Recurrent unresponsive otitis is a frequent indication for aural surgery in the dog. Certain breeds are predisposed such as the spaniels due to their pendulous ears, Shar-Peis with their narrow ear canals, and poodles due to excessive hair growth. Cavalier King Charles can develop secretory otitis media and cocker spaniels may have increased cerumen production.
Inflammation from otitis may be a precursor to tumour development and increased glandular dysplasia. Many aural tumours are linked to chronic inflammation. Benign lesions include cholesteatomas, inflammatory polyps, papilloma, basal cell tumour, and ceruminous gland adenoma. However, malignancies such as ceruminous gland adenocarcinoma and squamous cell carcinoma can also be seen. Cats will commonly be evaluated for inflammatory polyps or squamous cell carcinoma of the ear tip.
In addition to the otoscopic examination it is important to perform a complete neurological assessment and thorough external palpation of the external ear canal. Local extension of infection or neoplasia can cause facial nerve deficits, Horner’s syndrome, and/or peripheral vestibular signs. Intracranial extension of the process can cause forebrain, brainstem, cerebellar or central vestibular signs. Identification of neurological deficits warrants pre-operative CT or MRI. Differential diagnoses such as Chiari like malformation should be considered for at risk breeds.
In most cases of severe persistent otitis a total ear canal ablation is the most practical management option. Medical therapy should be based on culture and sensitivity and administered prior to surgery to optimize surgical conditions; however, in most cases, extensive delay is not prudent as this can result in development of multi drug resistant organisms while not addressing the underlying cause. A lateral ear canal resection is often reserved for disease processes limited to the lateral vertical canal (such as a focal neoplasia). Lateral ear canal resections for severe otitis typically will result in stricture due to the profound inflammation and inability to maintain an adequate aural opening.
Adequate analgesia should be provided prior to, during and following a total ear canal ablation and can include full agonist opioids, local blocks or infusions and anti-inflammatories. The surgical approach is well described, attention should be given to avoiding damage to the retroglenoid/retroarticular vein (rostral), facial nerve and carotid artery and maxillary vein. Pre-operative CT will assist in determining the extent of middle ear involvement; however, a bulla osteotomy is almost invariably required in cases of severe otitis. The placement of a drain following surgery remains controversial and is not considered mandatory. In instances of subsequent abscessation this is more likely associated with inadequate debridement of the epithelial lining of the bulla rather than the lack of drain placement.
Post-operative care is based around providing adequate analgesia. Management of facial nerve paralysis in hospital is required in some cases with reports describing up to 36% of dogs developing transient facial nerve paralysis and up to 13% permanent paralysis (these numbers are expected to be higher in cats).
Pinnectomy is performed most often for neoplastic lesions, commonly squamous cell carcinoma in the cat. Margins should be 1–2 cm and skin is brought over the cut edge of the cartilage (usually from the convex surface) and then sutured.
Ventral bulla osteotomy is a common management option for cats with inflammatory polyps and those with disease limited to the tympanic bulla. The true middle ear is separated from the larger hypotympanic cavity and must be concurrently accessed. Cats are positioned in dorsal recumbency and incision centred over the tympanic bulla. Relevant anatomical structures encountered during the approach include the salivary gland, bifurcation of the linguofacial and maxillary veins, hypoglossal nerve, and lingual artery.
The incidence of neurological deficits following otic surgery is higher in cats than in dogs however attempts to avoid excessive curettage of the promontory can help reduce the risk of Horner’s syndrome when performing the ventral bulla osteotomy.