Q04.0
BillableCongenital malformations of corpus callosum
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q04.0 an HCC code?
Yes. Q04.0 maps to Spinal Cord Disorders/Injuries under the CMS-HCC V28 risk adjustment model (and Spinal Cord Disorders/Injuries under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for Q04.0
For Q04.0 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed Q04.0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q04.0 is the ICD-10-CM diagnosis code for congenital malformations of corpus callosum. A birth defect where the corpus callosum, the main structure connecting the two sides of the brain, is malformed or underdeveloped. Q04.0 sits in the ICD-10-CM chapter for congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (q00-qa0), within the section covering congenital malformations of the nervous system (q00-q07).
Under the CMS-HCC V28 risk adjustment model, Q04.0 maps to Spinal Cord Disorders/Injuries (HCC 182) with a community, non-dual, aged base RAF weight of 0.282. Under the older V24 model, Q04.0 mapped to the same category but with a base RAF weight of 0.464 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Specify whether the corpus callosum is absent, hypoplastic, or has other structural abnormalities. Because Q04.0 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Q04.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Specify whether the corpus callosum is absent, hypoplastic, or has other structural abnormalities
- •This may be associated with other brain malformations; code those separately if present
Clinical Significance
Congenital malformations of the corpus callosum can cause significant cognitive, motor, and behavioral impairments due to disrupted interhemispheric communication. These conditions require multidisciplinary care and long-term developmental support services.
Documentation Requirements
- ✓Documentation of corpus callosum malformation identified on neuroimaging
- ✓Specific description of malformation type (agenesis, dysgenesis, hypoplasia)
- ✓Neurological examination findings and developmental assessment
- ✓Associated neurological or developmental deficits
- ✓Neuroimaging studies confirming corpus callosum abnormality
- ✓Assessment of cognitive and motor function impacts
- ✓Documentation of associated brain abnormalities if present
- ✓Treatment and developmental intervention plans