Page 78 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 5 · Surgery of the ear

to be noted even after TECA. Additionally, animals that inflammatory polyps (see section below) that are too
undergo bilateral TECAs may have postoper ative pharyn- extensive for removal by traction avulsion or have recurred
VetBooks.ir dissection and may develop respiratory distress, requiring consider ventral bulla osteotomy to be the treatment of
following traction avulsion. Many dermatologists also
geal swelling or hyoid apparatus damage from extensive
choice for effusive OM in cats because thorough lavage
temporary tracheostomy. When faced with this daunting
list of potential complications, many practitioners will opt
ventromedial compartments of the tympanic bulla can be
to refer patients to a specialist veterinary surgeon for of inflammatory exudates from both the dorsolateral and
this procedure. difficult owing to the presence of the bony septum sepa-
rating the compartments. Ventral bulla osteotomy may also
Prognosis: Long-term results are excellent in 58%, good be necessary in animals that develop recurrent infections
in 34% and poor in 8% of animals undergoing the proce- and fistulas after TECA and (lateral or ventral) bulla oste-
dure. Surgery is successful in alleviating signs in 92–95%, otomy, particularly if the ear canal epithelium was com-
and auditory function is usually not decreased because pletely removed at a prior surgery but the bulla was not
patients have been, and will be, reliant on bone and tissue opened or adequately cleared of infected contents.
vibration for conduction of sounds.
Patient positioning: The animal is placed in dorsal recum-
bency with the legs pulled caudally, neck extended and
Ventral bulla osteotomy head cradled by towels, a sandbag or suction cushion.
The clinical features of OM may include hearing loss and The rostral mandible can be taped to the table to improve
pain when opening the mouth or on palpation of the bulla. stability.
However, in many patients with OM secondary to exten-
sion of infection through a compromised tympanic mem- Surgical approach in dogs: The approach is through a
brane, chronic OE is the only clinical sign of concurrent ventral paramedian incision, starting medial to the ramus of
OM. With progression or chronicity, the vestibular portion the mandible and ending about 1 cm caudal to the level
of the inner ear may be damaged, causing signs of periph- of the ear canal. In dogs the bulla is not palpable. Once
eral vestibular disease (ataxia, head tilt and nystagmus). the skin and subcutaneous tissues have been incised, the
Cats may develop Horner’s syndrome because of damage spiky paracondylar process, the caudal attachment site
to sympathetic fibres within the bulla. Septic OM often for the digastricus muscle, is located. The bulla is about
occurs as a result of OE, and patients that have both con- 0.5 cm rostral and 0.5 cm medial to this bony process,
ditions usually require TECA and lateral bulla osteotomy. dorsal to the digastricus muscle. The incision is centred at
The decision on which procedure is appropriate depends a point midway between the ramus and the wing of the atlas
on the condition of the horizontal ear canal and whether it vertebra. The linguofacial vein is retracted if necessary.
is necessary to preserve air-conducted hearing. Bacterial
OM can, however, occur with minimal or no external ear Surgical technique in dogs: Blunt dissection is per-
canal changes or secondary to sinonasal or nasopharyn- formed between the digastricus muscle laterally and the
geal disease (most commonly seen in cats), and ventral myelohyoideus and hyoglossus muscles and the hyo-
bulla osteotomy may be required to relieve clinical signs. glossal nerve medially, keeping the scissors parallel to the
Bacterial OM without concurrent OE is most commonly long axis of the head to avoid damaging nerves and
encountered in cats. Other conditions that can lead to vessels. Self-retaining retractors, such as Gelpis, are used
signs of OM include congenital clefts of the hard and soft to keep the wound open. The digastricus muscle is
palate, Cryptococcus neoformans infection, polyps and retracted laterally and any remaining muscle tissues are
bluntly dissected from the bulla. The stylohyoid bone can
neoplasia. Radiography of the tympanic bulla (Figure 5.6)
is useful to evaluate for evidence of OM, as is CT. be palpated in the lateral part of the surgical field and
can be followed dorsally to its insertion on the lateral
Ventral bulla osteotomy provides drainage and removal
aspect of the bulla.
of fluids and inflamed tissues, and allows access to the
middle ear for cultures, biopsy and mass removal. It is The bulla is opened with an intramedullary pin or burr
and the opening is enlarged with the burr or with rongeurs.
most frequently performed in animals that have middle
If preservation of hearing is important, mechanical burrs
or inner ear disease and no significant changes in the
external ear canal, and is particularly indicated in cats with should be used sparingly because the vibration caused by
these instruments can have detrimental effects on the
cochlear apparatus. Samples of the bulla contents are
5.6 taken for culture and histological evaluation.
The ventral, medial and lateral portions of the bulla
Radiographic
appearance of are curetted and all contents aspirated. Curettage of the
otitis media in a epitympanic recess should be avoided because this will
dog. In this almost certainly damage the auditory ossicles. After it has
open-mouth view been inspected for residual epithelial tissue, the bulla is
of the skull soft flushed gently with warm saline. Closure is routine. Drains
tissue density fills are usually not needed but may be placed into the area
the left bulla
(arrowed). and exited through a new skin incision if severe infection
is present.
Postoperative care: Antibiotics are given if infection is
present, and treatment for OE is continued as needed.
Postoperative complications: Complications of ventral
bulla osteotomy are usually from inner ear damage and
include nystagmus, circling, head tilt and ataxia.

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