G12.23
BillablePrimary lateral sclerosis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G12.23 an HCC code?
Yes. G12.23 maps to Motor Neuron Disease, Including Amyotrophic Lateral Sclerosis under the CMS-HCC V28 risk adjustment model (and Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease 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 G12.23
For G12.23 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 G12.23 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G12.23 is the ICD-10-CM diagnosis code for primary lateral sclerosis. A rare progressive neurological disease that primarily affects upper motor neurons, causing gradual weakness and stiffness in muscles. G12.23 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering systemic atrophies primarily affecting the central nervous system (g10-g14).
Under the CMS-HCC V28 risk adjustment model, G12.23 maps to Motor Neuron Disease, Including Amyotrophic Lateral Sclerosis (HCC 190) with a community, non-dual, aged base RAF weight of 0.935. Under the older CMS-HCC V24 model, G12.23 maps to Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease (HCC 73) with a community, non-dual, aged base RAF weight of 0.896. 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.
Confirm diagnosis distinguishes PLS from ALS by documenting absence of lower motor neuron signs. Because G12.23 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 G12.23 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm diagnosis distinguishes PLS from ALS by documenting absence of lower motor neuron signs
- •Note the slower progression pattern typical of PLS compared to other motor neuron diseases
Clinical Significance
Primary lateral sclerosis is a rare upper motor neuron disease causing progressive spasticity and weakness without the lower motor neuron involvement seen in amyotrophic lateral sclerosis. It has a significantly better prognosis than amyotrophic lateral sclerosis with survival often exceeding 10-20 years, but still causes substantial disability and requires long-term neurological management.
Documentation Requirements
- ✓Upper motor neuron signs documented (spasticity, hyperreflexia, Babinski sign)
- ✓Absence of lower motor neuron signs (no muscle atrophy, no fasciculations) on examination
- ✓Electromyography showing no denervation to support absence of lower motor neuron involvement
- ✓Slow progression pattern over at least 3-4 years (to distinguish from early amyotrophic lateral sclerosis)
- ✓Brain and spinal MRI to exclude structural causes
- ✓Serial examinations documenting stable upper motor neuron pattern over time
Commonly Confused Codes
- •G12.21 — Amyotrophic lateral sclerosis: involves both upper and lower motor neurons; primary lateral sclerosis is upper only
- •G04.1 — Tropical spastic paraplegia: infectious etiology (HTLV-1) rather than degenerative
- •G11.4 — Hereditary spastic paraplegia: inherited with family history, while primary lateral sclerosis is sporadic
- •G12.20 — Motor neuron disease, unspecified: should not be used when primary lateral sclerosis is clearly documented