ABSTRACT: a first branchial cleft anomaly. First branchial

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Last updated: October 1, 2019

ABSTRACT: Collaural fistula (or cervico aural fistula) is a first branchial cleft anomaly. First branchial cleft anomaly is rare and accounts for less than 8% of all brachial cleft anomaly .Due to its relatively rare occurrence and varied presentation it is often misdiagnosed and inappropriately treated. Thus it may present to a general surgeon, ENT specialist, head and neck surgeon, paediatrician, or general practitioner. In this paper, we report one such case of a 14 year old girl with collaural fistula, who presented to us as a case of persistent recurrent neck abscess.

Here we highlight on clinical picture, examination, evaluation, treatment, and outcome together with a good understanding on relevant embryology and regional anatomy. Thus the lesion could be easily diagnosed in early presentation with a chance for best out comeKEY WORDS: Collaural fistula, First Brachial cleft anomaly,  First brachial cleft anomaly usually present as a cyst, swelling, sinus or as fistula in the pre-auricular or post-auricular area or high in the neck, which may become infected 1. Failure to recognize these unusual cases may result in misdiagnosis, inadequate treatment, and subsequent recurrence. Further definitive surgery may thus be complicated 1. The external ear canal is a derivative of the first branchial arch. Anomalies of the first branchial cleft, therefore involve external ear structures which are normally managed in otology practice. However in duplication anomalies, clinical features are varied and patients may present to a General Surgeon.

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This paper reports a case to highlight specific diagnostic clinical picture of collaural fistula- history, clinical features, signs and symptoms-with special reference to embryology, anatomic and histological classification and relevant surgical managementCase report: A 14 year old female was referred to us with recurrent neck swelling and pus discharge from upper part of neck, behind angle of mandible on right side,of 4 months duration. In the Past, she had a similar swelling at same site at age of 1 year which was treated by Incision & Drainage. Again it recurred at 4 years of age and multiple times after words. She was wrongly diagnosed as Tuberculous lymphadenitis and had a course of anti-tuberculous treatment. She also had right ear discharge, multiple episodes, which was diagnosed as CSOM and was treated conservatively in the past.

Present swelling was diagnosed as recurrent tuberculous abscess/sinus and was on ATT for past 4 months, before being referred to us.  On examination there was a 2×1 cm firm swelling, with an overlying scar and discharging sinus, 4 cm below right angle of mandible. Discharge was purulent in nature.

An ultrasound scan of neck showed multiple enlarged lymph nodes, few with necrotic changes. Pus culture and fungal culture was negative. No Acid Fast Bacilli were seen. Thus a diagnosis of persistent neck sinus was made with a doubtful infective aetiology as cause. Patient was posted for surgery under GA, prior to surgery sinus was probed and methylene blue was injected into sinus to delineate the tract but dye was found to be draining through the right ear. Thus a clinical diagnosis of collaural fistula was made. On detailed ENT examination there was a central tympanic membrane perforation and a fistula opening in postero-inferior part of bony external auditory canal.

Surgical excision was carried out through a horizontal skin incision including an ellipse surrounding the cutaneous neck opening. Tract was dissected from cervical end to aural end. There was fibrosis at cervical end of tract, may be due to repeated infections.

Dissection was done along the subcutaneous plane, with the track being carefully separated from the surrounding tissue. Methylene blue, which was injected prior to surgery served as a useful guide to trace the tract. The tract was then followed till its opening in the external auditory canal. In the upper part tract was cartilaginous and was found to open into the bony part of external auditory canal. It was found that the tract was passing lateral to the trunk of the facial nerve. Tract was excised off its attachments to surrounding structures and ear canal. Postoperative recovery was un eventful, There was no facial nerve weakness.

Histological examination of the specimen shows a tissue lined by stratified squamous epithelium. Focal area shows hair follicles, keratin flakes. Sub epithelium shows lobules of cartilage and focal serous glandsDISCUSSION: First brachial cleft anomalies are rare and there are only around 200 reported cases published 2.

It accounts for less than 5% of all brachial cleft anomalies 1,3,6. Although congenital in origin, first branchial cleft anomalies can present later in life. Swelling in the neck and post auricular region is the most common presenting feature .Clinically, they may present with repeated episodes of infection of the lesion. This may manifest itself with a cystic swelling or discharge from a fistulous opening either pre-auricularly or post-auricularly in the cheek, or high in the neck. A thorough otological examination should be performed in all cases as this may reveal a pit visible in the external canal at the site of entrance of a sinus or a fistula. A sinus/fistula opening in the external auditory canal is present in only 44% of patients, and even if such an opening is present, it may not be obvious 5. There may however be a complete absence of signs in the external auditory canal.

First branchial cleft anomalies are thought to develop as a result of incomplete obliteration of the cleft between the mandibular process of the first arch and the second arch and if the failure occurs during the time of formation of the closing membrane, a fistula extending into the middle ear may develop. A sinus will have an opening in the upper neck or in the floor of the external auditory canal, and a fistula will have an opening in both of these sites. The first branchial cleft anomalies have been classified as Type I or Type II by Work 7 Classification: In 1971, an anatomic classification by Arnot 8 designated Type I anomalies as defects in the parotid region, appearing during early or middle adult life. Type II defects appear in the anterior cervical triangle with a communicating tract to the external auditory canal and usually develop during childhood.

In 1972, Work proposed a histological classification 7. Type I anomaly is a defect of ectodermal origin, arising from duplication of the membranous external auditory canal. It can have a tract running medial and parallel to the external auditory canal, superior to the facial nerve and sometimes extend to the meso tympanum. Type II defects are ectodermal and mesodermal in origin, containing skin with adnexal structures as well as cartilage. Embryology: During the 4th week of human embryological development, 6 pairs of branchial arches appear which will form the future lower face and neck 4, and they disappear by the 7th week. Mesodermal in origin, these arches are separated from each other by the 5 branchial clefts (ectoderm) externally and 5 pharyngeal pouches internally (endoderm). First branchial cleft anomalies are a result of incomplete closure of the cleft 5. The chance of malformations occurring nearer the ear and parotid is greater than that occurring at the hyoid region, as obliteration of the cleft proceeds from ventral to dorsal.

Although the lesion normally has a close relationship to the parotid and facial nerve, the relationship is variable. For a Type II lesion, an early identification of the facial nerve at the stylo-mastoid foramen is recommended. If this part is affected by a disease, identifying the facial nerve proximally in the temporal bone and tracing it distally are probably the safest option. Poncet’s triangle is the anatomical triangle where first branchial cleft cysts or sinus orifice are typically located 7. The limits of the Poncet’s triangle are the external auditory canal above, the mental region anteriorly and the hyoid bone inferiorly.

The aim of treatment is to remove the lesion completely and safely with preservation of facial nerve and to reconstruct otological structures if needed. It is best achieved by early diagnosis and expert complete surgical excision. If the sinus/fistula opening involve the external auditory canal, it is removed with skin and cartilage. A primary closure is normally possible but if more than 30% of the circumference of the external auditory canal is denuded, split-thickness skin grafting and stenting are recommended. If the tympanic membrane or middle ear structures are involved, a reconstructive otologic surgery may be necessary. Surgical exploration and excision is the definitive treatment of these defects and this should only be undertaken when any acute infective episode has cleared. An acute infection makes dissection more difficult and also increases the risk of injury to the surrounding structures. The potential postoperative complications are facial nerve paralysis and recurrence of the lesion.

Conclusion: although the external ear canal is derived from the first brachial cleft, the clinical manifestation of its duplication anomalies are not necessarily confined to ENT, its rarity and diverse presentation have frequently led to misdiagnosis and inadequate treatment. An inflammatory process in the region of Poncet’s triangle should immediately raise an index of suspicion. A thorough otological examination and careful history should be taken into consideration. If suspected, patients should be referred for a specialist otological opinion as attempted drainage may further complicate definitive surgery.

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