- 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)
- 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)
- Multiple Sclerosis (often presents with bilateral internuclear ophthalmoplegia)
- Cerebrovascular disease
- Malignancy located in brainstem and 4th ventricle
- CN III palsy
- Neurologic exam
- The use of optokinetic tape is highly sensitive for testing for INO
- 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
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.