Bilateral aural atresia in a beagle puppy

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A six-month-old female beagle presented to Animal Referral Hospital (ARH) for suspected bilateral aural atresia. At her second puppy vaccination with her regular veterinarian, it was noted that she had absence of ear canal openings bilaterally.

During consultation at ARH there was no history of pain in her ears, but she appeared less responsive to verbal cues. She was otherwise a very bright and energetic puppy. On physical examination bilateral aural atresia was observed (Figure 1a and 1b), while all other aspects of the examination were within normal limits. 

PCV/TP and Creatinine blood test were performed and noted to be within normal limits. Computed tomography (CT) was performed which confirmed bilateral aural atresia, demonstrating blind ending of the vertical ear canals at the level of the skin near the base of the pinnae (Figure 2). Bilaterally, the horizontal and vertical ear canals were moderately torturous and filled with soft tissue/fluid attenuating material. The left tympanic bulla was gas-filled while the right was of soft tissue/fluid attention. 

Surgical intervention including reconstruction with anastomosis of the ear canals and total ear canal ablation with bulla osteotomy (TECA-BO) were discussed with the client. TECA-BO is a salvage procedure that is generally performed in cases of chronic, severe, end-stage disease or neoplasia.1 As the CT report demonstrated that chronic change was not present, opening of the blind ending sac and anastomosis of the vertical ear canal to the external acoustic meatus was recommended with an associated good prognosis. 

Bilateral, single-session reconstruction and anastomosis was performed when the patient was nine months old. A repeat CT was performed immediately prior to surgery, with similar findings to the initial scan. The left ear was operated first. A skin incision was made from the tragus and extending ventrally over the vertical ear canal. Cartilage at the base of the pinna was sharp dissected and removed to create a neo-meatus for the external ear canal. The blind ending ear canal was isolated and excised to access the vertical canal. A moderate amount of grey, ceruminous fluid exuded from the canal, and a sterile swab was used to sample the fluid for culture and sensitivity. 

The fluid was suctioned, the canal lavaged and the vertical ear canal cartilage and epithelium was anastomosed to the cartilage and skin at the neo-meatus with 3/0 polydioxonone (PDS) simple interrupted sutures in a single-layer, appositional pattern. The ventral skin incision was closed with 3/0 PDS simple interrupted sutures. 

The surgical technique was repeated on the right ear (Figure 3a and 3b). 

bilateral aural atresia

Post-operatively, a soft-padded head bandage (Soffban, conforming and Vetwrap) was placed with the ears exteriorised and placed dorsally to allow for drainage and to minimise swelling. The patient was hospitalised overnight and received intravenous fluid therapy (Hartmanns, 3ml/kg/hr). Analgesia was provided with fentanyl CRI (3mcg/kg/hr) for four hours post-operatively, followed by intermittent methadone (0.3mg/kg SC q4hr). 

The following day the head bandage was removed. There was mild swelling at the base of the pinna with mild discharge from the surgery sites. The patient was otherwise bright and comfortable and was discharged that afternoon with a seven-day course of oral Meloxicam (0.1mg/kg PO SID) and Amoxycillin-Clavulanic Acid (15mg/kg PO BID). An Elizabethan collar was recommended to be worn at all times. 

The culture and sensitivity report was received for both ears. The right ear had no bacterial growth. The left ear had growth of Staphylococcus pseudintermedius, sensitive to Amoxycillin-Clavulonic acid. 

At 10 days post-surgery, a recheck was performed, at which time the patient was noted to have a three-day history of discharge and malodour from the surgical sites bilaterally. The ears had a moderate amount of dry, crusted discharge along the pinna and brown, purulent/sebaceous discharge from the ear canals. The ears were cleaned with Chlorhexidine aqueous solution (diluted 0.05%) and sterile swabs. The surgical sites had mild erythema, with no evidence of dehiscence. A seven-day course of Amoxycillin-Clavulanic Acid (20mg/kg PO BID) was dispensed. 

Rechecks were also performed at 2.5- and 3.5-weeks post-operatively. Each time there was less discharge production and minimal malodour. The ears were cleaned similarly to the previous visit (Figure 4a and 4b). There was a mild amount of erythema and granulation tissue forming on the right ear at the 3.5-week recheck, suggesting mild superficial skin dehiscence, and healing via secondary intention. All tissue appeared healthy, and the remaining external sutures were left in place. Response to verbal commands was evident at the 3.5 week recheck (Figure 5). 

Aural atresia can be congenital or secondary to trauma.2 Given the bilateral presentation and lack of noted trauma in this case, congenital malformation was presumed. 

The ear develops from ectodermal cells as an embryo to form the external acoustic meatus,3,4 but with developmental malformation aural atresia can occur. Glandular epithelium is still present within the blind-ending ear canal and can lead to an accumulation of ceruminous fluid debris,2 as seen in this case. If aural atresia is not diagnosed early, the accumulation of fluid can result in rupture of the tympanic membrane, chronic pain (otalgia) and possible abscessation.4 In chronic cases, TECA-BO has been reported,4 which can lead to complications such as facial nerve paralysis (damage to cranial nerve VII adjacent to the ear canal) or Horner’s syndrome (damage to sympathetic fibres within the middle ear).1,2 In cases diagnosed early such as the example above, ear canal anastomosis has shown to have fewer complications and a lower morbidity when compared to TECA-BO, as the surgical approach avoids important regional neurovascular structures.2,5 Additionally and importantly, ear canal anastomosis also allows recreation of almost normal anatomy and preservation of auditory function.


References:

1. Johnston SA, Tobias KM. Veterinary Surgery Small Animal. 2nd ed. Elsevier, St Louis, 2018.

2. Coomer AR, Bacon N. Primary anastomosis of segmental external auditory canal atresia in a cat. J Feline Med Surg 2009;11:864–868.

3. Caine AR, Herrtage ME, Ladlow JF. Imaging diagnosis – Ear canal distension following external auditory canal atresia. Veterinary Radiology and Ultrasound 2008;49:267–269.

4. Simpson D. Atresia of the external acoustic meatus in a dog. Aust Vet J Australian Veterinary Association, 1997;75:18–20.

5. King J, Mouatt J, Corfield G. Pre- and post-operative computed tomography and reconstructive surgery for canine atresia. Australian Veterinary Practitioner 2019;49:59–62.


Dr Farrah Harris

bilateral aural atresia

(BVSc (Hons))
Animal Referral Hospital

Dr Farrah Harris graduated from the University of Queensland in 2020, and she is currently completing a surgical internship at Animal Referral Hospital, Sinnamon Park. She has a special interest in small animal surgery and hopes to complete a small animal surgical residency as part of her career plans. 

Acknowledgement: To Dr Lance Wilson for his input and mentorship in this case. 

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