Cochlear Implant Atlas
Cochlear Implants
An interactive teaching atlas of cochlear implantation — its arts, science, and technology. Built chapter by chapter; 35 chapters are live now — the auditory-physiology foundations, the brain-plasticity foundations, and the deep dive into objective electrophysiological measures — with 0 further chapters in build.
Chapters
How a 200-year-old idea became a routinely restored sense — from Volta's first jolt to Nucleus, speech coding, and global manufacturing.
Hearing from first principles: sound, the outer and middle ear, cochlear mechanics and tonotopy, hair cells, and the pathway to the cortex.
How the environment wires the hearing brain — neural plasticity, the sensitive period, and cross-modal reorganisation after deafness.
How deafness and the implant remodel the auditory pathway, cell by cell — the structural companion to the plasticity chapter.
The scale of hearing loss in numbers — India first, then the world: how it is measured, graded, and counted.
The molecular roots of deafness, and why the gene predicts the implant's result — GJB2 and beyond.
Why people lose hearing, and why the cause shapes the implant — the many roads to sensorineural deafness.
The perceptual science of electric hearing - narrow dynamic range and loudness, temporal and spectral resolution, channel interaction, and pitch - and why implants struggle with noise and music.
How the implant codes hearing — turning sound into electrical stimulation that imitates the normal cochlea.
The functional limits of the damaged cochlea, and why amplification eventually falls short of an implant.
How hearing is actually measured — the audiologist's full diagnostic battery, and the foundation of every candidacy decision.
Who should be implanted, and how that is decided — the clinical cornerstone, and the most comprehensive chapter in the atlas.
An MRI-predominant, selective-HRCT philosophy for the CI work-up — the rational checklist, the malformations and gates that change the plan, and the structured report.
Manufacturers and systems, lateral-wall vs mid-scala vs perimodiolar arrays, coverage, and electric-acoustic stimulation.
The full genealogy of speech coding — single-channel and CIS, the feature-extraction era, n-of-m peak-picking, fine structure, current steering, and the AI/optical future.
From decision to theatre — completing the work-up, vaccinating, counselling, consenting, and setting realistic expectations so the implant meets the life it is meant to change.
The operation itself, end to end: anatomy and anaesthesia, the mastoidectomy and facial recess, round-window versus cochleostomy and atraumatic insertion, securing the device, the ossified and malformed cochlea, intraoperative verification, revision, robotics, and the road to switch-on.
The watchful side of implant surgery: facial-nerve monitoring, intraoperative objective measures and imaging to verify electrode placement and device function, and the science of hearing preservation — soft-surgery technique, atraumatic arrays, topical steroids, and real-time electrocochleography to protect residual hearing for electric-acoustic stimulation.
The clinical fitting workflow end to end: the MAP and its dynamic range, the first switch-on, setting threshold and comfort levels and balancing loudness, frequency allocation, strategy/rate/maxima, front-end processing, programming children, objective measures at the fitting, troubleshooting, the poor performer, bimodal/bilateral and SSD, EAS and special maps, and longitudinal datalogging, remote care and verification.
The clinical outcome of cochlear implantation, end to end: what outcome means and how it is tested, the adult learning curve, the variability problem and its predictors (duration, age, the ear and nerve, cognition), paediatric language and literacy, hearing in noise and space, music and voice, two-ear benefit, patient-reported outcomes, special groups, and prediction and benchmarking.
Teaching the brain to listen: the therapy that turns access into communication — auditory training, auditory-verbal therapy and family coaching, adult aural rehabilitation and repair strategies, music and real-world training, telepractice, school support, and measuring progress.
Does the implant make life better, and is it worth it? Measuring quality of life and the cost-effectiveness of the cochlear implant — QALYs, cost per QALY, and value from the child to the global south.
Candidacy beyond the prototypical patient: SSD and ANSD, cochlear nerve deficiency, malformed and ossified cochleae, the diseased ear, the very young and the very old, additional disabilities, syndromic deafness, prelingual late implantation, the only-hearing and complex ear, ABI candidates, and the global access gap.
The malformed inner ear from embryology to the OR: the Jackler, Sennaroğlu and Grover classifications, the full IP/Mondini/EVA/common-cavity spectrum, cochlear nerve deficiency and the CI-vs-ABI decision, the gusher and aberrant facial nerve, electrode choice, outcomes, and a prognosis-oriented diagnostic algorithm.
Restoring two-eared hearing: the binaural cues (ITD, ILD), head shadow, summation and squelch, localization and speech-in-noise gains, simultaneous vs sequential surgery and the inter-implant interval, bilateral CI in children and adults, bimodal hearing (CI + hearing aid) and how to fit it, why two implants are not two normal ears, and the cost and future of binaural hearing.
Balance and the cochlear implant — how implantation affects vestibular function, the test battery, dizziness, ear selection, and the vestibular implant.
The safety net of implantation: classifying and counting complications, wound, flap and infection, intraoperative complications, electrode misplacement, hard and soft device failure, facial-nerve stimulation and non-auditory percepts, dizziness, the structured workup of the poor performer, revision and reimplantation, MRI and external-hazard safety, and prevention.
What is coming next: robotics-assisted and image-guided surgery, drug-eluting and next-generation arrays, closing the electrode-neuron gap, totally implantable devices, AI and remote self-fitting, hair-cell and neural regeneration, gene therapy restoring hearing, the optical (optogenetic) implant, closed-loop fitting, and the bionic future — with an honest word on timelines and global equity.
Why music is the implant's hardest sound: pitch, timbre and rhythm through electric hearing; how it is measured and limited by coding and the electrode-neuron interface; children, bimodal and electric-acoustic listeners; training; quality of life; and the road to better musical hearing.
Applying implant technology beyond hearing: why the implant usually suppresses tinnitus (mechanisms, evidence, SSD, the rare worsening, measurement and counselling), how implantation affects balance, and the vestibular implant that restores the balance signal in bilateral vestibular loss — toward a combined cochleovestibular device.
Bone-conduction and active middle-ear implants - how they work, who they suit, and how to choose between a BCD, a middle-ear implant and a cochlear implant.
Restoring hearing above the cochlea: the auditory brainstem implant - target, candidacy (NF2, nerve aplasia, ossified cochleae), surgery, programming, side-effects, outcomes, and the auditory midbrain implant.
The ethics, culture and controversy of the implant: Deaf identity, the core debate over implanting children, the open-future and language-deprivation arguments, equity, and counselling families with cultural humility.
Closing the gap between the booth and daily life: noise, reverberation and distance; directional mics, noise reduction and remote/FM microphones; telecoil, Bluetooth and streaming; accessories, verification and counselling.
The electrophysiology toolbox — impedance, ECAP/NRT, the electrical stapedius reflex, and eABR — the implant measured in action.
Audience levels
Every section is tagged for an audience level. Foundation (F) is for medical students and foundation trainees; Trainee (T) is for ENT, audiology, and neurotology trainees; Clinician (C) is for qualified clinicians. Modules teach all three levels in sequence so a learner can stop at the depth that suits them.