Complications of cortical mastoidectomy

1. Dural injury and CSF leak

• Exposing a small area of dura without significant abrasion is common and rarely matters.
• A tear, or an abrasion with arachnoid herniation, needs repair whether or not CSF is leaking. Consider a broad-spectrum antibiotic that penetrates CSF.
• Repair in layers. Use fascia or perichondrium plus rigid support such as bone or cartilage. If the dura is actually torn, place part of the graft intradurally. Pack with Gelfoam, with or without fibrin glue.
• Late consequences are meningitis, encephalocele and brain abscess.

2. Facial nerve injury

• Cummings calls the facial nerve the key to mastoid surgery. Injury is rarely due to an anomalous course. It is usually caused by:
  • excessive manipulation of a diseased or dehiscent tympanic segment, or
  • drill misadventure at the second genu or the mastoid segment.
• In one series of 416 cholesteatoma operations, facial nerve dehiscence occurred in about 20%. The most common site was near the oval window.
• Opening the fallopian canal or minor abrasion of the sheath is usually harmless.
• Management depends on the depth of injury:
  • Transection of less than 30-40% of the nerve diameter: decompress 3-4 mm each side of the injury, incise the epineurium, and give steroids.
  • Transection of more than 40-50%: resect the injured segment, then primary anastomosis or an interposition graft.
• Delayed palsy (onset after days) usually recovers with steroids and observation. Explore if electroneuronography shows more than 90% degeneration within 2 weeks.
• Immediate palsy that was not recognised at surgery needs prompt re-exploration, though a delay of 1-2 days is acceptable.
• Mastoidectomy was the most common procedure behind iatrogenic facial palsy (55% in one series of 22 patients). Facial nerve monitoring helps but does not replace knowing the anatomy (Shambaugh Surgery of the Ear, Facial Nerve Injury).

3. Labyrinthine injury

• A horizontal semicircular canal fistula was found in 6.5% of cholesteatoma operations. It was more than twice as common when the facial nerve was dehiscent.
• If the canal is entered by the drill, close it at once, usually with bone wax. Give a short course of antibiotics and steroids.
• Risks are bacterial labyrinthitis, vertigo and severe sensorineural hearing loss (a "dead ear"). Early recognition and sealing limits the damage. Some transient dizziness is expected.

4. Sigmoid sinus and jugular bulb injury

• Their anatomy varies, so they are easily injured. In a poorly pneumatised mastoid the sinus can lie just under the cortex, less than 1 cm from the posterior canal wall.
• Control bleeding with digital pressure first. Use bone wax for small tears and cellulose packing for larger ones. Cover the packing with bone wax if you need to keep drilling.
• Significant injury can cause sinus thrombosis and otitic hydrocephalus. New headache or visual change after surgery calls for MRI/MR venography and fundoscopy.
• Emissary vein bleeding is controlled with bipolar cautery or bone wax. Avoid coagulating too close to the sinus (Scott-Brown's Otorhinolaryngology, Vol 2).
• If packing is pushed into the lumen of the jugular bulb, pulmonary embolism is a risk (Shambaugh Surgery of the Ear).

5. Other complications

• General surgical: haemorrhage or haematoma, wound infection, perichondritis, and postauricular wound problems.
• Ear-specific: conductive hearing loss from ossicular injury or dislocation, tympanic membrane perforation, and external canal stenosis. Taste disturbance from chorda tympani injury and tinnitus are also described.
• Disease-related: recurrent or residual cholesteatoma, which is the usual reason for second-look surgery.

Prevention

• Identify landmarks: the tegmen, sinodural angle, sigmoid sinus, antrum, horizontal canal, and the digastric ridge for the facial nerve.
• Use a large cutting burr first, then a diamond burr near vital structures, with constant irrigation to avoid thermal injury.
• Use facial nerve monitoring. Get CT in revision cases. Give patients a documented consent covering these risks.

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