• Double vision
    • Simultaneous perception of 2 images
    • Can be oriented horizontally, vertically, or diagonally from one another
    • Two types: monocular (ophthalmologic causes) and binocular (neurologic causes)
    • Binocular and sixth nerve palsies most common
  • Diplopia is usually due to abnormal movement of the extraocular muscles (EOMs), which are innervated by 3 cranial nerves (CNs):
    • CN 3 – superior, inferior, and medial rectus and inferior oblique muscles
    • CN 4 – superior oblique muscle
    • CN 6 – lateral rectus muscle
  • Brainstem lesions can damage CN nuclei or their connections (medial longitudinal fasciculus, MLF), causing an internuclear ophthalmoplegia (INO)
  • CN dysfunction:
    • Compression as they traverse the subarachnoid space and venous sinuses
    • Inflammation
    • Elevation (or reduction) of CSF pressure can cause CN 6 palsy
  • Disease affecting the orbits and the bony skull can cause restriction of motion of one or both eyes or EOMs


  • Traumatic diplopia:
    • Orbital fracture
    • Contusions
    • Hematoma
    • Rarely brainstem contusion or hematoma
  • Monocular diplopia:
    • Nearly always due to an intrinsic eye problem
    • Corneal surface keratoconus
    • Subluxation of the lens
    • Structural defect within the eye
    • Functional disorders such as conversion disorder, factitious disorder, or somatization
  • Nontraumatic binocular diplopia:
    • Brain and brainstem dysfunction:
      • Stroke
      • Multiple sclerosis
      • Cerebral cortical problems (e.g., migraine) are rare
    • CN dysfunction:
      • Aneurysm of posterior communicating artery (CN 3 palsy)
      • Chronic lymphocytic meningitis (multiple CN deficits)
      • Pseudotumor cerebri (CN 6 palsy)
      • Low pressure (spontaneous intracranial hypotension) (CN 6 palsy)
    • Bony skull and orbits:
      • Tumor
      • Thyroid disease
      • Inflammation (Tolosa-Hunt)
    • Neuromuscular junction (NMJ) of EOMs:
      • Myasthenia gravis (MG)

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