Temporal bone pathology in congenital anomalies of the oval window and the facial nerve

Endoscopic Anatomy of the Chorda Tympani: Systematic Dissection, Novel Anatomic Classification, and Surgical Implications

HYPOTHESIS

A transcanal endoscopic approach enables visualization of the variable course of the chorda tympani inside the middle ear.

BACKGROUND

The chorda tympani is the longest intrapetrous branch of the facial nerve. Despite having been investigated in several studies, a description of its tympanic tract from an endoscopic point of view is lacking in the literature.

METHODS

We performed transcanal endoscopic dissections of 44 human cadaveric head and ear specimens. The entry point of the chorda tympani into the middle ear was classified into four categories according to its location, and as covered or dehiscent according to its appearance. The chordal eminence (CE) was defined as absent, shallow, intermediate, prominent, or fused, based on its shape and extension. The relationship of the chorda tympani to adjacent bony and ligamental structures was assessed.

RESULTS

The tympanic tract of the chorda tympani was divided into three portions. The periannular segment was dehiscent in 54.5% of specimens, with type II being the most frequent entry point configuration (52.3%). In the interossicular segment, the nerve consistently passed lateral to the incus and medial to the malleus. The course of the intrapetrous segment was independent from the conformation of the tensor fold and supratubal recess.

CONCLUSION

The transcanal endoscopic approach allows a detailed description of tympanic segment of the chorda tympani. Novel anatomic classifications of the chorda tympani and CE are proposed herein to highlight their possible surgical implications during otologic procedures.

Surgical Management for Dysplastic or Congenitally Absent Oval Window

OBJECTIVE

To evaluate surgical findings and hearing results for patient's undergoing the described surgical approach for congenitally absent or dysplastic oval window (OW).

STUDY DESIGN

The Institutional Review Board approved retrospective review of patients with conductive hearing loss (CHL) operated on from 1992 to 2016.

SETTING

Academic tertiary center.

PATIENTS

Patients with CHL, an intact tympanic membrane (TM), and without history of chronic infection underwent middle ear exploration. Eleven patients and 13 ears underwent an oval window drill-out (OWD) procedure.

INTERVENTION

Eleven patients presented, all with dysplastic or congenitally absent oval window (CAOW). CHL was identified using audiometry and tuning forks, many patients also had preoperative computed tomography temporal bones. A transcanal approach was used and an OWD was performed with a variety of prostheses placed.

MAIN OUTCOME MEASURE

Audiometric studies before and after intervention were compared with 12 month and long-term follow-up (1-22 yr).

RESULTS

Preoperative air-bone gaps ranged from 40 to 60 dB and averaged 55.1 dB. Postoperative air-bone gaps ranged from 0 to 60 dB and averaged 24.1 dB. The preoperative pure-tone average (PTA) ranged from 55 to 99 dB and averaged 71.3 dB. Postoperative PTA ranged from 21 to 108 dB and averaged 49.6 dB.

CONCLUSION

Dysplastic and CAOW are uncommon congenital major ear anomalies. OWD is a viable treatment option, though careful counseling is critical, as significant complications are possible, especially with facial nerve (FN) abnormalities. This series demonstrates successful closure of the air-bone gap for many patients with this technique.

Oval window atresia: a novel surgical approach and pathognomonic radiological finding

OBJECTIVES

The facial nerve usually occupies the oval window area in patients with oval window atresia. During exploration, if the facial nerve is discovered to lie in the oval window area, this is usually regarded as a contraindication for further surgical intervention. The aim of the present paper is to demonstrate the preoperative pathognomonic radiological sign and describe a new surgical approach for this difficult situation.

METHODS

3 patients and 4 ears were operated due to conductive hearing loss by the same surgeon in a tertiary referral center. Their clinical presentation, radiological findings, surgical findings and final outcomes were evaluated and correlated.

RESULTS

Surgical findings were identical in all 4 ears: facial nerve was running over the oval window and tympanic portion was completely dehiscent. Incus long arm was medially displaced due to abnormal development of the stapes suprastructure. In each ear a successful vestibulotomy and teflon piston placement was achieved. Preoperative mean air-bone gap of 47.5dB was improved to 21.5dB. There were no complications.

CONCLUSION

Oval window atresia is a rare middle ear anomaly usually regarded as a contraindication for surgical intervention. In this study we present a novel surgical approach with succesful results. However the best approach is to inform the family by showing the nerve on tomography, showing the operation video, informing the family about the sensorineural hearing loss and letting the family choose the treatment option.

The dehiscent facial nerve canal

Accidental injury to the facial nerve where the bony canal defects are present may result with facial nerve dysfunction during otological surgery. Therefore, it is critical to know the incidence and the type of facial nerve dehiscences in the presence of normal development of the facial canal. The aim of this study is to review the site and the type of such bony defects in 144 patients operated for facial paralysis, myringoplasty, stapedotomy, middle ear exploration for sudden hearing loss, and so forth, other than chronic suppurative otitis media with or without cholesteatoma, middle ear tumors, and anomaly. Correlation of intraoperative findings with preoperative computerized tomography was also analyzed in 35 patients. Conclusively, one out of every 10 surgical cases may have dehiscence of the facial canal which has to be always borne in mind during surgical manipulation of the middle ear. Computerized tomography has some limitations to evaluate the dehiscent facial canal due to high false negative and positive rates.

Clinical anatomy of the chorda tympani: a systematic review

OBJECTIVE

The chorda tympani is at risk of iatrogenic injury throughout its course. This paper reviews the clinical anatomy of the nerve in adults.

DESIGN

Systematic literature review.

METHOD

Relevant English-language articles were identified using five electronic databases and one search engine. Data from approximately 70 scientific papers were supplemented with information from selected reference texts.

RESULTS

The anatomy of the chorda tympani differs from standard descriptions, particularly regarding its exit from the middle ear and area of lingual innervation. Whilst it is known to convey taste sensation from the anterior two-thirds of the tongue and parasympathetic innervation to the submandibular and sublingual salivary glands, the chorda tympani probably has additional sensory and secretomotor functions.

CONCLUSION

A detailed understanding of the anatomy of the chorda tympani may help to reduce the risk of iatrogenic injury during head, neck and middle-ear surgery, and to explain the variable consequences of such injury.

Rare middle ear anomaly in a patient with Turner's syndrome

A patient with Turner's syndrome presented with a rare anomaly of absent oval window, inferiorly placed facial nerve, and abnormal stapes. To our knowledge, this is the first report of this combination of malformations.

Congenital anomalies limited to the middle ear

Congenital anomalies of the middle ear are occasionally encountered during surgery for conductive hearing loss and are unexpected in patients with no other deformities. We reviewed 12 such patients operated on at The New York Eye and Ear Infirmary from 1985 through 1989. Nine of the patients (75%) had unilateral conductive hearing loss whereas three (25%) had bilateral symptoms. One had bilateral congenital middle ear anomalies. Three patients (25%) had anomalies limited to the malleus and scutum. Five patients (47%) had agenesis of the oval window. After reconstructive surgery, 72% of patients had hearing improvement ranging from 13 to 38 dB. The etiology of these anomalies is discussed and their evaluation and surgical indications are presented.