G80.4
BillableAtaxic cerebral palsy
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G80.4 an HCC code?
Yes. G80.4 maps to Cerebral Palsy, Except Quadriplegic under the CMS-HCC V28 risk adjustment model (and Cerebral Palsy 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 G80.4
For G80.4 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 G80.4 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G80.4 is the ICD-10-CM diagnosis code for ataxic cerebral palsy. A type of cerebral palsy characterized by poor coordination, balance problems, and unsteady movements due to damage to the cerebellum. G80.4 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering cerebral palsy and other paralytic syndromes (g80-g83).
Under the CMS-HCC V28 risk adjustment model, G80.4 maps to Cerebral Palsy, Except Quadriplegic (HCC 192) with a community, non-dual, aged base RAF weight of 0.368. Under the older CMS-HCC V24 model, G80.4 maps to Cerebral Palsy (HCC 74) with a community, non-dual, aged base RAF weight of 0.000. 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.
Ataxic cerebral palsy is the least common form; document gait disturbance and coordination difficulties. Because G80.4 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 G80.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ataxic cerebral palsy is the least common form; document gait disturbance and coordination difficulties
- •May present with tremor and hypotonia; ensure accurate documentation of muscle tone characteristics
Clinical Significance
Ataxic cerebral palsy represents a rare form of cerebral palsy with cerebellar involvement, resulting in significant coordination and balance deficits that affect all aspects of daily function. This diagnosis is critical for risk adjustment as it identifies patients requiring ongoing multidisciplinary care including physical therapy, occupational therapy, and adaptive equipment. Accurate capture ensures appropriate resource allocation for this lifelong neurological condition.
Documentation Requirements
- ✓Specific type of cerebral palsy documented as 'ataxic'
- ✓Description of cerebellar signs: poor coordination, intention tremor, wide-based gait, dysmetria
- ✓Functional impact on activities of daily living and mobility
- ✓Muscle tone assessment (typically hypotonia in ataxic type)
- ✓Current treatment plan including therapies and assistive devices
- ✓Status as active, ongoing condition being monitored or treated
Commonly Confused Codes
- •G80.0 Spastic quadriplegic cerebral palsy — involves all four limbs with spasticity rather than ataxia
- •G80.1 Spastic diplegic cerebral palsy — primarily affects lower extremities with spasticity, not coordination deficits
- •G80.8 Other cerebral palsy — used for mixed types; ataxic should use G80.4 when clearly documented
- •G11.0 Congenital nonprogressive ataxia — hereditary ataxia not related to cerebral palsy
- •R27.0 Ataxia, unspecified — symptom code only, not used when cerebral palsy is the established diagnosis