Epidemiological analysis of Microtia: A retrospective study in 345 patients in China

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Abstract

Objective

To study the epidemiologic characteristics of microtia in China and to investigate the possible risk factors with respect to the classification of microtia.

Methods

A total of 345 patients with microtia were studied. All patients were taken an intentional physical examination and classified into five types. A detailed questionnaire concerning the maternal conditions during pregnancy was filled out by patient's mother. The frequencies of the relative factors were counted and the variables were statistically analyzed using Chi Square and Fisher's tests in the five types of microtia.

Results

Most cases of microtia (88.12%) were sporadic and 72.75% of all cases occurred in males. It was more seen unilateral, especially affected on the right side (55.94%). A total of 195 patients (56.52%) were isolated microtia. In the rest of non-isolated microtia patients, 37.97% of the cases had hemifacial microsomia, which was the most common associated deformity. Thirty-four patients (9.86%) belonged to typical familial microtia. Three maternal factors showed significant differences in the five types of microtia, which were perinatal virus infection, high prior miscarriages and prevention treatments for threatened abortion.

Conclusions

The majority of microtia cases in China are sporadic and usually more common in males. Mothers who have prior miscarriages over 3 times or perinatal virus infection seem to be more likely to have severe microtia infants.

Introduction

Microtia is defined as a malformation of the auricle, ranging from minimal abnormalities to major structural alterations or even total absence of the external ear. The incidence of microtia is reported varying from 0.83 to 17.4 per 10,000 births [1], [2]. Although some patients with microtia (2.9–33.8%) are hereditary, the majority of the cases are sporadic [3], [4]. It has also been found that microtia is more frequently seen in males, and most cases are unilateral, especially on the right side (60%) [3], [4], [5], [6], [7].

The pathogenesis of microtia is still unclear. The hereditary factors are the most probable causes since microtia is usually involved in some specific syndromes with chromosomal abnormalities, such as Goldenhar syndrome, Treacher Collins syndrome, trisomy 21 and trisomy 18 [3], [4], [5]. Some maternal conditions are also considered as the risk factors of microtia, including high pregnant age [1], high parity [1], [3], perinatal drugs using [3] and low education [5]. It has been reported that mothers of high parity (4+) have considerably higher possibility of delivering infants with microtia [1], and the rate of birth defects increases significantly in the women who are over 30 years old [1], [6]. Shaw et al. [5] observed a higher incidence of non-isolated microtia in offspring whose mothers were educated less than 12 years. Microtia infants are generally common with multiple births, low birth weight (<2500 g), and short gestational age (<38 weeks) [6]. In addition, the racial variability of microtia was reported, which had lower incidence in African-Americans and Caucasians than that in Hispanics and Asians [1], [5], [6], [8].

Most of the epidemiologic investigations on microtia have been studied in Americans and Europeans, whereas it is limited in Asians. The purposes of the current study are to describe the epidemiologic characteristics of microtia in China, to investigate the possible risk factors of microtia, and to compare them with the existing literatures.

Section snippets

Materials and methods

From 2006 to 2008, a total of 345 patients of microtia had undergone or been ready to receive the ear reconstructive surgery in our department, who were collected as the subjects of the study. All patients were taken an intentional physical examination and therefore classified into five types according to the classifications of Marx [9] and Nagata [10]. Type 1 is conchal-form microtia, in which the ear lobule, concha, acoustic meatus, tragus, and incisura intertragica are present to variable

Results

Of the 345 cases, 251 patients (72.75%) were male and 94 patients (27.25%) were female, which were shown in Table 1. Regarding the laterality, 193 cases (55.24%) were suffered on the right side, whereas 127 cases (36.81%) were on the left side. By microtia classification category (Table 2), type 1 (conchal-form microtia), type 2 (small conchal-form microtia), type 3 (sausage-form microtia), type 4 (lobule-form microtia), and type 5 (anotia) consisted of 72 cases (20.87%), 32 cases (9.27%), 199

Discussion

In this study, the classification of microtia was referred to the methods of Marx [9] and Nagata [10]. The four microtia appearance types which proposed by Nagata [10] were corresponded to the four degrees of the severity of microtia that proposed by Marx [9]. The comparison results in these types were equivalent to that of the severity by degrees correspondingly. Thus, the clinical case materials can be directly perceived through the appearances classification. Generally, microtic ear in

Acknowledgments

The authors wish to thank all participants in the study, who completed the questionnaires seriously and fully supported our investigation. Dr Sufan Wu and Miss WenChing Chin are acknowledged for the revision of the manuscript.

References (20)

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