| S04.20 | Injury of trochlear nerve, unspecified side | NON-BILLABLE CODE |
| S04.20XA | Injury of trochlear nerve, unspecified side, initial encounter | BILLABLE CODE |
| S04.20XD | Injury of trochlear nerve, unspecified side, subsequent encounter | BILLABLE CODE |
| S04.20XS | Injury of trochlear nerve, unspecified side, sequela | BILLABLE CODE |
| S04.21 | Injury of trochlear nerve, right side | NON-BILLABLE CODE |
| S04.21XA | Injury of trochlear nerve, right side, initial encounter | BILLABLE CODE |
| S04.21XD | Injury of trochlear nerve, right side, subsequent encounter | BILLABLE CODE |
| S04.21XS | Injury of trochlear nerve, right side, sequela | BILLABLE CODE |
| S04.22 | Injury of trochlear nerve, left side | NON-BILLABLE CODE |
| S04.22XA | Injury of trochlear nerve, left side, initial encounter | BILLABLE CODE |
| S04.22XD | Injury of trochlear nerve, left side, subsequent encounter | BILLABLE CODE |
| S04.22XS | Injury of trochlear nerve, left side, sequela | BILLABLE CODE |
