Injury of trochlear nerve, left side, initial encounter

This code signifies damage to the fourth cranial nerve on the left side, which is responsible for innervating the superior oblique muscle of the eye. Injury to this nerve typically results in impaired downward and outward gaze, often leading to vertical diplopia (double vision).

Apply this code for a newly diagnosed or treated injury affecting the left trochlear nerve. Documentation should clearly indicate the left side of involvement and that the patient is in the active phase of treatment for this specific injury. This includes initial evaluations, surgical interventions, or early stages of conservative management.

• Ensure documentation specifies "left side" to differentiate from right or bilateral involvement.
• Confirm the encounter is "initial" for the injury; subsequent encounters will require different seventh characters.
• Distinguish from other cranial nerve palsies, especially oculomotor (CN III) or abducens (CN VI), which affect different eye movements.