Tinnitus

What is tinnitus?

• Perception of sound without external source.
• First split: pulsatile vs non-pulsatile.
• Pulsatile tinnitus is more likely to have an identifiable structural cause and usually warrants imaging.
• Subjective (patient only) vs objective (examiner can hear, e.g. vascular bruit).

Differential diagnosis

Pulsatile

• Arterial:
  • Aberrant ICA
  • Persistent stapedial artery
  • Carotid/vertebrobasilar aneurysm
  • Carotid stenosis/dissection
  • AVM / dAVF
• Venous:
  • High jugular bulb
  • Jugular bulb diverticulum
  • Sigmoid sinus dehiscence/diverticulum
  • Venous sinus stenosis (IIH-related)
• Hypervascular tumours:
  • Glomus tympanicum / jugulare
• Osseous (third window):
  • Superior semicircular canal dehiscence (SSCD) → Tullio phenomenon

Non-pulsatile

• CPA/IAC:
  • Vestibular schwannoma
  • Meningioma
• Inflammatory:
  • Labyrinthitis
  • Otomastoid disease
• Others:
  • Otosclerosis
  • Enlarged vestibular aqueduct (EVA)
  • Cochlear anomaly
  • Temporal bone fracture

AICA vascular loop is controversial and often incidental.

Imaging approach

• MRI IAC protocol:
  • Best for CPA/IAC tumours and retrocochlear pathology
• CTA/MRA:
  • Arterial causes, AV shunts
• CTV/MRV:
  • Venous causes (sinus stenosis, sigmoid/jugular abnormalities)
• HRCT temporal bone:
  • SSCD, otosclerosis, jugular bulb variants, middle ear detail

Exam pearls

• Pulsatile tinnitus = think vascular until proven otherwise.
• Retrotympanic mass on otoscopy strongly suggests paraganglioma or vascular variant.
• Unilateral tinnitus with asymmetric SNHL → exclude vestibular schwannoma.
• Most bilateral non-pulsatile tinnitus is non-structural (low imaging yield).