3.1 Characteristics of patients
All seven EC-LSC patients were women with a mean age of 45.9 years and a
disease duration of 4–25 years. Two of the patients (patients ID5 and
ID7) received revision surgery due to postoperative recurrence. All
seven patients suffered from middle ear cholesteatoma. Three patients
had concomitant tympanosclerosis and one patient had concomitant
adhesive otitis media. Canal wall down mastoidectomy was performed in
all patients, and concurrent ossicular chain reconstruction was
performed in four patients (total ossicular replacement prosthesis
[TORP], three; partial ossicular replacement prosthesis [PORP],
one) (Table 1).
The most common site of ossification was the tympanic antrum (6/7
patients), followed by the attic. Complete ossicle damage occurred in
two patients. The fusion of the osseous tissue and the ossicles was
observed in the other five patients, resulting in abnormalities in
ossicle morphologies. Fusion also occurred between the osseous tissue
and lateral semicircular canal, which obstructed the aditus ad antrum
and induced local drainage disorders in severe cases. The bone tissue
was visible upon postoperative pathological examination. As the density
of osseous tissue formed from ossification is close to or slightly lower
than that of the normal bone, it is often difficult to distinguish
between osseous tissue and the bone of the semicircular canal during
surgery. Cholesteatoma tissue or granulation tissue is usually concealed
between the osseous tissue and normal bone, as shown in Figure 1②
(patient ID2) and Figure 2. In two of the seven patients, semicircular
canal fistulas of differing degrees were found intraoperatively (Patient
1: the “blue line” of the lateral semicircular canal was exposed
intraoperatively and the membranous semicircular canal was intact
(Figure 1③); Patient 2: a 2-mm semicircular canal fistula occurred
intraoperatively during bone grinding).
Fascial patching and temporal
muscle filling were separately adopted for the closure of the lateral
semicircular canal fistulas, and
dexamethasone was administered
intraoperatively and postoperatively. Both patients with lateral
semicircular canal fistula experienced postoperative vertigo, which
subsided at 1 month and 3 months postoperatively, respectively, with the
administration of symptomatic treatment.