Diagnostic Investigations in ENT

Hearing Tests - Sounding It Out

• Tuning Fork Tests (TFTs): Screening with 512 Hz fork.
  • Rinne Test: Compares Air Conduction (AC) vs Bone Conduction (BC).
    • Normal/SNHL: AC > BC (Rinne Positive).
    • CHL: BC > AC (Rinne Negative).
    • 📌 False Negative Rinne: Severe unilateral SNHL (sound heard in better ear).
  • Weber Test: Bone conduction; tests sound lateralization.
    • SNHL: Lateralizes to better ear.
    • CHL: Lateralizes to poorer/affected ear.
  • Schwabach Test: Compares patient's BC to examiner's (normal BC).
    • SNHL: Schwabach shortened.
    • CHL: Schwabach prolonged.
• Pure Tone Audiometry (PTA):
  • Gold standard for quantifying hearing thresholds (dB HL).
  • Plots AC & BC thresholds across frequencies (250-8000 Hz).
  • Air-Bone Gap (ABG): Difference > 10-15 dB between AC & BC indicates CHL.
  • Identifies type (CHL, SNHL, Mixed) and degree of hearing loss.

  ⭐ Carhart's Notch: A characteristic bone conduction dip, typically at 2000 Hz, seen in otosclerosis.

Vestibular Tests - Wobble Wizards

Evaluates balance; localizes peripheral vs. central vestibular lesions.

• Clinical (Bedside):
  • Romberg: Sway with eyes closed.
  • Unterberger/Fukuda: Marching, >45° turn indicates lesion side.
  • Head Impulse Test (HIT): VOR check; corrective saccade = peripheral lesion.
  • Head Shaking Nystagmus (HSN): Nystagmus post 20 head shakes.
• Instrumental:
  • ENG/VNG: Records nystagmus.
    • Caloric Test: Warm (44°C) / Cool (30°C) irrigation. 📌 COWS (Cold Opposite, Warm Same side nystagmus).
  • VEMP (cVEMP/oVEMP): Assesses saccule/utricle & respective nerve pathways.
  • vHIT (Video Head Impulse Test): Objective HIT for all 6 semicircular canals.
  • Rotary Chair Test: Evaluates VOR, useful in bilateral weakness.

⭐ In caloric testing, a significant unilateral canal paresis (difference >25% between ears using Jongkees' formula) strongly suggests a peripheral vestibular lesion on the side of reduced response.

Imaging & Endoscopy - Peeking Inside

• X-rays: Screening. Views: Waters' (sinuses), Schuller's (mastoid), Townes' (IAM). Uses: Fractures, FBs, sinusitis.
• CT Scan: Gold standard (bone).
  • HRCT Temporal: Mastoiditis, cholesteatoma, ossicles.
  • CT PNS: Sinusitis (FESS), polyps.
  • Contrast: Abscesses, vascular lesions.
• MRI: Best for soft tissue.
  • Acoustic neuroma (Gad), CPA lesions, perineural spread.
  • DWI: Cholesteatoma (↓ADC) vs abscess. 📌
• Angiography: Vascular (JNA, glomus), pre-op embolization.
• Endoscopy: Direct view/biopsy.
  • DNE (Diagnostic Nasal Endoscopy): Nose, sinuses (OMC), NPx.
  • Laryngoscopy:
    • Flexible (NPL): OPD, VC mobility.
    • Direct (DL): GA, biopsy/procedures.
    • Stroboscopy: VC vibration, wave.
  • Otoendoscopy: EAC, TM, ME (perf.).

⭐ MRI with Gadolinium is IOC for suspected acoustic neuroma.

Lab Workup - Tiny Clues

• Microbiology:
  • Swabs (throat, ear, nasal): Culture & Sensitivity (C&S) for pathogen ID & antibiotic choice.
  • Stains: Gram (bacteria), Ziehl-Neelsen (TB), KOH mount (fungi).
  • Serology: ASO titre (rheumatic fever), EBV antibodies (IMN).
• Pathology/Cytology:
  • Biopsy: FNAC, incisional/excisional for Histopathology (HPE) - malignancy, granulomas.
  • Nasal smear: Eosinophils (allergic rhinitis).
• Hematology:
  • CBC: WBC (↑bacterial, ↓viral), ESR/CRP (↑inflammation markers).

⭐ FNAC is a key initial, minimally invasive test for palpable head & neck masses (e.g., lymph nodes, thyroid).

High‑Yield Points - ⚡ Biggest Takeaways

• X-ray Water's view is key for maxillary sinusitis; Schuller's for mastoid air cells.
• CT scan is gold standard for paranasal sinuses and temporal bone anatomy.
• MRI excels for soft tissue tumors, acoustic neuroma, and intracranial extension.
• Pure Tone Audiometry (PTA) differentiates conductive from sensorineural hearing loss.
• Tuning fork tests (Rinne, Weber) are crucial bedside tools for hearing assessment.
• FNAC is primary for neck mass evaluation; biopsy confirms malignancy.