Auditory Brainstem Implant in India and UAE | Complete Patient Guide

• CONFIRMED ELIGIBILITY CRITERIA:

• Bilateral absence or aplasia of the cochlear (auditory) nerve confirmed on high-resolution MRI (3T CISS/FIESTA sequences) or CT temporal bone

• Neurofibromatosis Type 2 (NF2) with bilateral vestibular schwannomas requiring surgical removal (ABI placed at time of tumor resection)

• Bilateral cochlear ossification (labyrinthitis ossificans) rendering cochlear implantation technically impossible, confirmed on CT

• Bilateral cochlear aplasia (Michel deformity or common cavity deformity with absent cochlear nerve) — particularly relevant for pediatric non-NF2 ABI candidates

• Post-traumatic bilateral auditory nerve avulsion with absent auditory nerve on MRI

• Failed bilateral cochlear implantation with absent or inadequate cortical auditory evoked responses

• Children aged ≥12 months (non-NF2) who meet audiological and developmental candidacy criteria per team evaluation

• REQUIRED PRE-OPERATIVE DIAGNOSTICS:

• High-resolution 3T MRI of the internal auditory canals and posterior fossa (CISS or FIESTA protocol) to assess cochlear nerve presence and schwannoma extent

• High-resolution CT of the temporal bones (0.625mm slices) to evaluate cochlear anatomy and ossification

• Pure tone audiometry and speech discrimination testing (to document degree of hearing loss)

• Electrically evoked auditory brainstem response (EABR) testing where feasible (promontory stimulation)

• Full audiological evaluation by ABI-specialized audiologist

• Neuropsychological and speech-language pathology assessment (critical for pediatric candidates)

• Gadolinium-enhanced MRI brain and posterior fossa to assess tumor burden in NF2 patients

• Pre-operative anesthesia assessment including cardiopulmonary evaluation (ECG, echocardiogram if indicated)

• Genetic counseling and NF2 mutation analysis (where NF2 is suspected but unconfirmed)

• CONTRAINDICATIONS:

• Active brainstem lesion, multiple sclerosis plaque at cochlear nucleus level, or brainstem malformation precluding safe electrode placement

• Absence of any functional central auditory pathway (cortical deafness)

• Medical comorbidities precluding prolonged general anesthesia or posterior fossa neurosurgery (severe cardiopulmonary disease, uncontrolled coagulopathy)

• Active systemic or intracranial infection

• Significant intellectual disability or autism spectrum disorder that would preclude participation in intensive post-operative auditory rehabilitation

• Patient/family inability or unwillingness to commit to long-term audiological follow-up and auditory-verbal rehabilitation

• Presence of MRI-incompatible implanted devices if postoperative MRI surveillance (NF2 tumor monitoring) is planned (note: newer ABI systems are 1.5T and 3T conditional — verify device compatibility before implantation)

STANDARD SURGICAL APPROACH — RETROSIGMOID CRANIOTOMY:

The retrosigmoid (suboccipital) approach is the most widely used technique for ABI placement, particularly in NF2 patients undergoing concurrent vestibular schwannoma resection. A 4–6 cm retrosigmoid craniotomy is performed with the patient in the semi-sitting, park-bench, or lateral decubitus position. The cerebellopontine angle cistern is opened and the tumor (schwannoma) is carefully dissected from the brainstem and cranial nerves under continuous intraoperative neurophysiological monitoring (facial nerve EMG, BAER, cranial nerves IX–XI monitoring). Following tumor removal, the lateral recess of the fourth ventricle is identified and gently opened. The ABI electrode paddle (typically 21 contacts arranged in a flat or slightly curved array) is positioned on the dorsal cochlear nucleus surface. Electrode position is confirmed by intraoperative EABR and neural response telemetry, with adjustment until consistent auditory percepts are identified. The lead is secured and tunneled subcutaneously to the receiver-stimulator, which is anchored in a surgically created titanium well in the temporal squama. Total operative time ranges from 5 to 10 hours depending on tumor complexity.

TRANSLABYRINTHINE APPROACH:

The translabyrinthine craniotomy provides a direct, wide-angle corridor to the cerebellopontine angle and lateral recess with minimal cerebellar retraction. It is favored when residual hearing is already absent (which is the rule in most ABI candidates). The mastoid and labyrinth are drilled away, providing broad exposure of the internal auditory canal and posterior fossa dura. This approach is particularly useful for large NF2 tumors and is associated with reduced cerebellar manipulation. The ABI electrode placement technique is the same as in the retrosigmoid approach.

NON-TUMOR (PEDIATRIC AND ADULT) ABI:

For non-NF2 candidates (children with cochlear nerve aplasia, adults with cochlear ossification), the ABI is placed as the primary procedure without concurrent tumor resection. The retrosigmoid approach is standard. Intraoperative anatomy identification of the cochlear nucleus is more challenging without the landmark provided by the schwannoma, requiring meticulous neuroanatomical knowledge and EABR guidance. Pediatric non-NF2 ABI candidates require earlier implantation (ideally before age 3–5 years) to exploit auditory cortex neuroplasticity, and consistently demonstrate superior speech perception outcomes compared to adult NF2 patients.

INTRAOPERATIVE NEUROPHYSIOLOGICAL MONITORING TECHNOLOGIES:

• Continuous facial nerve EMG monitoring (mandatory)

• Intraoperative EABR (electrically evoked auditory brainstem response) for electrode array positioning confirmation

• Neural response telemetry (NRT) — device-specific software for real-time feedback on cochlear nucleus activation

• Motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SSEPs) for brainstem integrity monitoring

• Continuous EEG monitoring where indicated

DEVICE SYSTEMS IN CLINICAL USE:

• Cochlear Nucleus ABI 541 (Cochlear Ltd.): 21-electrode array, MRI-conditional at 1.5T and 3T (with magnet removed), compatible with Kanso 2 and Nucleus 7 sound processors

• MED-EL ABI (MED-EL GmbH): 12-electrode array, broader electrode spacing, MRI-conditional at 1.5T

• Oticon Medical ABI: available in select European and international centers

POST-OPERATIVE DEVICE PROGRAMMING (MAPPING):

Initial device activation occurs 4–6 weeks post-surgery, once surgical swelling has resolved. Audiological mapping involves systematic stimulation of each electrode, identification of auditory versus non-auditory (tingling, pain, dizziness) percepts, and creation of a customized stimulation map. Multiple mapping sessions over 6–12 months are required to optimize the program. Ongoing auditory-verbal rehabilitation with a speech-language pathologist is essential and constitutes a major determinant of functional outcome.

PHASE 1 — PRE-OPERATIVE EVALUATION (WEEKS 1–3 BEFORE SURGERY):

• GAF Healthcare coordinates remote review of existing MRI and CT imaging by the destination center's neurotological team

• Virtual consultation with the operating surgeon and ABI audiologist to confirm candidacy and set realistic outcome expectations

• Submission of complete medical records for pre-operative anesthesia clearance

• Arrangement of e-Medical visa (India) or visit visa (UAE) through GAF Healthcare's documentation support

• Arrival in country 3–5 days before surgery for in-person pre-operative workup: repeat dedicated MRI/CT if required, full audiological evaluation, pre-anesthetic assessment, blood work, ECG, and consenting

PHASE 2 — SURGERY DAY:

• Admission to neurosurgical ICU-capable facility the evening before surgery

• General anesthesia induction; neurophysiological monitoring arrays placed

• Retrosigmoid or translabyrinthine craniotomy performed (5–10 hours)

• Intraoperative EABR confirms cochlear nucleus activation; ABI array secured

• Receiver-stimulator implanted and anchored in temporal bone well

• Wound closure; patient transferred to neurosurgical ICU

PHASE 3 — ACUTE HOSPITAL RECOVERY (DAYS 1–7 IN ICU/WARD):

• Days 1–2: ICU monitoring for neurological status, cranial nerve function, CSF leak signs, and hemodynamic stability; serial neurological assessments

• Day 2–3: Step-down to neurosurgical ward if stable; mobilization begins with physiotherapy

• Days 3–5: Wound inspection, drain removal, audiological team reviews the external processor fitting plan

• Days 5–7: Oral intake restored, ambulation achieved, discharge planning initiated

• Typical hospital discharge: Day 7–10 post-surgery

PHASE 4 — IN-COUNTRY RECOVERY (WEEKS 2–6 POST-SURGERY):

• Wound healing monitored by neurotological team at outpatient visits (Week 2 and Week 4)

• Suture/staple removal at 10–14 days

• Headache management, vestibular rehabilitation exercises commenced

• NO device activation during this phase — external processor not worn

• Patients instructed to avoid strenuous activity, nose-blowing, and airplane travel

• GAF Healthcare-arranged accommodation within 15 minutes of the hospital

PHASE 5 — DEVICE ACTIVATION AND INITIAL MAPPING (WEEK 5–6):

• First audiological mapping session: systematic stimulation of all electrode contacts; auditory versus non-auditory percept identification; initial program created

• Baseline aided sound-field testing and speech perception testing

• Patient and family/caregiver trained on device handling, maintenance, and processor troubleshooting

• Clearance for international air travel given after satisfactory wound review and first successful mapping session (typically Week 6–8)

PHASE 6 — LONG-TERM REHABILITATION (MONTHS 2–24):

• Remote mapping sessions arranged via telemedicine through GAF Healthcare's partner centers (every 1–3 months in Year 1)

• Intensive auditory-verbal therapy with home-country speech pathologist (coordinated by GAF Healthcare where possible)

• Annual in-person follow-up strongly recommended, particularly for NF2 patients requiring MRI tumor surveillance

• Realistic milestones: Environmental sound awareness by Month 2–3; improved lip-reading by Month 6; some open-set word recognition possible by Month 12–18 in optimal non-NF2 candidates