By Meghan Sullivan, DVM, DACVS
Otitis externa is a very common condition in dogs that is a result of inflammatory changes in the lining of the ear canal. The epithelium within the ear canal becomes inflamed, hyper-pigmented and hyperplastic. The end result of this process is narrowing or stenosis of the ear canal as well as fibrosis, mineralization and finally, occlusion of the ear canal. In cases of severe otitis externa, the tympanic membrane can rupture and result in otitis media. Rarely, in worse cases, dogs and cats can develop otitis interna and get secondary vestibular signs or hearing loss.
Allergic disease, immune-mediated skin disease, or other systemic disease may be the underlying cause of otitis externa. Bacteria and yeast are rarely the primary cause of the disease as they are mostly opportunistic organisms: recurrent infections can result in the development of resistant organisms. On average, twenty-five percent of dogs with food allergies have otitis externa as the only clinical sign. If a dog has chronic recurrent ear infections, they most likely have underlying allergies or atopy. Certain breeds are predisposed to otitis, such as Cocker Spaniels who tend to have excessive production of cerumen in the ear canal.
Diagnosis of otitis is made with otoscopic exam, cytology and sometimes biopsy. Radiographs, CT and MRI are imaging options to further evaluate the ear canal and bullae. CT is the most helpful modality for assessing the canal, any fluid or soft tissue in the middle ear, and any mineralization of the canal or potential masses. A normal ear is filled with air in the external and middle ear canal. Advanced otitis externa and media will present as narrowed or stenotic canals; fluid or tissue density may be noted in the bulla. CT allows the surgeon to assess both bullae for bone thickening or destruction. A CT is performed under general anesthesia and can be scheduled immediately prior to the surgical procedure. CT is considered superior to conventional radiographs of the area, and the cost is comparable to conventional radiographic views.
This is a patient with severe bilateral otitis externa (ear canals completely filled with thickened tissue and both bulla are filled with soft tissue density).
The preferred surgery to help alleviate the symptoms of otitis is total ear canal ablation and bulla osteotomy (TECA-bo). During this procedure, an incision is made through the skin and the entire external ear canal (vertical and horizontal) is removed. The entrance to the bulla is enlarged. The secretory epithelium inside of the bulla is completely removed by careful curettage of the bulla cavity so that no further secretions can reform. Care is taken during dissection to prevent trauma or stretching of the facial nerve which is located caudoventrally at the level of the horizontal ear canal. Caution is also exercised to prevent dissection in the dorsal region of the bulla because the round window and internal ear structures are in that location. Total ear canal resection and bulla osteotomy is often performed bilaterally during the same anesthesia period for end stage otitis externa. In some cases, the surgeon may schedule each TECA-bo separately, depending on the health status of the patient and severity of the disease present in each ear.
Pain control is generally performed with an infusion of a local anesthetic such as bupivacaine into the surgical site before closure. Other strategies include placing a wound soaker catheter to deliver intermittent doses of bupivacaine every 6-8 hours overnight, or injecting Nocita into the subcutaneous and subcuticular tissues. Nocita is a long acting local anesthetic that is made up of a liposomal encapsulated bupivacaine in an injectable suspension. When injected into the surgical site of canine stifle surgery, Nocita was found to be extended release for approximately 3 days.1 Nocita is FDA approved for use in surgical sites of dog stifle surgery; any other location or surgical site is considered off label and not approved. At Angell, we have been using Nocita on stifle surgery as well as other non-FDA approved sites such as TECA, amputations, mastectomies, fractures, etc. with very good success. An added benefit of Nocita versus placing a soaker catheter is that there is less fluid collection into the surgical site which might add to seroma development or poor healing.
This is a patient with unilateral otitis externa and media. The normal bulla is black (air-filled) the abnormal is filled with soft tissue or fluid density (grey). The ear canal should have black air-filled appearance. The abnormal has grey soft-tissue density filling the external ear canal.
Complications of ear canal surgery include bleeding (which can usually be controlled well intraoperatively), dehiscence, nerve damage (Horner syndrome, facial, vestibular) and hearing concerns. These potential complications should be discussed with the pet owner prior to surgery. The majority of neurologic complications can be self-limiting and improve over several weeks, though some may be permanent. Although uncommon, damage to the branches of the maxillary artery can be challenging to control: in severe cases, ligation of the ipsilateral carotid artery may be indicated. Horner syndrome can occur because of damage to the sympathetic nerves running through the middle ear. This manifests as third eyelid protrusion, miosis and enophthalmos. Horner syndrome is much more common in cats than dogs. Horner syndrome can be seen in 6% of cats before surgery and up to 17% to 42% of cats after TECA-bo and can be permanent in 14% to 27% of cats.2 Facial nerve damage can also occur secondary to ear surgery. Facial nerve damage may occur in 6% of cats preoperatively and 12% to 56% postoperatively with up to 28% permanent.2 In dogs, facial nerve damage can occur in 13% to 36% of dogs after TECA-bo and can be permanent in 4% to 13% of dogs.2 Patients with extensive thickening and enlargement of the ear canal are at greater risk of facial palsy secondary to the surgical dissection required to resect the diseased tissues. Head shaking, pawing at the ear, suture pattern failure, or postoperative infection can result in dehiscence. Another complication that can develop later in the postoperative period is draining tract formation: this is commonly associated with the retention of secretory epithelium remaining within the bulla or remnant of the ear canal lining. A resistant infection associated with the bulla and adjacent soft tissues also can result in tract formation. Culturing the bulla at the time of surgery is useful to select the most appropriate antibiotic for residual bacteria present prior to surgical closure.
One of the most common questions regarding ear surgery for owners is if their pet will be deaf. Pets actually have hearing loss prior to surgery as a consequence of their end-stage otitis externa, especially if they are affected bilaterally.2 Frequently after surgery, owners will report that their pets can actually hear and respond to loud or high pitched noises.3,4 One study of 7 dogs showed that after bilateral ear canal ablation, all dogs could hear and were able to respond to loud noises and voices, but their brain stem auditory-evoked responses (BAER) to air-conducted stimulation were lost.2 Ears that responded to bone-conduction stimulation before surgery also responded after surgery.2,5
While small localized tumors may be removed with partial canal removal (vertical, lateral ear canal resection), larger and more diffuse neoplasms may require total ear canal ablation. The surgical outcome is best if the tumor is limited to the vertical or horizontal ear canal. If the mass is more extensive and involves the bulla, the prognosis is generally considered poor. Cats with malignant masses in the external ear have a worse prognosis than dogs. Squamous cell carcinoma is the most common ear tumor found in cats. A cat that has neurologic signs prior to surgery is a poor prognostic indicator when associated with squamous cell carcinoma and ceruminous gland adenocarcinoma. CT scan is a helpful diagnostic tool to diagnose a tumor and to determine surgical options. Adjunctive radiation therapy and chemotherapy are options to consider for problematic tumors.
In summary, total ear canal ablation and bulla osteotomy is a successful surgery and carries about a 57-94% success rate. This surgery has the potential of eliminating the chronic pain associated with chronic otitis externa. It also is an option for removing problematic neoplasms involving the external ear canal.
- Lascelles BDX, Rausch-Derra L, Wofford JA et al. Pilot, randomized, placebo-controlled clinical field study to evaluate the effectiveness of bupivacaine liposome injectable suspension for the provision of post-surgical analgesia in dogs undergoing stifle surgery. BMC Vet Res. 2016; 12 (1): 168.
- Tobias, KM and Johnston SA. Veterinary surgery: Small Animal. 1st Edition, Elsevier, Saunders, 2059-2077.
- White RAS, Pomeroy CJ: Total ear canal ablation and lateral bulla osteotomy in the dog. J Small Anim Pract 31: 547-553, 1990.
- Smeak DD, DeHoff WD: Total ear canal ablation: clinical results in the dog and cat. Vet Surg 15:161, 1986.
- Krahwinkel DJ: External ear canal. In Slatter D, editor: Textbook of small animal surgery, ed 3, Philadelphia, 2003, Saunders, pp 1560-1567.
- Fossum, T.W. (2007) Small Animal Surgery. 3rd Edition, Elsevier, Mosby, 289-315.