Internuclear opthalmoplegia

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.