1. Fig 2. Arrow indicating obliteration of the oval window
Congenital Absence of the Oval Window Sharon Ovnat Tamir, MD, Tal Marom, MD Department of Otolaryngology – Head & Neck Surgery, Edith Wolfson Medical Center, Tel-Aviv University, Sackler School of Medicine, Israel
INTRODUCTION
DISCUSSION
Congenital absence of the oval window (CAOW) is uncommon [1], and considered as a minor congenital ear anomaly
Due to its embryological origin, CAOW is closely related to facial nerve and stapedial anomalies
It may be associated with other anomalies of the ossicular chain, atresia of the EAC, and rarely with inner ear malformations
The presenting symptom is congenital, maximal, non- progressive, conductive hearing loss, in the presence of a normal tympanic membrane
CAOW is suspected in any patient with maximal conductive hearing loss, even in those with a history of chronic otitis media
Once suspected, HRCT is an important tool for evaluation. A bony plate in the expected region of the oval window is an important radiological clue for CAOW. In these cases, it is important to assess the ossicular chain integrity, the course of the facial nerve and presence of associated inner ear malformations
Diagnosis of CAOW is determined during middle ear exploration
Despite its first description as early as 1955 (2), there has been limited literature and progress in the understanding and management of this condition
Surgery such as oval window drill-out / vestibulotomy/ fenestration of the scala vestibuli of the cochlea are feasible but controversial, carrying the risk of injury to the inner ear and the facial nerve
Literature reports mixed success rates in the long run. In a series of 56 operated ears (3), 29 cases achieved >15dB improvement in hearing after 6 months of follow up, but no hearing gain was observed in 10 patients and 6 patients underwent revision operations for worsening hearing. In another series of 13 patients (4), all patients enjoyed hearing improvement 1 month after surgery, but several lost these initial gains in hearing over time. Revision surgery was not successful in restoring hearing
Considering the advantages and disadvantages of the described operations, bone-bridge and hearing aids are good alternatives that should be discussed with the patient prior to surgery leading both the surgeon and patients to an evidence based clinical decision strategy
Fig 1. Arrow indicating a malrotated incus with a malformed stapes suprastructure
CASE PRESENTATION
A 15 year-old male presented with a maximal right ear conductive hearing loss
History was remarkable other than for recurrent ventilating tube insertions during childhood, with a residual tympanic membrane perforation that was operated by myringoplasty at the age of 13 years
High resolution CT (HRCT) of the temporal bone showed calcification of the right oval window, an aberrant facial nerve course and a malrotated incus with a malformed stapes suprastructure (Fig 1,2)
The patient deferred any treatment except surgery
Middle ear exploration revealed complete absence of the oval window with no anatomical landmarks, a malformed stapes with only one crura and no foot plate were found. The incudo-stapedial joint was malformed with no capitulum (Fig. 3). It was impossible to assess the position of the facial nerve
Following recovery, the option of bone-bridge was discussed again with the patient, who may consider it in the future
Fig 2. Arrow indicating obliteration of the oval window
Fig 3. Arrow indicating a malformed stapes with obliteration of the oval window
REFERENCES
1. J. Hasegawa, T. Kawase, H. Hidaka, T. Oshima, and T. Kobayashi, “Surgical treatment for congenital absence of the oval window with facial nerve anomalies.,” Auris Nasus. Larynx, vol. 39, no. 2, pp. 249–55, Apr
2. McAskile K, Sullivan JA. Surgical management of congenital atresia of the ear. J Laryngol Otol 1955;69:
3. Su Y , Yuan H, Song YS et al. Congenital middle ear abnormalities with absence of oval window: diagnosis, surgery and audiometric outcomes. Otology & Neurotology 2014;35(7):
4. Alarcon A, Jahrsodoerfer RA, et al. Cogenital Absence of Oval Window. Otology & Neurotology 2007;29:23-28.
CONTACT INFORMATION
Sharon Ovnat Tamir, MD
Department of Otolaryngology –
Head and Neck Surgery, Edith Wolfson Medical Center, Holon, Israel