Improved outcomes in auditory brainstem implantation with the use of near-field electrical compound action potentials.

OBJECTIVE: To compare the outcomes (auditory threshold and open-set speech perception at 48-month follow-up) of a new near-field monitoring procedure, electrical compound action potential, on positioning the auditory brainstem implant electrode array on the surface of the cochlear nuclei versus the traditional far-field electrical auditory brainstem response. STUDY DESIGN: Retrospective study. SETTING: Tertiary referral center. SUBJECTS AND METHODS: Among the 202 patients with auditory brainstem implants fitted and monitored with electrical auditory brainstem response during implant fitting, 9 also underwent electrical compound action potential recording. These subjects were matched retrospectively with a control group of 9 patients in whom only the electrical auditory brainstem response was recorded. Electrical compound action potentials were obtained using a cotton-wick recording electrode located near the surface of the cochlear nuclei and on several cranial nerves. RESULTS: Significantly lower potential thresholds were observed with the recording electrode located on the cochlear nuclei surface compared with the electrical auditory brainstem response (104.4 ± 32.5 vs 158.9 ± 24.2, P = .0030). Electrical brainstem response and compound action potentials identified effects on the neighboring cranial nerves on 3.2 ± 2.4 and 7.8 ± 3.2 electrodes, respectively (P = .0034). Open-set speech perception outcomes at 48-month follow-up had improved significantly in the near- versus far-field recording groups (78.9% versus 56.7%; P = .0051). CONCLUSIONS: Electrical compound action potentials during auditory brainstem implantation significantly improved the definition of the potential threshold and the number of auditory and extra-auditory waves generated. It led to the best coupling between the electrode array and cochlear nuclei, significantly improving the overall open-set speech perception.

Mesenchymal phosphaturic tumour: early detection of recurrence.

The case of a recurrent phosphaturic mesenchymal tumour of the maxillary sinus 10 years after the first surgical excision is reported. The neoplasm first presented with paraneoplastic osteomalacia causing a pathological femur fracture. A right maxillary sinus tumour was identified and treated thereafter. The patient had no local symptoms and serum electrolytes returned to normal after surgical removal of the tumour. However, 10 years later, the patient's urine Ca and P levels increased and an octreoscan detected a new tumour in the right maxillary sinus. Early diagnosis prevented the effects of the paraneoplastic activity of the neoplasm. This case emphasises the importance of specific, close follow-up, because the neoplasm rarely produces local signs indicating its position. To our knowledge, this is the first reported case of a late relapse presenting without relevant symptoms (local pain or swelling or pathological fractures).