Zur
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.
Surgery:
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.
Postoperative
care:
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.
Complications:
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
www.Hamburger-Fortbildungstage.de
Dr.
Bruce Christie, Melbourne
Dr. Itamar Tsur, Jerusalem