Cochlear stenting: how I do it

Post-meningitis cases with profound sensorineural hearing loss are known to have progressive labyrinthine ossification; such cases need to be implanted early. In our region, often a substantial amount of time is spent procuring the necessary finances for a cochlear implant; therefore, here we describe our technique of maintaining cochlear lumen patency in post-meningitis cases with early ossification, for a complete functional electrode insertion at a later date. This is a descriptive case study of a patient having post-meningitis profound deafness, with imaging studies showing early cochlear ossification, who was rehabilitated with a cochlear implant. At a tertiary referral centre, a 1-year-old child with post-meningitis bilateral profound sensorineural hearing loss was rehabilitated with cochlear implantation. The left cochlea with early ossification was stented with a customised sterile electrode to prevent scalar occlusion; 3 months later the stent was replaced with a commercial Nucleus Contour Advance implant. A complete insertion of the functional electrode array replaced the stent. Categories of auditory performance (CAP) were used to assess the outcome in our case. The pre-operative CAP score was 1 (detects environmental sounds) and the score at 15 months post implant was 6 (understands some spoken words). In post-meningitis cases with progressive cochlear ossification, stenting the cochlear lumen prevents scalar occlusion and ensures a complete insertion of a functional electrode at a later date.

Computed Tomography measurements of the normal and the pathologic cochlea in children

BACKGROUND

Radiological investigation is frequently undertaken to assess the aetiology of sensorineural hearing loss (SNHL).

OBJECTIVE

To establish the CT measurements of the normal cochlea in children and to determine radiological criteria correlated with SNHL.

MATERIALS AND METHODS

A retrospective study of temporal bone CT performed in 159 children, age range from 3 days to 16 years between February 1999 and July 2004. A control group (n = 88) comprised children without SNHL; the SNHL group comprised 71 children. The width of the second turn of the cochlea (CW), the cochlear height (CH), and the width of the bony canal for the cochlear nerve (WCN) were measured on a reference plane containing the modiolus, the posterior semicircular canal, the footplate, and the stapes arch.

RESULTS

Width of the canal measurements <or=1.7 mm or >or=2.5 mm supported the diagnosis of SNHL with a specificity of 97% and 91%, respectively. Cochlear width was found to be significantly smaller in the SNHL group (5.61 +/- 0.51 mm) than in the control group (5.75 +/- 0.31 mm, P < 0.02), a size <5.4 mm being highly suggestive of SNHL with a specificity of 90%. No significant variations of all measurements were found with age.

CONCLUSION

Appropriate measurements of WCN and CW are highly correlated with SNHL.

Applications of the marchbanks transcranial-cerebral sonography technique in neurootology: preliminary report

Transcranial-cerebral sonography (TCCS) is a noninvasive technique that allows clinicians to detect nanoliter (billionths of a liter) displacements of the tympanic membrane. This technique was developed to assess cerebrospinal fluid (CSF) pressure in cases of shunted hydrocephalus; it takes advantage of the CSF connection to the inner ear through the cochlear aqueduct. The movements of the tympanic membrane that are observed in TCCS are those evoked by the acoustic stapedius reflex and those spontaneous movements generated by intracranial arterial, venous, and respiratory pulses transmitted through the inner ear to the stapes and thence to the tympanic membrane. Analysis of the amplitude and direction of these displacements has enabled neurosurgeons and neurologists to estimate CSF pressures accurately in patients evaluated by TCCS. TCCS allows for applications in neurootology, particularly in those patients who present with symptoms of pulsating tinnitus, dizziness and imbalance, or hearing loss. This preliminary report describes the test and its application in a series of patients whose diagnoses included pulsating tinnitus, idiopathic intracranial hypertension, Ménière's disease, perilymphatic fistula, perilymphatic hypertension, arterial stenosis, and Arnold-Chiari syndrome. We conclude that TCCS is a valuable addition to the armamentarium of neurootologists.

Cochlear implantation in obstructed cochleas: the effect of the degree of obstruction on the number of activated electrodes and the amount of postoperative speech perception

OBJECTIVE

With cochlear implantation, insertion of the electrodes can be hampered by cochlear obstructions. The aim of this study was to investigate the effects of these obstructions on the number of activated electrodes and postoperative speech perception.

STUDY DESIGN AND SETTING

Retrospective analysis of the operation reports and CT-scans of patients who underwent cochlear implantation, at the Department of Otorhinolaryngology of the University Medical Center of Utrecht (n = 295).

PATIENTS AND INTERVENTIONS

Fifty patients with a certain degree of cochlear obstruction were included. Based on the surgical intervention to overcome these obstructions they were subdivided into first-, second- and third degree obstructions. The number of implanted and activated electrodes was determined.

MAIN OUTCOME MEASURES

Three different speech perception tests after 12 months of cochlear implant use.

RESULTS

The number of activated electrodes significantly diminished with increasing obstruction degree (P < 0.01). This was caused by a lower amount of implanted electrodes combined with a higher amount of switched off electrodes. With a higher degree of obstruction the amount of postoperative speech perception decreased significantly (P < 0.01). This is partly explained by the lower number of activated electrodes and partly explained by the fact that a higher obstructions degree correlates with a higher degree of (retro-) cochlear pathology. Significantly more electrodes can be inserted into the severely obstructed cochlea using a Double Array Cochlear Implant.

CONCLUSION

Cochlear obstructions pose a surgical threat and negatively influence the postoperative speech perception results. Fortunately, due to surgical techniques, first and second degree obstructed cochleas can often be bypassed. Implanting of a Double Array implant brightens the prospects of patients with third (severe) degree obstructed cochleas.

Fistula of the Cochlear Labyrinth in Noncholesteatomatous Chronic Otitis Media

OBJECTIVE

To discuss the clinical aspects and management of promontory fistula of the cochlear labyrinth.

STUDY DESIGN

Case report and review of the literature.

SETTING

University hospital, tertiary referral center.

PATIENT, INTERVENTION, AND RESULTS

The authors describe an unusual case of cochlear fistula localized to the promontory discovered during tympanoplasty for noncholesteatomatous chronic otitis media in a 59-year-old woman. Bone conduction was slightly impaired after operation and hearing improved after a revision myringoplasty performed for reperforation.

CONCLUSION

Erosion of the bone of the labyrinth can also be observed in noncholesteatomatous otitis media. The presence of a fistula is not always associated with profound hearing loss. Overlying pathologic tissue can be removed without damaging the membranous labyrinth.

Computed tomography findings of labyrinthitis ossificans secondary to meningitis: a case report

A 26-year-old man was admitted to our hospital with chronic left ear drainage. He had a history of meningitis when he was a child. Computed tomography (CT) of the temporal bone showed complete obliteration of the otic labyrinth by sclerotic tissue. Based on CT findings, the patient was diagnosed as labyrinthitis ossificans. Computed tomography is an appropriate method of examination for the identification of labyrinthitis ossificans and is of particular importance for the evaluation of patients before cochlear implantation.

Recurrent acute otitis media associated meningitis in a patient with a contralateral cochlear implant and bilateral cochleovestibular dysplasia

OBJECTIVE

To illustrate that a patient with a cochlear implant may be at increased risk of meningitis secondary to developmental anatomic abnormality associated with the underlying sensorineural hearing loss, as opposed to the implant itself.

METHODS

Case report.

RESULTS

Our 12-year-old patient has bilateral cochlear dysplasia, profound sensorineural hearing loss and no prior history of recurrent acute otitis media or meningitis. He underwent a left cochlear implant at 8 years of age and subsequently experienced three episodes of right acute otitis media and meningitis over the next 4 years. Middle ear exploration revealed a cerebrospinal fluid leak. A right radical mastoidectomy with closure of the external auditory canal, removal of the tympanic membrane, malleus, and incus, closure of the Eustachian tube, and obliteration of the mastoid and middle ear with abdominal fat has prevented further episodes.

CONCLUSION

Meningitis in a patient with a cochlear implant is not necessarily related to the implant.

Localized Pericochlear Hypoattenuating Foci at Temporal-Bone Thin-Section CT in Pediatric Patients: Nonpathologic Differential Diagnostic Entity?

PURPOSE

To evaluate the prevalence of localized hypoattenuating areas in the cochlear otic capsule at temporal-bone thin-section computed tomography (CT) in pediatric patients and correlate the findings with clinical information.

MATERIALS AND METHODS

Temporal-bone thin-section CT images obtained in 73 patients aged 0-9 years (20 Austrian, 53 Finnish; 36 female and 37 male patients) were evaluated for the presence of localized hypoattenuating foci in the region of the fissula ante fenestram of the otic capsule. Clinical information collected for all patients was also evaluated. The data were analyzed with a logistic regression model.

RESULTS

Hypoattenuating areas in the region of the fissula ante fenestram were observed in 23 of 73 patients (32%). Hypoattenuating foci were substantially more prevalent in patients younger than 3 years than in those 3 years or older (odds ratio, 0.14; 95% CI: 0.04, 0.52; P =.001). The prevalence did not differ between sexes or according to clinical diagnosis. Only three of the 23 patients with hypoattenuating foci had clinical findings suggestive of otosclerosis, and none had osteogenesis imperfecta. After adjustment for age and sex, the finding was more prevalent among the Finnish patients (odds ratio, 5.4; 95% CI: 1.19, 24.52; P =.02) than among the Austrian patients.

CONCLUSION

Hypoattenuating areas in the region of the fissula ante fenestram in the otic capsule at thin-section CT are prevalent among children younger than 3 years in the absence of clinical evidence of otosclerosis or osteogenesis imperfecta and appear in children up to 9 years old.

High resolution computed tomography and magnetic resonance imaging in the pre-operative assessment of cochlear implant patients

Optimal imaging protocols for cochlear implantation have yet to be determined. Pre-operative computed tomography (CT) and magnetic resonance image (MRI) scans are used to assess cochlear anatomy and patency, to delineate surgical access, and to aid in choice of side for implantation. However, opinion still differs as to which modality provides more information in pre-operative assessment, or if, indeed, a combination of the two is superior. The first 88 patients on the Irish National Cochlear Implant Programme (NCIP) were retrospectively studied to determine the accuracy of pre-operative CT and MRI in predicting abnormalities at the time of surgery. Correlation with surgical findings was determined in three separate groups of patients (those who had CT only, those who had MRI only, and those who had both CT and MRI performed). Of the 24 patients that had both CT and MRI performed, both modalities had a 79 per cent correlation with surgical findings. CT and MRI reports concurred in 75 per cent of cases. Specificity and negative predictive value were high (86 per cent and 90 per cent, respectively). CT alone (47 cases) correlated with surgery in 39 cases (83 per cent); MRI alone (17 cases) correlated in 15 cases (88 per cent). The findings of this study suggest that CT and MRI are effective at predicting normal inner ear anatomy, and thus at predicting the patient and the cochlea most suitable for implantation. Both modalities are useful in determining the side of implantation, thus avoiding potential surgical difficulties in cases of unilateral abnormalities. There was no significant difference between the ability of MRI and CT to detect abnormalities at the time of surgery. In this series the combination of CT and MRI has not been shown to be superior to either modality used alone, although anecdotal evidence to the contrary was noted.

[A comparison between findings of high resolution computed tomography and magnetic resonance imaging in the preoperative assessment of cochlear implant patients]

OBJECTIVES

We compared the preoperative findings of high resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) with those observed during surgery to determine their value for cochlear implant patients.

PATIENTS AND METHODS

A retrospective assessment was made on preoperative HRCT and MRI scans of 124 cochlear implant patients (71 males, 53 females; mean age 15 years; range 2 to 63 years). Congenital cochlear anomalies, cochlear ossification, new bone formation in the middle ear, and structures in the internal auditory canal were evaluated and compared with intraoperative findings.

RESULTS

Cochlear anomalies detected in five patients by HRCT and MRI were confirmed intraoperatively. Cochlear ossification encountered in six patients during surgery was only demonstrated in four patients; HRCT and MRI scans only showed a narrow basal turn in the remaining two patients. During surgery, eight patients were found to have cochlear fibrosis: this finding was documented in five patients (62.5%) by MRI, and in none by HRCT scans.

CONCLUSION

Although HRCT provides valuable information for surgical planning, its limitations may justify the additional use of MRI before cochlear implantation.

[Multi-channel cochlear implant in cochlear ossification]

Cochlear ossification, considered until only a few years ago as a contraindication for cochlear implants (C.I.), may now be managed by means of a wide variety of surgical techniques. In cases with massive ossification, the drill-out circummodiolar technique described by Gantz et al. in 1988 and successively modified by Balkany et al. in 1997 may be adopted. The technique of electrode insertion in the scala vestibuli, perfected by Steenerson et al. in 1990, may be used when cochlear ossification has spread no further than the scala tympani. Other methods call for a groove to be drilled along the proximal tip of the basal turn of the cochlea (Cohen and Waltzman, 1993), the insertion of electrodes through the middle cranial fossa (Colletti et al., 2000), or the utilization of a double electrode array (Bredberg et al., 1997, Lenarz et al., 2001). This study reports the experience conducted at the Cochlear Implants Centre of the Otorhinolaryngoiatrics, Otological and Otoneurological Microsurgery Section of the University of Parma in a group of 15 patients who underwent C.I. in the presence of varying degrees of ossification. In 3 cases the ossification was limited to the region of the round window and a few millimetres of the scala tympani; cochleostomy was performed anteriorly and inferiorly to the anterior niche of the round window. In 11 cases (of which 3 of pediatric age), the ossification had spread to the horizontal portion of the scala tympani; in these cases, the electrodes were inserted in the scala vestibuli. The scala vestibuli was opened by drilling anteriorly to the round window and superiorly to the spiral ligament. In the only case of massively ossified cochlea, it was possible to partially insert the electrodes in a circum-modiolar tunnel. In the 12-month follow-up hearing test, the 3 patients with ossification of the round window region and the first millimetres of the scala tympani respectively averaged 61.6% in recognizing 2-syllable words and 59% in recognizing words embedded in phrases. The averages on the 12-month follow-up hearing test in the 8 adult patients who received the implant in the scala vestibuli were 80.6% in recognizing 2-syllable words and 89.1% in recognizing words in phrases. The 3 pediatric patients were classified on the Geers and Moog scale, which situated 2 of them in the 6th category of perception and 1 of them in the 4th category of perception. As regards the only case of massive cochlear ossification, the patient underwent surgery recently, and the sole follow-up available is the one conducted after only 3 months; the vowel identification average was 55%; the average on the VCV test was 31%; and the 2-syllable word recognition average was 20%.

Nucleus multichannel cochlear implantation in partially ossified cochleas using the Steenerson procedure

OBJECTIVE

The purpose of this study was to report hearing results obtained in a group of subjects who received scala vestibuli implantation because of cochlear ossification and to compare these results to those in patients with scala tympani implantation.

STUDY DESIGN

Retrospective analysis of consecutive cochlear implant procedures.

SETTING

Department of Otolaryngology, University of Parma.

PATIENTS

Five postlingually deafened adults with an electrode array placed into the scala vestibuli were compared with the speech performance of matched controls who had the electrode array inserted into the scala tympani.

MAIN OUTCOME MEASURES

Measures included vowel and consonant speech identification scores, bisyllabic word and sentence speech recognition scores, and common phrases comprehension scores.

RESULTS

No significant difference was detected on speech performances between the subjects with scala vestibuli implantation and the control group.

CONCLUSION

Scala vestibuli implantation appears to be an excellent alternative in cases in which scala tympani is found to be not patent.

The otolithic organ as a receptor of vestibular hearing revealed by vestibular-evoked myogenic potentials in patients with inner ear anomalies

The human vestibule has preserved an ancestral sound sensitivity and it has been suggested that a reflex could originate from this property underlying cervical muscle micro-contractions secondary to strong acoustic stimulation. Previous studies have established that an early component of loud sound-evoked myogenic potentials from the sternocleidomastoid muscle originate in the vestibule. This is based on findings that the response can still be obtained from patients with complete loss of cochlear and vestibular (semi-circular canal) function. Our data confirm, in a more direct way, a saccular origin of this short-latency acoustic response and verifies that a saccular acoustic response persists in the human ear. The contribution of this response to the perception of loud sounds is discussed. It is concluded that vestibular response to sound might be used to assist in the rehabilitation of deafness.

[The clinico-dopplerographic characteristics of the initial manifestations of cerebral circulatory insufficiency in patients with vertebral artery hypoplasia combined with osteochondrosis of the cervical spine]

In the examination of 44 patients with primary hypoplasia of the vertebral artery (less than 2.5 mm in diameter) associated with osteochondrosis of the cervical segment of the vertebral column there have been revealed the following neuropathological manifestations of cerebral circulation insufficiency in the vertebral-basilar basin: cephalalgia, cochlear syndrome, vestibulocerebellar syndrome, vegetovascular dystonia. Ultrasound investigation of the vertebral arteries bloodflow showed a decrease in bloodflow in the intracranial length of the hypoplastic artery and an increase in the resistance to bloodflow in the extracranial segments (V2, V3). Ten patients with functional disorders in the cervical portion of the spine were exposed to orthopedic therapy directed to restoration of mobility and of topography of individual motor segments of the spinal cervical section. The studies made showed that hypoplasia of vertebral arteries can present as cerebral circulatory insufficiency in the vertebral-basilar basin, which tends to increase or reveals itself in a concurrent development of vertebrogenic reflex vasoconstriction. Restoration of the spine function (mobility) is an effective medico-prophylactic measure aimed to resolve the vertebrogenically caused spasm of the artery.

A three-array cochlear implant: a new approach for the ossified cochlea

The ossified cochlea, although rare, represents a challenge for cochlear implantation. While it is no longer considered an absolute contra-indication to implantation, insertion may be technically difficult and the results may be suboptimal. Techniques which have been employed are reviewed. The new Digisonic multi-array implant, which was designed specifically for use in the ossified cochlea is described, along with the technique used for its insertion. In the first patient to be implanted with this new implant, all electrodes lie within the cochlea and are functional. The new Digisonic multi-array implant may have advantages over other solutions for the ossified cochlea.

Implantation of the CLARION cochlear implant in an ossified cochlea

This report describes the successful implantation of the CLARION Multi-Strategy Cochlear Implant electrode in the totally ossified cochlea of a 5-year-old child via a radical mastoidectomy approach. Postoperatively, the child demonstrated responses to auditory stimuli, even though the electrode array contacted only bone and muscle graft tissue with no visible evidence of nerve fibers or cochlear lumen. Responses to sound did not begin to emerge until 10 weeks following initial stimulation and improved slowly over time. Although the child's postoperative auditory performance is more limited than that of most implanted children, she derives substantially more benefit from her implant than she did from conventional hearing aids.

Using the CLARION cochlear implant in cochlear ossification

This paper is a retrospective review of 5 patients with various degrees of cochlear ossification who were implanted with the CLARION Multi-Strategy Cochlear Implant. Preoperative computed tomography scans, intraoperative findings, surgical technique, and hearing outcomes are discussed in a case report format. Full implantation was achieved in all cases by a systematic approach that included drill-through of proximal obstruction (2 cases), scala vestibuli insertion (2 cases), and complete drill-out (1 case). The only complication was delayed wound healing in a patient with sickle cell disease, chronic active hepatitis, and steroid dependency on antimetabolite therapy. Early results show that the 4 patients with at least 3 months of experience have a mean open-set sentence recognition score of 55% and a mean open-set word recognition score of 24%. The conclusion is that implantation of the Clarion device in ossified cochleas can be successful in all degrees of ossification and can provide significant hearing benefit.

X-linked deafness with stapes gusher in females

A 22-year-old woman presented with severe mixed hearing loss and a flow of cerebrospinal fluid in the middle ear during stapes surgery (stapes gusher). HRCT of the temporal bones showed characteristic abnormalities of the inner ear (bulbous dilatation of the lateral portion of the internal acoustic meatus with incomplete separation from the cochlea, and widening of the first part of the facial nerve canal) described in X-linked progressive mixed deafness with stapes gusher. The evaluation of the patient's family revealed a sister with the same clinical history and identical HRCT findings, and 11 normal male relatives. This is the first report with typical findings of this entity that affects only female members of a family, suggesting another type of inheritance.

Cochlear implants in children: what constitutes a complication?

The surgeon must ultimately accept the responsibility for any complications that occur as the result of a cochlear implant. Listening to the cochlear implant team members and responding to their needs may enhance the child's progress. Surgical complications, (i.e., skinflap problems, infection, and facial paralysis) are indeed infrequent, but nonsurgical problems are not. Surgical and nonsurgical experiences were reviewed in 55 children. Ages ranged from 23 months to 18 years at the time of cochlear implantation, which occurred from 1984 to 1995. There were no surgical complications. However, the most common surgical obstacle was ossification, which was present in 40% and undetected by computed tomographic scanning in 16.3% of children. Ossification occurred at the round window and scala tympani in 32.7% and involved the cochlea more extensively in 7.3% of children. In only one child was the cochlea entirely ossified. There were, however, many nonsurgical problems that were viewed as complications in patient management. The single most important complication was device failure. This occurred in 10.9% (5/46) of children with the Cochlear Corporation multichannel implant. Head banging and other temper tantrums, parental interference with rehabilitation, socioeconomic factors, poor compliance by the family unit, equipment problems, educational deficiencies, and impatience with habilitative training were some of the other problems.

Camurati-Engelmann disease presenting as 'juvenile otosclerosis'

Camurati-Engelmann disease (CED, MIM # 131300) was diagnosed in a 27-year-old woman, who had pain in her lower legs. There was no history of hearing loss (or CED) in her family. She had been suffering from progressive hearing impairment since childhood. Serial audiograms demonstrated progressive mixed hearing loss from the age of 11 years onwards, for which she underwent successful stapes surgery bilaterally at the age of 13-18 years. Clinical ('juvenile') otosclerosis was found with stapes footplate fixation. Unfortunately, the sensorineural hearing loss component proved to be progressive bilaterally after surgery. At the age of 30 years, she experienced more rapid deterioration of her hearing loss in the right ear and episodes of vertigo. Vestibular examinations demonstrated progressive vestibular impairment 'otospongiotic' lesions with encroachment on the cochlear and vestibular labyrinth were found on high resolution CT scans at the age of 40 years; the internal auditory canal was normal bilaterally. CED may have formed a chance combination with juvenile otosclerosis in our patient, or otosclerosis may be part of the CED phenotype.

Systematic Approach to Electrode Insertion in the Ossified Cochlea

Ossification of the fluid spaces of the cochlea occurs often in candidates for cochlear implantation, especially children. When noted before surgery on computerized tomography, ossification previously was thought to contraindicate cochlear implantation because of possible mechanical obstruction and uncertainty about the level of function that could be achieved by stimulating an ossified cochlea. However, during the preceding 6 years, techniques have been developed that permit implantation in ossified cochleas. We present a systematic approach that has been developed to treat the three clinically important categories of cochlear ossification: round window niche obliteration, inferior segment obstruction, and upper segment obstruction. Case reports are presented for each of these three drill-out procedures, demonstrating results often similar to those expected for implantation of the nonossified cochlea.

Accuracy of High-Resolution Computed Tomography in Cochlear Implantation

Multichannel cochlear implants are a proven method for the auditory rehabilitation of individuals who have severe-to-profound sensorineural hearing loss. These devices typically require insertion into the scala tympani of the cochlea to provide auditory stimulations. A patent scala provides the best chance for an adequate insertion of the electrode array. Preoperative high-resolution computed tomography imaging has traditionally been used to determine the patency of the scala tympani. Its ability to accurately predict the patency of the cochlea has been questioned in several retrospective studies. A prospective study was undertaken in 28 consecutive individuals undergoing cochlear implant surgery to compare the findings on high-resolution computed tomography with the surgical findings in an attempt to determine high-resolution computed tomography's accuracy. Cochlear obstruction caused by ossification was accurately predicted in six of six individuals but overestimated in the round window region in three individuals. High-resolution computed tomography accurately predicted patent cochleas in 19 individuals. No false-negative results were encountered. In this study sensitivity of high-resolution computed tomography was 100%, and specificity was 86%. High-resolution computed tomography appears to be more helpful than previously reported for determining cochlear patency.

CT of postmeningitic deafness: observations and predictive value for cochlear implants in children

PURPOSE

To demonstrate CT abnormalities encountered in children with postmeningitic deafness and to assess the value of CT in the prediction of cochlear implantation difficulties.

METHODS

Thirteen children with postmeningitic deafness were evaluated with high-resolution, thin-section CT. CT findings were correlated with surgical anatomy at the time of cochlear implantation, with particular regard to the prediction of implant success.

RESULTS

CT findings included normal scans (3 of 13, 23.1%), cochlear stenosis (5 of 13, 37.7%), cochlear fibroossific change (1 of 13, 7.7%), cochlear ossification (4 of 13, 30.8%), and osseous hypertrophy at the round window niche (4 of 13, 30.8%). Nine of 10 patients with abnormal findings had incomplete or difficult implantations (90%); 7 (88.8%) of these 9 received limited electrode insertions.

CONCLUSION

Attention to subtle otological abnormalities on thin-section CT is helpful in the prediction of early success or failure of implantation in children with postmeningitic deafness. Those with CT abnormalities had a 90% risk of incomplete or difficult insertions with a 70% chance of limited electrode insertion.

High-resolution computed tomography in evaluation of cochlear patency in implant candidates: a comparison with surgical findings

High-resolution computed tomography (HRCT) is important in the evaluation of cochlear implant candidates. This study examines the accuracy of radiological assessment of cochlear patency in relation to findings at the time of surgery. Older and newer HRCT methods and attending and senior radiologist interpretations are compared in a large series of cochlear implant patients. Subjects were 50 adults (22 to 74 years) and 31 children (2.4 to 11.7 years) who received either a 3M/House or a Nucleus 22-channel cochlear implant. Attending radiologist reports were obtained by chart review and the scans were re-reviewed for this study by a senior radiologist. Accuracy in detecting cochlear ossification ranged from 86.4 per cent for attending radiologists, with all HRCT scans, to 94.7 per cent for the senior radiologist with newer HRCT scans. False positives were rare, but false negatives did occur. Overall, best results were obtained with newer HRCT scans and a senior radiologist. Knowledge of the presence and extent of cochlear ossification is important to the implant surgeon and for patient counselling. Technical guidelines and a check list for interpretation of results are presented.

[The radiological pattern of cochlear otosclerosis. A CT study of 14 patients]

In this review of cochlear otosclerosis 14 cases were studied by CT scan aiming to establish a densitometric pattern of the capsular foci and relating it to the hearing and vestibule dysfunctions. Severe demineralization with characteristics of probable activity (increased lucency of 30-40%) was demonstrated in the capsular foci. These were mainly cochlear with endosteal involvement (93%): large (64%) or discrete (29%). Cochlear otosclerosis was widespread in 64% of the patients, with coexisting foci in the semicircular canals (38%), vestibule aqueduct (43%) and internal auditory canal (43%). The antefenestral component with stapes involvement was 85%, mostly of the anterior polar and crural varieties (64%) and signs of activity. In 2 patients there was a conductive hearing loss in the tonal audiometry, pure or combined; in 2 others there was only a pure perceptive hypoacusis of type IV. A direct relationship was noted (64% of cases) between the most serious hypoacusis (type III and IV) and the endosteal extension of the cochlear foci. Vertigo occurred in 36% of the patients and was attributed to the posterior labyrinth foci.

Holmium: YAG laser surgery in obliterated cochleas: an experimental study in human cadaver temporal bones

A pulsed holmium:YAG laser (lambda = 2120 nm) was used to reopen the basal turn of artificially obliterated human cochleas in freshly dissected cadavers. This allowed intracochlear insertion of the stimulation electrode of a cochlear implant under simulated surgical conditions. Laser energy was transmitted through a 400-microns nylon fiber via the opened facial recess directly to the round window niche. At an energy level of 500 mJ per 2.5 microseconds pulse, a repetition rate of 2 Hz, and an exposure time of 20-30 s, the photo-ablative mechanism of laser-bone interaction led to a 8-10 mm recanalization of the basal turn of the cochlea without damaging surrounding structures. The artificial bony occlusion and the recanalized basal turn of the cochlea were visualized by means of computed tomography and studied under light microscopy, using a histologic thin-section technique.

Imaging of otosclerosis

Imaging studies play an important role in the diagnosis of otosclerosis and in the clinical management of this disease. CT scanning at present is the tool of choice for the assessment of the labyrinthine windows and cochlear capsules. MR imaging thus far has had limited applications in the examination of the cochlear capsules but has been more useful in the assessment of the cochlear lumen prior to cochlear implant in patients with profound bilateral hearing loss.

Cochlear implants in children: reliability of computed tomography

Preoperative temporal bone computed tomography (CT) can demonstrate anatomic details relevant to surgical management and is therefore essential in the presurgical evaluation of patients receiving cochlear implants. The purpose of this study was to evaluate preoperative CT studies and compare them to surgical findings in 34 children who received the Nucleus multichannel cochlear implant. The focus of this report is to discuss the dependability of CT scans in predicting surgical findings at the time of cochlear implantation. Results indicate that agreement of CT interpretations with surgical findings is partially related to the etiology of hearing loss and the experience of the surgeon and neuroradiologist. Advantages and limitations of the CT scans in predicting surgical findings are discussed.

[Radiologic anatomy of the labyrinth artery]

Carotid and vertebral angiographic investigations were performed to study x-ray anatomy of the artery of the labyrinth (AL) in 96 inpatients admitted to the N. F. Sklifosovsky emergency care clinic. According to the angiograms, AL originated from the distal parts of the inferior anterior cerebellar artery in 66.3% of the patients. In this case it has a straight form. When initiating from the proximal parts of the basilar artery (33.7% of the patients), AL was shorter (0.8 +/- 0.3 against 2.5 +/- 0.8 cm) and curved. In any case AL was situated along the upper edge of the pyramid before it entered the internal acoustic meatus. By the meatus or inside it AL forms a characteristic loop or semiloop. A complete AL left-right symmetry was observed in 61.8% of the cases.

The basal turn of the cochlea

The coils of the cochlea are now readily demonstrated by thin-section high-resolution computed tomography (CT) in the axial plane. This assessment has become important in severely deaf patients who are candidates for cochlear implant surgery. The commonest abnormality shown in these cases is post-meningitic or tympanogenic labyrinthitis ossificans, which can obstruct the passage of the electrode. Severe otosclerosis can cause a similar problem. Congenital deformities of the labyrinth are rarely suitable for implantation, but the procedure may be indicated for the true Mondini deformity. Implantation is contraindicated for severe dysplasia of the cochlea and for the recently described variety of x-linked deafness with deficient bone at the fundus of the internal auditory meatus.

Radiographically confirmed cochlear otospongiosis among the Chinese

A high-resolution computed tomography (HRCT) study on 55 patients with surgically confirmed clinical otosclerosis confirms the existence of cochlear otospongiosis among the Chinese. Positive radiographic results of cochlear otospongiosis (13 ears, 12%) were found in patients with mixed-type deafness but in none with conductive hearing loss. Although there is a positive correlation between audiologic and radiographic findings, the HRCT results showed a lower positive rate and less severity than anticipated from the audiologic results. However, compared with the occurrence and extension of radiographic findings in similar studies of white people, it would seem to support our previous contention that the disease is indeed milder in Chinese people. Cochlear otospongiosis with extensive labyrinthine demineralization was found in three young patients with rapidly progressive hearing loss. This is important evidence of the overlooked fact that cochlear otospongiosis may also be one of the causes of sensorineural hearing loss in the Chinese. Thus, a high index of suspicion of the existence of this inner ear disorder is of paramount importance, and in such cases an HRCT study should be performed and sodium fluoride given to prevent further hearing deterioration.

Cochlear otosclerosis presenting in children: a case report

A case of cochlear otospongiosis in a 14-year-old is reviewed. The patient, who had a strong family history of otosclerosis corrected with stapes surgery, presented with a mild-to-moderate predominantly neurosensory hearing loss and absent stapes reflexes. A CT scan demonstrated changes characteristic of otospongiosis. The relevant literature was reviewed and fluorides as a possible therapy discussed.

Labyrinthine ossification after meningitis: its implications for cochlear implantation

Labyrinthine ossification can be found in a high percentage of patients with profound deafness resulting from bacterial meningitis. Radiographic evidence of ossification can be found as early as 2 months after the acute infection, indicating that the intracochlear process probably begins much earlier. If long, intracochlear cochlear implants are to be most successfully used in these patients, an aggressive approach to clinical management following the meningitis should be taken. Illustrative case reports and suggested guidelines for evaluation and treatment are given.

Imaging for cochlear implants

Insertion of a sound amplification device into the round window niche (extracochlear implant) or into the coils of the cochlea (intracochlear implant) can give significant benefits to some carefully selected, severely deaf patients. Imaging has an essential role in selective and pre-operative assessment. Severe otosclerosis and post-meningitic labyrinthitis ossificans are common causes of deafness in these patients and can be demonstrated by computed tomography (CT). The most suitable side for operation can be assessed. We describe our experiences with 165 patients, 69 of whom were found suitable for implants. Thin (1 mm) section CT in axial and coronal planes is the best imaging investigation of the petrous temporal bones but the place of magnetic resonance scanning to confirm that the inner ear is fluid-filled and polytomography to show a multichannel implant in the cochlea is discussed. No implants were used for congenital deformities, but some observations are made of this type of structural deformity of the inner ear.

The prognostic value of round window electrical stimulation in cochlear implant patients

The use of preoperative round window stimulation has been advocated for its possible predictive value in cochlear implant patients. We have attempted to correlate cause of deafness, preoperative radiologic study, and postoperative stimulability and performance with preoperative stimulation. Round window stimulation procedures consisted of measurements of electrical thresholds and comfort levels, gap detection, and temporal difference limen. Radiologic studies were performed using high-resolution computerized semi-axial and coronal tomography with 1.5-millimeter overlapping cuts. Patient performance was measured using a standard audiologic test battery. Sixteen postlingually, profoundly deaf adults who received the Nucleus multichannel cochlear implant were studied. All 16 patients who responded to preoperative stimulation had acceptable CT scans for the ear operated on and stimulated postoperatively with the prosthesis. The lowest level at which a patient could reliably detect a gap between two signals ranged from 10 to 150 milliseconds, which was not predictive. For the temporal difference limen task, the patients who could reliably identify the longer of two pulses when the difference was less than 100 milliseconds did achieve varying amounts of open-set speech discrimination postoperatively. In summary, results indicate that the preoperative psychoacoustic electrical stimulation test battery provides useful information in predicting postoperative performance.

[High-resolution computed tomography in diseases of the inner ear]

High-resolution CT of the petrous bone was carried out in 259 patients with clinically diagnosed abnormalities of the inner ear; in some the lesions were bilateral. In 62 patients (approximately 20%), the scans showed findings which related to the signs and symptoms. Patients with hearing loss and vestibular neuronitis showed no abnormalities. Amongst the remaining patients, the most common findings were acoustic neuromas (17 cases), cochlear otospongiosis (14 cases), malformations (13 cases) and tumours or cholesteatomas of the labyrinth (13 cases) as well as single rare isolated lesions.