Cochleariform Process Research Articles

Quantitative morphology of facial nerve based on three-dimensional reconstruction of temporal bone

To investigate an effective method of quantitative analysis of the facial nerve and its adjacent structures on the basis of three-dimensional (3D) CT image reconstruction of the temporal bone. The inner structures of the temporal bone from CT images of 34 healthy adults were reconstructed. Precise measurement of the facial nerve and its adjacent structures were accomplished by using Able Software 3D-DOCTOR. 3D images of temporal bone structures, including facial nerve, tympanic annulus, cochleariform process, cochlea, semicircular canals, jugular fossa, and carotid artery, were reconstructed. Quantitative data of the facial nerve and its adjacent structures were analyzed, especially the detailed spatial relationships between the facial nerve and the surface of the mastoid process or tympanomastoid fissure. 3D reconstruction of CT images clearly displayed the detailed structures of the temporal bone. Quantitative data of the facial nerve and its adjacent structures are very useful for temporal bone surgery.

Incidence of Dehiscence of the Facial Nerve in 416 Cases of Cholesteatoma

To determine the incidence and location of dehiscence of the facial nerve in patients with cholesteatoma. Prospective case series. Tertiary referral centers. Charts and operative details from 1,372 consecutive chronic ear cases performed by a single surgeon were reviewed for anatomic details regarding the facial nerve. The study group was limited to the 416 ears in which cholesteatoma was confirmed at the time of surgery. Facial nerve dehiscence was graded as present or absent for both the tympanic and mastoid segments; the location of dehiscence in the tympanic segment was further characterized in regard to its relationship to the oval window and cochleariform process. Adherence of cholesteatoma to any area of dehiscence was also noted as was the presence of any coexisting inner ear fistula. Dehiscence of the tympanic segment was present in 18.8% (78 of 416) of ears in the study group. There were five cases of mastoid dehiscence. Approximately 80% of nerves that were dehiscent involved the area just superior to the oval window, and 12% involved the nerve anterior to the cochleariform process. Adults in the study were more likely to have dehiscence than those 18 years and younger (p = 0.0003, chitest), and inner ear fistula was also more common in those with dehiscence (p = 0.0118, chitest). Case studies of cholesteatoma adherent to the facial nerve are reviewed. This study represents the largest group of patients evaluated to date for dehiscence of the facial nerve in the setting of cholesteatoma. Dehiscence is common, especially in patients with cholesteatoma, and the careful surgeon can avoid damage to the facial nerve through understanding of this anatomic variation.

Reconstruction of the tensor tympani tendon

We describe a case in which reconstruction of the tendon of the tensor tympani muscle was necessary for the successful restoration of sound conduction. The right ear of a nine-year-old boy was treated for cholesteatoma with staged surgery. During the first operation, the tendon was cut to ensure good visibility in the tympanic cavity. Post-operatively, maintenance of aeration of the middle ear required ventilation tubes at first and Valsalva manoeuvres later on. The position of the reconstructed tympanic membrane varied a great deal, moving between the medial wall of the tympanic cavity and extreme bulging. This made exact measurement of a columella for ossicular reconstruction impossible. The preserved handle of the malleus was bound to the cochleariform process with ionomer cement, using a piece of surgical suture material as a substitute for the tendon. This arrangement prevented the tympanic membrane from undergoing excessive lateral movement after inflation and the ossicular chain was replaced with a successful ossiculoplasty with an autogenous bone 'drum to footplate' columella. The pre-operative 55.0 dB air-bone gap decreased immediately to 3.3 dB, widening after three years to 15.0 dB.

Correlation of CT analysis and audiometry in Japanese otosclerosis

Objective: To determine the extent of audiometric correlation with CT findings. Methods: Forty-four patients (82 ears) with surgically confirmed otosclerosis underwent preoperative CT examination. Based on the computed tomography (CT) findings, the ears were classified into five groups as follows: Group A, the group with no pathological CT findings; Group B1, the group with demineralization localized in the region of the fissula antefenestram; Group B2, the group with demineralization extending towards the cochleariform process from the anterior region of the oval window; Group B3, the group with extensive demineralization surrounding the cochlea; and Group C, the group with thick anterior and posterior calcified plaques. Results: There were 32 ears (39.0%) in Group A, 21 ears (25.6%) in Group B1, 16 ears (19.5%) in Group B2, 7 ears (8.5%) in Group B3, and 6 ears (7.3%) in Group C. The mean bone conduction levels were greater in the order of the extent of demineralization: Groups A, B1–B3 suggesting positive relationship between the cochlear function and the degree of labyrhinthine otosclerosis. Conclusion: A good correlation between the preoperative CT findings and audiometry findings suggests that CT with a slice intervals between 0.5 and 1 mm could provide useful informations in assuming the extent of otosclerosis in the inner ear.

A Rapid and Safe Middle Fossa Approach to the Geniculate Ganglion and Labyrinthine Segment of the Facial Nerve

The middle fossa approach provides neurotologic surgical access to lesions of the geniculate ganglion and the labyrinthine portion of the facial nerve as well as to the internal acoustic canal, and therefore helps preserve cochlear function. Although this approach is widely used, surgeons are still not certain which anatomic landmarks are best to locate the facial nerve and internal acoustic canal without causing labyrinthine damage. The purpose of this article is to describe a fast and safe technique to expose the geniculate ganglion and the labyrinthine portion of the facial nerve in two structures of the middle ear: the cochleariform process and the tympanic portion of the facial nerve. We prospectively evaluated 32 patients who underwent surgical facial nerve exploration via the middle fossa approach. Our goal was to determine the incidence of intraoperative difficulties and complications; we found none, and hearing levels could not be maintained in only one of the 32 patients. Our technique allowed us to decompress the first genu and the labyrinthine segment of the nerve. It also allowed us to reach and manipulate its tympanic segment in a very short amount of surgical time.

The nucleus double array cochlear implant: a new concept for the obliterated cochlea.

To increase the number of intracochlear electrodes that may be inserted into a totally obliterated cochlea, a special implant has been developed in collaboration with Cochlear Limited. This implant features two separate electrode carriers containing 11 and 10 active electrodes, respectively, as well as a reference electrode located on the receiver-stimulator package. The potential stimulation modes available with this device therefore include monopolar and bipolar stimulation, and stimulation between both arrays. A cochleostomy anterior to the round window provides access to the basal turn (both the scala tympani and the scala vestibuli), and new built connective tissue and bone can be removed until the anterior wall of the basal turn is approached. A second cochleostomy is performed at the second turn caudal of the cochleariform process and 2 mm anterior of the oval window after removal of the incus. New tissue should also be removed if necessary. The two electrode carriers are then placed into the scala tympani of the basal and the scala vestibuli of the second turn, respectively. The remaining surgical procedure is identical with that used for cochlear implantation in patients without obliterated cochleas. In this clinical study, 10 patients aged 32 to 66 years with an obliterated cochlea each received a double array cochlear implant. All patients had total obliteration of the basal turn either on preoperative imaging or during surgery. Intraoperatively, the second turn was not obliterated in only 4 of 10 patients. Postoperatively, a standard audiologic test battery was used to determine auditory improvement over time. POSTOPERATIVE RESULTS: All patients achieved significantly improved speech understanding when the additional apical electrode array was used, compared with the use of each electrode array independently. No complications occurred. In patients with a totally obliterated cochlea, the number of intracochlear electrodes can be increased by use of the Nucleus double array implant. As a result, patients achieve significantly better auditory results.

Microsurgical anatomy of the perigeniculate ganglion area as seen from a translabyrinthine approach.

Detailed anatomic knowledge of the microsurgical anatomy of the perigeniculate ganglion area is essential to probing adjacent to the facial nerve by a translabyrinthine approach. This study was designed to investigate the surgical anatomy of the perigeniculate ganglion area of the facial nerve from a translabyrinthine point of view. We dissected 15 human temporal bones under a microscope, measured the lengths of the tympanic segment and the labyrinthine segment by a middle cranial fossa approach, and measured the angle between the tympanic and labyrinthine segments by a translabyrinthine approach. The distance of the facial nerve from the cochleariform process to the geniculate ganglion was 3.8+/-0.7 mm. The length of the labyrinthine segment of the facial nerve was 4 +/-0.8 mm. The angle between the tympanic and labyrinthine segments from a translabyrinthine point of view was 26 degrees +/-5 degrees. Precise knowledge about the microsurgical anatomy of the perigeniculate ganglion area of the facial nerve from a translabyrinthine viewpoint is imperative for facial nerve decompression by a translabyrinthine approach.

The Nucleus Double Array Cochlear Implant: a new concept in obliterated cochlea

In order to increase the number of intracochlear electrodes to be inserted into a totally obliterated cochlea a special implant has been developed in collaboration with Cochlear Ltd. The implant features two separate electrode carriers containing 11 and 10 active electrodes, respectively, and a reference electrode on the receiver stimulator package. The potential stimulation modes include monopolar and bipolar stimulation as well as stimulation between both arrays. A cochleostomy at the round window provides access to the scala tympani. Newly formed bone is removed as far as the anterior portion of the basal turn. Care is taken to identify and preserve the osseous border of the cochlea. A second cochleostomy is performed immediately caudal to the cochleariform process after removal of the incus. New tissue can be removed here in the same way. The two electrode carriers are then placed into the first and the second turn respectively. The remaining procedure corresponds to the procedure for cochlear implantation in cases in which the cochlea is not obliterated. For the purpose of a clinical study n = 10 patients aged between 32-66 years with an obliterated cochlea were fitted with a double array cochlear implant. All patients showed signs of total obliteration of the basal turn either in preoperative imaging or during surgery. Intraoperative inspection revealed that the second turn was not obliterated in 4 of 10 patients. POSTOPERATIVE RESULTS: Postoperatively, a standard test battery was used to determine auditory performance over a period of time. All patients achieved significantly better speech understanding due to the additional apical electrode array. No complications occurred. In cases involving an obliterated cochlea, the number of intracochlear electrodes can be increased with the double array implant. As a result, the patients achieve significantly better auditory results.

Cochlear Hook Anatomy: Evaluation of the Spatial Relationship of the Basal Cochlear Duct to Middle Ear Landmarks

The cochlear hook is an important anatomical area for the otologist performing cochlear implants and other otological procedures, who requires knowledge of the basal cochlea. A total of 15 human temporal bones were dissected and the spatial relationship of the hook segment of the cochlear duct to the stapes, round window, cochleariform process and ductus reuniens were evaluated. Inter-individual variability was noted for widths of scala tympani (average width 1.36 +/- 0.25 mm) and scala vestibuli (average width 1.18 +/- 0.18 mm) in the region of typical cochlear implant placement, with the scala vestibuli occasionally being wider than the scala tympani. The cochlear duct was in closest proximity to the stapes at the midportion of the footplate, with an average distance of 1.23 mm at this narrowest width. A fibrous anchor, not previously described in otology literature, was identified securing the most basal end of the cochlear duct. Knowing the spatial relationship of the cochlear duct to the middle and inner ear structures could prevent damage to the basilar membrane in procedures around or involving the basal cochlear, such as cochlear implantation, stapedotomy, or implantable hearing devices.

Anatomic relationships between surgical landmarks in type b and type c infratemporal fossa approaches.

Anatomic relationships of the structures exposed in type B and C infratemporal fossa approaches were studied in 20 temporal bones. The intrapetrous carotid artery (ICA), cochlea (CH), eustachian tube (ET), foramen spinosum (FS), foramen ovale (FO) and anterior foramen lacerum (AFL) were exposed by drilling of the glenoid fossa and base of middle cranial fossa. The relationships of the ICA with the cochleariform process (CP), CH, ET, FS, FO and AFL were noted along with associated measurements. The CP was lodged at a mean distance of 9.2 mm from the ICA genu. The ET was found to intersect the ICA. The mean distance of the ICA to the CH was 1.6 mm. The carotid canal was dehiscent on its horizontal portion in 30% of the bones studied and on its vertical portion in 5%. The periarterial venous plexus was found in 70% of the bones. No obvious branch was observed emerging from the vertical portion of the ICA. The FS was found to be a canal having a mean length of 5.8 mm.

The Precochlear Approach to the Anterior Petrous Apex: An Anatomic Study

The petrous apex is the most inaccessible portion of the temporal bone and surgical exposure presents considerable challenge. The transmastoid precochlear approach offers a direct intra temporal route to this region, providing good visual exposure with cochlea preservation. An anatomic study of 20 human temporal bones was performed to delineate the landmarks for this approach. Measurements to the tegmen tympani, carotid artery, and the anterior-superior limit of the cochlea were made from the cochleariform process, a constant landmark in the middle ear. Distances to the tegmen averaged 5.4 mm (range: 3.5-9 mm), to the carotid artery 9.3 mm (8-11 mm), and the cochlea 3.1 mm (2-5 mm). The entry to the apex admitted an average burr size of 3.5 mm (2-7 mm). We anticipate this approach will prove useful in the treatment of benign petrous apex lesions.

Facial Canal Dehiscence: Histologic Study and Computer Reconstruction

The incidence, location, shape, and dimensions of dehiscences in the facial canal to the middle ear space were studied in 160 temporal bones obtained from 129 individuals 24 gestational weeks to 109 years of age at death by means of light microscopy and our computer reconstruction and measurement method. Dehiscences were observed in 95 of the 129 individuals (74%) and in 119 of the 160 bones (74%). The incidence was found to be quite high among fetuses and newborns, lowest in individuals in their twenties and then again quite high in the geriatric population (chi 2 test, chi 2 = 5.45 and 4.41, p < .05). The most frequent site of dehiscence was the oval window area, particularly in its posterior half (57% of all ears) on the inferior to inferomedial aspects of the canal; these dehiscences were clearly demonstrated in reconstructed images. The incidence of dehiscence in the area of the cochleariform process was 16%, and all these dehiscences were on the lateral to superolateral aspect of the canal. The second genu area and the mastoid portion were sites of dehiscence in 21% and 18%, respectively, of specimens; more than half of the dehiscences in the second genu area and mastoid portion were on the lateral to anterolateral and posterior aspects of the facial canal, respectively. The shape of the dehiscence tended to be oval in the oval window area, but rather irregular in the other areas. The dehiscences ranged from 0.4 to 2.64 mm in length, from 0.12 to 1.59 mm in width, and from 0.03 to 1.87 mm2 in surface area. The proximity of these dehiscences to the field of otologic surgery is stressed.

Surgical Landmarks for the Facial Nerve

A number of different approaches can be used to expose the facial nerve. The route taken will depend on the pathology and the portion of the nerve that requires exposure. When performing a parotidectomy approach to the extratemporal portion of the facial nerve, the tragal pointer is a key landmark, but other landmarks also should be used to identify the facial nerve safely. The lateral semicircular canal, the chorda tympani nerve, the digastric ridge, and the cochleariform process are some of the useful landmarks in the mastoid and middle ear. When performing a middle fossa approach, the superior semicircular canal, the greater petrosal nerve, and a window through the tegmen tympani into the attic are useful guideposts. The surgeon should use as many of the available landmarks as feasible to perform safe facial nerve surgery.

The petrous carotid artery: Anatomic relationships in skull base surgery

Advanced transcranial lesions may be successfully resected through a variety of contemporary skull base approaches. The identification and isolation of the internal carotid artery throughout its petrous course is essential in most of these surgical techniques. Anatomic landmarks normally used to identify this vital structure, however, may be severely distorted by tumor involvement or previous operative dissection. In an effort to define surgical landmarks that may be used in the identification of the petrous carotid artery, histologic sections of 100 temporal bones from adults were examined and microscopic measurements were recorded from the anatomic dissection of 10 fresh cadaver halfheads. On the basis of these studies, structures we have found useful in identification of the vertical petrous carotid artery during lateral skull base approaches include the: base of the styloid process, bony vascular crest, basal turn of the cochlea, medial wall of the eustachian tube, and the cochleariform process. Identification of the horizontal segment can be achieved by the preliminary delineation of the middle meningeal artery, greater petrosal nerve, tensor tympani muscle, mandibular and maxillary divisions of the trigeminal nerve, and the eustachian tube. Specific anatomic relationships with associated measurements are detailed and correlated with selected, illustrative cases.

鼓室型先天性真珠腫症例と文献的考察

A 5-year-old boy with congenital cholesteatoma in the mesotympanum also had external abnormalities on the involved side: bat ear and low set ear. The cholesteatoma seemed to originate from the undersurface of the processus cochleariformis and the tendon of the tensor tympani muscle.We reviewed 208 reported cases of congenital cholesteatoma of the middle ear.In 28 cases it originated from the tympanic isthmus, as formerly reported. The incidence in boys was twice as high as in girls. A relatively high incidence of congenital malformations was found. These findings suggest that congenital cholesteatoma is the result of an embryologic error.

Anatomical characteristics of the fossula fenestrae vestibuli.

Anatomical characteristics of the fossula fenestrae vestibuli were tested and analysed precisely on 200 samples of temporal bones. The fossula is usually ovoid and shallow but can be, exceptionally, elongated, narrow and deep. It is surrounded by four walls. In 45.5 per cent of cases the upper wall is formed only by the facial canal and in 54.5 per cent of cases a bony lamella is found beneath the facial canal; the promontory forms the lower wall; the front wall is formed by the bony lamella and part of the processus cochleariformis; the back wall is clearly defined in only 22.8 per cent of cases and is formed by the bony lamella of the medial wall of the tympanic cavity. In 13.2 per cent of cases the floor of the fossula partially covers the prominence of the facial canal and in two per cent the eminentia pyramidalis. Bony recesses in this region occur fairly frequently: sinus subfacialis in 60 per cent, sinus retrofenestralis in 77.2 per cent, and sinus subrostralis in 25 per cent of the cases. These anatomical variations can influence the result of surgical intervention.

A review of twenty congenital cholesteatomas of the middle ear in children.

Cholesteatomas, arising within the middle ear space behind an intact tympanic membrane, have been detected more frequently in recent years. This article reviews 19 children (with a mean age of 4.3 years) who underwent surgery over a 7-year period for removal of cholesteatomas from behind intact tympanic membranes. Most of these children were referred by pediatricians who had detected an asymptomatic whitish middle ear mass. Many had histories of treatment for otitis media. Patients with similar histories were excluded from the series if there had been a prior perforation, myringotomy, or otologic surgery. In the series, one fourth of the children had associated congenital malformations, and there were 3 times as many boys as girls. In two thirds of the cases, the cholesteatoma was manifested as an anterior-superior middle ear mass that seemed to arise from the processus cochleariformis, undersurface of malleus area. Many could be removed via an extended anterior tympanotomy operative approach. The results of surgery are reviewed. The possible origins of these localized cholesteatomas are considered. Are they congenital defects that arise from misplaced keratinizing epithelium? Do they arise from mesenchymal cells whose differentiation is stimulated by inflammatory changes within the middle ear?

Proximal intratemporal facial nerve in Bell's palsy surgery. A study correlating anatomical and surgical findings.

This paper deals with the surgical approaches to that part of the intratemporal facial nerve lying proximal to the cochleariform process and focuses on two issues: the advisability of disarticulating the ossicular chain to reach this area and the accessibility of the labyrinthine segment via the transmastoid, extralabyrinthine, subtemporal route. Relevant anatomical features, which are based on 39 gross temporal bones, 47 histologic sections, and 10 cadaveric specimens are first considered. In the head specimens, it was possible to attempt exploration of the entire nerve with the transmastoid, extralabyrinthine, subtemporal operation and then remove the labyrinth to gauge the adequacy of this approach as an avenue to the labyrinthine segment. These anatomical findings, their bearing on the questions at hand, and the author's clinical experience are incorporated into descriptions of the operations currently in vogue for exploring the proximal nerve in patients with Bell's palsy.

Supraganglion�rer Verlauf des Nervus facialis durch Warzenfortsatz und Epitympanum; eine bisher nicht beobachtete Anomalie

In a boy of 10 with primary cholesteatoma of the right ear the following anomaly of the facial nerve was demonstrated: The nerve enters the mastoid posteriorly to the labyrinth, approximately in the angle formed by superior and posterior canal, there it makes a right-angles turn forward and runs in a horizontal, slightly upward direction through mastoid and antram, crossing the lateral canal, via the epitympanum in close association to body of incus and head of malleus, in which it had moulded a groove. It leaves the epitympanum superiorly to the processus cochleariformis, and joins the geniculate ganglion; from there completely normal course in tympanic and mastoid portion of fallopian canal. The mastoid was fairly well pneumatized, the celles partly destroyed by cholesteatoma. The ossicular chain was intact. The nerve could be preserved. Its identy was confirmed by electric stimulation.

A Histopathological Study of Congenital Atresia of the External Auditory Canal -A case report-

Temporal bones from a case of congenital atresia of the external auditory canal were histologically studied and reported. A 14 days old female infant died of aspiration pneumonia following upper respiratory distress due to marked hypoplasia of the mandibule. Malformations were found in the external as well as middle ears. The right external ear canal was occluded by a bony atresia plate which was a part of the squamous or tympanic bone. The canal of the left ear was filled with fibrous connective tissue. The middle ear anomalies included hypoplastic epitympanum, absence of the cochleariform process, anomalous course of the tensor tympani musle, misshaped malleus and incus, missing lenticular process, fixation of the short process of the incus, bony fusion of the malleus with the medial wall of the tympanic cavity, foot plate fixation and persistent stapedial artery.The bony and membranous labyrinths appeared normal, except the presence of the cyst-like structures in the crista of the left anterior and posterior ampullae and concretion in the base of the stria vascularis. The findings may be indicaticative of genetic disorder of the inner ear.