How do I code a head injury secondary to a motor‑vehicle accident using ICD‑10‑CM?

ICD-10-CM Coding for Head Injury Secondary to Motor Vehicle Accident

For a head injury resulting from a motor vehicle accident, you must assign two codes: a primary injury code from the S06 series (intracranial injury) or S02.0-S02.1 series (skull fracture) based on the specific clinical findings, plus a secondary external cause code from the V series to document the MVA mechanism.

Primary Diagnosis Coding Structure

Step 1: Identify the Specific Head Injury Type

The S06 codes (intracranial injury) have the highest positive predictive value at 96.9% when listed as the principal diagnosis and should be your primary code when intracranial injury is documented 1.

Common S06 codes include:

• S06.0 - Concussion (the most frequent brain injury in MVAs, occurring in approximately 1 out of 61 occupants in tow-away crashes) 2
• S06.1 - Traumatic cerebral edema 1
• S06.2 - Diffuse traumatic brain injury (includes diffuse axonal injury, which occurs in approximately 0.05% of tow-away crashes) 2
• S06.3 - Focal traumatic brain injury (includes contusions and lacerations) 3
• S06.4-S06.6 - Epidural, subdural, and subarachnoid hemorrhages 4, 3

For skull fractures without documented intracranial injury:

• S02.0 - Fracture of vault of skull 1
• S02.1 - Fracture of base of skull 1

Critical caveat: S02.0-S02.1 codes used alone (without co-existing S06 codes) have a very low positive predictive value of only 15.8% for true TBI, so these should only be used when skull fracture is the sole documented injury 1.

Step 2: Add Required 7th Character Extension

All S06 and S02 codes require a 7th character to indicate the encounter type 1:

• A - Initial encounter (use for the acute presentation and emergency department visit)
• D - Subsequent encounter (use for follow-up care)
• S - Sequela (use for late effects/chronic complications)

Step 3: Document Loss of Consciousness Duration

For S06 codes, the 5th and 6th characters specify loss of consciousness duration, which is clinically critical for severity classification 5:

• .0 - Without loss of consciousness
• .1 - With loss of consciousness of 30 minutes or less
• .2 - With loss of consciousness of 31-59 minutes
• .3 - With loss of consciousness of 1-5 hours 59 minutes
• .4 - With loss of consciousness of 6-24 hours
• .9 - With loss of consciousness of unspecified duration

External Cause Coding (Mandatory Secondary Code)

Step 4: Assign the MVA Mechanism Code

You must add a V-code to document the motor vehicle accident as the external cause 5, 2. The specific V-code depends on:

Vehicle occupant status:

• V43-V49 - Car occupant injured in collision
• V53-V59 - Pickup truck or van occupant
• V83-V86 - Special vehicle occupants

Collision type (4th character):

• .0 - Driver injured in collision with pedestrian or animal
• .3 - Car occupant injured in collision with car, pickup truck, or van
• .4 - Car occupant injured in collision with heavy transport vehicle
• .5 - Car occupant injured in collision with railway train or vehicle
• .6 - Car occupant injured in collision with other nonmotor vehicle
• .7 - Car occupant injured in collision with fixed or stationary object
• .9 - Car occupant injured in unspecified traffic accident

Occupant position (5th character):

• .0 - Driver
• .1 - Passenger
• .2 - Person on outside of vehicle
• .9 - Unspecified car occupant

Example: V43.52A = Passenger in car injured in collision with car in traffic accident, initial encounter 2

Clinical Documentation Requirements

To support accurate coding, your clinical documentation must specify 5, 3:

• Exact injury type (concussion, contusion, hemorrhage type, skull fracture location)
• Loss of consciousness duration (even if "none" or "unknown")
• Glasgow Coma Scale score (mild GCS 13-15, moderate GCS 9-12, severe GCS ≤8) 5
• Imaging findings (CT is the standard for acute head trauma to detect hemorrhage, herniation, and hydrocephalus) 5, 6
• Patient position in vehicle (driver vs. passenger)
• Seatbelt use (reduces severe head injury risk by 74.8%) 2

Common Coding Pitfalls to Avoid

Do not use S06 codes as the principal diagnosis unless there is provider-documented intracranial injury confirmed by clinical examination or imaging 1. When S06 codes are listed in any diagnostic position without this confirmation, the positive predictive value drops to 80.2%.

Never omit the external cause V-code, as this is required for trauma surveillance and fails to capture the complete clinical picture of MVA-related head injury 2, 1.

Avoid using unspecified codes (such as S06.9X9A for "unspecified intracranial injury with unspecified loss of consciousness") when specific clinical information is available in the medical record 1.

For rollover crashes, document this specifically, as these have the highest risk for severe head injury (AIS 4+) at 0.74% compared to 0.17% for rear impacts 2.