are described as a potential cause of this anomaly (Hunter and Yotsuyanagi 2005). Figure 97.12 Darwin’s tubercle.

Source: Hunter and Yotsuyanagi (2005). Reproduced with permission from Ear lobe indentations/pits John Wiley & Sons. Ear lobe pits occur most commonly in patients with Wiedmann‐ Beckwith syndrome (WBS). Various terminologies such as dim- ples, creases, pits, and indentations are used in the literature that an infarction or localized degeneration could cause poste- (Fig. 97.11). Irving (1967) published a series of 11 cases and rior helical bits. Embryonic exposure to retinoic acid has also described the occurrence of semi‐horizontal linear grooves in been suggested as a cause. the ear lobe. Kosseff et al. (1972) described the bilateral focal occurrence of 1–2 mm indented areas that were well demar- Darwin’s tubercle cated on the posterior helix rims in a patient with WBS. There is Darwin tubercle is a small blunt projection from the helix. no clearly defined cause of this anomaly. Best (1991) suggested Davis (1987) described it as a site of fusion between hillocks 4 and 5. Carey (1993) suggested that a Kossef tubercle persists in embryos up to seven weeks of age; after that it disappears. No association with any syndrome or other anomalies has been reported in the literature (Fig. 97.12).

Cup ears There is much confusion regarding the difference between cup ears and lop ears. Rogers (1968) described it as a deformity with features of both protruding ears and lop ears. In cup ears the protrusion results from overdevelopment of the concave con- cha. A shorter helix and faulty antihelix are a few of the common features it shares with lop ears. Due to the forward cupping of the lobule, the vertical height of the ear from the superior pole to the lobule bottoms is less than in a normal ear. Peterson and Schminke (1968) published a study of a family with 12 members from five generations with cup‐shaped ears. In addition to cup ears, the proband had Pierre Robin syndrome.

Variations of the auditory meatus

Aural atresia Figure 97.11 (a) Ear pits and (b) indentations. (c) Horizontal lobular Aural atresia is a congenital anomaly involving failure of devel- grooves in patient with Beckwith‐Weidemann syndrome. opment of the external acoustic meatus. Depending on sever- Source: Hunter and Yotsuyanagi (2005). Reproduced with permission from ity, it can involve the tympanic membranes, , John Wiley & Sons. , and . The incidence of this anomaly is 1174 Bergman’s Comprehensive Encyclopedia of Human Anatomic Variation

1:10,000–20000 live births. It is male‐predominant. The inci- • Major malformation: Mastoid cell has poor pneumatization, dence of unilateral atresia is 3–5 times higher than bilateral /footplate is either abnormal or absent, facial atresia, and in unilateral atresia the right ear is more commonly course in relationship to the footplate and are involved. The anomaly is usually sporadic but an autosomal abnormal. recessive mode of inheritance is also known. The association Schuknecht (1989) introduced another classification based of aural atresia with Pierre Robin, CHARGE, Treacher‐Col- on surgical techniques and intraoperative findings: lins, Crouzon’s, Goldenhar’s, Mobius, Klippel‐Feil, Fanconi’s, • Type A: Atresia involves cartilaginous external acoustic DiGeorge, and VATER syndromes has been reported in the lit- ­meatus, corrected with meatoplasty. erature. It also coexists with cleft palate, , • Type B: Cartilaginous and bony parts of external ­acoustic posterior cranial hypoplasia, hydrocephalus, and genitourinary meatus are narrow, with small tympanic membrane and abnormalities. mildly deformed and . Correction involves There are various classifications of aural atresia (Table 97.3): ­canalplasty with or without ossicular chain reconstruction. Altmann (1955) divided atresia into three degrees depending • Type C: Complete atresia of the external acoustic meatus. on severity: Mastoid cell and middle ear have normal pneumatization. 1. First‐degree: The external acoustic meatus is mildly deformed, • Type D: Complete atresia of external acoustic meatus with the has normal or hypoplastic characteristics, poorly pneumatized middle ear. the ossicles are deformed, and the mastoid is well aerated. Jahrsdoerfer et al. (1992) introduced a point‐based classifi- 2. Second‐degree: This includes intermediate deformities. The cation system using radiological findings of the external acoustic meatus either ends blindly or is absent, the obtained from high resolution CT scans. A total of 10 points tympanic cavity is narrow, the ossicles are either deformed or can be awarded on the basis of anatomical findings. Open oval fixed, and the mastoid cells are poorly pneumatized. window, normal middle ear space, normal course of facial 3. Third‐degree: This includes severe deformities. The external nerve, presence of malleus‐incus complex, well‐pneuma- acoustic meatus is absent, the middle ear is hypoplastic, the tized mastoid cells, normal incus– connection, normal ossicles are deformed, and there is no mastoid cell pneumati- , and normal appearance of external ear are zation. each awarded one point. Presence of stapes scores two points. De la Cruz and Teufert (2010) modified Altmann’s classifica- A score of 10 = excellent, 9 = very good, 8 = good, 7 = fair, tion into minor and major malformations: 6 = marginal and less than 5 counts as poor post‐surgical prog- • Minor malformations: Mastoid cell pneumatization is nor- nosis. A score of 8 corresponds to an 80% success rate in hear- mal, inner ear is normal, oval window footplate, and normal ing restoration to normal or near normal level. A score of less course in relationship to it are found. than 5 is not considered for surgical intervention. Siegert et al.

Table 97.3 Classifications of aural atresia. Data from Altmann (1995) and De la Cruz and Teufert (2010).

Altman Classification De la Cruz Classification

Degree Description Malformation Description

First External acoustic meatus has mild deformity, tympanic Minor Mastoid cell has normal pneumatization, normal inner cavity with normal or hypoplastic characteristics, ear, oval window footplate and normal facial nerve ossicles deformity and well aerated mastoid course in relationship to the footplate Second Includes intermediate deformities. External acoustic Major Mastoid cell has poor pneumatization, oval window/ meatus either ends blindly or is absent, tympanic footplate is either abnormal or absent, abnormal cavity is narrow, ossicles are either deformed or fixed, facial nerve course in relationship to the footplate and and poorly pneumatized mastoid cells abnormal inner ear Third Includes severe deformities. External acoustic meatus – – is absent, hypoplasia of middle ear, deformed ossicles, and absence of mastoid cell pneumatization

Schuknecht Classification Type Description A Atresia involves cartilaginous external acoustic meatus, corrected with meatoplasty B Cartilaginous and bony part of external acoustic meatus is narrow, small tympanic membrane and mildly deformed malleus and incus. Correction involves canalplasty with or without ossicular chain reconstruction procedure C Complete atresia of external acoustic meatus. Mastoid cell and middle ear has normal pneumatization D Complete atresia of external acoustic meatus with poorly pneumatized middle ear Chapter 97: Ear 1175

Table 97.4 Twenty‐eight point‐based prognostic scale for aural atresia Duplication of internal auditory canal surgical outcome. Adapted from Siegert et al. (1996). Duplication of the internal auditory canal is a rare anomaly. It mostly occurs unilaterally, but bilateral occurrences have been Entity Points reported. According to Weissman et al. (1991), the facioacous- External auditory meatus: bone atresia; soft tissue 0; 1; 2 tic primordium separates abnormally in this condition, which atresia; normal causes the fibers of the vestibulocochlear and facial to Mastoid cell aeration: absent; fair; excellent 0; 1; 2 follow aberrant courses and results in duplication. According Middle ear space: absent; medium; large 0; 1; 2 to Curtin and May (1986), chondrification of the internal audi- Middle ear aeration: absent; minor; major 0; 1; 2 tory canal’s mesenchymal precursor is delayed, which causes the facial nerve to follow a course away from the vestibulocochlear Facial nerve: major variation; minor variation; normal 0; 2; 4 nerve. The wide gap between the two nerves results in abnormal Vessels: major variation; minor variation; normal 0; 1; 2 ossification and therefore duplication. Malleus and incus: absent; deformed; normal 0; 1; 2 Stapes: absent; deformed; normal 0; 2; 4 Oval window: obliterated; open 0; 4 Variations of the facial nerve Round window: obliterated; open 0; 4 The two most common facial nerve anatomical variations encountered in the middle ear are displacement of the facial nerve and absence of the bony sheath due to dehiscence or (1996) introduced a more extensive 28‐point‐based prognostic absence of the fallopian canal. Dehiscence of the fallopian canal rating scale. In a patient with bilateral malformation, a score exposes the facial nerve due to lack of the bony sheath. The nerve greater than or equal to 15 is recommended for middle ear has only a thin layer of fibrous membrane and is vulnerable to reconstruction and in a unilateral malformation the cutoff is herniation into the tympanic cavity. Fallopian canal dehiscence 20 points (Table 97.4). occurs during ontogenetic development. During this period the Colman (1974) classified aural atresia patients with conduc- ossification process closes the facial nerve sulcus. Malformation tive hearing loss into three groups: of Reichert’s cartilage precludes closure of the sulcus and results • Group I: Consists of minor anomalies, meatus is narrow but in dehiscence or complete absence of the bony canal. There are open, ossicular fixation involves stapes. various hypothetical explanations of the facial nerve displace- • Group II: Pinna is deformed, external meatus is completely ment. One is based on the failure of late fusion between the closed, and middle ear has complex abnormalities. second brachial arch and otic capsule, which prevents anterior • Group III: Severe deformity of the pinna and the middle ear. migration of the facial nerve (Al‐Mazrou et al. 2003). Mastoid cell pneumatization is absent and there are cochlear Exposure of the facial nerve in the middle ear can be divided deformities. into three degrees: Group I had excellent post‐surgical results and group II had • First‐degree: Severe fallopian canal dehiscence without facial variable results. Group III had poor outcomes. nerve displacement. • Second‐degree: The facial nerve is completely herniated from the fallopian canal and lies on the oval window with minimal Variations of the internal auditory canal or no attachment to the stapes. • Third‐degree: The facial nerve lies over the promontory. Narrow internal auditory canal Rohrt and Lorentzen (1976) divided the facial nerve displace- Narrowing of the internal auditory canal coexists with anom- ment into four groups (Table 97.5): alies of the external middle and inner ear. The normal diam- • Group I: Stapes footplate is partially obliterated by the facial eter of the internal auditory is 4 mm with a range of 2–8 mm. nerve. The canal is considered narrow when the diameter is less than • Group II: Facial nerve bifurcation. 2 mm. It contributes to 12% of temporal bone defects. Vesti- • Group III: Oval window and stapes are deformed and the bulocochlear nerve has a trophic influence on the growth of facial nerve lies on the footplate. the internal auditory canal and hypoplasia or aplasia of the • Group IV: Facial nerve lies on the promontory. vestibulocochlear nerve results in abnormal development of Jahrsdoerfer (1981) published a case series of facial nerve the canal and therefore causes narrowing. Another hypothe- anomalies and divided them into three categories based on ana- sis is that a mechanical obstruction caused by bony stenosis tomical variation and ease of surgical correction (Table 97.5): results in aplasia or hypoplasia of the vestibulocochlear nerve. (1) facial nerve overlies the stapes and oval window; (2) dis- This hypothesis is less likely to be the cause because most cases placement of the facial nerve along with presence of the oval reported in the literature have normal facial function (Demir window; or (3) displacement of the facial nerve along with et al. 2005). absence of the oval window. 1176 Bergman’s Comprehensive Encyclopedia of Human Anatomic Variation

Table 97.5 Classification of facial nerve’s variations in the middle ear. Data from Rohrt and Lorentzen (1976) and Jahrsdoerfer (1981).

Rohrt Classification Jahrsdoerfer Classification

Group Description Category Description I Stapes footplate is partially obliterated by the facial nerve I Facial nerve overlies on the stapes and oval window II Facial nerve bifurcation II Displacement of facial nerve along with presence of oval window III Oval window and Stapes are deformed and facial nerve lies on III Displacement of facial nerve along with absence of oval window the footplate IV Facial nerve lies on the promontory – –

Vascular variations against the otic capsule. It can occur as an isolated anomaly or in combination with an aberrant internal carotid and Vascular variations of the middle ear are of great surgical impor- stapes and facial nerve anomalies. Association with Paget’s tance. The most commonly encountered include an aberrant disease, thalidomide exposure, and trisomy internal carotid artery, dehiscence of the carotid artery canal, 13 has been reported in the literature. Normally, the stapedial a high jugular bulb, dehiscence of the high jugular bulb, and artery originates from the hyoid artery during the fifth week a persistent stapedial artery. The incidence of aberrant internal of embryonic life. From its origin it travels intracranially via carotid artery is less than 1%, dehiscence of high jugular bulb the stapes obturator foramen. It divides into dorsal and ventral has an incidence of 1%, and the incidence of high jugular bulb branches. The middle meningeal artery arises from its dorsal ranges over 6–22%. branch. The ventral branch gives rise to the infraorbital and An aberrant internal carotid artery is a very important vas- inferior alveolar extracranially after its exit via the cular anomaly in terms of surgical significance as bleeding from . The ventral branches further anastomose it can be life‐threatening. It is caused by agenesis of the first with the developing external carotid artery. During the tenth embryonic segment of the internal carotid artery. It can pres- week of gestation, the stapedial artery degenerates through ent as pulsatile tinnitus, hearing loss, or serous . On reversal of blood flow at the foramen spinosum and separates a high‐resolution CT scan it presents as a retrotympanic mass the internal from the external carotid artery. The presence of with enlarged inferior tympanic canaliculus, absence of bony a stapedial artery in postnatal life indicates the absence of its plate and the vertical segment of the internal carotid artery passage through the foramen spinosusm so the anastomosis canal. Various hypotheses regarding the cause of this anomaly between the internal carotid and middle meningeal arteries have been presented in the literature. A persistent stapedial persists and results in PSA (Lau et al. 2004). artery during embryogenesis can cause traction on the internal carotid artery and displace it into the tympanic cavity, and the displacement can also be caused by bony agenesis. Variations of the round and oval windows A high jugular bulb is the most common anomaly in the mid- dle ear. It is mostly unilateral with a right side to left side ratio Round window atresia mostly occurs as part of a syndrome of 2:1, but bilateral cases have been reported. High jugular bulbs complex, for example mandibulofacial dysostosis, cretinism, can be medial or lateral. A lateral high jugular bulb protrudes stapes ankylosis, mondini anomaly, and extensive otosclerosis. into the middle ear cavity and a medial jugular bulb lies superior Its occurrence as an isolated anomaly has also been reported in and medial to the cochlea. The condition usually presents as a the literature. It can present both unilaterally and bilaterally. The pulsatile tinnitus. round window develops during the eleventh week of gestation. Dehiscent jugular bulb, as the name suggests, is dehiscence of It first appears as an embryonic connective tissue condensation the sigmoid plate and jugular bulb that extends superolaterally between the fossula of the cochlear fenestra and the scala tym- into the middle ear cavity. It has great surgical importance as pani. During otic capsule ossification, the presence of a carti- it has only a thin layer of mucosa and could cause catastrophic lage ring prevents ossification of the round window opening. In bleeding in the event of accidental intraoperative injury. It can the absence of the cartilaginous ring, ossification obliterates the present as a bluish discolored mass behind the tympanic cavity. opening and causes congenital atresia. In congenital absence of A persistent stapedial artery (PSA) is a rare vascular the oval window there is no connection between the otic cap- anomaly of the middle ear. The incidence of PSA is 0.2–4.8 sule bone and the vestibule. There is complete closure of the per thousand adults. It usually presents as pulsatile tinnitus oval window by a thick bony plate or a concentric narrowing. and due to ankylosis of the stapes. The foot plate and anular ligament are absent (de Alarcon et al. It can also present as sensorineural hearing loss by eroding 2007). Chapter 97: Ear 1177

Variations of the Table 97.6 Classification of inner ear anomalies. Adapted from Jackler et al. (1987). Anomalies of the Eustachian tube (ET) are not common and Category A (aplasia or cochlear malformations) mostly occur as part of a syndrome complex. Anatomical var- iations can involve the bony or more commonly the cartilagi- Complete aplasia of labyrinth Absence of inner ear development nous part. ET anomalies are reported to be associated with cleft Aplasia of cochlea Deveopmental absence of cochlea, vestibule palate deformities, Down syndrome, the oculoauriculoverte- and are normal or malformed bral spectrum, and Klippel‐Feil syndrome. The normal width Hypoplastic cochlea Small cochlea, vestibule and semicircular of the ET is 1.5 mm; enlargement of its bony portion is rare. canal are normal or malformed The oculoauriculovertebral spectrum is characterized by man- Incoplete partition of cochlea Cochlea small and incomplete, vestibule dibular hypoplasia, vertebral anomalies, microtia and epibulbar and semicircular canals are normal or dermoids and lipodermoids. Haginomori et al. (2003) reported malformed a case of enlargement of the bony part of the Eustachian tube in Common cavity Common cavity formation between cochlea a patient with oculoauriculovertebra spectrum; the diameter of and vestibule with absence of internal the ET was 7 mm. Jovankovičová et al. (2012) described a case architecture, semicircular canal is either of Klippel‐Feil syndrome with an enlarged right‐sided ET with normal or deformed. a width of 5.5 mm. Category B (normal cochlea) Vestibule and lateral Vestibule is enlarged and lateral. semicircular canal dysplasia Semicircular canal is short and dilated. Variations of the inner ear Enlarged Vestibular aqueduct is enlarged with normal semicircular canal. There are various classifications to describe inner ear malforma- tions. The most commonly used classification was introduced by Jackler et al. (1987) and was based on radiographic appearances. This was further modified by Marangos (2002) and Sennaroglu incomplete partition type I by fifth week arrest, hypoplasia and Saatci (2002). Jackler et al. divided the malformations into of the cochlea during sixth week arrest, Mondini deformity/ two categories, A and B. Category A entailed congenital anom- incomplete partition type II by seventh week arrest, and nor- alies with an absent or malformed cochlea, and category B mal development (Table 97.8). entailed congenital malformations with a normal cochlea. The radiological classification was based on radiographic Variations of the cochlea appearances with the following size reference ranges: the coch- According to Sennaroglu and Saatci (2002), cochlear malfor- lea was considered small if it was less than 7 mm measured mations can be subdivided into Michel anomaly/complete vertically (normal size 8–10 mm); and a vestibule greater than 5 mm in vertical measurement was considered enlarged. The intraosseous portion of the vestibular aqueduct with diameter Table 97.7 Classification of inner ear anomalies. Adapted from Marangos greater than 2 mm was categorized as enlarged. Internal audi- (2002). tory canals with greater than 10 mm vertical diameter and less than 3 mm vertical diameter were considered enlarged and nar- Category Types rowed, respectively (Table 97.6). A: incomplete embryonic Michel deformity/completely aplastic Marangos (2002) modified Jackler’s classification and divided development inner ear; common cavity; cochlear inner ear variations into four categories. Category A entailed aplasia or hypoplasia with normal malformations with deficient embryonic development, cate- development of posterior layrinth; gory B included aberrant embryonic development, category C posterior labyrinth aplasia or hypoplasia with normal development of cochlea; included isolated malformations, and category D included syn- completely hypoplastic labyrinth; dromic malformations (Table 97.7). dysplasia mondini type Sennaroglu and Saatci (2002) further categorized cochle- B: aberrant embryonic Vestibular aqueduct enlargement; ovestibular malformations into five subdivisions based on development internal auditory canal narrowing; longer cochlear, vestibular, semicircular canal, internal auditory lengthed crista transeversa; tripartitus canal, and vestibular defects. They also pro- of internal auditory canal; cochlea and meatus incompletely separated posed a categorization of cochlear malformations based on embryonic developmental arrest: Michel deformity caused by C: hereditary malformations Hearing loss of X‐linked origin of isolated origin developmental arrest at the third week, aplasia of the cochlea by late third week arrest, common cavity malformation dur- Category D Malformations with syndromic association ing fourth week arrest, cystic cochleovestibular malformation/ 1178 Bergman’s Comprehensive Encyclopedia of Human Anatomic Variation

Table 97.8 Classification of inner ear anomalies. Adapted from Sennaroglu anomaly there is no differentiation between the cochlea and and Saatci (2002). vestibule and a common cavity forms. The internal auditory canal dimensions are abnormal and vary among patients, as Category Types described by Sennaroglu and Saatci (2002). Enlarged internal Malformations of cochlea Michel deformity: complete aplasia of auditory canals were found in patients with large common cav- inner ear structures ities, and small dimensions were present in patients with small Aplasia of cochlea: complete absence common cavities. of cochlea Common cavity malformation Incomplete partition type I Hypoplastic cochlea This anomaly, also known as cystic cochleovestibular malfor- Incomplete partition I; II mation, is characterized by cystic dilatation of the cochlea and Malformations of vestibule Hypoplastic, dilated or absent vestibule, vestibule. The cochlea is empty. The cochlea and vestibule have common cavity and Michel deformity normal dimensions but lack internal structures. The cochlea Malformations of semicircular Absence, hypoplasia or enlargement of lacks the and cribriform areas, so the cystic cavity is canal semicircular canal empty. The cause is arrest of development at the fifth week of Malformations of internal Absence, narrowing or enlargement of intrauterine life (Sennaroglu and Saatci 2002). auditory canal internal auditory canal Malformations of vestibular Vestibular and cochlear aqueduct, Cochleovestibular hypoplasia and cochlear aqueduct either normal or enlarged This anomaly is believed to result from developmental arrest at the sixth week of intrauterine life. The cochlea is hypoplastic/ labyrinthine aplasia, cochlear aplasia, common cavity, cochlear smaller in size and the vestibule is either hypoplastic or absent. hypoplasia, and incomplete partition types I and II on the basis The dimensions of the internal auditory canal vary from normal of anatomical features and the time of arrest of development to smaller (Sennaroglu and Saatci 2002). during intrauterine life. Incomplete partition type II Michel anomaly/complete labyrinthine aplasia This anomaly, also known as Mondini malformation, results A Michel anomaly is characterized by complete aplasia of the from developmental arrest later than type I because the coch- labyrinthine structure, where there is complete absence of inner lea and vestibule have normal size and their internal struc- ear structure. It accounts for 1% of the congenital anomalies of tures are better developed. The vestibule has minimal dila- the inner ear. It is generally bilateral but unilateral cases have tation. It contributes to 50% of cochlear deformities, and is also been reported. Congenital absence of inner ear structure believed to be a result of arrested development at the seventh is due to otic placode arrest before the third week of embry- week of intrauterine life. The cochlea has 1.5 turns and its apex onic development. Michel (1863) described this anomaly in an between the middle and apical turns has an interscalar defect. autopsy report of a 12‐year‐old male with the bilateral defect. The basal part of the modiolus is developed in the cochlea so there are more nerve endings and spiral ganglia than in the Cochlear aplasia incomplete partition type I malformation (Sennaroglu and In this anomaly there is complete absence of the cochlea. The Saatci 2002). vestibule and semicircular canal can be normal, dilated, or hypoplastic. It can occur as a bilateral or unilateral anomaly. On Variations of the semicircular canal examination of the anterior part of the internal auditory canal, Aplasia of semicircular canal it presents as a dense otic bone. The absence of the cochlea Aplasia of the semicircular canal can present as an isolated results in anterior displacement of the labyrinthine segment of anomaly or part of a syndrome. The patient usually presents the from its usual course. This anomaly should be with sensorineural hearing loss. It is a common associated differentiated from common cavity and cochlear ossification. In anomaly in patients with CHARGE syndrome. The associa- cochlear ossification there is bulge in the promontory caused by tion of aplastic semicircular canals with CHARGE syndrome the basal turn of the cochlea, which is absent in cochlear aplasia. was first reported by Guyot et al. (1987) in a study based on It can be differentiated from common cavity by the absence of histopathological findings of temporal . Its association a cavity in the cochlear location, anteroinferior location of the with Noonan syndrome has also been reported. Superior internal auditory canal in relation to the malformed cavity, and semicircular canal development is usually complete at the bony sclerosis at the location of the absent cochlea (Sennaroglu 19th week of intrauterine life and the horizontal semicircular and Saatci 2002). canal by 22 weeks. The semicircular canal can develop any time up to 24 weeks. In Noonan syndrome, patients usually Common cavity present with mixed‐type bilateral severe hearing loss. The lit- Common cavity malformation results from arrested devel- erature reports 20% low‐frequency and 50% high‐frequency opment during the fourth week of intrauterine life. In this hearing loss. Chapter 97: Ear 1179

Variations of the vestibular Table 97.10 Classification of cochlear aqueduct based on CT findings. and cochlear aqueduct Adapted from Migirov and Kronenberg (2005).

Enlargement of vestibular aqueduct (VA) Type Description This is the most common radiologically detected anomaly in I Basal turn of cochlea and its opening into subarachnoid children affected by sensorineural hearing loss. It is a bilat- space is clearly visible eral anomaly with normal to mild impairment of hearing in II Cochlear aqueduct defined in the medial two‐thirds childhood and it deteriorates with age. Almost 40% of patients III Only medial third and/or external aperture can be defined develop sensory hearing loss. Valvassori and Clemis (1978) IV Undefined CA defined the enlarged VA using hypocycloidal polytomogra- phy. According to them the aqueduct should have dimensions greater than 1.5 mm at the midpoint. Arenberg et al. (1984) first proposed a classification of the VA basal turn; (2) the segment of the labyrinthine capsule with the on the basis of radiological findings. They divided the VA into CA running medially through it; (3) petrous apex segment; and five types (Table 97.9): type I, the VA measures 1–2 mm in the (4) medial orifice segment. distal one‐third of its course; type II measures less than 1 mm According to the study, the CA diameter is not consistent and in the distal two‐thirds of the aqueduct course; type III VA is is cochlear‐segment specific. The petrous and labyrinthine seg- greater than 2 mm in the distal one‐third and in close proximity ments with diameters up to 2 mm were considered normal by to the external aperture; in type IV the external aperture meas- Jackler and De la Cruz (1993). The median orifice segment has a ures 1–2 mm; type V lacks an external aperture. variable diameter in the range 0–11 mm with mean 4.5 mm. Migi- Dewan et al. (2009) recently proposed new “Cincinati crite- rov and Kronenberg (2005) published a classification of the coch- ria” based on CT findings from children with normal hearing. lear aqueduct based on CT findings (Table 97.10). They divided According to these criteria, a vestibular aqueduct with a 1.0 mm the CA into four types: (I) basal turn of cochlea and its opening midpoint and 2.0 mm opercular width, greater than the 95 per- into subarachnoid space is clearly visible; (II) cochlear aqueduct centile, is regarded as enlarged. They compared the Cincinnati defined in the medial two‐thirds; (III) only the medial third and/ criteria with the Valvassori criteria. According to their study, or external aperture can be defined; and (IV) undefined CA. the Cincinnati criteria identified enlargement of the vestibular In the literature, Mukherji et al. (1998) described a case of aqueduct in 44% patients and the Valvassori criteria identified it enlargement of the cochlear aqueduct in an 18‐month‐old in only 16%. Among those patients, 45% had unilateral and 55% patient with severe bilateral hearing loss. The mid‐portion diam- bilateral anomaly with the Cincinnati criteria, and 64% were eter was 1.2 mm and was considered enlarged. To justify their unilaterally affected and 36% bilaterally with the Valvassori cri- findings, the author examined 50 temporal bones radiologically teria. According to Dewan et al. (2009), the Cincinnati criteria using 1‐mm‐thick contiguous axial CT sections. The diameter were superior to the Valvassori criteria in identifying patients of the mid‐otic segment of the CA was 0.56±0.26 mm. Stimmer with enlargement of the vestibular aqueduct. (2010) published a report of radiological findings from 400 tem- poral bones using spiral CT. 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