Internuclear opthalmoplegia

(Redirected from INO)

Background

Internuclear opthalmoplegia, courtesy of sketchy medicine
  • Disruption of conjugate gaze.
  • Results in diplopia when looking contralateral (to affected eye).
  • Localized to Midbrain or Pons.
  • Paramedian Pontine Reticular Formation (PPRF) is the conjugate gaze center for horizontal eye movements. Innervates ipsilateral Abducens (CN VI) nucleus. Abducens nucleus signals ipsilateral lateral rectus to contract and sends a second via MLF to contralateral oculomotor (CN III) nucleus, causing contraction on the contralateral medial rectus.
  • Lesions in the Medial Longitudinal Fasiculus (MLF) result in intranuclear ophthalmoplegia (INO).
  • Associated with one and one-half syndrome (lesion involving the PPRF and ipsilateral MLF)

Clinical Features

  • Weakness in adduction of affected eye with limitation in horizontal gaze.
  • May result in horizontal diplopia
  • Horizontal nystagmus in unaffected eye
  • Convergence remains intact (differentiates CN III palsy from INO)

Differential Diagnosis

  • Multiple Sclerosis (often presents with bilateral internuclear ophthalmoplegia)
  • Cerebrovascular disease
  • Malignancy located in brainstem and 4th ventricle
  • CN III palsy

Evaluation

  • Neurologic exam
  • The use of optokinetic tape is highly sensitive for testing for INO
  • MRI

Management

  • Symtoms will often resolve on their own. Patients with cerebrovascular disease are less likely to have recovery.
  • Patching of eye can aid in relief of diplopia
  • Diframpadine, potassium channel blocker, has been used in patients with demyelinating disease

References

Ropper A, Klein J, Samuels M. Adams and Victor's Principles of Neurology 10th Edition. McGraw-Hill Education / Medical; 2014.

Serra A, Skelly MM, Jacobs JB, et al. Improvement of internuclear ophthalmoparesis in multiple sclerosis with dalfampridine. Neurology 2014; 83:192.

Authors:

Avi Ravilla