This paper describes the development of adult cochlear implantation in Birmingham over its first six years, from 1990 to 1996. During this time 366 patients were referred to the implant programme, female referrals outnumbered males 1.2:1. Eight per cent of referrals were over the age of 70.

The annual rate of referral suggests a fairly steady demand for the service. Approximately one third of patients referred each year were subsequently implanted. The centre is currently performing an average of 2 implants per month. The average time from referral to implant is approximately 19 months.

The greatest number of referrals originated from health districts closest to the implant centre. An examination of patients implanted suggested an imbalance in the uptake of the service amongst the different socio-economic groups.

We present the outcome of implantation in the first 100 adult patients treated under the Midland Cochlear Implant Programme. All patients were post-lingually deaf with profound or total hearing loss. Performance was tested in lip-reading, implant only and combined lip-reading and implant modes using BKB sentences, connected discourse tracking (CDT) and environmental sound recognition. Assessments were made at nine and 18 months post-implant.

The dominant aetiologies were idiopathic and meningitis. Meningitis was associated with the greatest numbers of ossified cochleas. Forty-three per cent of cases of partial ossification were identified only at surgery. Four per cent of patients became non-users of their devices, however the majority used their implants for more than 12 hours each day. The mean scores at nine months post-implant, in the implant only mode, were for environmental sound recognition 56.7 per cent, for BKB sentences 46.6 per cent (80 per cent of patients scored above 0 per cent) and for CDT 31.2 words per minute (w.p.m.) (62 per cent scored above zero per cent). In the combined lip reading and implant mode the mean scores, at nine months, were for BKB sentences 81.5 per cent and for CDT 65.8 w.p.m. All results were sustained at 18 months.

Patients reported that implantation significantly reduced their hearing handicap. Pre-operative measures of depression were also significantly reduced at nine months post-implant. Results were sustained at 18 months.

Post-operative audiological outcomes in the electrical stimulation only mode correlated significantly with length of profound deafness. Results suggest that performance outcome is also related to the number of active electrodes.

Of the first 100 patients implanted on the Midland Cochlear Implant Programme the commonest aetiologies of deafness were idiopathic 31 per cent, meningitis 28 per cent and cochlear otosclerosis 16 per cent.

The major complication rate was three per cent. The most severe was one individual who post-operatively developed a cerebral infarct and subsequently died. The minor complication rate was 39 per cent, all of which successfully resolved, and included 11 cases of wound infection, nine cases of vertigo, three transient facial palsies and two post-operative bleeds.

Older patients and men were most likely to have a post-operative medical complication. Women were more likely to have an abnormal electrode insertion. Meningitis and otosclerosis were the most complicated aetiologies in terms of cochlear ossification and electrode insertion. A non-patient cochlea was associated with fewer active electrodes. In six cases which had been reported pre-operatively as showing patent cochleas, some form of obstructional ossification was encountered. Patients functioning with greater than 15 active electrodes performed better on auditory tests than patients with fewer than 15 active electrodes.

At switch-on (first post-operative stimulation of the implant) and during subsequent reprogramming, electrodes can, in some patients, be found to be non-functional or to be performing sub-optimally for a number of reasons. This paper examines the reasons for the poor performance of these electrodes by means of a retrospective analysis of 100 patient records. All of these patients received the Nucleus multichannel device.

The most common reason for an electrode to require de-activation was found to be facial nerve stimulation, with poor sound quality and pain also being very common. Other reasons included absence of auditory stimulation, vibration, reduced dynamic range, throat sensations, absence of loudness growth or dizziness. The occurrence of these reasons along the electrode array was examined, more basal electrodes being found to be non-functional as a result of having a small dynamic range or poor sound quality. Pain and vibration were found to occur throughout the array and the more apical electrodes were found to be non-functional as a result of facial nerve stimulation. It is suggested that the electrodes at the basal end of the array are likely to be extra-cochlear or are at the site of the most cochlear damage, whereas the more apical electrodes lie in closer proximity to the facial nerve.

All patients in the Birmingham Cochlear Implant Programme underwent computerized tomography (CT) scanning and were assessed and images interpreted by the main author. Of the first 100 cases, 20 were considered to have abnormalities of the inner ears by CT imaging. It is concluded that the commonest abnormality was cochlear otospongiosis followed by labyrinthitis ossificans.

Otospongiosis is well shown by CT which gives a good predicator of luminal patency.

However, labyrinthus obliterans, although usually apparent on CT, is not reliably shown in all cases and T2 weighted magnetic resonance imaging (MRI) is better.

The relationship between tinnitus and cochlear implantation is an important issue that needs to be established because it may affect implant use. In this study 99 patients over 15 years of age completed pre-and post-cochlear implantation questionnaires, and underwent performance testing. The findings show that after implantation, there was marked suppression of tinnitus in both implanted and contralateral ears whilst the implant was off, and this was further enhanced when the implant was switched on. These effects are probably a combination of local and central factors. Presence of tinnitus, before or after implantation, had no detrimental effects on performance.

In conclusion, providing all other factors permit, this study recommends implanting the ear with the worst tinnitus.

Meningitis is an important cause of deafness and in some studies has been associated with poorer outcomes in adult patients following cochlear implantation. Of the first 100 adults implanted under the Midland Cochlear Implant Programme, 28 were deafened as a result of meningitis. We compare our experience with these patients with patients with a non-meningitic aetiology.

A degree of cochlear ossification was a more common finding in the meningitic group. In six cases (four meningitics, two non-meningitics) ossification was encountered only during surgery, not being apparent on pre-operative radiology.

The average scores achieved on auditory tests by the meningitic group were similar to those achieved by non-meningitic patients. At nine months, using only the implant, users were able to identify 54 per cent of common environmental sounds, achieved an average score of 30 words per minute on connected discourse tracking and identified an average of 42 per cent of words correctly in BKB sentences.

Poorer outcomes were more commonly associated with cochlear ossification. In patients with cognitive and neurological sequelae, benefits with the implant were not always apparent in the early months, however, with intensive therapy these patients can obtain measurable sustained benefit from their implant.

There are few accounts of cochlear implantation in adults with post-traumatic sensorineural hearing loss. We report our experience with multichannel implantation in three such patients.

Two patients experienced no cognitive or communication deficits as a result of their head injury. At nine months post-implant, compared with our experience of non-head-injured implantees, these patients achieved average or above average scores on audiological performance tests.

The third patient presented with cognitive, behavioural and communicative deficits. The level of improvement achieved by this patient, when lip-reading was supplemented with electrical stimulation, in both BKB sentence and connected discourse tracking (CDT) tests was comparable with that of the non-head-injured group. However, his absolute performance at nine months post-implant was well below average. Performance at 18 months on BKB sentences and environmental sound recognition showed little change, and was again well below average, however his score on CDT with lip-reading and electrical stimulation improved considerably and was similar to the average achieved by the non-head-injured group. The major difficulties experienced with this patient were increasing depression and low implant use. Considerably more time was spent in the assessment and rehabilitation of this patient and involved liaison with a number of other agencies. When considering such patients for cochlear implantation it is strongly recommended that these additional requirements are taken into account.