Cochlear Implant Made Easy by Bhopal Technique: Our Experience of 200 Patients

Abstract

Aim

The objective of this work is to present a modified Veria technique named as “Bhopal technique” for cochlear implantation and to discuss & compare its benefits and drawbacks with Posterior tympanotomy and Veria technique.

Materials and Methods

The study design is a surgical procedure description and prospective study on 800 patients who underwent Cochlear implantation by various techniques for bilateral profound sensorineural hearing loss at Divya Advanced ENT Clinic, Bhopal between 2014 and 2018 and followed up for 12–30 months. Implants used in were Digisonic SP, Cochlear CI24RE and Medel Sonata TI100. Out of 800 total patients, 200 patients were operated with Bhopal Technique. All the patients were reviewed on basis of total duration of surgery, intraoperative difficulties and development of any post-operative complications.

Result

All the patients were in the age range of 11 Months–7 years and the male: female ratio was of 2:1. In 200 patients operated with Bhopal Technique complications like electrode migration into the canal, excess electrode caught into suture, transcanal injury (Fig. 1c), corda nerve injury was not seen as against other technique in which 2 incidences of electrode migration and in 5 different cases transcanal injury, chorda nerve injury, tympanic membrane perforation was seen. The actual surgical time (excluding device testing) was less with Bhopal technique and ranged between 45 and 55 min.

Conclusion

Bhopal technique of Cochlear Implantation is a safe and versatile technique with good surgical outcomes which addresses shortcomings of Veria and posterior tympanotomy technique. It can be used for the implantation of all available devices with minimal operative risk and reduced operation time thus, offering prospects for better outcomes over other techniques.

Introduction

Cochlear Implantation is the most accepted method for treating bilateral severe to profound hearing loss since its clinical introduction 40 years ago. Cochlear implants have a remarkable history and a promising future. As the cochlear implant device has evolved, so has the surgical technique [1].

William House in 1976 first described the Mastoidectomy followed by posterior tympanotomy technique for Cochlear implantation [2]. This conventional or the classic technique which is commonly used worldwide has been the gold standard for cochlear implantation for decades [3]. However, it does have its disadvantages and complications [4] It is more time consuming & prone to various complications like facial nerve injury and difficulty in visualizing the round window area specially in small children with a small Facial Recess, anomalies of the cochlea, cochlear rotation etc. leading to aberrant placement of electrode [5].

This lead to search for alternative techniques for Cochlear implantation, like suprameatal approach, transcanal approach, canal wall dawn approach etc. [2].

In the era of minimal invasive techniques & need for better accessibility of the cochlea the Trans-canal or the Veria Technique by Dr. T. Kiratzidis is very helpful [5]. In the Veria technique, which is non mastoidectomy technique a suprameatal well and direct tunnel through posterosuperior bony canal wall is drilled for cochlear implantation [6]. In Veria technique risk of facial nerve injury is very less and visualization of round window area is very good as tympanomeatal flap is raised to get the panoramic view of middle ear. But, at times due to the shallow suprameatal well electrode array slips off in the canal or due to long transcanal pathway there is chance of injury to the canal wall with perforator, a special instrument used in Veria technique.

At Divya Advanced ENT Centre we started cochlear implantation with cortical mastoidectomy followed by posterior tympanotomy technique. But we switched over to Veria technique to avoid the risk of facial injury specially in young children. We have done more than 600 cases with this technique successfully. The main advantage was less surgical time and less general anesthesia in young children. But, we encountered certain complications with Veria technique like electrode migration into the canal (Fig. 1d), excess electrode caught into suture, transcanal injury, chorda nerve injury and tympanic membrane perforation.

Fig. 1.

Comparison of intraoperative difficulties and late post- operative complication between Bhopal and Veria Technique in percentage

All these complications stimulated us to modify our approach to a new more surgeon-friendly technique named as “Bhopal technique” of Cochlear implantation. This technique comprises of advantages of both posterior tympanotomy and Veria technique at the same time eliminates problems of both the techniques. Up till now we have done 200 cases with this technique without facing any major complication with minimal morbidity, comparable efficiency, and shorter operative time. Here, we present outline of our “Bhopal technique” of Cochlear implantation its results and advantages.

Materials and Methods

In this study 800 patients who underwent Cochlear implantation by various techniques for bilateral profound sensorineural hearing loss at Divya Advanced ENT Clinic, Bhopal between 2014 and 2018 were included.

All the patients underwent complete ENT examination, Audiological assessment, Psychological, Pediatric neurological evaluation and complete Radiological assessment (Combi scan) before surgery, immunization was done 2 weeks before surgery as per guidelines. Written informed consent was taken prior to surgery in all patients. Implants used were Digisonic SP, Cochlear CI24RE and Medel Sonata TI100.

All the patients were in the age range of 11 Months–7 years. Out of total 800 patients, 200 patients were operated with Bhopal Technique (Group A) and the rest 600 were operated by Veria technique (Group B). All the patients were assessed based following outcome variables on—

1. Total duration of surgery.

2. Intraoperative difficulties like Exposed Facial nerve, Chorda tympani nerve injury, transcanal injury, Difficult Round window exposure, Difficult insertion of electrode, excess electrode caught into suture and Injury of the Tympanic membrane or TM annulus.

3. Development of any Early post-operative complications like vomiting, vertigo, fever, Facial nerve paralysis or hematoma.

4. Development of any late post-operative complications like wound infection, migration of electrode extrusion, EAC stenosis or granulation, Retraction pocket in tympanic membrane or residual tympanic membrane perforation.

Surgical Technique: Bhopal Technique (In Group A Patients)

1. The surgery was performed under general anesthesia. The patient’s ear was cleaned with complete removal of debris.

2. Endaural approach to the middle ear with elevation of tympanomeatal flap was used. An inverted C shaped extension of the incision in the region of the squamous part of the temporal bone meeting the endaural incision was done.

3. The skin flap and temporalis muscle flap (anterior based flap) is elevated to expose the underlying temporal bone.

4. Postero-superiorly, a sub-periosteal pocket was made just large enough to admit receiver stimulator. The bed for the implant is marked in the most stable part of the squamous temporal bone. The bed is drilled to a depth where the endosteum is visualised. Margins of the bed are made at right angles which prevents the migration of the implant.

5. Inspection of the middle ear anatomy.

6. Straightening of the postero-superior bony canal wall, which is usually concave.

7. Drilling of cortical mastoidectomy to expose the short process of incus.

8. Drilling of the direct tunnel just below the short process of incus, which is the short pathway for the active electrode.

9. Cochleostomy is done using a 0.8 mm straight diamond burr antero-inferior to the round window niche through the outer ear canal.

10. Alignment of the direct tunnel to the cochleostomy is done.

11. The receiver stimulator part of device was put into place in the sub-periosteal pocket.

12. Insertion of the electrode was done with manipulating the excess of the electrode into the cortical mastoidectomy area and covering excess electrode with big piece of gel foam.

13. Temporalis fascia graft placed below the tympanomeatal flap in all cases to reinforce it.

14. Gel foam placed in the canal and Wound closed in three layers.

In Group B Patients

Surgical technique followed was standard Veria technique with drilling of Suprameatal hollow and trans canal wall direct tunnel with special burr and guard.

Intraoperative device function assessment was done in each patient. All patients were given postoperative antibiotic coverage. All patients proceeded to activation 2–4 weeks after surgery and went through rehabilitation programs (AVT) and were followed up for 6–30 months.

Results

Out of 800 total patients, 200 patients were operated with Bhopal Technique and rest 600 were operated with Veria technique. All the patients were in the age range of 11 Months–7 years and the male: female ratio was of 2:1.

There was a significant difference between the 2 groups as regard the total actual surgical time. In Bhopal technique time ranged between 45 and 55 min (mean 50 min) depending on the drilling time for the receiver package. Extra time spent in intraoperative testing was excluded. Operative Time in Veria technique was 70–90 min (mean 80 min).

In all 200 cases done with Bhopal technique (Group A) intra-operative difficulties like electrode migration into the canal, excess electrode caught into suture, transcanal injury, chorda nerve injury was not seen. However, in one patient (0.5%), intraoperative tympanic membrane injury occurred which had no postoperative impact as we placed temporalis fascia graft in every patient in Bhopal technique (Table 1).

Table 1.

Comparison of various outcome variables between Bhopal Technique and Veria Technique

S.No.	Outcome variables	Bhopal technique Group A	Veria technique Group B
1.	Total duration of surgery	45 to 55 min (Mean 50 min)	70 to 90 min (Mean 80 min)
2.	Intraoperative difficulties Exposed Facial nerve	Nil	Nil
	Chorda tympani nerve injury	Nil	5 (0.83%)
	Transcanal injury	Nil	5 (0.83%)
	Difficult Round window exposure	Nil	Nil
	Difficult insertion of electrode	Nil	Nil
	Excess electrode caught into suture	Nil	1 (0.16%)
	Injury of the Tympanic membrane	1 (0.5%)	5 (0.83%)
	Total	1 (0.5%)	16 (2.6%)
3.	Early post-operative complications like vomiting, vertigo, fever, Facial nerve paralysis or hematoma	Nil	Nil
4.	Late post-operative complications: Wound infection	Nil	Nil
	Migration of electrode	Nil	2 (0.33%)
	Extrusion of electrode	Nil	Nil
	Residual tympanic membrane perforation	Nil	2 (0.33%)
	EAC Granulation	Nil	1 (0.16%)
	Retraction pocket in tympanic membrane	Nil	Nil
	Total	Nil	5 (0.83%)

In Group B of Veria technique we encountered one (0.16%) incidence of excess electrode caught into suture, five (0.83%) cases of transcanal injury, five (0.83%) cases of chorda nerve injury and five (0.83%) cases of tympanic membrane perforation which were eventually grafted uneventfully without compromising the activation of the device (Table 1).

There was no significant difference between the 2 groups as regard the early postoperative complications as none were encountered in both the groups.

In all 200 cases done with Bhopal technique (Group A) any delayed post-operative complication like electrode migration into the canal, wound infection, EAC granulation or stenosis and residual tympanic membrane perforation was not seen.

In Group B of Veria technique we encountered two (0.33%) incidences of electrode migration into the canal, 2 (0.33%) patients had residual tympanic membrane perforation and one (0.16%) had granulation in EAC which were successfully managed (Table 1).

The overall incidence of intra operative difficulties in the Group A and Group B was 1 (0.5%) and 16 (2.6%) respectively. The late complication rate in the Group A was nil whereas in Group B it was 5 (0.83%) (Fig. 1).

Discussion

Different surgical approaches have been adopted for Cochlear Implantation since its introduction around 40 years back for treating bilateral severe to profound hearing loss.

The Gold standard classic technique of mastoidectomy with posterior tympanotomy has overall complication rate between 7 and 16% [2]. It is more time consuming and prone to various complications like facial nerve injury and difficulty in visualizing the round window area specially in small children with a small Facial Recess, anomalies of the cochlea, cochlear rotation, etc. leading to aberrant placement of electrode [5] and a long learning curve.

In Veria technique risk of facial nerve injury is very less as safe distance is maintained between facial nerve and tunnel and visualization of round window area is good as tympanomeatal flap is raised [6]. But, sometimes electrode array slips off in the canal due to shallow suprameatal well or due to long transcanal blind drilling of pathway there is chance of injury to the canal wall with perforator.

All these complications stimulated us to modify our approach to a new more surgeon-friendly technique named as “Bhopal technique” of Cochlear implantation.

The Major differences in Bhopal technique from Veria are:

1. In Bhopal technique, cortical mastoidectomy is done to expose the short process of incus there by reducing the length of transcanal tunnel drilling subsequently reducing chances of injury to the canal wall.

2. Perforator is used under vision just below the short process of incus to make the transcanal tunnel. This area is far away from facial nerve as we know from the facial recess approach (Fig. 1a).

3. In place of shallow suprameatal well we are making deep cortical mastoidectomy to accommodate longer excess electrode (Medel) to avoid its migration into the canal wall (Fig. 1a).

4. Temporalis facia graft placed in every case takes care of tympanic membrane perforation especially when membrane is in contact with excess electrode (Fig. 1b).

5. Big Piece of gel foam prevents excess electrodes to be caught in suture (Fig. 1b).

There was a significant difference between the two groups as regards the total actual surgical time. The mean duration of surgery was significantly shorter in Bhopal technique (50 min) than in Veria technique (80 min). In a study by Postelman et al., the mean duration of surgery by suprameatal approach was 111.7 min & by posterior tympanotomy it was 132.2 [7]. The main advantage in Bhopal technique was less surgical time and less general anaesthesia in young children especially those with comorbidities.

In the present work with Bhopal technique, there was intra operative injury to tympanic membrane in one patient out of 200 (0.5%) but it had no postoperative impact as we used temporalis fascia graft routinely in all cases, even in absence of injury or perforation. In group B by Veria technique we had five cases (0.83%) of tympanic membrane injury intraoperatively & 2 (0.3%) patients had residual tympanic membrane perforation out of 600 cases which were eventually grafted uneventfully without compromising the activation of the device. This was much less than that reported by Taibah et al. (5 cases out of 134 case 3.5%) in implantation performed through trans meatal approach [7].

In Group B of Veria technique we encountered five cases (0.83%) of chorda tympani nerve injury. Although chorda tympani injury in the classic approach was described as 5.2% to 20% there were no reported cases of chorda tympani nerve injury by the suprameatal approach or its modifications in many literatures [7].

In Group B of Veria technique we encountered one (0.16%) incidence of excess electrode caught into suture, five (0.83%) incidences of transcanal injury which was not seen in our technique. The reason for this is that as we are doing cortical mastoidectomy the length of transcanal tunnel is reduced and perforator is being used under vision just below the short process of incus subsequently, reducing chances of injury to the canal wall.

The “Bhopal technique” of Cochlear implantation has been performed in 200 cases till date without facing any major complication with comparable efficiency and shorter operative time. The analysis of the results and our experience shows that this technique of Cochlear implantation has advantage of being simple, having fast learning curve and is safe for the facial nerve and canal wall as the drilling of transcanal tunnel is not blind anymore.

Conclusion

“Bhopal technique” of Cochlear Implantation is clearly a good alternative technique as it addresses all the problems faced during Veria and posterior tympanotomy technique and comprises advantages of both techniques. It can be used for the implantation of all available devices and has minimal operative risk with good outcomes.