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Multidisciplinary approach for ABI recipients: surgical, electrophysiologic, and behavioral outcomes
International Congress Series 1273 (2004) 433 – 436
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Multidisciplinary approach for ABI recipients: surgical, electrophysiologic, and behavioral outcomes P. Ashley Wackym*, Christina L. Runge-Samuelson, Jill B. Firszt Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, WI 53226, USA
Abstract. Objective: To describe the multidisciplinary approach implemented at the Medical College of Wisconsin for treating deafness in patients with neurofibromatosis type II (NF2) using the Nucleus 24 auditory brainstem implant (ABI). Study design: The ABI protocol at the Medical College of Wisconsin includes microsurgical and endoscopic placement of the electrode pad, electrophysiologic testing in the operating room to ensure optimal placement, and psychophysical/behavioral testing for appropriate stimulation and longitudinal follow-up of the patient. Results: To date, five patients have received ABIs and all are active users of their devices. All showed electrically evoked auditory brainstem responses during surgical placement, although they varied in morphology and amplitude. Of a possible 20 active electrodes, patients receive usable auditory stimulation on an average of 15 electrodes. Interfering nonauditory stimulation is present on an average of four electrodes. Pure-tone thresholds range from 20 to 35 dBHL across patients. For two patients who have 1 year of device use, their scores were 65% and 90% on the four-choice spondee (auditory-only). Substantial vowel recognition (Iowa Vowel Test) was observed in two patients who had 1 year of implant use (91% and 81%, auditory and visual) and one patient who had 6 months of implant use (64%, auditory and visual). In addition, patients have provided subjective reports of satisfaction with their devices. Conclusion: The multidisciplinary approach to auditory brainstem implantation at the Medical College of Wisconsin has been successful in treating deafness in NF2 patients. Proper placement of the electrode and careful programming of the device are crucial for a positive outcome, and require synergy among surgical, electrophysiologic, and clinical disciplines. D 2004 Elsevier B.V. All rights reserved. Keywords: Acoustic neuroma; Auditory brainstem implant; EABR; Electrical auditory brainstem response; Electrophysiology; Endoscope; Neurofibromatosis type II; NF2
* Corresponding author. Tel.: +1 414 266 3750; fax: +1 266 2693. E-mail address: [email protected] (P.A. Wackym). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.08.035
434
P.A. Wackym et al. / International Congress Series 1273 (2004) 433–436
1. Introduction The restoration of auditory perception in individuals deafened by loss of the vestibulocochlear nerve is currently being provided by auditory brainstem implants (ABIs). The ABI is a device consisting of several electrodes placed on the brainstem surface to directly stimulate the cochlear nuclei. [1,2] Externally, it is coupled with a digital speech processor. Current studies have shown that such stimulation can provide useful perception and even open set speech comprehension. [1,2] There is only one ABI in the US marketplace, Cochlear Americas’ (Englewood, CO), which is used primarily with neurofibromatosis type II (NF2) patients undergoing resection of a vestibular schwannoma (acoustic neuroma), or in patients undergoing resection of an acoustic neuroma in an only-hearing ear [3]. Patients with NF2 are often left with complete sensorineural deafness due to the sacrifice of both cochlear nerves during resection of bilateral tumors. [4] It has a 21-electrode array with the electrodes embedded in a silastic paddle backed with Dacron mesh, and it is also used intraoperatively as a stimulating electrode for EABR to help refine implant position. [1] The recommended protocol with this device utilizes a translabyrinthine approach to the tumor and subsequent implantation of the ABI. [1] A FDA clinical trial of a new electrode array utilizing a penetrating electrode is underway and five patients have been implanted to date. Three of these five patients have had multiple penetrating electrodes provide sound perception, one patient has a single penetrating electrode that provides sound perception, and one of these patients has no auditory perception from any of their penetrating electrodes (Dr. Robert Shannon, personal communication, May 12, 2004). Optimal placement of the electrode onto the cochlear nucleus is difficult because the operating microscope is unable to directly visualize this complex via the surgical approaches used to recent these tumors. However, the use of the endoscope in placement of an ABI electrode array has been explored to accomplish this goal [5]. In addition, the endoscope has been employed successfully as an adjunct to resection of acoustic neuromas and surgery of the vestibular nerve [6]. Our team has taken a multidisciplinary approach in ABI electrode placement by utilizing endoscopic guidance and electrophysiologic mapping to optimize electrode placement.
Fig. 1. A 34-year-old woman with NF2. Right acoustic neuroma resected on December 2000. Left acoustic neuroma resection via retrosigmoid approach and ABI placement on December 2001 using endoscopic and EABR guidance. (B) A 52-year-old woman with NF2. Recidivistic right acoustic neuroma resected via translabyrinthine approach and ABI placement on March 2002 using endoscopic and EABR guidance. Magnetic resonance imaging (MRI) shows electrode paddle on the right cochlear nucleus and recidivistic left skull base meningioma.
P.A. Wackym et al. / International Congress Series 1273 (2004) 433–436
435
Fig. 2. A 52-year-old man with NF2. Left acoustic neuroma resected via retrosigmoid approach and ABI placement on January 2003 using endoscopic and EABR guidance. Note the small right distal acoustic neuroma. He has normal hearing on the right and uses his ABI while awake. (B) A 15-year-old girl with Wishart-type NF2. After resection of the right acoustic neuroma, left acoustic neuroma resection via retrosigmoid approach and ABI placement was completed on July 2003 using endoscopic and EABR guidance.
2. Patients and methods To date, our team has used a multidisciplinary approach in placing ABIs in five patients. Clinical information is summarized in Figs. 1–3. Intraoperative endoscopic placement of the electrode paddle was performed by the same surgeon (P.A.W.) as we have described previously. [5] Intraoperative EABR was also performed using the paradigm recommended by Cochlear Americas, with the exception that repeated mapping was completed until optimal placement, as defined by the maximum number of active auditory electrodes achieved. 3. Results Table 1 and Figs. 1–3 summarize patient outcome after combined electrophysiologic and endoscopy-assisted placement of the ABI electrode array. We had an average of 15 active electrodes, without side effects, compared to the 8.7 active electrodes observed in the 2002 US Clinical Trial data set from Cochlear Americas. Figs. 1–3 show the number of electrodes with auditory-only, auditory plus side effect, side effect only, and no response for each individual study subject. In addition, we studied the behavioral responses for each patient after activation. For the two patients who have 1 year of device use, their scores were 65% and 90% on the four-choice spondee (auditory-only). Substantial vowel recognition (Iowa Vowel Test) was observed in two patients who had 1 year of implant use (91% and 81%, auditory and visual) and one patient who had 6 months of implant use
Fig. 3. A 16-year-old girl with NF2. Left recidivistic acoustic neuroma resection via translabyrinthine approach and ABI placement on July 2003 using endoscopic and EABR guidance.
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P.A. Wackym et al. / International Congress Series 1273 (2004) 433–436
Table 1 Auditory brainstem implant programming outcomesa Number of channels
2002 US Clinical Trial (n=50)
Medical College of Wisconsin (n=5)
Average Minimum Maximum
8.7 3 18
15 6 20
a
2002 US Clinical Trial outcomes provided by Cochlear Americas.
(64%, auditory and visual). In addition, patients have provided subjective reports of satisfaction with their devices. 4. Discussion Localization of the brainstem surface overlying the dorsal cochlear nucleus, however, is difficult. Brackmann et al. [7] noted that the dorsal nucleus in lower mammals forms a characteristic bbulgeQ on the brainstem surface, which they have not observed in humans. We have seen this surface bulge in cadaveric specimens as well as in our patients when performing endoscopic placement, which may indicate that such a landmark is, at best, inconsistent and therefore unreliable [5]. Further complicating localization of the dorsal cochlear nucleus is its position within the lateral recess of the fourth ventricle, an area reported to be not directly visible within the standard translabyrinthine surgical field [8]. Additional reports have likewise noted that the site of implantation may be obscured in a translabyrinthine dissection [7]. As such, this region is difficult to localize in a clinical setting and the importance of surgical landmarks to guide the surgeon has been stressed [5]. We have found that the retrosigmoid approach provides a better view of the cochlear nucleus complex via the operating microscope. While others have utilized EABR to facilitate optimal placement of the electrode array, we have typically spent 30–60 min in mapping out this ideal location. However, we have taken up to 3 h to accomplish this task. This has resulted in excellent outcomes as measured by number of active electrodes and the number of electrodes that are nonresponsive or produce side effects (Table 1; Figs. 1–3). References [1] S.R. Otto, et al., The multichannel auditory brain stem implant: performance in twenty patients, Otolaryngol. Head Neck Surg. 118 (1998) 291 – 303. [2] R. Laszig, W.P. Sollmann, N. Marangos, The restoration of hearing in neurofibromatosis type 2, J. Laryngol. Otol. 109 (1995) 385 – 389. [3] S.R. Otto, et al., The multichannel auditory brainstem implant: 6-month coinvestigator results, Adv. Otorhinolaryngol. 52 (1997) 1 – 7. [4] R.T. Miyamoto, et al., Preservation of hearing in neurofibromatosis 2, Otolaryngol. Head Neck Surg. 103 (1990) 619 – 624. [5] D.R. Friedland, P.A. Wackym, Evaluation of surgical approaches to endoscopic auditory brainstem implantation, Laryngoscope 109 (1999) 175 – 180. [6] P.A. Wackym, D.H. Rice, S.D. Schaefer (Eds.), Minimally Invasive Surgery of the Head, Neck, and Cranial Base, Lippincott Williams & Wilkins, Philadelphia, PA, 2002, pp. 1 – 559. [7] D.E. Brackmann, W.E. Hitselberger, R.A. Nelson, et al., Auditory brainstem implant. I: issues in surgical implantation, (see comments)Otolaryngol. Head Neck Surg. 108 (1993) 624 – 633. [8] A. Kuroki, A.R. Moller, Microsurgical anatomy around the foramen of Luschka in relation to intraoperative recording of auditory evoked potentials from the cochlear nuclei, J. Neurosurg. 82 (1995) 933 – 939.
www.ics-elsevier.com
Multidisciplinary approach for ABI recipients: surgical, electrophysiologic, and behavioral outcomes P. Ashley Wackym*, Christina L. Runge-Samuelson, Jill B. Firszt Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, WI 53226, USA
Abstract. Objective: To describe the multidisciplinary approach implemented at the Medical College of Wisconsin for treating deafness in patients with neurofibromatosis type II (NF2) using the Nucleus 24 auditory brainstem implant (ABI). Study design: The ABI protocol at the Medical College of Wisconsin includes microsurgical and endoscopic placement of the electrode pad, electrophysiologic testing in the operating room to ensure optimal placement, and psychophysical/behavioral testing for appropriate stimulation and longitudinal follow-up of the patient. Results: To date, five patients have received ABIs and all are active users of their devices. All showed electrically evoked auditory brainstem responses during surgical placement, although they varied in morphology and amplitude. Of a possible 20 active electrodes, patients receive usable auditory stimulation on an average of 15 electrodes. Interfering nonauditory stimulation is present on an average of four electrodes. Pure-tone thresholds range from 20 to 35 dBHL across patients. For two patients who have 1 year of device use, their scores were 65% and 90% on the four-choice spondee (auditory-only). Substantial vowel recognition (Iowa Vowel Test) was observed in two patients who had 1 year of implant use (91% and 81%, auditory and visual) and one patient who had 6 months of implant use (64%, auditory and visual). In addition, patients have provided subjective reports of satisfaction with their devices. Conclusion: The multidisciplinary approach to auditory brainstem implantation at the Medical College of Wisconsin has been successful in treating deafness in NF2 patients. Proper placement of the electrode and careful programming of the device are crucial for a positive outcome, and require synergy among surgical, electrophysiologic, and clinical disciplines. D 2004 Elsevier B.V. All rights reserved. Keywords: Acoustic neuroma; Auditory brainstem implant; EABR; Electrical auditory brainstem response; Electrophysiology; Endoscope; Neurofibromatosis type II; NF2
* Corresponding author. Tel.: +1 414 266 3750; fax: +1 266 2693. E-mail address: [email protected] (P.A. Wackym). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.08.035
434
P.A. Wackym et al. / International Congress Series 1273 (2004) 433–436
1. Introduction The restoration of auditory perception in individuals deafened by loss of the vestibulocochlear nerve is currently being provided by auditory brainstem implants (ABIs). The ABI is a device consisting of several electrodes placed on the brainstem surface to directly stimulate the cochlear nuclei. [1,2] Externally, it is coupled with a digital speech processor. Current studies have shown that such stimulation can provide useful perception and even open set speech comprehension. [1,2] There is only one ABI in the US marketplace, Cochlear Americas’ (Englewood, CO), which is used primarily with neurofibromatosis type II (NF2) patients undergoing resection of a vestibular schwannoma (acoustic neuroma), or in patients undergoing resection of an acoustic neuroma in an only-hearing ear [3]. Patients with NF2 are often left with complete sensorineural deafness due to the sacrifice of both cochlear nerves during resection of bilateral tumors. [4] It has a 21-electrode array with the electrodes embedded in a silastic paddle backed with Dacron mesh, and it is also used intraoperatively as a stimulating electrode for EABR to help refine implant position. [1] The recommended protocol with this device utilizes a translabyrinthine approach to the tumor and subsequent implantation of the ABI. [1] A FDA clinical trial of a new electrode array utilizing a penetrating electrode is underway and five patients have been implanted to date. Three of these five patients have had multiple penetrating electrodes provide sound perception, one patient has a single penetrating electrode that provides sound perception, and one of these patients has no auditory perception from any of their penetrating electrodes (Dr. Robert Shannon, personal communication, May 12, 2004). Optimal placement of the electrode onto the cochlear nucleus is difficult because the operating microscope is unable to directly visualize this complex via the surgical approaches used to recent these tumors. However, the use of the endoscope in placement of an ABI electrode array has been explored to accomplish this goal [5]. In addition, the endoscope has been employed successfully as an adjunct to resection of acoustic neuromas and surgery of the vestibular nerve [6]. Our team has taken a multidisciplinary approach in ABI electrode placement by utilizing endoscopic guidance and electrophysiologic mapping to optimize electrode placement.
Fig. 1. A 34-year-old woman with NF2. Right acoustic neuroma resected on December 2000. Left acoustic neuroma resection via retrosigmoid approach and ABI placement on December 2001 using endoscopic and EABR guidance. (B) A 52-year-old woman with NF2. Recidivistic right acoustic neuroma resected via translabyrinthine approach and ABI placement on March 2002 using endoscopic and EABR guidance. Magnetic resonance imaging (MRI) shows electrode paddle on the right cochlear nucleus and recidivistic left skull base meningioma.
P.A. Wackym et al. / International Congress Series 1273 (2004) 433–436
435
Fig. 2. A 52-year-old man with NF2. Left acoustic neuroma resected via retrosigmoid approach and ABI placement on January 2003 using endoscopic and EABR guidance. Note the small right distal acoustic neuroma. He has normal hearing on the right and uses his ABI while awake. (B) A 15-year-old girl with Wishart-type NF2. After resection of the right acoustic neuroma, left acoustic neuroma resection via retrosigmoid approach and ABI placement was completed on July 2003 using endoscopic and EABR guidance.
2. Patients and methods To date, our team has used a multidisciplinary approach in placing ABIs in five patients. Clinical information is summarized in Figs. 1–3. Intraoperative endoscopic placement of the electrode paddle was performed by the same surgeon (P.A.W.) as we have described previously. [5] Intraoperative EABR was also performed using the paradigm recommended by Cochlear Americas, with the exception that repeated mapping was completed until optimal placement, as defined by the maximum number of active auditory electrodes achieved. 3. Results Table 1 and Figs. 1–3 summarize patient outcome after combined electrophysiologic and endoscopy-assisted placement of the ABI electrode array. We had an average of 15 active electrodes, without side effects, compared to the 8.7 active electrodes observed in the 2002 US Clinical Trial data set from Cochlear Americas. Figs. 1–3 show the number of electrodes with auditory-only, auditory plus side effect, side effect only, and no response for each individual study subject. In addition, we studied the behavioral responses for each patient after activation. For the two patients who have 1 year of device use, their scores were 65% and 90% on the four-choice spondee (auditory-only). Substantial vowel recognition (Iowa Vowel Test) was observed in two patients who had 1 year of implant use (91% and 81%, auditory and visual) and one patient who had 6 months of implant use
Fig. 3. A 16-year-old girl with NF2. Left recidivistic acoustic neuroma resection via translabyrinthine approach and ABI placement on July 2003 using endoscopic and EABR guidance.
436
P.A. Wackym et al. / International Congress Series 1273 (2004) 433–436
Table 1 Auditory brainstem implant programming outcomesa Number of channels
2002 US Clinical Trial (n=50)
Medical College of Wisconsin (n=5)
Average Minimum Maximum
8.7 3 18
15 6 20
a
2002 US Clinical Trial outcomes provided by Cochlear Americas.
(64%, auditory and visual). In addition, patients have provided subjective reports of satisfaction with their devices. 4. Discussion Localization of the brainstem surface overlying the dorsal cochlear nucleus, however, is difficult. Brackmann et al. [7] noted that the dorsal nucleus in lower mammals forms a characteristic bbulgeQ on the brainstem surface, which they have not observed in humans. We have seen this surface bulge in cadaveric specimens as well as in our patients when performing endoscopic placement, which may indicate that such a landmark is, at best, inconsistent and therefore unreliable [5]. Further complicating localization of the dorsal cochlear nucleus is its position within the lateral recess of the fourth ventricle, an area reported to be not directly visible within the standard translabyrinthine surgical field [8]. Additional reports have likewise noted that the site of implantation may be obscured in a translabyrinthine dissection [7]. As such, this region is difficult to localize in a clinical setting and the importance of surgical landmarks to guide the surgeon has been stressed [5]. We have found that the retrosigmoid approach provides a better view of the cochlear nucleus complex via the operating microscope. While others have utilized EABR to facilitate optimal placement of the electrode array, we have typically spent 30–60 min in mapping out this ideal location. However, we have taken up to 3 h to accomplish this task. This has resulted in excellent outcomes as measured by number of active electrodes and the number of electrodes that are nonresponsive or produce side effects (Table 1; Figs. 1–3). References [1] S.R. Otto, et al., The multichannel auditory brain stem implant: performance in twenty patients, Otolaryngol. Head Neck Surg. 118 (1998) 291 – 303. [2] R. Laszig, W.P. Sollmann, N. Marangos, The restoration of hearing in neurofibromatosis type 2, J. Laryngol. Otol. 109 (1995) 385 – 389. [3] S.R. Otto, et al., The multichannel auditory brainstem implant: 6-month coinvestigator results, Adv. Otorhinolaryngol. 52 (1997) 1 – 7. [4] R.T. Miyamoto, et al., Preservation of hearing in neurofibromatosis 2, Otolaryngol. Head Neck Surg. 103 (1990) 619 – 624. [5] D.R. Friedland, P.A. Wackym, Evaluation of surgical approaches to endoscopic auditory brainstem implantation, Laryngoscope 109 (1999) 175 – 180. [6] P.A. Wackym, D.H. Rice, S.D. Schaefer (Eds.), Minimally Invasive Surgery of the Head, Neck, and Cranial Base, Lippincott Williams & Wilkins, Philadelphia, PA, 2002, pp. 1 – 559. [7] D.E. Brackmann, W.E. Hitselberger, R.A. Nelson, et al., Auditory brainstem implant. I: issues in surgical implantation, (see comments)Otolaryngol. Head Neck Surg. 108 (1993) 624 – 633. [8] A. Kuroki, A.R. Moller, Microsurgical anatomy around the foramen of Luschka in relation to intraoperative recording of auditory evoked potentials from the cochlear nuclei, J. Neurosurg. 82 (1995) 933 – 939.