Microtia

The main cause of dysembriogenesis of the structures of the outer ear is a negative external influence on the development of the fetus during pregnancy. Hereditary microtia can be a component of one of the genetic syndromes – Nager, Treacher-Collins, Konigsmark, Goldenhar. The most common teratogenic factors that cause the development of pathology include:

• TORCH infections. This is a common name for infectious diseases in which there is a risk of intrauterine infection of the fetus and the formation of malformations. They include toxoplasmosis, herpes viruses of types 1, 2 and 3, rubella, syphilis, cytomegalovirus, parvovirus.
• Physical factors. Usually this is ionizing radiation during radiography or computed tomography, which are carried out for vital indications or with undiagnosed pregnancy. Also, this group includes radiation therapy for cancer pathology, treatment with radioactive iodine, prolonged hyperthermia.
• Bad habits. The use of alcoholic beverages, narcotic substances (most often cocaine), tobacco products has a detrimental effect on the intrauterine development of a child.
• Pharmacological preparations. Some medications can provoke congenital anomalies in a child. These are antibiotics (tetracyclines, penicillamine), hypotensive (enalapril, captopril) drugs, iodine or lithium-based drugs, anticoagulants (warfarin), hormonal agents (androgens).
• Endocrine pathologies. These include diabetes mellitus in the decompensation stage, phenylketonuria, folic acid deficiency, endemic goiter. Hormone–active tumors, including androgen-producing ones, are isolated separately.

In normal embryonic development, the tissues of the future auricle are formed from the mesenchyme surrounding the first ectodermal pocket - from the I and II gill arches. The first rudiments of ear cartilage occur at 20-22 weeks of intrauterine development. The sensory part of the hearing aid is formed earlier, which is why the sound-receiving structures are affected much less often. By 27-28 weeks, the shells already have the appearance and shape of a newborn baby. It is believed that a violation of the development process due to the influence of teratogens can occur in any of the above periods. There is a pattern: the earlier the negative factor acted– the more severe the future defects. Anomalies that occur before the 6th obstetric week are often accompanied by serious defects or a total absence of not only the outer, but also the middle ear.

In modern otolaryngology, the Marx classification is used, the practical significance of which lies in simplifying the choice of surgical tactics and method of hearing replacement for patients. Taking into account the severity of deformation of the shell of the outer ear and concomitant damage to the auditory canal, 4 degrees of severity are distinguished in it. According to this classification , microtia can have the following degrees:

• I (easy). It is manifested by underdevelopment (hypoplasia) of individual elements of the auricle. The auditory canal retains its physiological shape or narrows somewhat and fully performs its functions.
• II (medium). It is characterized by a significant deformation of the outer ear with the absence of some elements. There is a stenosis or atresia of the auditory canal, accompanied by hearing loss of the conductive type.
• III (heavy). The auricle is severely underdeveloped, it is a small vestige. The lumen of the auditory canal, the tympanic membrane are completely absent.
• IV (anotia). Complete absence of a sink. There is agenesis of the structures of the outer, middle ear, violation of the formation of the facial skeleton.

Based on morphological characteristics, 4 clinical forms of the disease are distinguished: true microtia, anotia, small and folded auricle. The most common is true. It is manifested by the presence of a vertical skin-cartilaginous roller with a lobe at the end. The latter, in comparison with the physiological location, is shifted upwards and anteriorly. The auditory canal is often overgrown or absent. The bones of the facial skull, as a rule, are not deformed. Anotia is the rarest form of microtia. Externally, it is characterized by the complete absence of an auricle or a cartilaginous tubercle that does not have a lobe. The entrance opening of the auditory canal may be preserved. It is often accompanied by anomalies in the development of the facial skeleton.

The folded shell of the outer ear is a variant of microtia, in which there is insufficient development of the upper half of the organ. Clinically, this is manifested by the fusion of the curl leg and the tragus. Because of this, the ear visually looks "collapsed", and its vertical size is significantly reduced. Antitumor is often underdeveloped. In severe cases, the upper edge of the curl is at the same level with the tragus. The entire auricle shifts anteriorly and downwards. The combination of these changes with dysplasia of the facial skeleton is the syndrome of the I gill arch. The lumen of the auditory canal is often fused, hearing on the side of the lesion is sharply reduced or completely absent. The small auricle is a type of disease in which there is a relatively formed curl and lobe, insufficiently developed antitumor and recesses of the outer ear, the auditory canal is stenosed or absent.

Complications of microtia are associated with untimely correction of existing defects of the auditory canal, hearing and speech disorders arising on this basis. Severe congenital bilateral conductive hearing loss prevents the normal development of the articulatory apparatus in a child, becomes the cause of deafness. The narrowing of the entrance opening of the outer ear disrupts the drainage of the exfoliated corneal epithelium and earwax. This contributes to the proliferation of pathogenic and conditionally pathogenic microflora, leads to external and middle otitis media, myringitis, mastoiditis, arthritis of the temporomandibular joints and other inflammatory lesions of this area.

Diagnosis is possible immediately after delivery on the basis of a visual examination. Subsequently, the child is sent to a pediatric otolaryngologist to identify concomitant lesions of the middle and inner ear, assess the functionality of the sound-conducting and sound-receiving systems. The structure of the diagnostic program depends on the age of the patient at the time of contacting a specialist. In addition to the external examination of the deformed auricle and the collection of anamnesis, it may include:

• The study of auditory perception. Based on talking or using sounding toys. This test allows you to conduct an initial assessment of the overall sound perception and sound conductivity of each ear separately. In infants, loud sudden sounds are used instead of speech.
• Tonal threshold audiometry. It makes it possible to evaluate air conduction and bone perception from the lesion. With mild, moderate and severe microtia, conductive hearing loss of up to 60-70 dB is observed. With anotia, there may be a lesion of the sound-receiving apparatus. Audiometry is used in patients aged 3-4 years, since the study requires an adequate perception of audio signals and an understanding of the essence of the test.
• Acoustic impedance measurement. It is used to assess the functional state of the eardrum, the adequacy of the response of the auditory ossicle chain to sound, and to determine the pathologies of the inner ear. On the basis of the results obtained, the expediency of hearing replacement is established. If necessary, this technique is supplemented with an ABR test that studies the reaction of the central nervous system to sound.
• Computer and magnetic resonance imaging. CT of the temporal bone in axial, frontal and coronary projections allows to visualize the lumen of the outer ear, the tympanic cavity and auditory ossicles in layers or to determine their absence. In children with a rudimentary passage of the outer ear, according to the results of the study, a decision is made on the nature and scope of the future operation, the presence of cholesteatoma is excluded. To diagnose potential soft tissue abnormalities and study the course of the facial nerve, an MRI of the temporal bone is shown.

The goals of treatment are to eliminate a cosmetic defect, improve auditory function, and prevent the development of complications. The main method of achieving them is surgical. The choice of surgical intervention depends on the severity of microtia, the degree of development of the auditory canal and concomitant dysplasia of regional bone structures. For social and psychological reasons, treatment is recommended to be carried out in the preschool period – in 5-6 years. In pediatric otolaryngology for this purpose are used:

• Auriculoplasty. Depending on the clinical situation, plastic surgery of the auricle is performed with its own tissues or (at III-IV art.) with the help of implants. In the second case, an autograft is used, taken from the cartilage of the VI, VII, VIII ribs on the opposite side of the lesion. The most common technique is multi–stage reconstruction according to Tanser-Brent.
• Meattimpanoplasty. It consists in the formation of a cosmetically and functionally acceptable auditory canal, if there is such an opportunity. Currently, meattimpanoplasty is usually performed according to the method of S. N. Lapchenko.
• Auditory prosthetics. With bilateral severe conductive hearing loss, hearing aids with a bone vibrator are used. While preserving the auditory canal, classical auditory parting or cochlear implants are shown.

The prognosis for the patient's health and the cosmetic result depend on the severity of the disease and the age of the therapeutic measures. In most cases, the violation of auditory function can be partially or completely compensated. Specific preventive measures against microtia have not been developed. Nonspecific prevention implies rational planning of pregnancy, limiting or minimizing the effect of teratogenic factors on the fetus: taking medications during pregnancy strictly according to the instructions of specialists, abandoning bad habits, early diagnosis and treatment of infectious pathologies, endocrine disorders.