Plz download this article that collected by Dr.Thang from Egypt.
Đây là bài viết tham khảo từ ” Current therapy in otolaryngology” 1999, tài liệu nghiên cứu từ Dr.Phước.
The method of CHARLES M.MYER III, M.D
A common cause of neonatal respiratory distress is choanal atresia. Although no definitive etiology is known, the condition occurs during the fourth week of embryonic life when the primitive nasobuccal membrane fails to rupture and the persistent atretic plate prohibits nasal breathing. Because neonates are obligate nasal breathers, bilateral choanal atresia is incompatible with life and definitive therapy is required to provide the neonate with an airway.
Patients with bilateral choanal atresia generally present as neonates with airway distress. Although they make vigorous respiratory effort, effective respiration does not occur until the children begin to cry and their nasal obstruction is bypassed. Once the crying stops, however, the mouth closes and a pattern of cyclical obstruction is established. Without intervention, the child will tire ultimately and effective respiration will cease, possibly resulting in death. In constrast to the patient with bilateral choanal atresia, children with unilateral choanal atresia usually do not present until later life. These patients most often are evaluated initially for persistent unilateral rhinorrhea and not respiratory distress.
The condition occurs is approximately 1 out of 8,000 live births, and there is some suggestion of famillial tendency. Most cases are unilateral, and it is seen in females more commonly than males. Although it is stated that choanal atresia is more frequently bony than membranous, in reality, most cases are combination of the two.
The diagnosis of bilateral choanal atresia is suspected in neonates with nasal obstruction when there is an inability to pass a #5 or 6 French feeding catheter through the nose into nasopharynx at least 3cm. One must be aware of the possibility of the tube kinking withing the nose, and direct observation of the oropharynx is imperative to confirm tube position. Once it has been determined that the tube cannot be passed into the nasopharynx, appropriate imaging should be obtained to confirm the diagnosis. In addition to confirming the diagnosis of choanal atresia, advanced imaging techniques allow other potential causes of nasal obstruction to be excluded ( Table 1). A computed tomographic ( CT) scan is the test of choice for diagnosing choanal atresia. Although a choanaogram may provide confirmation of the stenosis, CT demonstrates the surrouding anatomy in a superior manner that allows for more appriate surgical planning. Specifically, one can determine the thickness of the atretic plate as well as the medial encroachment of the posterior aspect of the medial maxilla.
When a neonate presents with respiratory distress secondary to nasal obstruction, the distress must be alleviated before investigative measures are begun. In the short term, placement of an oral airway or a McGovern nipple allows the respiratory distress to be bypassed.
Table 1 Potential causes of Nasal obstruction in the Neonate
Anterior nasal stenosis
Traumatic nasal deformity.
Generalized mucosa edema.
Concomitant with placement of these devices, gavage feedings must be instituated for feeding. Definitive surgical repair is undertaken before discharge of the patient from the hospital because I am uncomfortable making the child’s parents responsible for monitoring a potentially life-threatening problem should the airway inadvertently extrude. Given the fact, patients generally undergo surgical repair of their choanal atresia shortly after birth to avoid prolonhed hospitalization. If the neonate has other serious medical problems that prohibit discharge from the neonatal nursery, surgery can be delayed safely until hospital discharge is imminent. Although an oral airway is appropriate for initial airway management in most patients with bilateral choanal atresia, some affected individuals may require intubation for concomitant pulmonary disease, including bronchopulmonary dysplasia. In this situation, surgical repair can be coordinated with the advice of the attending neonatologist.
In up to 50 percent of patients, choanal atresia is associated with other anomalies ( Table 2). One must work diligently with the neonatologist and geneticist to identify any associated defects. Besides being important to the child and his or her ultimate development, this process may identify conditions that might impact adversely on the proposed surgical correction of the choanal atresia.
SURGICAL REPAIR: SỬA CHỮA BẰNG PHẪU THUẬT
There are multiple methods of approaching repair of choanal atresia. The most appropriate surgical method is determined by several factors, including the age of the patient and whether the atresia is unilateral or bilateral. The various approaches are discussed individually, focusing on the strengths and weaknesses of each. In all methods, there is difficulty in providing mucosal lining to the newly created posterior choanae, and granulation tissue formation with the potential for stenosis is present.
Table 2 Associated Congenital Anomalies___________________
Ear anomalies ( including deafness)
TRANSNASAL APPROACH: TIẾP CẬN QUA ĐƯỜNG MŨI
The most direct and simple technique for the repair of choanal atresia is through the tranasal route. Unfortunately, visualization is often a problem and this may preclude optimal results. Various techniques have been used with the transnasal route, ranging from blind puncture of the atretic plate with a blunt sound to elaborate microsurgical techniques using the operating microscope and the carbon dioxide laser. Preservation of posterior mucosal flaps is difficult both with this technique and others, and, as mentioned previously, granulation tissue may develop after repair. Whenever the transnasal approach is used, care must be taken to prevent injury to the skull base during the actual repair. Reported complications of this approach have included meningitis, cerebrospinal fluid leaks, brain injury, Grandenigo’s syndrome, and cervical vertebral subluxation.
Although the transnasal method is appealing, I generally use the transnasal route only for repair of purely membraneous stenoses or for dilation procedures after another method of repair. I am unconfortable using the laser with limited visibility to vaporize a bony plate posteriorly, and I do not feel that the lateral aspect of the stenosis is addressed adequately in most situations using this approach. Use of ear currettes may allow the lateral aspects of the stnosis to be removed, but this would be in a blind fashion frequently. Additionally, if a nasal speculum is opened sufficiently to provide adequate visualization, circumferential ulceration and eventual cicatricial scarring may result.
Once an adequate opening is created posteriorly, stenting is generally employed for approximately 12 weeks. In the normal newborn, a 3.5mm Silastic endotracheal tube is used as a stent. Red rubber catheters are passed through the nose and attached to the stent with silk sutures to place the stent in the child’s nose. As can be seen from figure 1, the stents are allowed to extend approximately 5mm beyond the nasal alae and are secured with a suture passed through a portion of the endotracheal tube. Use of an endotracheal tube bridge is imperative to prevent columellar erosion. The child’s parents are given specific instructions regarding the appropriate use of humidification with saline drops and suctioning. A suction catheter is measured in the operating room before the completion of the surgical procedure to provide the nurses and parents with a guide to the length of the stent that must be suctioned. Although the stents usually are left in place for approximately 12 weeks, they are changed in the operating room after 6 weeks to dilate the repaired region and to minimize the possibility of stent occlusion. Once the stents are removed, the use of topical corticosteroids may be necessary to diminish granulation tissue formation. In addition, choanal dilation may be necessary in some patients.
TRANSSEPTAL APPROACH: TIẾP CẬN QUA VÁCH NGĂN
This approach generally is reserved for older children with unilateral choanal atresia. Because the growth patterns of the septum and mid-face are not well understood, this technique is not recommended in the neonate. Additionally, the small size of the neonatal nose precludes adequate visualization for this approach. Stenting is accomplished in the method previously described. A sublabial extension of the transseptal approach has been described to improve superior visualization.
TRANSANTRAL APPROACH: TIẾP CẬN QUA XOANG HÀM.
Because of the development of teeth withing the maxillary sinuses, the transantral approach is viable only in older patients. Its utility appears limited, however, and this approach is rarely used.
TRANPALATAL APPROACH: TIẾP CẬN QUA KHẨU CÁI
I most frequently employ the transpalatal route for the repair of choanal atresia. Without question, visualization is superior with this method in comparison to those described previously. However, in the neonate or young child, the question of impaired palatal growth secondary to the surgical procedure must be kept in mind. However, I think this potential risk is worth accepting because my results are better with this technique.
The procedure is carried out with the patient in the supine position and the head hyperextended. A mouth gag with an appropriately small tongue blade is used to provide exposure, and, after infiltration of local anesthesia, a horseshoe-type incision is developed several millimeters posterior to the alveolar ridge. A periosteal elevator is used to develop a mucoperiosteal flap based on the greater palatine vessels. Once the posterior edge of the hard palate is reached, the mucosa is divided to provide access to the atretic plate. An attempt is made to maintain mucosal flaps on both sides of the atretic plate as the atretic plate, the posterior vomer, and the medial aspect of the posterior maxilla are removed with a diamond bur,otologic currete, or a rongeur. If mucosal flaps have been maintained. They can be transposed to provide covering of the superior and inferior surfaces of the choanae and stents are placed as described previously. The palatal flap is reapproximately loosely anteriorly with absorbable sutures.
OUTCOME: KẾT QUẢ
The repair of unilateral and bilateral choanal atresia is a challenging problem. Surgical fairlure is a real possibility in up to one-third of patients who undergo repair . Given this, careful counseling of the parents is important before embarking on surgical repair. Should stenosis develop after surgical repair, the patients generally have slowly progressive respiratory difficulties without acute distress. With this in mind, revision surgery or dilation, or both, may be carried out. Patients and their parents can expect an overall excellent outcome in the repair of this condition but should have realistic expectations regarding the length of time it may take to effect repair.