Myringoplasty

Definition

Indications

1. Recurrent otorrhoea - a perforation exposes the middle ear to repeated infection from external sources, with potential progression of middle ear pathology
2. Hearing loss - repeated infections and the perforation itself cause conductive hearing loss (CHL). Perforations >25% cause proportionally greater CHL; those >50% show the greatest pre-operative loss and greatest post-operative gain. Posterosuperior quadrant perforations cause larger CHL due to ossicular chain exposure
3. Social/swimming - desire to swim without ear protection, especially in children

Contraindications

Pre-operative Evaluation

• Detailed history: prior infections, drainage, previous surgery, PE tube placement
• Otomicroscopic exam: assess perforation size, classify as central (TM remnant surrounds all edges) or marginal (no TM remnant between perforation and bony canal wall at some point)
• Assess: ossicular chain mobility, middle ear mucosa, atrophic areas, myringosclerosis
• Estimate true perforation size after diseased segments excised (>50% has lower success)
• Evaluate external canal size - plan canalplasty if prominent anterior wall limits visualization
• Comprehensive audiometry - pure tone, speech, tuning fork tests
• Contralateral ear: a normal opposite ear predicts favourable ET function and better outcomes; abnormalities in the contralateral ear predict poorer graft take
• Radiographic evaluation not usually required for dry central perforation

Surgical Approaches

Access Incisions

1. Transcanal (endoscopic/microscopic) - suitable for small posteroinferior perforations with good visualization
2. Endaural incision - vertical limb from 12 o'clock at bony-cartilaginous junction extending into the incisura terminalis; gives access to temporalis fascia
3. Postauricular incision - 5-10 mm behind postauricular crease; standard for large perforations or when mastoid access may be needed

Graft Materials

Graft Placement Techniques

• Underlay (medial graft) - most widely used and accepted; graft placed medial to the TM remnant, acting as a scaffold for squamous epithelial regrowth. The rim of the perforation is excised to create a raw surface; mucosa on the undersurface near the perforation is scraped to provide a graft bed. Mucosa over the promontory should be carefully preserved to reduce post-operative adhesions
• Overlay (lateral graft) - graft placed lateral to the TM remnant; useful in certain situations but carries risks of lateralization
• Anterior perforations: anchoring the anterior graft margin beneath the annulus greatly reduces the higher failure rate seen with anterior perforations

Outcomes

Graft Take (TM Closure) Rate

• Expert surgeons: ~95% (closure rates of 97% reported in senior hands vs. 74-78% for trainees - outcome is significantly influenced by surgeon expertise)
• Large series across many surgeons: considerably lower
• Adults: 60-99%; Children: 35-94%
• Small perforations: ~74% closure; Large perforations: ~56%
• Long-term follow-up shows some initially intact ears develop recurrent perforation; success rates may fall from ~85% at 1 year to lower rates over time
• Revision surgery: only ~60% success rate - much lower than primary surgery

Hearing Outcomes

• Successful TM closure gives only a small improvement in hearing (~8 dB mean)
• Total closure of the air-bone gap is uncommon - closure of a perforation does not restore normal ear physiology
• Perforations >50% show greater pre-operative loss and greater post-operative gain
• Myringoplasty + ossiculoplasty can be staged or single-stage; staged procedures have nominally higher ossiculoplasty success as only well-healed ears proceed to stage 2

Factors Affecting Outcome

Role of Adjuvant Cortical Mastoidectomy

• Mishiro et al.: 94% (tympanoplasty alone) vs. 91% (with mastoidectomy) - no significant difference
• Balyan et al.: 91% vs. 86% in actively discharging ears - no significant difference
• Hall et al. review of 5 studies: no evidence mastoidectomy improves outcomes

Complications

• Sensorineural hearing loss: rare, ~1.5% (from infection or ossicular manipulation)
• Recurrent perforation / graft failure
• Post-operative middle ear adhesions (reduced by preserving promontory mucosa)
• Cholesteatoma (if squamous epithelium not fully excised in overlay technique)

Key Points Summary

• Myringoplasty = TM repair without ossicular work
• Preferred graft: temporalis fascia, underlay technique
• Cartilage increasingly favoured for difficult cases
• No evidence prophylactic antibiotics or mastoidectomy improve outcomes
• Active infection at time of surgery does not clearly worsen outcomes
• Surgeon expertise is the single largest determinant of success

Anesthesia in Myringoplasty

General vs. Local Anesthesia

• General anesthesia is the most common choice, particularly in the UK and for children
• Local anesthesia is well-established and is used by a significant proportion of surgeons (approximately 20% in the UK use LA routinely)
• Myringoplasty can frequently be performed under LA; this should be given particular consideration in patients with multiple medical comorbidities where the insult of a GA is a real risk - Scott-Brown's Otorhinolaryngology Head & Neck Surgery Vol. 2
• Day-case surgery for myringoplasty/tympanoplasty is increasingly the norm under either modality

Local Anesthetic Technique

• Lidocaine 2% with adrenaline (epinephrine) 1:20,000 to 1:200,000 injected around the ear canal and auricular nerve supply points
• Addition of adrenaline significantly prolongs anesthesia duration vs. plain lidocaine, and provides crucial vasoconstriction for a bloodless field
• The nerves supplying the auricle and ear canal (auriculotemporal, great auricular, lesser occipital, auricular branch of vagus) are blocked circumferentially
• Sedation (IV midazolam or other agent) may be added for anxious patients, though myringoplasty under LA without preoperative sedation has also been reported as well tolerated

Critical Point: Nitrous Oxide is Contraindicated

Nitrous oxide is contraindicated in middle ear surgery. It is 30 times more soluble than nitrogen and diffuses into closed gas spaces faster than nitrogen diffuses out - increasing gas volume and pressure within the middle ear. This can displace a freshly placed graft and cause graft failure.

• Sabiston Textbook of Surgery

TIVA (Total Intravenous Anesthesia) with Propofol

• Avoids nitrous oxide entirely
• Propofol has anti-emetic properties, reducing PONV (post-operative nausea and vomiting) - a significant concern in middle ear surgery due to vestibular stimulation
• Smooth emergence without agitation that could displace the graft

Summary of Preferred Approach