Paul Merkus

European multi-centre study of the Nucleus Hybrid L24 cochlear implant

Abstract Objectives: To investigate the preservation of residual hearing in subjects who received the Nucleus Hybrid L24 cochlear implant. To investigate the performance benefits up to one year post-implantation in terms of speech recognition, sound quality, and quality of life. Design: Prospective, with sequential enrolment and within-subject comparisons. Post-operative performance using a Freedom Hybrid sound processor was compared with that of pre-operative hearing aids. Study sample: Sixty-six adult hearing-impaired subjects with bilateral severe-to-profound high frequency hearing loss. Results: Group median increase in air-conduction thresholds in the implanted ear for test frequencies 125–1000 Hz was < 15 dB across the population; both immediately and one year post-operatively. Eighty-eight percent of subjects used the Hybrid processor at one year post-op. Sixty-five percent of subjects had significant gain in speech recognition in quiet, and 73% in noise (≥ 20 percentage points/2 dB SNR). Mean SSQ subscale scores were significantly improved (+ 1.2, + 1.3, + 1.8 points, p < 0.001), as was mean HUI3 score (+ 0.117, p < 0.01). Combining residual hearing with CI gave 22−26 %age points mean benefit in speech recognition scores over CI alone (p < 0.01). Conclusions: Useful residual hearing was conserved in 88% of subjects. Speech perception was significantly improved over preoperative hearing aids, as was sound quality and quality of life.

Uptake of melatonin into the cerebrospinal fluid after nasal and intravenous delivery: Studies in rats and comparison with a human study

AbstractPurpose. To investigate the possibility of direct transport of melatonin from the nasal cavity into the cerebrospinal fluid (CSF) after nasal administration in rats and to compare the animal results with a human study. Methods. Rats (n = 8) were given melatonin both intranasally in one nostril (40 μg/rat) and intravenously by bolus injection (40 μg/rat) into the jugular vein using a Vascular Access Port. Just before and after drug administration, blood and CSF samples were taken and analyzed by HPLC. Results. Melatonin is quickly absorbed in plasma (Tmax = 2.5 min) and shows a delayed uptake into CSF (Tmax = 15 min) after nasal administration. The melatonin concentration-time profiles in plasma and CSF are comparable to those after intravenous delivery. The AUCCSF/AUCplasma ratio after nasal delivery (32.7 ± 6.3%) does not differ from the one after intravenous injection (46.0 ± 10.4%), which indicates that melatonin enters the CSF via the blood circulation across the blood-brain barrier. This demonstrates that there is no additional transport via the nose-CSF pathway. These results resemble the outcome of a human study. Conclusions. The current results in rats show that there is no additional uptake of melatonin in the CSF after nasal delivery compared to intravenous administration. This is in accordance with the results found in humans, indicating that animal experiments could be predictive for the human situation when studying nose-CSF transport.

Hydroxocobalamin Uptake into the Cerebrospinal Fluid after Nasal and Intravenous Delivery in Rats and Humans

The possibility of direct transport of hydroxocobalamin from the nasal cavity into the cerebrospinal fluid (CSF) after nasal administration in rats was investigated and the results were compared with a human study. Hydroxocobalamin was given to rats (n=8) both intranasally (214 μg/rat) and intravenously (49.5 μg/rat) into the jugular vein using a Vascular Access Port (VAP). Prior to and after drug administration, blood and CSF samples were taken and analysed by radioimmunoassay. The AUCCSF/AUCplasma ratio after nasal delivery does not differ from the ratio after intravenous infusion, indicating that hydroxocobalamin enters the CSF via the blood circulation across the blood–brain barrier (BBB). This same transport route is confirmed by the cumulative AUC-time profiles in CSF and plasma, demonstrating a 30 min delay between plasma absorption and CSF uptake of hydroxocobalamin in rats and in a comparative human study. The present results in rats show that there is no additional uptake of hydroxocobalamin in the CSF after nasal delivery compared to intravenous administration, which is in accordance with the results found in humans. This indicates a predictive value of the used rat model for the human situation when studying the nose to CSF transport of drugs.

Less than 1% cerebrospinal fluid leakage in 1,803 translabyrinthine vestibular schwannoma surgery cases.

Objective: To determine the incidence rate of cerebrospinal fluid (CSF) leak after translabyrinthine vestibular schwannoma surgery since the alteration of the surgical procedure. To compare with previous series and other series in literature. Study Desig: Database analysis. Setting: Tertiary referral neurotologic private practice. Patients: A series of 1,803 patients who underwent translabyrinthine vestibular schwannoma surgery between 1993 and 2009. The result of this group was compared with corresponding series. Intervention: Translabyrinthine and extended translabyrinthine vestibular schwannoma surgery. Literature review and comparison. Main Outcome Measures: Rates of CSF leak in this series and historical perspective of the outcome. Results: Fifteen patients (0.8%) of 1,803 cases had CSF leaks. The method used since 1993 has shown a significant improvement compared with major case series of the last 10 years. Conclusion: The methods used in translabyrinthine vestibular schwannoma surgery in our center can reduce CSF leakage to an absolute minimum. Compared with all large series, this could be a new era of translabyrinthine vestibular schwannoma surgery.

Classification of cilio-inhibiting effects of nasal drugs.

Objective/Hypothesis Nasal drug formulations are widely used for a local therapeutic effect, but are also used for systemic drug delivery. In the development of new nasal drugs, the toxic effects on the mucociliary clearance and therefore on the ciliated tissue is of importance. In this study, the effect of nasal drugs and their excipients on the ciliary beat frequency (CBF) is investigated.

Auditory brainstem implants in NF2 patients: results and review of the literature

Objective Neurofibromatosis Type 2 (NF2) patients have multiple central nervous system tumors and, specifically, bilateral vestibular schwannomas (VSs) causing bilateral deafness. If the cochlear nerve is not preserved during tumor removal, the only hearing rehabilitation in these patients could be via an auditory brainstem implant (ABI). Study Design Retrospective case study and literature review. Setting Tertiary referral cranial base center. Patients In 24 NF2 patients, 25 ABIs were placed in the lateral recess of the fourth ventricle after VS surgery via a translabyrinthine approach. Results In this series, a large range of results are observed: from open speech and use of the telephone to no ABI use, because of the poor sound identification ability. Of the 24 patients, 19 use their ABI on a daily basis, 4 are nonusers, and 1 died of NF2 progression. A multivariate analysis did not reveal a good predictor for ABI outcome. In literature, the results of ABI in NF2 are difficult to compare, and the overall outcome was poor compared with cochlear implantation results. Conclusion Auditory brainstem implantation in NF2 patients directly after tumor removal is a safe procedure and the best means of hearing rehabilitation if the cochlear nerve is not preserved. The results in NF2 cases in the literature and these series are poor compared with cochlear implantation. If a cochlear implant is possible, it has the preference over an ABI, also in NF2. Nevertheless, the majority of the patients have benefit of the ABI during daily life particularly in combination with lip reading.

Dutch Cochlear Implant Group (CI-ON) Consensus Protocol on Postmeningitis Hearing Evaluation and Treatment

Objective: One of the most devastating sequelae of bacterial meningitis is profound hearing loss or even deafness. Although cochlear implantation is able to restore (some) hearing abilities, obliteration due to fibrosis and especially calcification of the cochlea in the postmeningitis period is limiting the success rate of an implantation. A national consensus assembled in a postmeningitis follow-up protocol has to increase awareness and thus the chances of an early detection and possible intervention when profound hearing loss occurs. Setting: All cochlear implant (CI) centers of The Netherlands located in the 8 academic otorhinolaryngology and audiology departments of The Netherlands, gathered in the Dutch Cochlear Implant Group (CI-ON, Cochlear Implant Overleg Nederland). Intervention: A protocol proposed by 3 centers was sent to all other CI centers in The Netherlands to review and agree on. Main Outcome Measures: The CI centers agreed on the need for, and use of, the proposed protocol. Keystones of the protocol are treatment with dexamethasone before start of antibiotics, early magnetic resonance imaging and repeated audiological follow-up, and urgent referral to a CI center in all cases with greater than 30 dB SNHL. Conclusion: The Cochlear Implant Centers in The Netherlands (CI-ON) have agreed on a protocolized follow-up after bacterial meningitis to increase the chances of an early detection and possible intervention should profound hearing loss occur.

Prognostic factors for sudden drops in hearing level after minor head injury in patients with an enlarged vestibular aqueduct: a meta-analysis.

Objective To identify factors associated with sudden drops in hearing level after minor head trauma in patients with an enlarged vestibular aqueduct (EVA). Methods A systematic review of the literature on sudden drops in hearing level after minor head trauma in patients with an EVA was conducted. The studies were retrieved from Embase, PubMed, CINAHL, and Cochrane and critically appraised using predefined criteria. Data on all described parameters were collected, and their relation with sudden drops after minor head trauma was statistically analyzed. Results Pooled data of 31 articles included 179 patients with 351 EVAs. Drops in hearing level after minor head trauma were experienced by 34% of the patients. We found a significant association between sudden deterioration of hearing after minor head trauma and preexisting fluctuating hearing loss (HL) (odds ratio, 8.6; p < 0.001; 95% confidence interval, 3.9–19.3). The diameter of the VA, type of preexisting HL, severity of HL, preexisting progressive HL, and the diagnosis Pendred syndrome were not significantly associated with sudden drops in hearing levels after head trauma. Conclusion Only one-third of the patients with a proven EVA experienced sudden drops in hearing level because of head trauma. There is a significant association between preexisting fluctuating HL and the chance of sudden drops in hearing level caused by trauma. Stringent lifestyle advices, like avoiding activities with a risk of minor head trauma such as contact sports, might be restricted to patients with a fluctuating HL and those with a history of sudden drops on minor head trauma.

The use of intratympanic gentamicin in patients with vestibular schwannoma and disabling vertigo

Objective To document the effect of intratympanic gentamicin as treatment of disabling vertigo secondary to a vestibular schwannoma in elderly patients. Patients Four elderly patients with a vestibular schwannoma, with an extrameatal diameter of less than 1 cm, experiencing disabling vertigo and followed a wait-and-scan policy. Intervention Intratympanic injection of gentamicin. Main Outcome Measures Subjective improvement of quality of life and audiologic and vestibular assessment. Results We obtained a subjective improvement in the quality of life for all the 4 patients. In fact, disabling vertigo disappeared in all cases; 3 patients recovered their posttreatment unsteadiness after a period of vestibular rehabilitation, whereas one of them complained of persistent unsteadiness. The hearing remained unchanged in 3 patients, whereas in one, the pretreatment severe sensorineural hearing loss progressed to anacusis. Conclusion This treatment represents an additional option in patients with small not-growing tumor affected by vestibular symptoms to be combined with a wait-and-scan policy.

Vestibular Schwannoma in the Only Hearing Ear: Role of Cochlear Implants

Objectives: We sought to delineate the role of cochlear implantation in the management of vestibular schwannoma or other cerebellopontine angle tumors in the only hearing ear. Methods: We performed a retrospective analysis in a quaternary referral skull base center of all patients who were affected by vestibular schwannoma (or other lesions of the cerebellopontine angle) in the only hearing ear and received a cochlear implant before or after tumor treatment (surgery or radiotherapy) or during the wait-and-scan follow-up. We also performed a systematic review of the English-language literature. Results: The clinical and audiological results of 10 patients are reported. All patients were managed with contralateral cochlear implantation. In 7 patients, cochlear implantation was performed before tumor removal, while hearing in the ear with the tumor was still present. In 3 patients, the implant was placed after curative surgery. Nine of the 10 patients routinely use their implant with subjective benefit and fairly good auditory performance (median disyllabic word recognition, 90%; median sentence comprehension, 75%). The literature search retrieved no major series with assessment of the long-term efficacy of cochlear implantation in this rare clinical scenario. Conclusions: Patients affected by vestibular schwannoma in their only hearing ear may significantly benefit from a cochlear implant on the contralateral side prior to tumor removal. Recent and significant hearing deterioration and tumor growth represent the main indications for cochlear implantation.