Chirurgie der chronischen Otitis externa und interna
Total ear ablation and lateral bulla osteotomy
Preparation of the patient:
Lavage and gently clean the ear canal with warm 0,9% saline. Remember that dilute aqueous solutions of chlorhexidine, povidone iodine and benzalkonium chloride are ototoxic if the tympanic membrane is ruptured.
Make a T-shaped incision with the horizontal arm just below and parallel to the tragus. Extend the vertical component to just below the level of the horizontal canal. This incision should include dense subcutaneous fascia and extend to the cartilage of the tragus dorsally and as far as the lobules of the parotid gland ventrally.
Continue the horizontal incision dorsally curved fashion around the external auditory meatus to include all diseased tissue. This incision will transsect the cartilage of the pinna.
Isolate and free the vertical and horizontal canal to the point where it enters to the skull. This requires care and precision when cartilage and soft tissue in the region is altered by chronic inflammation or massive accumulation of debris within the ear. Apply Allis forceps to the cartilage cone to aid manipulation during the dissection to avoid the the facial nerve caudoventrally and the retroglenoid vein rostrally. Some small nerves might be seen to penetrate the horizontal ear canal. These are branches of the facial nerve. Their transsection does not result in facial paralysis. Transsect the ligamentous attachment of the ear to the skull and remove hypertrophied integument from the lining of the bony external auditory meatus.
Carefully retract the tissue from the lateral wall of the bulla to expose the bone. Remove the ventro-rostral segement of the bony rim of the external ear canal and extend the excision with rongeurs laterally to expose the tympanic cavity. Obtain a sample of the contents of the cavity for culture and sensitivity, then gently curette in the dorso-medial direction to decrease the chance of damage to cochlear and round windows which will result vestibular signs and nerve deafness. Damage to the sympathetic nerve that passes over to the promontory is also possible. Injury to this structure will result in Horner´s syndrome.
Anchor a Penrose drain near the bulla with a fine suture that exits the skin near the caudal base of the ear. Exist this drain through a stab incision at dependent area ventral to the bulla then close the incision in layers.
Analgetics: Include a narcotic in the premedication, saturate the surgical site with bupivacain ( not greater than 2 mg/kg) before closing. NSAID´s can be helpful, Bandage over the ear, Elisabethancollar to protext the bandage, drain removal in 3 to 7 days, give appropriate antibiotics systemically rather than infuse them locally.
Major haemorrhage (retracting tissues from lateroventral bulla)
Facial paralysis (might be present before surgery)
Vestibular signs (damage to cochlea or round window)
Chronic fistula (infected material still present)
Horner´s syndrome (damage to the sympathetic nerve which passes over the promontory)
Institut für Tierärztliche Fortbildung Hamburg
Bruce Christie, Melbourne
Dr. Itamar Tsur, Jerusalem