Classification of facial nerve aberration in congenital malformation of middle ear: Implications for surgery of hearing restoration

Abstract

ObjectivesFacial nerve aberration is the most troublesome situation in congenital malformations of middle ear. The aim of our study is to investigate its imaging and clinical features as well as relevant choice of surgical techniques for hearing improvement.MethodsA retrospective study involving review of clinical data of 227 patients (256 ears) with congenital middle ear anomaly was undertaken, including preoperative computed tomography (CT) data, surgical records and videos.ResultsAberration involving intratemporal facial nerve was found in 82/256 ears (32.03%) with congenital middle ear anomaly. The most common forms of aberration included overhanging over the oval window (50/82 ears, 60.98%), bifurcation (3/82 ears, 3.66%) and transverse over the promontory (3/82 ears, 3.66%), counting for 68.29% (56/82) of the cases with facial nerve aberration. Concomitant stapes malformation was found in 76/82 ears (92.68%) and atresia or stenosis of the oval window in 27/82 ears (32.93%). In 9/82 ears (10.98%) both stapes and oval window was absent. Elective surgeries for the purpose of hearing improvement included stapodotomy + piston implantation, labyrinthotomy, labyrinthotomy + total ossicular replacement prosthesis (TORP) implantation and Vibrant Soundbridge (VSB) implantation.ConclusionThe majority of facial nerve aberration in congenital malformation of middle ear involves displacement of facial nerve, in addition to concomitant malformations of the stapes and/or oval window, which may influence the choice of surgery for hearing improvement. VSB implantation may be considered as a useful option.

Task force Guideline of Brazilian Society of Otology – hearing loss in children – Part II — Treatment

“…The usually anomalous split facial nerve configuration makes access difficult (even using intraoperative monitoring), and obliteration of the round window may lead to surgical failure. 98 , 99 …”

Internal auditory canal hypoplasia associated with bilateral vestibulocochlear nerve aplasia and deviant facial nerve course: A case report and MRI findings

“…The aberrant FN is not rare in patients with congenital anomaly of the middle ear. In their series of 227 subjects with middle ear anomalies, Hao and colleagues found aberration of FN in 32% of patients, with facial nerve displacement as the most commonly observed malformation [1]. The aberrant FN may cause blockage of the oval window and cross over other structures [1].…”

“…In their series of 227 subjects with middle ear anomalies, Hao and colleagues found aberration of FN in 32% of patients, with facial nerve displacement as the most commonly observed malformation [1]. The aberrant FN may cause blockage of the oval window and cross over other structures [1]. The majority of patients with FN anomaly do not present with clinical symptoms.…”

“…The majority of patients with FN anomaly do not present with clinical symptoms. However, when it is present, it is usually due to conductive hearing loss from an accompanying ossicular chain abnormality [1,2].…”

Unexpected Branch Malformation of the Facial Nerve during Stapes Surgery: Comparison between Intraoperative and Radiographic Findings

“…Splitting of the cranial nerves can occur at any point, but it is most dangerous during surgery if the nerves wrap around the stapes footplate and oval window [2]. In these cases, this could cause a large increase in the risks of stapes operation or an abandonment of the operation altogether because the deformity will narrow the operation space [3][4][5]. Given the severity of the risks, familiarity with the appearance and the location of the FN during an operation and its manifestation on a preoperative HRCT is important for training young ENT surgeons to reduce iatrogenic facial paralysis.…”