Sixth (Abducens) Nerve Palsy

Sixth (Abducens) Nerve Palsy 2018-01-30T16:37:18+00:00

Relevant physical signs

  • Abducens nerve palsy
    • Pure horizontal diplopia
    • Esotropia (inward deviation of the eye – unopposed medial rectus) on inspection
    • Paralysis of lateral gaze on the affected side
    • Nystagmus of the contralateral eye on looking towards the affected side
  • Features associated with non-isolated palsies
    • Orbital apex syndrome (II, III, IV, V1, VI)
    • Superior orbital fissure syndrome (III, IV, V1, VI)
    • Cavernous sinus syndrome (III, IV, V1, V2, VI, sympathetic fibres)
    • Pontine syndromes
      • Contralateral hemiparesis – corticospinal tract (Raymond’s)
      • Contralateral hemiparesis, ipsilateral facial nerve palsy –Millard-Gubler syndrome
    • Complex ophthalmoplegia
      • Tachycardia, goitre, tremor – thyroid eye disease
      • Fatigability – ocular myasthenia
      • Grip myotonia – myotonic dystrophy
      • Arreflexia – Miller-Fisher syndrome
      • Scars – trauma, previous surgery
    • Bilateral sixth nerve palsy – false localizing sign
  • Nuclear lesions
    • VI nucleus projects via the medial longitudinal fasciculus to the contralateral III nucleus
    • Nuclear lesions hence produce complete lateral gaze palsies
    • g. in right abducens nuclear lesion
      • Failure of abduction of the right eye when looking right
      • Failure of adduction of the left eye when looking right
    • Can be differentiated from a concomitant III nerve lesion by asking the patient to converge
      • Medial gaze not affected in this case

Differential diagnosis

  • False localizing sign (raised intracranial pressure), especially in bilateral VI palsies
  • Inflammatory
    • Demyelinating disease – multiple sclerosis
    • Giant cell arteritis
    • Sarcoidosis
    • Wegner’s granulomatosis
    • Churg-Strauss syndrome
    • Polyarteritis nodosa
    • Systemic lupus erythematosus
  • Infection
    • Lyme disease
    • Syphilis
    • Bacterial meningitis
  • Neoplastic
    • Pontine tumour
    • Leptomeningeal carcinomatosis
  • Vascular
    • Pontine stroke
    • Basilar artery aneurysm
  • Trauma

Sixth Nerve Palsy

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