Causes analysis of mastoid cavity infection after mastoidectomy and key techniques of revision mastoidectomy

Objective:To analyze the causes of infected mastoid cavity after mastoidectomy and explore the key techniques of revision mastoidectomy. Methods:Ninety-two patients, who underwent revision mastoidectomy due to mastoid cavity infection after mastoidectomy were retrospectively analyzed. There were 56 cases of canal wall up mastoidectomy plus tympanoplasty and 36 cases of canal wall down mastoidectomy plus tympanoplasty in previous surgery. The interval between the previous operation and this revision ranged from 7 months to 50 years, with a median of 9 years. By reviewing the general clinical data, preoperative HRCT scan of temporal bone and intraoperative findings, the defects of the previous operation and the region of the lesion were analyzed and counted. Results:Out of the 92 cases, 7 cases（7.6%） had sigmoid sinus antedisplacement and low-lying middle cranial fossa, and 45 cases（48.9%） with facial nerve canal loss. Among the 36 patients who underwent canal wall down mastoidectomy and tympanoplasty, mastoid cells were removed in completely; 26 patients had high facial ridge, accounting for 72.2%（26/36）. The defects of the previous operation included: stenosis of external auditory meatus（65/92, 70.7%）, obstruction of Eustachian tube（11/92, 12.0%）, and tympanitis（2/92, 2.2%）. Residual or recurrent lesions were most common in mastoid process and tympanic sinus（50/92, 54.3%）, followed by attic cell and anterior cavity（44/92, 47.8%）, posterior tympanic cavity（29/92, 31.5%）, perilabyrinthine cells（13/92, 14.1%）, sinus meningeal angle（13/92, 14.1%）, cells behind the facial nerve（12/92, 13.0%）, Eustachian tube（10/92, 10.9%）, and hypotympanum（9/92, 9.8%）. Conclusion:The main causes of mastoid cavity infecion after mastoidectomy include incomplete removal of the lesion and inadequate drainage conditions. The key techniques of revisional mastoidectomy include disc-shaped operative cavity, skeletonization of mastoid process, reduction of facial nerve ridge, management of Eustachian tube and conchaplasty. The above techniques are also key in the first operation in order to improve the success rate of operation and avoid revision operation.