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RD7.2 | Imaging in ENT — PBL Case

CLINICAL SETTING

Mrs. Lakshmi, a 48-year-old schoolteacher, presents to the ENT outpatient department of a teaching hospital. For the past year she has noticed that she increasingly holds the telephone to her right ear because the left 'just doesn't pick up words clearly', even though she can tell that someone is speaking. More recently she has had a constant high-pitched ringing in the left ear and, over the last two months, occasional unsteadiness when she turns quickly. Her otoscopy is completely normal in both ears. You are the small group of final-year students assigned to work up this patient with the ENT registrar, integrating the audiological and imaging findings into a management plan. Work through each trigger in order, stating your reasoning before the next trigger is revealed.

Trigger 1: The pattern of hearing loss

Pure-tone audiometry shows a left-sided sensorineural hearing loss with thresholds substantially worse than the right ear; speech-discrimination scores on the left are disproportionately poor compared with what the pure-tone average would predict. The right ear is normal. The registrar asks the group to characterise the loss before deciding on any imaging.

DISCUSSION POINTS

  • How would you classify this hearing loss (side, symmetry, type), and which clinical features here are 'red flags' that demand further investigation rather than reassurance?
  • Why does disproportionately poor speech discrimination, together with imbalance, raise concern about a retrocochlear (nerve) lesion rather than a cochlear cause?
  • Before ordering any scan, what is the single most important clinical principle that decides whether this patient with SNHL needs imaging at all?
Click to reveal Trigger 2: Choosing and interpreting the scan (discuss previous trigger first!)

Trigger 2: Choosing and interpreting the scan

The group agrees the patient needs imaging. The registrar asks which modality to request and what specific question it must answer. Imaging is arranged and the report reads: an enhancing mass centred at the left porus acusticus, with an intracanalicular component extending into the internal auditory meatus and a larger component in the cerebellopontine angle cistern, producing an 'ice-cream-cone' configuration; the bony labyrinth is normal and there is no brainstem compression.

DISCUSSION POINTS

  • Which imaging modality is the gold standard for this clinical question, and why is it preferred over HRCT here? Relate your answer to the rule that MRI characterises soft tissue and nerves while CT characterises bone.
  • What is the most likely diagnosis given the location and 'ice-cream-cone' appearance, and what makes this the commonest serious, treatable cause of asymmetric SNHL?
  • What safety screening must be completed before this particular scan is performed, and what alternative exists if that scan is contraindicated?
Click to reveal Trigger 3: From scan to decision (discuss previous trigger first!)

Trigger 3: From scan to decision

The registrar now wants the group to translate the imaging finding into a management decision and to counsel the patient. The patient asks the students directly: 'Is this a cancer? Will I need an operation? Will my hearing come back?' She also mentions that her sister has a cardiac pacemaker and wonders whether that is relevant to her own future scans.

DISCUSSION POINTS

  • How does the imaging finding (size, location, absence of brainstem compression) influence the broad management options of observation with serial imaging versus active treatment?
  • Why does RD7.2 sit at the 'knows-how' level — that is, how does this scan literally change what is done for the patient rather than simply describing anatomy?
  • How would you explain the diagnosis and the role of follow-up imaging to the patient in lay terms, and what is the relevance of her sister's pacemaker to MRI safety?

Group Task Assignments

  • Group A: Construct a one-page algorithm for the imaging work-up of a patient presenting with unilateral/asymmetric SNHL, from audiometry to definitive imaging, marking the decision points where imaging is and is not indicated.
  • Group B: Prepare a comparison table of HRCT temporal bone versus gadolinium-enhanced MRI IAM in SNHL — what each modality shows best, its indications, and its contraindications/limitations.
  • Group C: Draft a patient-friendly explanation sheet for vestibular schwannoma covering what it is, the watch-and-wait versus treatment options, and why repeat MRI scans are used for monitoring.

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [RD7.2] What clinical features of sensorineural hearing loss (asymmetry, sudden onset, poor speech discrimination, vertigo, paediatric/congenital, pre-implant) determine whether and how a patient should be imaged?
  2. [RD7.2] Why is gadolinium-enhanced MRI of the internal auditory meatus/posterior fossa the gold standard for asymmetric SNHL, and what are the typical imaging features of a vestibular schwannoma at the CPA/IAM?
  3. [RD7.2] What are the contraindications to MRI, how should patients be screened for them, and when is HRCT the appropriate alternative in the assessment of hearing loss?