G12.23 ICD-10-CM Code: Primary lateral sclerosis
G12.23 maps to CMS-HCC V28 190. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Systemic atrophies primarily affecting the central nervous system (G10-G14)
G12.23
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidancePrimary lateral sclerosis
A rare progressive neurological disease that primarily affects upper motor neurons, causing gradual weakness and stiffness in muscles.
Buddy Insight
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.
CMS-HCC V28
MappedHCC 190
Code-level coefficient reference
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 111
Code-level coefficient reference
ESRD/PACE
MappedHCC 73
Code-level coefficient reference
RXHCC
MappedHCC 154
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for G12.23. Check the code and parent instructions in the Code Book.
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from G00-G99
- certain infectious and parasitic diseases (A00-B99)Inherited from G00-G99
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from G00-G99
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from G00-G99
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from G00-G99
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from G00-G99
- neoplasms (C00-D49)Inherited from G00-G99
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from G00-G99
Related Codes
Includes
OfficialNo Includes notes are included in this display for G12.23. Check the code and parent instructions in the Code Book.
Excludes 1
OfficialNo Excludes 1 notes are included in this display for G12.23. Check the code and parent instructions in the Code Book.
Code First
OfficialNo Code First sequencing instructions are included in this display for G12.23. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for G12.23. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for G12.23. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is G12.23 an HCC code?
Yes. G12.23 (Primary lateral sclerosis) maps to HCC 190, Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease, Spinal Muscular Atrophy under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 1.175. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: G12.23 is billable and maps to V28 HCC 190, Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease, Spinal Muscular Atrophy. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- G12.23
- Description
- Primary lateral sclerosis
- HCC (V28)
- HCC 190 — Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease, Spinal Muscular Atrophy
- RAF reference coefficient
- 1.175
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work G12.23 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for G12.23
For G12.23, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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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 Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease, Spinal Muscular Atrophy (HCC 190) with a source-labeled community, non-dual, aged reference coefficient of 1.175. No V24 mapping is shown for G12.23; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Confirm diagnosis distinguishes PLS from ALS by documenting absence of lower motor neuron signs. For G12.23, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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