368.3 🏥 內科專科考前版

368.3.1 Mechanistic Deep Dive

368.3.1.1 Semicircular Canal Anatomy

  • Posterior (most BPPV)
  • Lateral (horizontal)
  • Superior (anterior)
  • Otoconia displacement → cupular deflection

368.3.1.2 Vestibular Pathway

  • Hair cells → vestibular nerve (CN VIII) → vestibular nuclei (brainstem) → cerebellum + thalamus + cortex
  • VOR (vestibulo-ocular reflex) — keeps eyes on target

368.3.1.3 Endolymphatic Hydrops

  • Meniere disease
  • Excess endolymph in cochlear duct
  • Idiopathic

368.3.2 Recent Trials & Updates

368.3.2.1 Vestibular Migraine

  • Increasingly recognized
  • May benefit from CGRP mAbs (anecdotal)

368.3.2.2 Particle Repositioning

  • Epley most common (posterior canal)
  • Semont maneuver (alternative)
  • Gufoni for horizontal canal
  • Yacovino for anterior canal

368.3.2.3 Vestibular Implant

  • Experimental
  • For bilateral vestibular loss

368.3.2.4 Intratympanic Gentamicin

  • Vestibulotoxic
  • Ablates affected ear
  • For severe unilateral Meniere
  • Preserves hearing

368.3.3 High-Yield Specialist Points

368.3.3.1 Acute Vestibular Syndrome Workup

  1. HINTS exam (most important)
  2. Other neuro exam
  3. MRI if HINTS central or any uncertainty
  4. Note: MRI within 48 hr can miss small strokes — HINTS more sensitive

368.3.3.2 Dix-Hallpike Maneuver

  • Patient supine, head turned 45° toward affected
  • Lower head 20° below horizontal
  • Look for latency (5-10 sec), nystagmus (geotropic torsional + upbeat for posterior), fatigability

368.3.3.3 Epley Maneuver

  • For posterior canal BPPV
  • Series of head positions
  • 95%+ effective
  • May repeat
  • Brandt-Daroff exercises home alternative

368.3.3.4 Vestibular Rehabilitation Therapy

  • For chronic vestibular dysfunction
  • Adaptation, substitution, habituation exercises
  • Effective for many conditions

368.3.3.5 Mal de Debarquement

  • Persistent rocking after travel (boat, plane)
  • Better with motion, worse stationary
  • Often resolves
  • Vestibular rehab

368.3.3.6 Persistent Postural-Perceptual Dizziness (PPPD)

  • Chronic dizziness > 3 months
  • Worse upright, with visual stimuli, with motion
  • Functional disorder
  • Treatment: SSRIs, CBT, vestibular rehab

368.3.3.7 Vestibular Paroxysmia

  • Brief attacks (seconds)
  • Recurrent
  • Vascular loop compressing CN VIII
  • Treatment: carbamazepine, oxcarbazepine

368.3.3.8 Superior Canal Dehiscence

  • Bony dehiscence over superior canal
  • Sound/pressure-induced vertigo (Tullio)
  • Autophony
  • CT confirms

368.3.3.9 Acoustic Neuroma (Vestibular Schwannoma)

  • Slowly progressive unilateral hearing loss
  • Tinnitus
  • Imbalance (not severe vertigo)
  • MRI with gadolinium
  • Observation, radiosurgery, or surgery

368.3.3.10 Cerebellar Stroke Emergency

  • Posterior fossa mass effect
  • Can lead to:
    • Brainstem compression
    • Obstructive hydrocephalus
  • Suboccipital craniectomy decompression
  • Monitor closely

368.3.4 Pearls

  • Vertigo = illusion of motion
  • HINTS exam more sensitive than early MRI for posterior stroke
  • BPPV = brief positional → Epley
  • Vestibular neuritis = sustained days, no hearing → steroids
  • Meniere tetrad
  • Vestibular migraine = migraine + vertigo
  • AICA stroke can mimic labyrinthitis (hearing loss + vertigo)
  • Cerebellar stroke can cause obstructive hydrocephalus → decompression
  • Vestibular rehab for chronic
  • PPPD functional chronic dizziness