Surgery for Otitis Media and Otitis Interna

Chapter 62 Surgery for Otitis Media and Otitis Interna



Harry W. Boothe


Selection of a surgical procedure to treat otitis media and otitis interna is based on duration of clinical signs, response to previous treatment, status of the external ear canal, and the surgeon’s familiarity with related anatomy and technique. Surgical options for treating otitis media and otitis interna include myringotomy (see Chapter 61), lateral bulla osteotomy, and ventral bulla osteotomy. Nasopharyngeal polyps are most appropriately excised using a bulla osteotomy in combination with other excision techniques. Potential complications of bulla osteotomy surgery include facial nerve injury, Horner’s syndrome (ptosis, miosis, enophthalmos, nictitating membrane protrusion), and vestibular signs. See Chapter 61 for diagnosis and medical treatment of otitis media and otitis interna.



ANATOMY



• The tympanic membrane slopes downward, forward, and inward—toward the middle ear cavity. The membrane is composed of a larger, more peripherally located pars tensa and a smaller, triangular-shaped pars flaccida.

• The air-filled tympanic cavity constitutes the major portion of the middle ear and is connected to the nasopharynx by the auditory (eustachian) tube.

• Structures located within the dorsal aspect of the tympanic cavity include the three auditory ossicles, associated muscles and ligaments, and tympanic nerve.



Key Point


The feline tympanic cavity is divided into a larger ventromedial and a smaller dorsolateral compartment by a nearly complete thin bony septum.



• Surgically important structures near the tympanic bulla are the facial nerve (ventrolaterally), the carotid artery (medially), and the hypoglossal nerve (ventrally).


LATERAL BULLA OSTEOTOMY



Preoperative Considerations



• Thoroughly examine the external ear canal.

• Evaluate the radiographic appearance of the tympanic bulla and the microbiologic status of the middle ear before lateral bulla osteotomy. Computed tomography, or CAT scan, (see Chapter 4) is particularly helpful in assessing disorders of the tympanic bulla.

• Lateral bulla osteotomy is simplest when performed in conjunction with a total ear canal ablation. If the external ear canal is normal or only mildly affected by infection, bulla osteotomy can be performed via a lateral (without ear canal ablation) or ventral approach. The ventral approach is preferred by most surgeons.

• Assess the integrity of the facial nerve preoperatively.


Surgical Procedure



Objectives



• Provide access to the tympanic cavity to obtain samples for diagnosis.

• Provide drainage and access to the middle ear cavity for therapeutic intervention (e.g., flush, curettage, and resection of abnormal tissue).


Equipment



• Standard general surgery pack and suture

• Periosteal elevator, Steinmann pin, hand chuck, and rongeurs

• Warm saline solution and tubing for flushing the tympanic cavity


Technique for Lateral Bulla Osteotomy without Total Ear Canal Ablation



1. Position the patient in lateral recumbency, and prepare the lateral aspect of the head and neck.

2. Incise the skin over the vertical ear canal to a point ventral to the horizontal ear canal (Fig. 62-1).

3. Bluntly dissect between the parotid salivary gland and the ventral aspect of the horizontal ear canal to reveal the facial nerve.

4. Retract the facial nerve ventrocaudally near its exit from the stylomastoid foramen.

5. Elevate the soft tissue overlying the lateral aspect of the osseous bulla using a periosteal elevator.

6. Enter the tympanic cavity ventral to the horizontal ear canal with the Steinmann pin and hand chuck.

7. Enlarge the osteotomy site ventrally with rongeurs.

8. Obtain microbiologic samples, and flush the middle ear cavity using warm saline solution. If curettage is performed, avoid traumatizing the inner ear structures on the dorsomedial aspect of the bulla.

9. Place and secure a drain tube (e.g., Penrose drain) into the tympanic cavity by suturing it to the adjacent soft tissue with fine absorbable suture material.

10. Routinely close the subcutaneous tissue (simple interrupted, absorbable suture) and the skin (simple interrupted, nonabsorbable suture).

11. Position the drain tube so that it exits the skin adjacent to the primary incision.

image

Figure 62-1 Skin incision for performing a lateral bulla osteotomy without total ear canal ablation.



Technique for Lateral Bulla Osteotomy with Total Ear Canal Ablation



1. Position the patient in lateral recumbency, and prepare the lateral aspect of the head and neck, including the external ear canal.

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  4. Otitis Media and Otitis Interna

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Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Surgery for Otitis Media and Otitis Interna

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