Hearing Status After Ossiculoplasty in Open Cavity Mastoidectomy

To evaluate the hearing outcome in canal wall down mastoidectomy with middle ear reconstruction, prospective longitudinal study was done at National Institute of ENT, Dhaka from March 2015 to September 2016. Total 22 patients were included in the study undergoing canal wall down mastoidectomy with 6 months postoperative followup. Hearing outcomes were observed and compared with the preoperative hearing tests. Among the 22 patients 9 (39.1% of subjects) patients had hearing gain, 12 (52.2%) had hearing loss and 1 (4.3%) had no change in hearing postoperatively.Although disease clearance is the main objective in canal wall down mastoidectomy, hearing gain can be achieved if combined with ossiculoplasty and tympanoplasty. The hearing gain or loss depends upon the extension of disease and status of the ossicular chain. Most patients usually experience hearing loss more than the preoperative period due to removal of ossicle or ossicles for the sake of disease clearance. 1. Associate Professor, National Institute of ENT, Tejgaon, Dhaka 2. Associate Professor, Dhaka Medical College, Dhaka 3. Assistant Professor, ShahidSuhrawardy Medical College, Dhaka 4. Registrar, National Institute of ENT, Tejgaon, Dhaka 5. Assistant Registrar, National Institute of ENT, Tejgaon, Dhaka 6. Medical Officer, National Institute of ENT, Tejgaon, Dhaka Address of Correspondence: Dr. Md. Zakaria Sarker, Associate Professor,NIENT. E-mail : zakaria.sarker@ymail.com Introduction Patients with canal wall down mastoidectomy had little to no hope of hearing reconstruction previously. With modern techniques of tympanoplasty and ossiculoplasty new hope for hearing reconstruction has developed. In clinical practice up to 50% of ears with active chronic otitis media is associated with cholesteatoma among 5% CSOM prevalence rate in our country. Surgery is the mainstay of treatment. Primary aim in surgical treatment is to remove the disease and render the ear safe, and second in priority is to preserve or reconstruct hearing but never at the cost of the primary aim. Two types of surgical procedures are done to deal with cholesteatoma.Canal wall down procedures leave the mastoid cavity open into the external auditory canal so that the diseased area is fully exteriorized. The commonly performed operations for atticoantral disease are atticotomy, modified radical mastoidectomy and rarely, theradical mastoidectomy.Canal wall up procedures. Here disease is removed by combined approach through the meatus and mastoid but retaining the posterior bony meatal wall intact, thereby avoiding an open mastoid ENT 23 (2), 2017 196 cavity. It gives dry ear and permits easy reconstruction of hearing mechanism. However, there is danger of leaving some cholesteatoma behind. Incidence of residual or recurrent cholesteatoma in these cases is very high and therefore long-term follow-up is essential. Re-exploration in casses after 6 months or so may be required. Therefore Canal wall up procedures are advised only in selected cases. The ultimate goal of a canal wall down mastoidectomy is to create an ear in which the meatus is large enough for easy examination and provides appropriate ventilation of the external canal and mastoid cavity.Furthermore, the resultant mastoid cavity should be small and lined with healthy keratinizing epithelium. A canal wall down mastoidectomy is often accompanied by reconstruction of the middle ear and a tympanoplasty. The most common ossiculoplasty performed is an incus interposition with the patient’s incus (autograft) or, occasionally, a cadever incus (homograft). Augmentation ossiculoplasty entails increasing the height of the stapesabove the fallopian canal when a canal wall down mastoidectomy is performed and the malleus is absent. This technique frequently uses the body of the incus, thehead of the malleus, a cortical bone graft or a cartilage i.e,conchal or septal cartilage. The term partial ossicular replacement prosthesis (PORP) is used when a synthetic biocompatible prosthesis is positioned from the head of stapes super structure to the tympanic membrane, graft, or malleus. In cases with an absent stapes superstructure along with other ossicles, a TORP is a good option. A cartilage shield with a fenestra in its center and a cartilage piston is a better option for stability of the prosthesis and better hearing gain. However the outcome still depends on clearance of disease, proper placement of the prosthesis (if used), wide meatotomy and meatoplasty and regular postoperative follow up.


Introduction
Patients with canal wall down mastoidectomy had little to no hope of hearing reconstruction previously. With modern techniques of tympanoplasty and ossiculoplasty new hope for hearing reconstruction has developed 1 . In clinical practice up to 50% of ears with active chronic otitis media is associated with cholesteatoma among 5% CSOM prevalence rate in our country 2 .
Surgery is the mainstay of treatment. Primary aim in surgical treatment is to remove the disease and render the ear safe, and second in priority is to preserve or reconstruct hearing but never at the cost of the primary aim. Two types of surgical procedures are done to deal with cholesteatoma.Canal wall down procedures leave the mastoid cavity open into the external auditory canal so that the diseased area is fully exteriorized. The commonly performed operations for atticoantral disease are atticotomy, modified radical mastoidectomy and rarely, theradical mastoidectomy.Canal wall up procedures. Here disease is removed by combined approach through the meatus and mastoid but retaining the posterior bony meatal wall intact, thereby avoiding an open mastoid cavity. It gives dry ear and permits easy reconstruction of hearing mechanism. However, there is danger of leaving some cholesteatoma behind. Incidence of residual or recurrent cholesteatoma in these cases is very high and therefore long-term follow-up is essential. Re-exploration in casses after 6 months or so may be required. Therefore Canal wall up procedures are advised only in selected cases 3 .
The ultimate goal of a canal wall down mastoidectomy is to create an ear in which the meatus is large enough for easy examination and provides appropriate ventilation of the external canal and mastoid cavity.Furthermore, the resultant mastoid cavity should be small and lined with healthy keratinizing epithelium. A canal wall down mastoidectomy is often accompanied by reconstruction of the middle ear and a tympanoplasty 4 .
The most common ossiculoplasty performed is an incus interposition with the patient's incus (autograft) or, occasionally, a cadever incus (homograft). Augmentation ossiculoplasty entails increasing the height of the stapesabove the fallopian canal when a canal wall down mastoidectomy is performed and the malleus is absent. This technique frequently uses the body of the incus, thehead of the malleus, a cortical bone graft or a cartilage i.e,conchal or septal cartilage. The term partial ossicular replacement prosthesis (PORP) is used when a synthetic biocompatible prosthesis is positioned from the head of stapes super structure to the tympanic membrane, graft, or malleus. In cases with an absent stapes superstructure along with other ossicles, a TORP is a good option 5 . A cartilage shield with a fenestra in its center and a cartilage piston is a better option for stability of the prosthesis and better hearing gain.
However the outcome still depends on clearance of disease, proper placement of the prosthesis (if used), wide meatotomy and meatoplasty and regular postoperative follow up.

Aim of study
To evaluate the hearing outcome in canal wall down mastoidectomy with middle ear reconstruction

Data Collection
Pre and postoperative hearing assessments were done by PTA. Every patient was routinely followed up for at least 6 months of the postoperative period.
Inclusion Criteria -Patients with squamosal chronic otitis media -who gave written and informed consent for the study were included.

Discussion
Inour study most of the cases had extensive long standing disease. The presence or absence of the stapes suprastructure influences the hearing result 6 . The air bone gap was shown to have decreased to 20dB in69% of the patients with intact stapes undergoing CWDM, 30% in cases of absent stapes (Cook et al,1996) 7  We had done more than 40 cases in the study period. But a lot of patients did not comply for regular postoperative follow up owing to poor socio economic condition, long distance travel and no postoperative complications.

Conclusion
Although disease clearance is the main objective in canal wall down mastoidectomy, hearing gain can be achieved if combined with ossiculoplasty and tympanoplasty. The hearing gain or loss depends upon the extension of disease and status of the ossicular chain. Most patients usually experience hearing loss more than the preoperative period due to removal of ossicle or ossicles for the sake of disease clearance.