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DEAF MUTISM — Evaluation and Management (50-Mark Answer)

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DEFINITION

Dhingra (Diseases of Ear, Nose & Throat, 7th ed): "A child born deaf, or who becomes deaf in the pre-lingual period, does not develop speech and is therefore called deaf mute."

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CLASSIFICATION / ETIOLOGY

A. By Time of Onset

B. By Site of Lesion (Scott Brown, 8th ed; Cummings Otolaryngology, 7th ed)

DEAF MUTISM
├── CONDUCTIVE (rarely causes deaf mutism alone)
│   ├── Atresia of EAC (congenital)
│   ├── Ossicular anomalies
│   └── Middle ear malformations
│
└── SENSORINEURAL (major cause of deaf mutism)
    ├── A. Hereditary / Genetic
    │   ├── Non-syndromic (70%)
    │   │   ├── Autosomal Recessive (DFNB) — 80%
    │   │   │   └── DFNB1: Connexin 26 (GJB2), Connexin 30 (GJB6) — 50% of all AR cases
    │   │   ├── Autosomal Dominant (DFNA) — 15%
    │   │   └── X-linked (DFNX) — 1–2%
    │   └── Syndromic (30%)
    │       ├── Pendred syndrome (goitre + EVA)
    │       ├── Waardenburg syndrome (pigmentation + SNHL)
    │       ├── Usher syndrome (SNHL + retinitis pigmentosa)
    │       ├── Jervell & Lange-Nielsen (SNHL + long QT)
    │       ├── Alport syndrome (SNHL + nephritis)
    │       ├── Branchio-oto-renal (BOR) syndrome
    │       └── CHARGE association
    │
    └── B. Acquired
        ├── Prenatal / Intrauterine
        │   ├── TORCH infections (Rubella — commonest pre-vaccination)
        │   ├── Ototoxic drugs (thalidomide, quinine, aminoglycosides)
        │   └── Maternal diabetes, hypothyroidism
        ├── Perinatal
        │   ├── Birth asphyxia / Hypoxia
        │   ├── Prematurity (<32 weeks)
        │   ├── Hyperbilirubinemia (kernicterus → hair cells)
        │   └── Forceps delivery trauma
        └── Postnatal (pre-lingual)
            ├── Meningitis (commonest acquired cause)
            ├── Measles, mumps, encephalitis
            ├── Ototoxic drugs (gentamicin, streptomycin)
            └── Head trauma

Zakir Hussain (Textbook of ENT & Head Neck Surgery): "Connexin 26 (GJB2) mutation is the single most common cause of genetic non-syndromic sensorineural deafness, accounting for up to 50% of autosomal recessive cases."

Clinical Evaluation and Etiologic Diagnosis of Hearing Loss (Retrieved Source, p.3): "The DFNB1 locus, which includes the GJB2 gene encoding connexin 26 and the GJB6 gene encoding connexin 30, accounts for an estimated 50% of all autosomal recessive nonsyndromic HL and 15–40% of all deaf individuals across populations."

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EVALUATION / ASSESSMENT OF DEAF-MUTE CHILD

Hazarika (Textbook of ENT): Assessment of a deaf-mute child requires a multidisciplinary team approach — ENT surgeon, audiologist, paediatrician, speech-language pathologist, ophthalmologist, and geneticist.

FLOWCHART 1: Overall Evaluation Approach

SUSPECTED DEAF-MUTE CHILD
          │
          ▼
┌─────────────────────────────┐
│   DETAILED HISTORY          │
│ • Age of onset of deafness  │
│ • Antenatal/perinatal hx    │
│ • Family history (consang.) │
│ • Drug/infection exposure   │
│ • Milestones (speech, motor)│
└────────────┬────────────────┘
             │
             ▼
┌─────────────────────────────┐
│   PHYSICAL EXAMINATION      │
│ • General: dysmorphisms     │
│ • Ear: EAC, TM, mastoid     │
│ • Neck: goitre (Pendred)    │
│ • Eyes: pigmentation,       │
│   heterochromia (Waardenburg│
│   dystopia canthorum)       │
│   retinitis (Usher)         │
│ • Skin: vitiligo/white      │
│   forelock (Waardenburg)    │
└────────────┬────────────────┘
             │
             ▼
┌─────────────────────────────┐
│   AUDIOLOGICAL EVALUATION   │◄─────── See Flowchart 2
└────────────┬────────────────┘
             │
             ▼
┌─────────────────────────────┐
│   RADIOLOGICAL EVALUATION   │
└────────────┬────────────────┘
             │
             ▼
┌─────────────────────────────┐
│   LABORATORY / GENETIC      │
│   WORKUP                    │
└────────────┬────────────────┘
             │
             ▼
┌─────────────────────────────┐
│   SPECIALIST REFERRALS      │
│   (ophthalmology, cardiology│
│   nephrology, genetics)     │
└────────────┬────────────────┘
             │
             ▼
     DIAGNOSIS + MANAGEMENT PLAN

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I. HISTORY

1. Antenatal history: maternal rubella, CMV, toxoplasmosis, syphilis (TORCH); ototoxic drug intake; maternal thyroid disease; consanguinity
2. Perinatal history: birth asphyxia, prematurity, birth weight, NICU stay, jaundice, exchange transfusion
3. Postnatal history: meningitis, encephalitis, measles, mumps, aminoglycoside use, head trauma
4. Family history: deaf siblings, consanguinity (suggests AR inheritance)
5. Developmental milestones: did the child babble at 6 months? (a deaf child stops babbling ~4–6 months); did child turn to sound? (should by 3–4 months)

II. PHYSICAL EXAMINATION

A. General Examination — Syndromic Markers

B. Ear Examination

• Pinna: microtia, atresia, preauricular tags/pits/sinuses
• External auditory canal: atresia, stenosis
• Tympanic membrane: perforation, retraction, effusion (OME), cholesteatoma
• Tuning fork tests: Weber lateralises to better ear; Rinne negative = conductive; positive with reduced loudness = SNHL

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III. AUDIOLOGICAL EVALUATION

Age-Related Hearing Loss (Retrieved Source, p.17): "PTA is considered the gold standard for detecting hearing loss. It establishes the pattern of hearing loss at various frequencies, differentiates the degree (mild, moderate, severe, profound), and configuration of the hearing loss."

FLOWCHART 2: Audiological Workup Based on Age

CHILD REFERRED WITH SUSPECTED DEAFNESS
                │
        ┌───────┴───────┐
        │               │
   Age < 6 months  Age 6 months–3 years
        │               │
        ▼               ▼
     OAE +          Behavioural
     AABR (BERA)    Audiometry
   (Newborn Hearing  (BOA / VRA /
     Screening)      Play audiometry)
        │               │
        └───────┬───────┘
                │
                ▼
    Age > 3–4 years (cooperative)
                │
                ▼
    Pure Tone Audiometry (PTA)
    [Air conduction + Bone conduction]
                │
                ▼
         Speech Audiometry
       (SRT, SDS/WRS, PB max)
                │
                ▼
       Impedance Audiometry
     (Tympanometry + Acoustic reflexes)
                │
          ┌─────┴─────┐
          │           │
     Conductive    Sensorineural
       Pattern        Pattern
          │           │
          ▼           ▼
   Type B or C     Type A tympanogram
   tympanogram     Absent stapedial
   Absent/Present  reflexes at high
   reflexes        threshold
                        │
                        ▼
               BERA / ABR
           OAE (TEOAE / DPOAE)
           ASSR (Auditory Steady
           State Response)
                        │
                        ▼
              Retrocochlear
              lesion ruled in/out
              (MRI VIII nerve)

A. Subjective / Behavioural Tests (age-dependent)

B. Objective Tests (do not require cooperation)

Tympanogram Types (Jerger Classification)

C. Degree of Hearing Loss (ISO Classification)

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IV. RADIOLOGICAL EVALUATION

A. High-Resolution CT Temporal Bone (HRCT)

• First-line imaging for suspected structural/conductive cause
• Evaluates: EAC atresia, ossicular chain, oval/round windows, cochlear morphology (Mondini malformation), semicircular canals, facial nerve canal, mastoid air cells
• Mondini dysplasia: incomplete partition of cochlea — 1.5 turns instead of 2.5; associated with connexin mutations, Pendred

B. MRI Internal Auditory Meatus (MRI IAM)

• Gold standard for cochlear nerve aplasia/hypoplasia — critical for cochlear implant pre-assessment
• Identifies: cochlear aplasia (Michel deformity), cochlear nerve aplasia, enlarged vestibular aqueduct (EVA)
• MRI VIII nerve assessment essential before cochlear implant

Inner Ear Malformation Classification (Modified Jackler / Sennaroglu)

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V. LABORATORY / GENETIC WORKUP

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MANAGEMENT

Stell & Maran (Head & Neck Surgery, 5th ed); Cummings Otolaryngology (7th ed): Management of deaf mutism must be early, comprehensive, and multidisciplinary. The goal is early auditory rehabilitation followed by speech-language habilitation.

FLOWCHART 3: Management Algorithm

CONFIRMED PROFOUND SNHL / DEAF MUTISM
              │
    ┌─────────┴──────────┐
    │                    │
Conductive component  Pure SNHL
identifiable           (no correctable cause)
    │                    │
    ▼                    │
Surgical correction      │
(atresiaplasty, BAHA)    │
    │                    │
    └─────────┬──────────┘
              │
              ▼
      AGE OF CHILD?
   ┌─────────┴─────────┐
   │                   │
< 12 months         > 12 months
(optimal window)    (still implant
   │                if <5 yrs)
   ▼                   │
COCHLEAR IMPLANT ←──────┘
(if profound bilateral SNHL
 + intact cochlear nerve
 + no medical contraindication)
              │
              ▼
   POST-IMPLANT REHABILITATION
   • Auditory Verbal Therapy (AVT)
   • Speech-Language Therapy
   • Special education
   • Parental counselling

If NOT cochlear implant candidate:
              │
              ▼
    HEARING AID FITTING
  (if residual hearing >30dB)
    + Speech therapy
    + Special school
    + Sign language (if needed)

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I. PREVENTION

II. HEARING AIDS

• Type and degree of HL (PTA, ASSR)
• Speech discrimination score (SDS — the better the SDS, the better the prognosis with HA)
• Dynamic range of hearing
• Age and cooperation

III. COCHLEAR IMPLANT (CI)

Scott Brown's Otorhinolaryngology, Head & Neck Surgery (8th ed, Gleeson): "Cochlear implantation is the most significant advance in the management of profound sensorineural deafness in children."

A. Candidacy Criteria

B. Contraindications to CI

• Michel aplasia (absent cochlea)
• Cochlear nerve aplasia (absent VIII nerve on MRI)
• Active middle ear infection (relative; should be treated first)
• Central auditory processing disorders (rare)
• Lack of rehabilitative support

C. Components of Cochlear Implant

COCHLEAR IMPLANT SYSTEM
│
├── EXTERNAL
│   ├── Microphone (picks up sound)
│   ├── Sound processor (digitizes, encodes)
│   └── Transmitter coil (sends signal across skin)
│
└── INTERNAL
    ├── Receiver-stimulator (under skin)
    └── Electrode array (inserted into scala tympani
        of cochlea — 12–22 electrodes)
        → Directly stimulates spiral ganglion neurons
        → Signal travels via auditory nerve to brain

D. Pre-operative Assessment for CI

1. Full audiological workup (PTA, BERA, ASSR, OAE, aided audiogram)
2. HRCT temporal bone — cochlear anatomy, patency, facial nerve
3. MRI IAM (1.5T or 3T) — cochlear nerve, cochlear morphology
4. Speech and language assessment
5. Psychological assessment
6. Medical fitness (ENT, anaesthesia, paediatrics)
7. Vestibular function (rotation tests, VEMPs)

E. Surgical Steps (Simplified)

1. Post-auricular incision
2. Cortical mastoidectomy
3. Posterior tympanotomy (facial recess approach)
4. Cochleostomy (adjacent to round window) or round window insertion
5. Electrode array insertion into scala tympani
6. Receiver-stimulator placed in bony well posterior to mastoid
7. Wound closure
8. Switch-on: 4–6 weeks post-op; mapping begins

F. Outcomes

• Pre-lingual children implanted <2 years develop near-normal oral language
• Results best when: early implantation, strong family involvement, intensive AVT
• Post-lingual adults: excellent outcomes — speech understanding in quiet ~80–90%
• Pre-lingual adults: poor outcomes — limited by absent auditory memory

IV. BONE ANCHORED HEARING AID (BAHA / BAHS)

• Conductive/mixed HL with chronic discharge (cannot wear conventional HA)
• Congenital aural atresia (before atresiaplasty or when surgery not feasible)
• Single-sided deafness (SSD)

V. MIDDLE EAR IMPLANTS

• For moderate–severe SNHL where conventional HAs give inadequate benefit
• Vibrant Soundbridge (VSB), Esteem implant
• Transducer attached to ossicular chain or round window

VI. AUDITORY BRAINSTEM IMPLANT (ABI)

• Used when cochlear nerve is absent/non-functional (e.g., NF2, cochlear nerve aplasia)
• Electrode placed on cochlear nucleus in lateral recess of IV ventricle
• Outcomes inferior to CI but better than no device

VII. SPEECH AND LANGUAGE HABILITATION

A. Auditory Verbal Therapy (AVT)

• Goal: teach child to listen and speak; no sign language used
• Intensive, parent-mediated therapy
• Best outcomes when started earliest

B. Auditory Oral Approach

• Listening + lip reading (speech reading) combined
• No sign language

C. Total Communication

• Combines speech, lip reading, sign language, and written language
• Used when oral communication inadequate

D. Sign Language / Cued Speech

• Used when auditory-oral methods fail
• Indian Sign Language (ISL) in India

E. Special Education

• Special school for hearing impaired: structured oral education
• Mainstream school with resource teacher (after CI rehabilitation)
• Individual Educational Plan (IEP)

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VIII. TEAM APPROACH — MULTIDISCIPLINARY MANAGEMENT

DEAF-MUTE CHILD
       │
       ├── ENT Surgeon (CI surgery, hearing aid prescription, diagnosis)
       ├── Audiologist (PTA, OAE, BERA, ASSR, HA fitting, CI programming/mapping)
       ├── Speech-Language Pathologist (speech therapy, AVT)
       ├── Paediatrician (infections, jaundice, syndromes)
       ├── Ophthalmologist (Usher, Waardenburg, Alport)
       ├── Cardiologist (Jervell–Lange-Nielsen ECG)
       ├── Nephrologist (Alport)
       ├── Geneticist (GJB2, SLC26A4 mutation counselling)
       ├── Psychologist (family counselling, adjustment)
       └── Special Educator (IEP, school integration)

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RECENT ADVANCES

(Scott Brown 8th ed; Cummings 7th ed; Recent Literature)

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PROGNOSIS

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SUMMARY TABLE — INVESTIGATIONS AT A GLANCE

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KEY REFERENCES

1. Scott Brown's Otorhinolaryngology, Head & Neck Surgery (8th ed, Gleeson) — Vol 3: Otology; Chapters on pediatric deafness, cochlear implant
2. Cummings Otolaryngology — Head and Neck Surgery (7th ed, Flint et al.) — Chapter 146: Cochlear Implant; Chapter 145: Pediatric Audiology
3. Stell & Maran's Textbook of Head and Neck Surgery and Oncology (5th ed) — Otology section
4. Zakir Hussain — Textbook of ENT & Head Neck Surgery — Chapter on Deafness and hearing aids
5. Dhingra — Diseases of Ear, Nose & Throat (7th ed) — Chapter 14: Diseases of the Inner Ear; Deafness, Deaf-mutism
6. Hazarika — Textbook of Ear, Nose & Throat Diseases — Chapter on Deafness
7. Harrison's Principles of Internal Medicine (21st ed, p.1022) — Hearing loss algorithm
8. JCIH 2019 Position Statement — Year 2019 Position Statement: Principles and Guidelines for Early Hearing Detection and Intervention Programs
9. Clinical Evaluation and Etiologic Diagnosis of Hearing Loss — JAMA/Otolaryngology-HNS (retrieved, p.3): Connexin 26 genetics
10. Sennaroglu L — Cochlear implantation in inner ear malformations — Cochlear Implants International, 2010
11. Omichi R et al. — Gene therapy for hearing loss — Human Molecular Genetics, 2019
12. Lenarz T — Cochlear implant — state of the art — GMS Current Topics in Otorhinolaryngology, 2017

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