Sixth Nerve Palsy

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Symptoms

  • Horizontal uncrossed diplopia (distance>near), especially when looking temporally
  • Children: onset often after viral infections, vaccinations, trauma, otitis media
    • usually benign and self-limiting

Work-up

Isolated Sixth Nerve Palsy

  • Complete ophthalmological examination
    • Motility 1
    • Other cranial nerves?
    • Optic disc edema?
  • Neurological symptoms?
  • Patients > 50/60 years with risk factors for cardiovascular disease and unilateral palsy
    • microvascular aetiology very likely – consider watchful waiting
    • signs of giant cell arteritis? if suspected: take blood samples (blood count, CRP, ESR) and consider further investigations
    • within the first 2 weeks after onset, a temporary worsening of symptoms may occur, which should be followed by an improvement
    • if palsy increases after 6 – 8 weeks: MRI head
    • if no improvement after approx. 3 months: MRI head
  • In younger patients <50/60 and/or without known risk factors for cardiovascular disease
    • MRI head (within 1 week, not emergency)
  • In case of Sixth Nerve palsy and Herpes Zoster ophthalmicus
    • MRI/MRA head incl. black blood sequences: signs of cerebral vasculitis? if so: intravenous antiviral therapy is indicated!

In case of Sixth Nerve Palsy in combination with other neurological symptoms or in case of combined cranial nerve paresis

  • Emergency, send patient to Neurology for a thorough neurological examination

Differential Diagnosis

  • Myasthenia gravis (can mimic almost any eye movement disorder)
  • Restrictive thyroid eye disease (most commonly affects the medial rectus muscle -> limited abduction)
  • Blow-out fracture of the medial orbital wall (with entrapment of the medial rectus muscle)
  • Orbital myositis affecting the lateral rectus muscle (painful eye movement)
  • Duane Retraction syndrome (restriction of abduction and narrowing of the palpebral fissure on adduction)
  • Convergence spasm (typically young adults, convergence with miosis and increased accommodation)
  • Divergence paralysis (rare; contrary to Sixth Nerve palsy, esotropia remains the same or decreases when looking sideways)
  • Infantile Esotropia

Hess-Weiss-Test / Tangent scale

  • Simple useful test, indicates type of palsy
  • possible from approx. 6 years of age
  • A normal binocular vision is required
  • Red marks = Right eye
  • Blue marks = Left eye
  • 1 square on Hess-Weiss corresponds to 5 prism diopters, and 5° in the tangent scale
  • Left Sixth Nerve Palsy

Sources