Injury of trochlear nerve, unspecified side, sequela

This code signifies a long-term effect or complication resulting from a past injury to the trochlear nerve (cranial nerve IV), which controls the superior oblique muscle responsible for downward and outward eye movement. The "sequela" indicates that the original injury has healed, but residual symptoms or deficits persist. The unspecified side means the laterality of the nerve injury is not documented.

Use this code when documenting a current condition directly attributable to a previous trochlear nerve injury, such as persistent diplopia, strabismus, or impaired eye movement, after the acute phase of the original injury has passed. Documentation should clearly link the current symptoms to a prior trochlear nerve trauma and indicate that the original injury is no longer active.

• Requires a seventh character "S" to indicate sequela, meaning the residual effect of a past injury.
• Do not use for acute trochlear nerve injuries; those would be coded with the appropriate acute injury code.
• Ensure documentation specifies the causal link between the past injury and the current neurological deficit.