A comparison of intra- versus post-operatively acquired electrically evoked compound action potentials.

The objective of this study was to compare the electrically evoked compound action potentials, intra- versus post-operatively, in cochlear implant patients. In a prospective study twenty-five consecutively implanted adult patients received a multichannel cochlear implant. In all patients, electrically evoked compound action potentials were recorded immediately after cochlear implantation and in a post-operative setting nine months later. The threshold of the electrically evoked compound action potential was determined in both settings. A high success rate (97.4%) was found in the intra-operative setting when recording the electrically evoked compound action potential threshold per patient. The success rate per patient was significantly lower (53.4%) in the post-operative setting. Correlations between the intra- versus the post-operative ECAP thresholds were statistically significant for all electrodes tested. The ECAP thresholds were not significantly different for the two settings. The intra-operative setting is preferable for acquisition of the ECAP threshold.

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.

Preoperative imaging protocol for cochlear implant candidates.

OBJECTIVE: To formulate and test a CT imaging protocol for preoperative scanning of the temporal bone in cochlear implant candidates. MATERIAL AND METHODS: A human head was scanned in three CT planes: axial, axiopetrosal and semilongitudinal. Multiplanar reformats (MPRs), based on axial slices, were created and compared with the corresponding images obtained by direct scanning in the respective planes. All scans were analyzed on a viewing workstation. RESULTS: The axial plane image allowed for an overview of the temporal bone. The width of the facial recess and the cochlear nerve canal could be studied on combined axial and axiopetrosal images. Cochlear patency could be evaluated using combined axial and semilongitudinal images. Axiopetrosal and semilongitudinal MPRs were able to replace the images obtained by direct scanning in the respective planes. CONCLUSION: The combination of the axial CT plane image and MPRs was found to be sufficient for preoperative analysis of the temporal bone morphology.

Intelligibility of vowels produced by post-lingually deafened cochlear implant users.

The present study addresses the effect of cochlear implantation on the intelligibility of vowels produced by 20 post-lingually deafened Dutch subjects. All subjects received the Nucleus-22 cochlear implant (3 WSP and 17 MSP processors). Speech recordings were made pre-implantation and three and twelve months post-implantation with the implant switched on and off. Vowel intelligibility (monophthongs only) was determined using a panel of listeners. For all implanted subjects intelligibility was measured in a noisy background. For seven poorly speaking subjects it was also measured in a quiet background. After implantation with the Nucleus-22 device the results showed that vowel intelligibility, measured for all subjects in a noisy background, increased for most of them (about 15), while it increased for about half the number of poorly speaking subjects measured in a quiet background. Twelve months after implantation vowel intelligibility, measured for all subjects in noise, appeared to be based on first and second formant information. This was also found for the subgroup of seven subjects performing poorly pre-implantation when analysed separately. However, vowel intelligibility for this subgroup, when measured in a quiet background, was based also on vowel duration. The differences between the overall result in noise and the results of the subgroup in quiet should be attributed mainly to the noise and not to aspects of poor speech production in the subgroup. In addition, this study addresses the relationship between the intelligibility scores and objective measurements of vowel quality performed in a previous study. The results showed that the vowel intelligibility scores are mainly determined by the position of the second formant frequencies.

Predictors of cochlear implant performance.

Open set speech understanding with cochlear implants, without speechreading, is nowadays a common finding. However, there is a large variation in speech understanding between cochlear implant users. We tried to find pre-operative parameters which predicted the post-operative results. Thirty-seven adult post-lingually deafened Nucleus cochlear implant users with a mean age of 46 years (range 16 68) and a mean duration of deafness of 15 years (range 1.5-47) were studied. Pre-operatively, we performed pure-tone audiometry, round window and ear canal electrical stimulation, psychological tests and imaging. Additionally, we measured pre-operatively speech understanding in the auditory, the visual and the audiovisual conditions with several tests which were also administered after 6 and 12 months' implant experience. Correlation analysis between the pre-operative variables and the post-operative factors showed that duration of deafness and residual hearing are the most important predictors. The temporal difference limen in pre-operative round window electrical stimulation is a secondary predictor.

Effect of cochlear implantation on voice fundamental frequency in post-lingually deafened adults.

The present study addresses the effect of cochlear implantation on the voice fundamental frequency at which 20 post-lingually deafened Dutch subjects utter speech materials. All subjects received the Nucleus 22 cochlear implant (3 WSP and 17 MSP processors). Speech recordings were made pre-implantation and three and twelve months post-implantation with the implant switched on and off. The fundamental frequency (f0) was sampled while reading a text. The pre-implantation results show that in some subjects, f0 was too high compared with the range in f0 of normally-hearing subjects. Post-implantation, with the implant switched on, we found that the abnormally high f0 values pre-implantation changed toward the normative values. In addition, post-implantation we found that the range over which f0 varied within a subject while reading the text, the f0 sway, decreased for most subjects who, pre-implantation, had their f0 sway outside the normative ranges, the normative range being defined as the interval between the mean plus/minus one standard deviation of the f0 sway found for normally-hearing subjects. Voice fundamental frequency of post-lingually deafened adults is characterized by large interindividual variability in the pre-implantation f0 values. This large interindividual variability is found also in the effect of cochlear implantation on f0.

A functional anatomic study of the relationship of the nasal cartilages and muscles to the nasal valve area.

The functioning of the nasal valve area is largely determined by the stability and the mobility of the lateral nasal wall. To gain insight into the kinematics of the lateral nasal wall, we studied the functional anatomy of the nasal muscles and the intercartilaginous and osseous-cartilaginous junctions. We performed gross and microscopic nasal dissection and serial sectioning in 15 human cadaveric noses. In addition, two noses were used for three-dimensional reconstruction of the nasal cartilages. We conclude that the lateral nasal wall can be seen as made up of three parts. At the level of the osseous-cartilaginous chain of bone, lateral nasal cartilage, and lateral crus, the lateral nasal wall is relatively stable, limited mobility being allowed by translation and rotation in the intercartilaginous joint and a coupled distortion of the cartilages. At the level of the hinge area the lateral nasal wall is supported by one or more accessory cartilages, embedded in soft tissue, and therefore much more compliant. The alar part of the nasalis muscle, which originates from the maxilla and inserts on these cartilages, may dilate the valve area by drawing this hinge area laterally. The third and most compliant part of the lateral nasal wall is the part that is not supported by cartilage, the ala. The dilatator naris muscle largely occupies the ala and is attached to the lateral crus; it opens the vestibule and nostril. The third nasal muscle that influences the lateral nasal wall is the transverse part of the nasalis muscle. It overlies the nose but is not attached to it. This muscle stabilizes the lateral nasal wall, in particular, the lateral nasal cartilage, the intercartilaginous junction, and the hinge area, by moving the nasal skin.

Changes in vowel quality in post-lingually deafened cochlear implant users.

The present study addresses the effect of cochlear implantation on vowel production of 20 post-lingually deafened Dutch subjects. All subjects received the Nucleus 22 implant (3 WSP and 17 MSP processors). Speech recordings were made pre-implantation and three and twelve months post-implantation with the implant switched on and off. The first and second formant frequencies were measured for eleven Dutch vowels (monophthongs only) in an h-vowel-t context. Twelve months post-implantation, the results showed an increase in the ranges of the first and second formant frequency covered by the respective vowels when the implant was switched on. The increase in the formant frequency range was most marked for some subjects with a relatively small formant range pre-implantation. Also, at 12 months post-implantation with the implant switched on we found a significant shift of the first and second formant frequency towards the normative values. Moreover, at this time the results showed significantly increased clustering of the respective vowels, suggesting an improvement in the ability to produce phonological contrasts between vowels. Clustering is defined as the ratio of the between-vowel variance of the first and second formant frequency and the within-vowel variance of three tokens of the same vowel.

Effect of cochlear implantation on nasality in post-lingually deafened adults.

The present study addresses the effect of cochlear implantation on nasality in 21 post-lingually deafened Dutch subjects. All subjects received the Nucleus 22 implant (MSP version). Speech recordings were made pre-implantation and 3 and 12 months post-implantation with the implant switched on and off. Nasality measurements were performed on a standard text and on two sentences without nasal phonemes. The results show that post-lingual deafness in individuals can result in a deviant degree of nasality in speech production. However, the nasalance value of 86% of the subjects of our study fell within the normative range defined as the mean +/- 2 standard deviations of the normal population. After implantation we found no statistically significant effect of implant use. However, individual nasality values outside the normative range may improve. Furthermore, 12 months post-implantation we found a significant decrease in the variability of the nasalance values obtained for two sentences without nasal phonemes.

Review of the functional anatomy of the cartilages and muscles of the nose.

This paper reviews the anatomy of the nasal cartilages and muscles. Accurate anatomical knowledge of these structures may facilitate the design of a model to study the mobility and support of the lateral nasal wall and ala and may thus provide information on the dynamics of valve area. It is concluded that a uniform description of nasal cartilages and muscles is still lacking. This is especially true for the attachments of the nasal cartilages to neighbouring structures, as well as the location and function of the muscles influencing the valve area. The use of uniform, preferably anatomical, terminology is encouraged.

Electromyography of the human nasal muscles.

Electromyographic (EMG) activity of six nasal muscles was monitored in 17 male volunteers without nasal complaints. Surface electrodes were placed on the nasal skin in such a way that they selectively recorded the activity of these muscles. Recordings were made under different breathing conditions and during voluntary nasal movements. Inspiratory EMG activity was observed during nasal and oral breathing in one or more of the following muscles: dilator naris, nasalis muscle (alar and transverse parts) and apicis nasi. EMG activity increased markedly in response to physical exercise and was more often present in subjects with decreased nasal patency. During voluntary nasal movements a combined activity of the six nasal muscles was consistently found. We conclude that the function of the dilator naris, the nasalis muscle and the apicis nasi strongly relates to respiration. These muscles probably contribute to the prevention of collapse of the nasal valve. The role of the procerus and levator labii superioris alaeque nasi seems to be primarily concerned with facial expression.

Phoneme recognition by deaf individuals using the multichannel nucleus cochlear implant.

Experiments have been carried out to determine which cues are used in phoneme identification by deaf individuals using a cochlear implant. Five deaf individuals with a Nucleus 22-channel cochlear implant were tested with open set speech audiometry in free field without lipreading. Speech material consisted of lists of Dutch words of the Consonant-Vowel-Consonant type (CVC-words). Word scores ranged from 0 to 22%, phoneme scores from 11 to 54%. For each subject the responses to the initial consonant, the vowel and the final consonant were entered into separate confusion matrices. Kruskal analysis, which provided a geometric representation of these confusions, showed that in the recognition of consonants the feature of voicing is all important. Vowels were identified on the basis of the frequencies of the first and second formants. In one subject the electrode array could only partially be inserted into the cochlea, leaving roughly half the second formant area of the electrode array outside the cochlea. For this subject vowel identification was based upon the first formant and vowel duration; there was no contribution of second formant information to vowel identification. Compressing the first and second formant frequency to the limited intracochlear array did not enhance transmission of second formant information and did not improve performance. The basic findings for consonant and vowel recognition could be explained by the speech coding strategy of the Nucleus speech processor in which voicing determines stimulus periodicity and formant frequencies determine channel selection. Kruskal analysis of phoneme confusions may aid in programming and evaluating the performance of the Nucleus cochlear implant.

An inverted papilloma with intracranial extension.

Inverted papilloma can be found in the lateral wall of the nose, the ethmoidal sinus, the maxillary sinus, the sphenoidal sinus and the frontal sinus. To our knowledge there are no reports of papillomas with intracranial extension. This case report describes the history of a patient with long-standing inverted papillomas, which eventually grew intracranially. The treatment of this patient and the treatment of inverted papilloma in general are discussed.

Influence of the stimulus repetition rate on brain-stem-evoked responses in man.

In order to record brain-stem-evoked responses as fast as possible, the influence of the stimulus repetition rate was investigated. The repetition frequency was varied from 2.5 to 80 Hz. The amplitudes of N2-N4 diminish uniformly with increasing stimulus rate. The repetition rate has little or no influence on the amplitude of N5; however, increasing the repetition frequency about 10 Hz causes an increase in the latencies of N2-N5. It seems that the decrease in the amplitude of N2-N4 and the increase in the latencies of N2-N5 are of cochlear origin, since the amplitude and the latency of the cochlear responses are influenced in the same way by the repetition rate as the above-mentioned brain stem responses.

Distribution of brain stem responses to acoustic stimuli over the human scalp.

Responses to acoustic stimuli are generated in neurons of nuclei on both sides of the brain stem. In order to determine whether there are electrode positions which can be used to record activity predominantly generated in the neurons of nuclei of one side, the distribution of brain stem responses to acoustic stimuli over the human scalp was investigated. The response is found to be maximum at the vertex, and diminishes gradually toward the nasion, inion and the mastoid process. There are no significant differences between responses to ipsi- and contralateral stimulation. It follows that there are no electrode positions, which can be used to record the activity generated in the neurons of nuclei of one side. There are, however, indications that monolateral pathology of brain stem nuclei may be detectable by comparing responses to stimuli presented on the right, the left and bilaterally.