T. Rader

Effect of cochlear implantation on horizontal semicircular canal function.

The objective of this study was to assess the influence of a cochlear implant (CI) on horizontal semicircular canal (hSCC) function, to test the correlation with symptomatic vertigo and to identify possible risk factors for a postoperative vestibular impairment. In a prospective observational study design, forty-seven adult patients who had undergone cochlear implantation at Cochlear Implant Center at a tertiary referral university hospital, Munich, between 2003 and 2007, were studied. Postoperative vertigo symptoms were assessed using a questionnaire followed by a structured interview. Patients were subjected to caloric and rotational chair vestibular function tests pre- and postoperatively. The CI operation was performed with a retroauricular transmastoidal approach by three different surgeons. Thirty-six implants were Cochlear Nucleus 24 devices and 11 implants were MedEl devices. Twenty-one (45%) patients reported vertigo symptoms after CI. Functional testing of the hSCC yielded valid results in 45 of the 47 patients. Thirty-two percent of patients had a substantially reduced hSCC function after CI. Responses of caloric irrigation showed a significant worsening postoperatively in the CI ears. No direct correlation between a decrease in caloric response and risk of postoperative vertigo symptoms could be established. For the criteria age, sex, implant type, surgeon, cause of deafness, petrous bone CT findings and preoperative vertigo, there were no significant differences between the patients with and the patients without postoperative vertigo. Besides morphological changes, a cochlear implantation also causes functional damage of vestibular parts of the labyrinth. Our study showed a significant worsening of the caloric response. However, this alteration did not lead to vertigo complaints in all patients. It is therefore presumed that additional damage to sensory or visual afferents and central vestibular compensatory mechanisms play a role.

A case of bilateral cochlear implantation in single-sided untreated acoustic neurinoma

Acoustic neurinoma affects the acousticofacial nerve and therefore in many cases is a contraindication for cochlear implantation and an indication for brainstem implant. Nevertheless benefit in these patients has been shown after tumour removal and cochlear implantation. The first case of bilateral cochlear implantation in a patient with single-sided untreated acoustic neurinoma is described here. In a 49-year-old woman with progressive hearing loss during the last 12 years we preoperatively diagnosed an acoustic neurinoma of the left side. After cochlear implantation of the right side she was sequentially implanted on the affected side as well. Before surgery radiological control of the tumour for signs of growth was performed and the patient was thoroughly informed of the situation and possible therapies and dangers. Speech discrimination scores obtained in the second implanted ear came up to the performance of the first implant after 6 months.

Hörerhaltende Cochlea-Implantation: Besser Hören mit neuer Technik

Preservation of residual hearing after cochlear implantation allows patients the synergetic use of electric and acoustic stimulation (EAS). The application of specific surgical and therapeutic techniques enables the reduction of inner ear trauma, which leads otherwise to complete hearing loss. Due to simultaneous electric and acoustic stimulation, speech understanding is improved especially in noise. EAS is a well-accepted therapeutic treatment for subjects with profound hearing loss in the higher frequencies and no or mild hearing loss in the low frequencies. Several Manufacturers offer individual soft electrodes specially designed for hearing preservation as well as combined electric-acoustic audio processors.