Surgical and Audiological Outcomes of Endoscopic Stapes Surgery

Otosclerosis is a pathological bone remodeling process that affects the middle and inner ears. It was first reported by Antonio Maria Valsalva in 1735 and subsequently described pathologically by Adam Politzer in 1839 .

In otosclerosis, the normal, dense endochondral bone of the otic capsule around the inner ear labyrinth is replaced by irregularly laid spongy bone, which subsequently hardens and leads to fixation of the stapes footplate . Otosclerosis causes progressive conductive hearing loss that typically presents with a normal tympanic membrane. However, a reddish shadow on the promontory of the cochlea may be seen in some cases (Schwartze sign) if the tympanic membrane is clear enough.

Initial symptoms of otosclerosis include decreased sensitivity to low-frequency sounds, such as whispers. Patients may also paradoxically deny difficulty hearing conversation in loud background noise, which is termed "paracusis Willisii" or "paracusis of Willis,. Tinnitus may worsen as the disease progresses. Vertigo is usually mild, but as the disease progresses, balance may deteriorate, mimicking Ménière disease. .

On physical examination, patients with otosclerosis may speak in low volume and monotonous voices. Otoscopy may reveal no abnormalities at all. With active otosclerosis, however, increased vascularity of the cochlear promontory may be visible through the tympanic membrane A Weber test performed with a 512 Hz (Hertz) fork will generally lateralize toward the ear with the conductive loss or toward the ear with the greater conductive loss in cases of bilateral otosclerosis . In most cases of otosclerosis, pure tone audiometry shows low frequency decreases in air conduction thresholds. Bone conduction, however, typically remains normal. A "Carhart notch" is often seen, which is an artifactual dip in the bone conduction line by 20-30 dB(disciple) at 2,000 Hz due to the resonance frequency of the ossicular chain .

There is no medical therapy that is curative for otosclerosis. Though sodium fluoride is prescribed to slow the progression of otosclerosis, its efficacy is still controversial and In stapes surgery different surgical techniques, approaches and prostheses in order to restore sound transmission have been described. Stapedectomy was first described by Shea.Jr in 1956.

Surgical techniques for treatment of otosclerosis have been improved, updated, or adjusted over time to lower intraoperative and post-operative problems and boost overall effectiveness .

The treatment of choice is stapedotomy or stapedectomy, along with the placement of a prosthesis. In these procedures, either a hole is drilled in the center of the stapes footplate with a high-speed microdrill or a laser (stapedotomy), and a prosthesis is placed between the long process of the incus and the oval window membrane via the hole in the stapes footplate, or the stapes footplate is removed partially or in its entirety and a prosthesis placed between the incus and the oval window, typically with a vein or fascia graft used to protect the oval window membrane (stapedectomy). In both procedures, the crura of the stapes are fractured, and the incudo stapedial joint is divided in order to permit the removal of the stapes superstructure.

Surgical treatment for otosclerosis generally produces good outcomes, irrespective of the approach employed, provided appropriate patient selection. For patients with bilateral otosclerosis, the ear with greater hearing loss is typically addressed first; both ears are not operated under the same anesthetic in order to avoid the very unlikely scenario in which total sensorineural hearing loss occurs bilaterally as a result of surgery. A 2018 review published by Cheng et al indicated comparable results between stapedotomy and stapedectomy, with a slight advantage in terms of high- frequency hearing and complication rate for stapedotomy .

Microscopic trans canal or end aural approach is the most preferred technique in stapes surgery . Although microscopes provide good magnification and let both hands use, sufficient exposure of stapedial structures might not be possible under microscopic approach without bone curettage .

In microscopic approaches, extensive curettage of scutum may result in complications such as chorda tympani nerve injury, impaired taste sensation, subluxation of ossicles, retraction pockets and postoperative higher pain levels .