✅ Model Answer:
• Diagnosis: Autosomal recessive nonsyndromic sensorineural hearing loss, most likely GJB2 (Connexin 26) mutation — bilateral profound SNHL, negative CMV PCR, normal MRI/CT, consanguineous parents suggesting autosomal recessive inheritance.
• Any other test: Genetic testing (GJB2, GJB6, SLC26A4, mtDNA mutations), ophthalmology exam (rule out Usher syndrome), ECG (rule out Jervell & Lange-Nielsen syndrome – prolonged QT), renal ultrasound (if syndromic suspected).
• What to do next: Hearing aid fitting (by 1 month post-diagnosis). Early intervention (Part C – speech therapy, audiology). Genetic counseling for family. Evaluate for cochlear implant candidacy (severe-profound SNHL).
• Follow-up plan: Serial audiometry q6-12 months. Monitor speech/language development. Family support, Deaf mentors. Annual ophthalmology, ECG, and audiology follow-up.

✅ Model Answer:
• GJB2 gene: Located on chromosome 13q12, encodes Connexin 26 protein.
• Connexin 26: Forms gap junctions in the cochlea, allowing potassium recycling in the inner ear (essential for hair cell function).
• Inheritance: Autosomal recessive (most common), autosomal dominant (rare).
• Prevalence: Most common cause of genetic SNHL (up to 50% of autosomal recessive SNHL).
• Mutation: 35delG is the most common mutation (carrier frequency 1 in 35 in Caucasians).
• Phenotype: Usually bilateral, symmetric, severe to profound SNHL, non-progressive, no inner ear malformations.

✅ Model Answer:
• JCIH risk factors for SNHL:
- Genetic: Family history of childhood hearing loss, consanguinity
- Congenital infections: CMV (most common), rubella, toxoplasmosis, syphilis, Zika
- Ototoxic medications: Aminoglycosides (gentamicin), loop diuretics, chemotherapy (cisplatin)
- Perinatal: Prematurity (<32 weeks), NICU stay >48 hours, hyperbilirubinemia requiring exchange transfusion, low Apgar scores, ECMO
- Structural: Craniofacial anomalies (ear malformations, cleft palate), syndromes (Waardenburg, Pendred, Usher)
- Infections: Bacterial meningitis, encephalitis
- Trauma: Head injury, noise exposure

✅ Model Answer:
• CMV is the most common non-genetic cause of congenital SNHL (20-30% of cases).
• Testing:
- Saliva/urine PCR: Sensitive, should be done within 3 weeks of life (congenital) or within 3 months for delayed-onset
- Dried blood spots: Can be tested retrospectively
• Why test?
- If positive and symptomatic (microcephaly, calcifications, hepatosplenomegaly) → valganciclovir treatment may improve hearing outcomes.
- Prognosis: CMV-related hearing loss can be progressive or delayed-onset → requires serial audiometry.
- Negative CMV + normal imaging + consanguinity → genetic cause more likely.

✅ Model Answer:
• Hearing aids:
- Indication: Mild to severe hearing loss (<70-90 dB HL)
- Mechanism: Amplifies sound, works best with residual hearing
- Benefits: Non-invasive, less expensive, good for speech perception in quiet
- Limitations: Limited benefit in severe-profound loss, may not help in noisy environments
• Cochlear implants:
- Indication: Severe to profound SNHL (>90 dB HL), especially if hearing aids provide limited benefit
- Mechanism: Bypasses damaged hair cells → directly stimulates the auditory nerve via electrode array
- Benefits: Better speech perception in noisy environments, improved language outcomes
- Limitations: Invasive (requires surgery), more expensive, requires rehabilitation

✅ Model Answer:
• 1-3-6 guidelines (JCIH):
- 1 month: Hearing screening completed by 1 month of age
- 3 months: Diagnosis confirmed by 3 months (ABR, OAE)
- 6 months: Intervention started by 6 months (hearing aids, early intervention)
• Why is this important?
- Critical period: Brain development for speech and language occurs in the first 3-5 years
- Outcomes: Early diagnosis and intervention (by 6 months) leads to age-appropriate language development
- Delays: Late diagnosis (>6-12 months) is associated with persistent language delays
- Equity: Reduces disparities in access to hearing services

✅ Model Answer:
• Syndromes to consider:
- Usher syndrome: SNHL + retinitis pigmentosa (night blindness, progressive vision loss). Screen with ophthalmology and ERG.
- Pendred syndrome: SNHL + enlarged vestibular aqueduct (EVA) + goiter (SLC26A4 mutation). Screen with CT temporal bone and thyroid function.
- Waardenburg syndrome: SNHL + pigmentary abnormalities (white forelock, heterochromia iridis, dystopia canthorum).
- Jervell & Lange-Nielsen syndrome: SNHL + prolonged QT interval (arrhythmia risk). Screen with ECG.
- Alport syndrome: SNHL + renal disease + ocular abnormalities.
- Neurofibromatosis type 2: Bilateral vestibular schwannomas (MRI needed).

✅ Model Answer:
• Prognosis:
- Excellent with early diagnosis and intervention (by 6 months)
- Non-progressive in most cases (but should be monitored)
- Hearing aids: Effective for mild-moderate loss; cochlear implant for severe-profound loss
- Speech/language: Age-appropriate development possible with early intervention
• Long-term outcomes:
- Educational: Mainstream schooling possible with appropriate support
- Communication: Spoken language, sign language, or both based on family choice
- Quality of life: Good with family support, Deaf community involvement
- Genetic counseling: 25% recurrence risk for future siblings (autosomal recessive).
- No other medical complications (nonsyndromic).