Injury of trochlear nerve, left side, sequela

This code signifies a long-term or late-effect complication resulting from a past injury to the trochlear nerve (cranial nerve IV) on the left side. Such an injury typically impairs the superior oblique muscle, leading to vertical diplopia (double vision) and difficulty looking down and in. Sequelae can include persistent strabismus, compensatory head tilt, or chronic visual disturbances.

Apply this code when documenting residual neurological deficits or chronic symptoms directly attributable to a previous injury of the left trochlear nerve, after the acute phase of the injury has passed. Documentation should clearly state a history of trochlear nerve injury and ongoing related symptoms or conditions. This code is appropriate for conditions like chronic left superior oblique palsy or persistent diplopia due to past trauma.

• Always sequence this sequela code after the code for the specific residual condition (e.g., H50.412 for left superior oblique palsy).
• Ensure the medical record explicitly links the current condition to a past trochlear nerve injury on the left side.
• Do not use this code for acute injuries; instead, use the appropriate acute injury code from the S04.2- series without the "S" seventh character.