CLINICAL INVESTIGATION OF OSSICULAR ANOMALIES
Introduction
Ossicular anomalies (OA) are known to cause congenital, non-progressive, and conductive hearing loss. They may occur with a normal tympanic membrane, and many of them are unilateral lesions. Usually, patients are not aware of their hearing loss until testing, because they have no other symptoms. However, we often encounter patients with OA who remember when they first noticed hearing loss.
The purpose of this study was to investigate when the patients first noticed their hearing loss and evaluate the operating methods and post-operative hearing progress of OA treatment.
Materials and methods
Thirty-two patients (35 ears) with OA were diagnosed upon operation in the Tokyo Medical University during the period from 1998 to 2011. There were 15 males and 17 females (age range, six-67 years; mean 26.1 years). The patients were classified according to Funasaka’s classification (Fig. 1).1 This classification divides monofocal OA into three groups. Cases which had more than two types of dysplasia were defined as Multifocal-type anomalies. These cases were also classified into three groups by the time of manifestation: ‘infancy’, ‘enrollment for medical examination’ and ‘acquired’. In the first two groups, the patients were not aware of their hearing loss. In the last group, they remembered when they lost their hearing.
Fig. 1. Funasaka’s classification. OA are classified into three groups: I-S separation, M/I fixation, and S fixation. Cases which have more than two types of dysplasia are defined as multifocal type anomalies.
Hearing level was investigated before and after surgery. The air-bone gap (A-B gap) and 2-kHz bone conduction threshold dip (Carhart’s notch) were investigated by pure tone audiogram (PTA) before the operation, and the A-B gap was also investigated after the operation.
Operation outcomes were evaluated by the American Academy of Otolaryngology (AAO-HNS) guidelines (1995). In these guidelines, success is defined as when the A-B gap becomes less than 10 dB.
Results
There were 26 ears in the incudostapedial (I-S) joint separation group, one ear in the malleus and/or incus (M/I) fixation group, and four ears in the stapes (S) fixation group (Table 1). Multifocal-type anomalies were seen in the other four ears. There were no differences in OA between the genders. Age was higher in the I-S separation group. There were seven ears with complex anomalies.
Table 1.
The time of manifestation is shown in Table 2. Many of the patients with OA had been diagnosed upon when they first went to school. There were nine ears in the acquired group. Seven out of nine patients in the acquired group belonged to the I-S-separation group. These acquired OA represented 25.7% of all of the OA cases.
Table 2.
The mean hearing level in each group before and after operation is shown in Figure 2. Before operation, the A-B gap was present across the low-to-high frequencies in the I-S-separation group, and the stiffness curve was seen in the M/I-fixation and S-fixation groups. In multifocal-type anomalies, these hearing defects were combined. Carhart’s notch was observed not only in the S-fixation group but also in the other groups. Ossicular reconstruction was performed in the I-S separation and M/I-fixation groups and stapes surgery was performed in the S-fixation group. In one I-S-separation case, bone putty was used to cement the loose the I-S joint because there was not enough space to insert cartilage between the incus and stapes. After operation, decrease of the A-B gap was attained in all groups, but this decrease was less pronounced in multifocal-type anomalies.
The success rate of the operation was 29.4% in the I-S-separation group, 66.7% in the S fixation group, and 29.2% in all cases (Table 3).
Fig. 2. Pure-tone audiogram. Pre-operative and post-operative hearing levels are shown. Before surgery, an A-B gap was present across the low-to-high frequencies in the I-S separation group, stiffness curve was seen in the M/I fixation and S fixation groups, and both were combined in multifocal type anomalies. In all groups, the A-B gap had improved after surgery, but there was less improvement in Multifocal-type anomalies. White dots: before surgery, black dots: after surgery, round dots: air conduction, square dots: bone conduction.
Table 3.
Discussion
Acquired manifestation of hearing loss was seen in 25.7% of patients with OA, and most of these patients were in the I-S-separation group. Therefore, the age was higher in the I-S-separation group. There are two hypotheses regarding the etiology of acquired OA. The first proposes an acquired defect of the ossicular chain, which is thought to be due to the disappearance of existing cholesteatoma2 or some atrophic changes.3. The second hypothesis proposes that acquired OA are due to congenital anomalies and associated acquired pathology. The build up of stiffness of the ossicular chain is involved in this acquired pathology. It was reported that the Valsalva maneuver had been performed to improve hearing in a patient with a loose I-S joint. In this case, the Valsalva maneuver enhanced the stiffness of the ossicular chain, but the patient started complaining about hearing loss after the Valsalva maneuver became ineffective.4
Considering the A-B-gap pattern during PTA measurement, when the A-B gap is present across the low-to-high frequencies, it raises suspicion of I-S-separation-type anomaly. If a stiffness curve can be seen, M/I-fixation- or S-fixation-type anomalies are suspected. In the current study, it was found that Carhart’s notch was observed not only in S-fixation-type anomalies but also in other types of OA. It was reported previously that Carhart’s notch was not specific for S fixation, and it also could be seen in various conditions of the middle ear.5 Therefore, the lesions of OA can be inferred from the A-B-gap pattern during PTA analysis.
Surgery was performed with conventional methods in most types of OA. When a conventional operation cannot be performed because of the shape of the ossicular chain, we should consider other methods. For I-S separation, cartilage is useful to bridge and raise the stiffness of the ossicular chain. When there is not enough space to insert cartilage, bone putty can be used as cement instead. To improve hearing, the stiffness of the ossicular chain should be increased, and the ossicles should be kept away from the wall of the tympanic cavity.
Post operatively, complete closure of the A-B gap in OA is difficult, except for S fixation. In the current study, the success rate in the I-S-separation group seemed to be slightly lower than past reports,6–8 although each criterion used for evaluation is not the same in every report. To improve the success rate for I-S separation, division of new surgical techniques may be necessary.
Conclusion
Acquired OA mainly consists of I-S-separation-type anomalies. The type of OA can be suggested from the A-B-gap pattern of the PTA analysis. Bone putty is useful to cement loose I-S joints.
References
1.Funasaka S. Congenital ossicular anomalies without malformations of the external ear. Arch Otorhinolaryngol 224:231–240, 1979
2.Kodama K, et al. Two cases of spontaneous regression of congenital cholesteatomas. Int J Pediatr Otorhinolaryngol 76:142–144, 2012
3.Imauchi Y, Karino S, Yamasoba T. Acquired atrophy of the long process of the incus. Otolaryngol Head Neck Surg 132:156–158, 2005
4.Shimogori H. A case of bilateral ossicular chain abnormality with hearing improved by Valsalva experiment. The Oto-rhino-and laryngological clinic 104:791–795, 2011
5.Kashio A, et al. Charhart notch 2-kHz bone conduction threshold dip. Arch Otolaryngol Head Neck Surg 137:236–240, 2011
6.Hashimoto S, Yamamoto Y, Satoh H, Takahashi S. Surgical treatment of 52 cases of auditory ossicular malformations. Auris Nasus Larynx 29:17–18, 2002
7.Kisilevsky VE, Bailie NA, Dutt SN, Halik JJ. Hearing results of stapedotomy and malleo-vestibulopexy in congenital hearing loss. Int J Pediatr Otorhinolaryngol 73:1712–1717, 2009
8.Thomeer HG, Kunst HP, Cremers CW. Congenital stapes ankylosis associated with another ossicular chain anomaly: surgical results in 30 ears. Arch Otolaryngol Head Neck Surg 137:935–941, 2011
Address for correspondence: Taro Inagaki, inataro@tokyo-med.ac.jp
Cholesteatoma and Ear Surgery – An Update, pp. 273–276
Edited by Haruo Takahashi
2013 © Kugler Publications, Amsterdam, The Netherlands