1 INTRODUCTION
Lateral semicircular canal prominences, which have relatively fixed
positions, are key anatomical landmarks used to locate the facial nerve
in middle ear surgery. The color and bone density of these prominences
differ distinctly from those of the compact bone around the tympanic
antrum, which enables easy identification of them during middle ear
surgery. Hence, these prominences often serve as key structural
landmarks during temporal bone dissection. Extensive ossification over
the lateral semicircular canal (EC-LSC) is a complex condition
encountered by surgeons during middle ear surgery that usually occurs in
patients with a long history of chronic otitis media or cholesteatoma.
Clinical cases of EC-LSC were first reported by Fleury et al. in
1978,1 who categorized EC-LSC into three types:
massive, diffuse attico-antral, and localized.2However, the literature has since featured relatively scant reports on
EC-LSC. Hoshino et al.3 performed surgeries on 89
patients with attic cholesteatoma over three and a half years. In eight
patients, they identified bony tissue proliferation at the tympanic
antrum or aditus ad antrum as typical characteristics of EC-LSC. A
previous study suggested that infectious stimuli at an early stage of
the disease might stimulate such osteoplastic
activity,3 while another study indicated that EC-LSC
might be induced by trauma.4 Regardless of its
etiology, the membranous labyrinth are apparent in such patients.
Notably, the bony lateral semicircular canal carina, a key landmark, is
often encased in dense bone. Hence, difficulties usually arise upon
encountering the facial nerve and membranous labyrinth, and – as the
incidence of iatrogenic fistula during surgery is extremely high –
inexperienced otologists may be prone to operating errors. In the
present study, we retrospectively analyzed all the data of patients who
underwent surgery for otitis media or cholesteatoma within the 3 years
to elucidate the clinical characteristics of EC-LSC. Findings from this
study will help inform preoperative planning, intraoperative procedures,
and postoperative management of symptoms.