Bhopal Technique of Cochlear Implantation: A Surgical Review of 50 Cases

Abstract

Cochlear Implant is the new age treatment for profound deafness especially in children who are unable to hear since birth. This is a life changing technology where in a surgically implanted device can stimulate the auditory nerve through electrical currents enabling the generation of auditory potential. Various surgical techniques have been described in literature but debate exists over Posterior Tympanotomy and Trans-canal “Veria” technique. We are presenting our experience of 50 cases with modified trans-canal technique “The Bhopal Technique” which combines the best of both. 50 patients with bilateral profound deafness in age group 1–5 years were included in this observational study. These children underwent cochlear implantation by Bhopal Technique. The data was categorised into age, gender, certain surgical parameters like time taken; exposure and complications. In present study. The average time taken for surgery was 77.6 min, with electrode insertion in first attempt in about 43 cases. Round Window exposure was adequate in 37 cases while scala tympani was entered in 49 cases. Average time taken for cochleostomy was 44.6 s. Most common complication was wound hyperemia followed by Perilymph Gusher. Explantation was seen in 1 case. Minor complications included Vertigo and Tinnitus. There was one tympanic membrane perforation at 3 months follow up and response to AVT was excellent in 12 children at 6 month follow up. Bhopal technique is emerging as a promising technique for upcoming cochlear implant surgeons due to its low complication rate, better exposure of surgical landmarks and comparable outcomes to Veria and Posterior tympanotomy techniques.

Introduction

Cochlear implants have a well-established field track of hearing rehabilitation. In addition to severe and profound sensorineural hearing loss, the indications for cochlear implants have been extended over the past few years (younger age at implantation, bilateral implantations, single sided deafness, hearing preserving techniques, and electroacoustic devices) [1–4]. The quality of life benefit for children receiving cochlear implants has been well documented thus making Cochlear implants the treatment of choice for auditory rehabilitation of patients with sensory deafness. They restore the missing function of inner hair cells by transforming the acoustic signal into electrical stimuli for activation of auditory nerve fibers. Due to the very fast technology development, cochlear implants provide open-set speech understanding in the majority of patients including the use of the telephone. Children can achieve a near to normal speech and language development provided their deafness is detected early after onset and implantation is performed quickly thereafter.

Until recently the facial recess approach for cochlear implant (CI) surgery, as described by House, has been the most commonly used worldwide. While the canal wall up mastoidectomy is a commonly practiced technique, the facial recess (also called posterior tympanotomy) approach to the middle ear requires appropriate training, experience, and long learning curve of otologists to successfully perform surgery. Current reports of facial nerve injury during facial recess surgery for CI show a consistent rate of 1%, with several studies reporting a rate of 0.7% making it most frequently used technique worldwide. The so-called ‘classic’ technique, uses a mastoidectomy and a posterior tympanotomy approach to the middle ear and the cochlea, but uneasiness of many surgeons drilling near the facial nerve has led to development of alternate techniques of cochlear implantation. Surgery for cochlear implants has undergone several modifications since the beginning of cochlear implantations to overcome the difficulties of facial recess approach and thus preventing facial nerve injuries [5–7].

Hoffman et al. showed that the facial nerve was anomalous in 16% of patients with cochlear malformations and One third of the patients with either common cavity mal formation or hypoplastic cochlea have aberrantly coursing facial nerves. Current gold standard posterior tympanotomy approach has a number of disadvantages and complications: facial paralysis, taste disturbances, misplacement, carotid injury, injury to the external canal, dural injury, or sigmoid injury. In some difficult anatomical situations (sclerotic mastoid, prominent sinus, and low placed dura) it may be impossible or extremely difficult to overcome these difficulties [8–11]. Number of alternative techniques to the facial recess approach are detailed throughout the CI literature, includeng: (1) Suprameatal approach (SMA), (2) Middle fossa approach, (3) transcanal (“Veria”) technique, (4) the Pericanal electrode insertion technique (PEIT), and (5) the transmastoid labyrinthotomy technique. However despite of these numerous alternative techniques available only Veria technique could be made more popular technique to overcome the difficulties of standard posterior tympanotomy technique. Even though It was safe technique without many complications, it did had disdavantage as it was a blind technique when a tunnel was made through the attic without drilling the mastoid.

However to over come the disadvantages of both classical posterior tympanotomy and classical transcanal veria technique, present study aims to propose a new surgical technique with modifications to over come the shortcomings of earlier technique.

Material and Methods

Present observational study was conducted in In Patient Department of Otolaryngology of Sri Guru Ram Das University of Health Sciences, Amritsar from May 2017 to February 2020. Total of 50 patients who were having bilateral severe to profound hearing loss between age group of 1–5 year were selected. All the necessary ethical clearance were taken from ethical committee of institute before the recruitment of patients and study was in compliance with principles of Declaration of Helsinki. STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) were adopted for reporting the current study.

All the necessary consent regarding candidacy, surgery, immediate and delayed complication of cochlear implantation and general anesthesia, outcomes, need for AVT therapy and stringent regular follow-up were fully explained in language best understood by patient. Every effort was made to maintain patient confidentiality a every point of time.

Selection of Patients

As per institutional policy of Universal Neonatal Screening, every newborn was screened from audiology department of ENT with OAE test. Those patient who were signalled “REFER” were again called for routine follow up at 3 months and then at 6 months, those patient who had strong suspicion of hearing loss were subjected to BERA and ASSR.

Every patient who was diagnosed with severe to profound hearing loss was given binaural amplification and those patient who were not responding to binaural amplification were carefully selected for cochlear implantation after social and psychological counselling of parents.

Inclusion Criteria

All children between age group of one year to 5 years who were prelingual and were having severe to profound hearing loss on audiological testing and were not getting any benefit with binaural amplification were selected for surgery.

Exclusion Criteria

In our study, we excluded postlingual children, cases with congenital inner ear anomalies, post meningitis cases, and cases with history of chronic suppurative otitis media and children elder than 5 years.

Pre-Operative Preparation

1. Pre-operative audiological preparation: OAE, BERA, ASSR,

2. Pre-operative radiological preparation: HRCT temporal bone, MRI cochlea and auditory nerve

3. Psychological assessment and IQ assessment

4. Paediatric evaluation to rule out any mental retardation and syndrome

5. Complete immunisation with anti -pneumococcal and anti meningococcal vacciones atleast 4–6 weeks before surgery

6. General anaesthesia fitness for surgery

Surgical Procedure

1. Endaural approach to the middle ear with elevation of a standard tym- panomeatal flap

2. The bed is drilled at an adequate location depending on the model of the implant used, however as in present study only nucleus company implant with straight electrode was used we started drilling the well on a flat surface about three finger breadths above the superior border of the pinna

3. Complete cortical mastoidectomy till the visualization of short process of incus was done. The mastoid well created during  cortical mastoidectomy also helps in accommodating extra electrode (Figs. 1 and 2).

4. Transcanal tunnel was made with help of drill just below it leaving the incus bridge as landmark

5. Inspection of the middle ear anatomy (cochlea, fallopian canal, round window niche)

6. Straightening of the posterosuperior bony canal wall

7. Cochleostomy in anterior inferior site to round window

8. Insertion of the electrode

9. Manipulation of the excess electrode in the cortical mastoidectomy and covering it with gel-foam so that it should not accidentally come in sutures (Figs. 2 and 3)

10. Reinforcing Tympanic membrane with temporalis fascia (Fig. 3)

11. NRT was done before closure

 Fig. 1.

The complete cortical mastoidectomy is being done

Fig. 2.

Adjustment of extra electrode array in the mastoid antum after cochleostomy

Fig. 3.

The extra elcetrode array in the mastoid cavity is covered with a piece of gel foam and the Temporalis fascia graft has been placed while the surgeon is repositing and adjusting the graft. Tympanomeatal flap with intact Tympanic membrane is seen superiorly resting against the canal wall

All patients were given IV antibiotics and discharged on 7th post-operative day suture removal were done on 10th day and early switch on protocols (2 weeks) were followed.

Funding  Details:

In present study all patient were fully funded.

Funding Agencies: Ali Yavar Jung National Institute of Speech and Hearing Disabilities (ADIP) and Sri Guru Ram Das University of Health Sciences (SGRDUHS Statistical analysis: SPSS software.

Results

In present study there were 3 children below the age of 2 years (Table 1). There were 31 males and 19 females (Table 2). The average time taken for surgery was 77.6 min, with electrode insertion in first attempt in about 43 cases. Round Window exposure was adequate in 37 cases while scala tympani was entered in 49 cases. Average time take foe cochleostomy was 44.6 s (Table 3). Most common complication was wound hyperemia (8/50) followed by Perilymph Gusher (3/50). Explanation was seen in 1 Case (Table 4). Minor complications included Vertigo and Tinnitus (Table 5). There was one tympanic membrane perforation at 3 months follow up and response to AVT was excellent in 12 children at 6 month follow up (Table 6) (Fig. 1).

Table 1.

Age distribution

Age	Number
Below 2 years	03
2–3 years	11
3–4 years	15
4–5 years	17
Above 5 years	04

Table 2.

Gender distribution

Gender	Number
Male	31
Female	19

Table 3.

Technical parameters of the surgery

Time for completion of surgery	77.6 min ( including NRT)
Ease of insertion of electrode
A. First attempt	43
B. Two attempts	03
C. > 2 attempts	03
D. Abandon procedure	01
Round window exposure
A. Transcanal drilling required	13
B. Transcanal drilling not required	37
Ease of cochleostomy
A. Average time for cochleostomy	44.6 s
B. Scala tympani entered	49
C. Procedure abandoned	01

Table 4.

Major complications

Serial No.	Complication	Number of patients affected
1	Meningitis	None
2	Perilymph Gusher	03
3	Flap necrosis and wound breakdown	01
4	Device failure	None
5	Electrode extrusion or migration	None
6	Facial nerve paralysis	01 (temporary)
7	Wound hyperemia	08
8	Skin wound over receiver-stimulator	01
9	Tympanic membrane perforation	01
10	EAC cholesteatoma	None
11	Keloid	None

Table 5.

Minor complications

Serial No.	Complication	Number of patients affected
1	Facial nerve stimulation patients	None
2	Electrode migration	None
3	Tinnitus	03
4	Vertigo	06

Table 6.

Follow up

Functional parameters of the device	All patients follow up at 3 months	All patients follow up at 6 months
Explanations	01	0
Tympanic membrane Perforation	01	0
AVT response
A. Poor	06	02
B. Average	10	06
C. Good	30	30
D. Excellent	04	12

Discussion

In order to address shortcomings and disadvantages of standard techniques of cochlear implantation we formulated new technique “Bhopal technique” which combined advantages of standard techniques like posterior tympanotomy and transcanal technique and at same time addressed all the shortcoming and disadvantages of both techniques. In study of 50 patients by Bhopal technique wherein following steps were incorporated, it was found that “Bhopal technique” was not only less time consuming but it was much safer with far fewer complication with good post-op healing and good AVT Response. Following steps were incorporated to standard transcanal technique:

1. Cortical mastoidectomy was done upto to the short process of incus and making the transcanal tunnel just below it after leaving the incus bridge —making it as landmark based trans canal tunnel.

2. Cortical mastoidectomy also helped in accommodating long excess cable conveniently preventing it migration in post of period

3. Covering the cable with gelfoam to prevent it from getting caught accidentally while suturing

4. In every case putting Temporal is facia graft to give strength to TM flap and avoid constant contact of the cable with TM thus preventing Delayed perforation of tympanic membrane

5. Making transcanal tunnel with Piezotome to prevent heat transmission to facial nerve

Limitation and strengths of present study

Though there were many strengths of present study like well-designed Cohort, homogenous population, carefully selected patients according to the standard candidacy guidelines, well designed surgical strategy incorporating newer steps after extensive study of available literature, stringent and strict follow-up with very specific and tailor made AVT session for each child, there were also fewer limitation like present study is observational study whereby there is urgent need of randomised controlled trial to further prove the recommendations of present study, also there are concerns regarding internal and external validity and generalizability of results.

The Key findings included that all children with congenital deafness who underwent implantation before the age of 6 years appeared to benefit from the implant. Intervention before the age of 4 years seemed to be critical to avoid irreversible auditory performance losses, and intervention before the age of 2 years seemed to be critical to achieve optimal results and this recommendation was in accordance with Present study there were 31 males and 19 females with most common age group between 4 and 5 years followed by 3–4 years and 2–3 years. There were 17 children who were operated between age group of 4–5 years, followed by 15 children and 11 children in age groups of 3–4 years and 2–3 years respectively. Three children were below 2 years and four children were above 4 years [12].

In present study average time to complete surgery including NRT was 77.6 min where in 43 patients out of 50 patients electrode was inserted in first attempt and only one patient was abandoned that is because of malrotation of cochlea. The study conducted by Sayed Mahmoud Makhemar and Magda Abdel-Latif Mohamed showed that average time for cochlear implantation via posterior tympanotomy was 150–180 min whereas average time ranged from 55–70 min in trans additus technique which was in accordance with finding of present study, however additional time for posterior tympanotomy is attributed mainly to procedure and training of surgeon [13].

Difficulty for visualization of round window associated with the cortical mastoidectomy is related to the degree of mastoid aeration and the height of the tegmen, and that the difficulty associated with facial recess is related to the presence/absence of an air cell around facial nerve [14].

The round window is usually partially hidden by the bony round window niche and this familiar landmark must be identified before the bony niche can be drilled away to fully expose the round window membrane.

Other advantage of Present technique was excellent exposure of round window where 37 cases out of 50 cases (74%) no trans-canal drilling was required and Average time of cochleostomy with present technique was 44.6 s and scala tympani was entered in 49 cases out of 50 cases (98%) and just one patient was abandoned because of malrotation of cochlea Complication rates after surgery are one of main predictor for successful outcome of surgery Complications following CI at Odense University Hospital were frequent, with more than half of the implantations (57.1%) being accompanied by at least one surgical complication (62.5% of the patients). However, the majority of these complications were minor and self-resolving. Major complications were observed following 24 implantations only (7.8%) and we therefore consider CI to be a safe procedure [15].

The overall complication rate in various series is around at 2.3–8% for major complications and 3.8–16% for minor complications [16–20]. Rate of major and minor complication in present technique was far less than what was reported with other techniques in literature which can attributed to the fact that present technique was.

Wound Hyperemia was most common major complication of present technique (8 patients out of 50) out of 8 patients 6 patients fully recovered without any active intervention while 1 patients had wound over receiver site which recovered after expensive wound care and 1 patient had flap necrosis for which explanation was planned and done, Other complication was intra-operative perilymph Gusher (3 patients out of 50), but all three patients underwent complete surgery with sealing of cochleostomy with soft tissue. Just one patient had perforation of tympanic membrane after attack of acute otitis media which was healed with conservative treatment. There were also few minor complication like temporary facial weakness, vertigo and tinnitus which fully resolved without any active intervention.

Follow up

Results at follow up at 6 months were very encouraging with present technique. The device was fully functional in all patients. Just one patient had explanation during 6 months follow up and all patients had satisfactory outcome with AVT therapy during 6 months follow up.

Conclusion

The modified trans-canal technique (Bhopal Technique) is a very encouraging technique for cochlear implantation as it has a short learning curve with good exposure of surgical landmarks and less complications.

Funding

This study is funded by SGRDUHS and ADIP Scheme.

Compliance with ethical standards

Conflict of interest

No conflict of interest.

Ethical statement

Before starting the study ethical clearance was taken from institutional ethical committee as per Declaration of Helsinki.

Informed consent

Informed consent Informed consent was taken by all the patients before surgery and enrolment into the study.