Round window chamber and fustis: endoscopic anatomy and surgical implications

Abstract

The round window region is of critical importance in the anatomy of the middle ear. The aim of this paper is to describe its anatomy from an endoscopic point of view, emphasizing structures that have important surgical implications, in particular the fustis and the subcochlear canaliculus. The fustis, a smooth bony structure that forms the floor of the round window region, is a constant and important structure. It seems to indicate the round window membrane and the correct position of scala tympani. A structure connecting the round window region to the petrous apex, named the subcochlear canaliculus, is also described. A retrospective review of video recordings of endoscopic dissection and surgical procedures, carried out between June 2014 and February 2015, was conducted across two Tertiary university referral centers. A total of 42 dissections were analyzed in the study. We observed the fustis in all the cases and we identify two different anatomical conformations. The subcochlear canaliculus was found in 81.0 %, with a pneumatization direct to the petrous apex in 47.7 %. Conformation and limits of the round window niche may influence the surgical view of the round window membrane. Endoscopic approaches allow a very detailed view, which enables a comprehensive exploration of the round window region. Accurate knowledge of the anatomical relationships of this region has important advantages during middle ear surgery.

Endoscope-Assisted Cochlear Implantation

“…Recent studies underlined the importance of preoperative high resolution computed tomography (CT) findings and reported that the radiological evaluations correlated with the visibility of the RW [ 24 , 25 ]. Although the anatomical variations of the posterior tympanum and RW region were described in detail [ 26 ], problems in surgical orientation such as mistaking a wide subcochlear canaliculus with the RW niche may lead to inadvertent implantation attempts resulting in failure and other major complications may arise.…”

Facial sinus endoscopic evaluation, radiologic assessment, and classification

“…In literature, several authors have already studied the anatomy of this region. In particular, present authors have already described from an endoscopic perspective the ST, the pyramidal eminence with the subpyramidal space, the sinus subtimpanicus, and the round window niche with the subcochlear canaliculus . In 1969, Proctor had already described the microscopic surgical anatomy of the posterior tympanic wall and defined a system of sinuses around several permanent projections of the styloid complex, such as the pyramidal eminence, the styloid eminence, and the chordal eminence .…”

“…In particular, present authors have already described from an endoscopic perspective the ST, 2,3 the pyramidal eminence with the subpyramidal space, 4 the sinus subtimpanicus, and the round window niche 9 with the subcochlear canaliculus. 5 In 1969, Proctor had already described the microscopic surgical anatomy of the posterior tympanic wall and defined a system of sinuses around several permanent projections of the styloid complex, such as the pyramidal eminence, the styloid eminence, and the chordal eminence. 10 The sinuses of the retrotympanum were the ST and PTS (positioned medial to the facial nerve), and the LTS and FS (positioned lateral to the facial nerve).…”

“…In the recent literature, the present authors have already studied the endoscopic and radiologic anatomy of the retrotympanum, describing the variations in shape and relationship of the sinus tympani, the pyramidal eminence with the subpyramidal space, and the round window niche …”

“…In the recent literature, the present authors have already studied the endoscopic and radiologic anatomy of the retrotympanum, 1 describing the variations in shape and relationship of the sinus tympani, 2,3 the pyramidal eminence with the subpyramidal space, 4 and the round window niche. 5 However, until now no studies have focused on the endoscopic anatomy of the facial sinus (FS) and its relationship with surrounding structures.…”