Congenital Absence of Oval Window

Abstract

Oval window agenesis with obvious craniofacial ear deformity is a rarely diagnosed condition. This finding is noticeable nowadays as a result of the development of microsurgery of the ear. The vestibule is the central chamber of the bony labyrinth of the inner ear. It has a lateral opening at the medial wall of the middle ear, which is called the oval window (fenestra ovale), and lies above and slightly behind the promontory, and below the horizontal portion of the facial nerve. It is closed in life by the footplate of the stapes and its annular ligament. It has an area of approximately 3x1.4 mm 2 and a depth of 2.5-3 mm. 2The stapes has a double origin. The main structures derive from the second branchial arch, but the inner (vestibular) aspect of the footplate differentiates from the otic capsule itself. This area is termed the "lamina stapedialis." As development proceeds, the cells immediately adjacent to this lamina normally form the annular ligament, and the lamina becomes incorporated into the footplate of the stapes. Teratogenic agents might affect any stage of the process, producing anomalies including congenital absence of the oval window and others.3 The oval window is indispensable for the transmission of sound waves into the inner ear (cochlea). In the case of oval window occlusion or absence, the stapes is not normally developed and may be rudimentary, hanging above an undifferentiated oval window niche, causing conductive loss of hearing. The adjacent lateral wall of the bony canal of the facial nerve is also developed from the second branchial arch. 4,5The facial nerve may be exposed or displaced downwards. Congenital facial nerve dehiscence of the bony facial canal in the oval window region, a very common finding at tympanotomy, was present at 31% of normal temporal bones examined by Leonard and Alexander in 1968. 6 Differentiation of the otocyst and otic capsule to inner ear is developed independently of the middle ear, which explains the presence of agenesis of footplate as a separate anomaly, and the presence of normal inner ear with deformity of the ossicular chain.5 If the stapes is totally absent, there may be no depression or other indication of the site of the vestibular window, and the facial nerve may be displaced downwards. 7 Case ReportA 24-year-old Jordanian female presented to the Otorhinolaryngology Department at King Hussein Medical Centre, Amman, Jordan, in 1995, with a history of bilateral loss of hearing since childhood. There was no positive family history of hearing loss or history of trauma. She was a good lip reader. ENT examination revealed normal tympanic membranes with outstanding small auricles (microtia). Pure tone audiogram showed bilateral, almost symmetrical conductive loss of hearing of 45 dB (Figure 1). Cochlear function and caloric test were normal. Tympanogram showed normal middle ear pressure, and compliance was within the wide normal variation range.After the condition was explained to the patient, she was asked to decide between having a hearing aid fit...

Congenital Oval Window Aplasia: An Unusual Cause of Conductive Hearing Loss in an Adult

“…Table 1 summarizes the reports of several authors on various methods for hearing improvement ranging from the most conservative approach such as conventional hearing aids to more invasive approaches such as malleostapedotomy or incudostapedotomy following oval window drill out or platinotomy or vestibulotomy and shows the studies where details on the laterality as well as the surgical technique utilized. [5][6][7][8][9][10][11] A variety of prosthesis such as a Teflon piston, and a cartilage columella have been used. 6 Thomeer's report published in 2012 provided a summary of 70 cases in several series from 1950-2010 mostly comprising Class 1-3, with the largest series of 144 cases reported from Nijmegen by Cremers and colleagues while only ten percent (14 patients from 1986-2001) of cases were of the rarest class 4a type anomaly.…”

“…9 Given this, Conventional prosthesis was chosen Case 1 malleostapedotomy via endaural approach on second surgery, facial nerve rolled, 0.6-mm window drilled using 0.4-mm Skeeter drill, piston wire prosthesis bent 20°, modified to 7-mm length and fixed on normal malleus Case 2 stapedotomy after "facial roll" and 0.6-mm window using 0.4-mm Skeeter drill, piston wire 7-mm-long used, transient House-Brackmann Grade III recovered by 1 month Case 1 Vestibulotomy using a pick then teflon prosthesis Case 2 tragal cartilage, incus long process with bone cement as complex at footplate, postoperative hearing gain 42 dB and air conducting hearing level 20 dB on right side Transcanal approach for exploratory tympanotomy and malleostapedotomy, hearing improved but deteriorated in long term Inner ear fenestration in 3 followed by piston; exploratory tympanotomy only in 1; hearing improved in all cases after surgery and to within 25 db in two and within 45 db in one both conventional hearing aids and passive or active bone conduction devices remain viable options, especially in bilateral cases. 7,13 Long term hearing improvement has been notable in these novel active bone conduction devices in recent reports. 12 For unilateral cases, no consensus has been reached but recent literature points to a more aggressive approach that involves surgically correcting the unilateral loss for better hearing in noise and sound localization.…”