ICD-10-CM > S00-T88 > S00-S09 > S04 > S04.2 S04.2 Injury of trochlear nerve Non-Billable/Non-Specific Applicable To Injury of 4th cranial nerve Codes S04.20Injury of trochlear nerve, unspecified sideS04.20XA..., initial encounterS04.20XD..., subsequent encounterS04.20XS..., sequelaS04.21Injury of trochlear nerve, right sideS04.21XA..., initial encounterS04.21XD..., subsequent encounterS04.21XS..., sequelaS04.22Injury of trochlear nerve, left sideS04.22XA..., initial encounterS04.22XD..., subsequent encounterS04.22XS..., sequela