Objective Measures in Cochlear Implants

Michelle Hughes, PhD, CCC-A Dr. Michelle Hughes is the Coordinator of the Cochlear Implant Program and Director of the Cochlear Implant Research Laboratory at Boys Town National Research Hospital in Omaha, Nebraska. She is also an adjunct assistant professor in the Department of Special Education and Communication Disorders at the University of Nebraska-Lincoln. Her NIH-funded research program is aimed at investigating the relationships between physiological and perceptual measures in cochlear implant recipients. She has published numerous peer-reviewed journal articles on evoked potentials in cochlear implants, and has presented her work nationally and internationally.

Foreword by Series Editors Terry Zwolan and Jace Wolfe vii Preface ix Acknowledgments x About the Author xi PART I. LAYING THE FOUNDATION 1 1 The Basics of a Cochlear Implant 3 Introduction 3 Anatomy of Severe to Profound Hearing Loss 4 Basic Principles of Electrical Stimulation of the Auditory System 7 Basic Parts and Functions of a Cochlear Implant 8 Past and Present Devices 12 Candidacy 27 2 Signal Delivery 31 Channels Versus Electrodes 31 Signal Type 34 Stimulus Timing 36 Electrode Configuration 37 Electrode Design 40 Summary 41 PART II. NONPHYSIOLOGICAL OBJECTIVE MEASURES 43 3 Electrode Impedance 45 Introduction 45 The Basics of Electrode Impedance 45 How Impedance Is Measured Clinically 54 Clinical Uses for Impedance Measures 62 Summary 64 4 Electrical Field Potentials 67 Basic Description 67 Measurement 69 Clinical Uses for Electrical Field Potentials 69 Summary 72 5 Averaged Electrode Voltages 75 Basic Description 75 Measurement 75 Factors Affecting AEV Measures 78 Typical Patterns 78 Atypical Patterns 84 Clinical Uses for AEVs 86 Summary 90 PART III. PHYSIOLOGICAL OBJECTIVE MEASURES 91 6 Electrically Evoked Stapedial Reflexes 93 Introduction to Physiological Objective Measures 93 Basic Description 93 Measurement 94 Clinical Uses for ESRTs 95 Summary 98 7 Electrically Evoked Compound Action Potential 101 Basic Description 101 Measurement 102 Clinical Uses for ECAPs 118 Summary 121 8 Electrically Evoked Auditory Brainstem Response 123 Basic Description 123 Measurement 124 Clinical Uses for EABRs 130 Summary 131 9 Electrically Evoked Auditory Middle Latency Response 133 Basic Description 133 Measurement 135 Clinical Uses for EAMLRs 136 Summary 136 10 Electrically Evoked Auditory Cortical Potentials 139 Introduction 139 Electrically Evoked Auditory Late Response 140 Electrically Evoked Acoustic Change Complex 144 Mismatch Negativity 146 P300 Response 148 Summary 149 References 151 Index 161