What is it called if a patient is unable to move their extraocular muscles (EOM)?

Ophthalmoplegia: Inability to Move Extraocular Muscles

Ophthalmoplegia is the medical term for paralysis or paresis of one or more extraocular muscles (EOMs), resulting in the inability to move the eyes in certain directions. 1

Types of Ophthalmoplegia

• Complete ophthalmoplegia: Paralysis of all extraocular muscles
• Partial ophthalmoplegia: Weakness or paralysis of specific extraocular muscles
• External ophthalmoplegia: Affects only the extraocular muscles
• Internal ophthalmoplegia: Affects the pupillary muscles
• Total ophthalmoplegia: Affects both external and internal eye muscles

Anatomical Classifications

Based on Cranial Nerve Involvement

• Oculomotor (CN III) palsy:

  • Impaired adduction, elevation, and depression
  • May involve pupil (pupil-involving vs. pupil-sparing)
  • Often presents with ptosis 2

• Trochlear (CN IV) palsy:

  • Impaired intorsion and depression
  • Often caused by trauma 2

• Abducens (CN VI) palsy:

  • Impaired abduction
  • May indicate increased intracranial pressure 3

Based on Location

• Nuclear ophthalmoplegia: Damage to cranial nerve nuclei in brainstem
• Fascicular ophthalmoplegia: Damage to nerve fascicles within brainstem
• Peripheral ophthalmoplegia: Damage to cranial nerves outside brainstem
• Neuromuscular junction ophthalmoplegia: Defect in neuromuscular transmission
• Myopathic ophthalmoplegia: Primary disease of extraocular muscles

Specific Syndromes

• Internuclear ophthalmoplegia (INO):

  • Impaired adduction on attempted lateral gaze
  • Associated with multiple sclerosis 3

• Progressive supranuclear palsy:

  • Decreased velocity of saccades
  • Vertical gaze palsy (especially downward gaze) 3

• Chronic progressive external ophthalmoplegia (CPEO):

  • Slowly progressive bilateral ophthalmoplegia and blepharoptosis
  • Associated with mitochondrial disorders
  • MRI shows minimal EOM volume reduction despite severe weakness 4

• Myasthenia gravis:

  • Fluctuating ophthalmoplegia
  • May show fatiguability with sustained gaze
  • Can become treatment-resistant with endomysial collagen buildup 5

• Cavernous sinus syndrome:

  • Multiple ipsilateral cranial nerve palsies affecting CN III, IV, and VI 3

Diagnostic Approach

1. Clinical examination:

   • Test both versions (binocular motility) and ductions (monocular motility)
   • Document limitations, overactions, or incomitance
   • Assess pupillary involvement (critical for CN III palsy) 2
   • Evaluate for compensatory head posture 3

2. Imaging:

   • MRI brain for subacute, slowly progressive presentations
   • CT head without contrast for initial imaging in acute settings
   • MRA/CTA when vascular causes are suspected 2
   • High-resolution orbital MRI for suspected CPEO 4

Clinical Pearls

• Pupil-involving third nerve palsy requires urgent evaluation for posterior communicating artery aneurysm 2
• Isolated CN VI palsy may indicate increased intracranial pressure without direct nerve compression 3
• Extraocular muscles have fundamentally distinct properties from other skeletal muscles, making them selectively vulnerable to certain disorders 6
• The pattern of involvement can usually lead to the anatomical localization of the offending lesion 2

Understanding the specific pattern of ophthalmoplegia is crucial for accurate diagnosis and appropriate management of the underlying condition.