Internuclear ophthalmoplegia, left eye

This code signifies internuclear ophthalmoplegia affecting the left eye. This condition results from a lesion in the medial longitudinal fasciculus (MLF), leading to impaired adduction of the left eye during conjugate gaze and nystagmus in the abducting right eye. It indicates a specific neurological deficit impacting ocular motility.

Assign this code when documentation clearly specifies internuclear ophthalmoplegia localized to the left eye. This typically occurs in patients presenting with diplopia, gaze palsies, or other neurological symptoms indicative of brainstem pathology, such as multiple sclerosis or stroke. Supporting documentation should include neurological exam findings confirming the left eye's adduction deficit and abducting nystagmus of the contralateral eye.

• Differentiate from internuclear ophthalmoplegia affecting the right eye (H51.21) or bilateral involvement (H51.23).
• Always code the underlying cause of the internuclear ophthalmoplegia, such as multiple sclerosis (G35.-) or stroke (I63.-), as the primary diagnosis when known.
• Ensure the laterality (left eye) is explicitly stated in the physician's documentation to support this specific code.