Internuclear ophthalmoplegia, bilateral

This code describes a neurological disorder affecting both eyes, characterized by impaired adduction (inward movement) of the eye on attempted lateral gaze, along with nystagmus (involuntary eye movements) in the abducting eye. It results from a lesion in the medial longitudinal fasciculus (MLF) in the brainstem, disrupting the coordination between cranial nerves III and VI.

Apply this code when documentation explicitly states bilateral internuclear ophthalmoplegia. This is often seen in conditions like multiple sclerosis, stroke, or brainstem tumors affecting both MLFs. The physician's notes should clearly indicate the bilateral nature of the gaze abnormality and nystagmus.

• Ensure documentation specifies "bilateral" involvement; otherwise, a unilateral code may be more appropriate.
• Always code the underlying cause of the internuclear ophthalmoplegia first, such as multiple sclerosis (G35) or cerebral infarction (I63.-).
• Do not confuse with other gaze palsies or ophthalmoplegias that do not specifically involve the MLF or present with the characteristic disconjugate gaze.