Crystal's MCW Coder Hub🧠 ICD-10-CM G35.B1 — Active Primary Progressive Multiple Sclerosis
Billable Code Confirmed — FY2026 New Code
ICD-10-CM G35.B1 is a valid, billable ICD-10-CM code new for FY2026, effective October 1, 2025. It is the designated billable code for primary progressive multiple sclerosis with documented disease activity — defined by new gadolinium-enhancing lesion(s), new T2/FLAIR lesion(s) on MRI, or a superimposed clinical relapse.
CRITICAL FY2026 Change — G35 and G35.B Are Not Billable
- ❌ G35 — Non-billable parent code as of October 1, 2025
- ❌ G35.B — Non-billable subcategory header — never submit alone
- ✅ G35.B1 — Billable code for PPMS with confirmed active disease
Submitting standalone G35 or G35.B after October 1, 2025 is invalid and will reject. When PPMS with active disease is confirmed by the treating physician, G35.B1 is the required code.
Physician Documentation Required — Coders Cannot Assign G35.B1 from MRI Alone
ICD-10 CM G35.B1 requires explicit physician documentation confirming that the PPMS is currently active. A radiology report showing a gadolinium-enhancing lesion is not sufficient on its own — the treating neurologist must interpret that finding and document active disease status in their note, consult, or discharge summary. This is the #1 compliance risk with the new FY2026 MS activity codes.
Code Classification
ICD-10-CM Diagnosis Code — Fields for wRVU, assistant payable, and global period are not applicable. For associated inpatient procedure coding, see the ICD-10-PCS Crosswalk section below.
🔍 Code Description
ICD-10-CM G35.B1 classifies active primary progressive multiple sclerosis — the subtype of MS defined by a gradual, continuous worsening of neurological function from symptom onset (primary progressive course), combined with current inflammatory disease activity as evidenced by new MRI lesion formation or a superimposed clinical relapse.
The distinction between active (G35.B1) and non-active (G35.B2) PPMS is clinically and administratively critical. Activity in the context of the FY2026 MS code family is defined per the 2013 Lublin et al. MS phenotype framework as the presence of clinical relapse activity (discrete new neurological episode lasting >24 hours with objective deficit) and/or MRI activity (new T1 gadolinium-enhancing lesion or new T2/FLAIR lesion on MRI compared to a prior scan within the monitoring period). A single qualifying criterion — clinical OR MRI — is sufficient to classify disease as active.
G35.B1 is the code subtype that most directly supports ocrelizumab (Ocrevus) authorization in PPMS patients, as the pivotal ORATORIO trial was conducted in patients with active PPMS (Gd+ lesions or recent clinical activity). Payers increasingly use ICD-10-CM subtype codes to validate DMT authorization — accurate G35.B1 assignment supports the medical record’s alignment with the prescriber’s authorization request.
🌳 Code Tree / Hierarchy
G35 — Multiple Sclerosis ❌ Non-billable parent (FY2026)
│
├── G35.A — Relapsing-Remitting Multiple Sclerosis ✅ Billable
│
├── G35.B — Primary Progressive Multiple Sclerosis ❌ Non-billable header
│ ├── G35.B0 — Primary Progressive MS, Unspecified ✅ Billable — see [[G35.B0]]
│ ├── G35.B1 — Active Primary Progressive MS ◀ THIS CODE ✅ Billable
│ └── G35.B2 — Non-Active Primary Progressive MS ✅ Billable
│
├── G35.C — Secondary Progressive Multiple Sclerosis ❌ Non-billable header
│ ├── G35.C0 — Secondary Progressive MS, Unspecified ✅ Billable
│ ├── G35.C1 — Active Secondary Progressive MS ✅ Billable
│ └── G35.C2 — Non-Active Secondary Progressive MS ✅ Billable
│
└── G35.D — Multiple Sclerosis, Unspecified ✅ Billable — see [[G35.D]]
The Activity Distinction — Active vs. Non-Active in PPMS
Finding Activity Status Correct Code New Gd+ lesion on MRI Active G35.B1 New T2/FLAIR lesion vs. prior MRI Active G35.B1 Clinical relapse superimposed on PPMS Active G35.B1 Stable MRI — no new lesions Non-active G35.B2 Activity not documented after query Unspecified G35.B0 Activity must be physician-documented, not coder-inferred from the radiology report.
✅ Includes
The following clinical terms and documentation patterns map to G35.B1 when PPMS is confirmed with documented active disease:
- Primary progressive MS, currently active
- PPMS with new gadolinium-enhancing lesion(s) on MRI — physician confirmed
- PPMS with new T2/FLAIR lesion(s) compared to prior MRI — physician confirmed
- Primary progressive MS with clinical relapse superimposed on progressive course — physician documented
- Active PPMS — physician-stated in clinical note, consult, or discharge summary
❌ Excludes
Excludes 1 — Cannot Be Coded Simultaneously with G35.B1
| Code | Description | Note |
|---|---|---|
| G37.9 | Demyelinating disease of CNS, unspecified | Mutually exclusive — confirmed PPMS excludes G37.9 entirely |
| G35.B0 | Primary progressive MS, unspecified | Mutually exclusive — G35.B1 (active) replaces G35.B0 when activity is confirmed |
| G35.B2 | Non-active primary progressive MS | Mutually exclusive — active and non-active are a binary; cannot code both |
Excludes 1 — Never Assign Both G35.B1 and G35.B0 or G35.B2
Excludes 2 — May Be Coded in Addition if Separately Present
| Code | Description | Note |
|---|---|---|
| G36.0 | Neuromyelitis optica (Devic disease) | Excludes 2 — may code alongside G35.B1 only if both conditions are separately confirmed and clinically documented |
📋 Clinical Overview
Defining “Active” in PPMS — The 2013 Lublin Framework
The FY2026 MS activity codes are grounded in the 2013 revised MS phenotype descriptions by Lublin et al., which introduced “active” and “non-active” as modifiers across all MS subtypes. For PPMS specifically, activity is defined by:
| Activity Criterion | Definition | ICD-10 Impact |
|---|---|---|
| Clinical relapse | New discrete neurological episode lasting >24 hours with objective deficit, superimposed on the progressive baseline | Supports G35.B1 |
| MRI activity — T1 Gd+ | New gadolinium-enhancing lesion on T1-weighted post-contrast MRI | Supports G35.B1 |
| MRI activity — T2/FLAIR | New or enlarging T2/FLAIR hyperintense lesion compared to a prior MRI within the monitoring interval | Supports G35.B1 |
| Stable / no new lesions | No new clinical activity and no new MRI lesions on surveillance imaging | Supports G35.B2 |
The Single Most Important Compliance Rule for G35.B1
Physician documentation of activity is mandatory. The coder cannot look at a radiology report showing a Gd+ lesion and assign G35.B1 independently. The treating neurologist must document something equivalent to: “MRI shows new gadolinium-enhancing lesion — PPMS currently active” or “Active primary progressive MS.” Without physician interpretation in the clinical note, G35.B0 is the appropriate code and a CDI query is the correct pathway.
Pathophysiology
Active primary progressive MS shares the same foundational neurodegeneration of PPMS — progressive axonal loss from a smoldering innate immune response in the spinal cord and brain — but is distinguished by the concurrent presence of focal inflammatory demyelination with active lesion formation. The gadolinium-enhancing lesion represents breakdown of the blood-brain barrier at a site of active inflammatory activity — macrophage infiltration, reactive astrogliosis, and ongoing myelin destruction — superimposed on the chronic progressive substrate.
The presence of MRI activity in PPMS has critical therapeutic implications because it indicates that the adaptive immune arm (B-cell and T-cell driven focal inflammation) is still contributing to disease activity alongside the innate neurodegeneration. This is the mechanistic rationale for ocrelizumab — an anti-CD20 B-cell depleting agent — being most effective in active PPMS (G35.B1) compared to non-active PPMS (G35.B2).
Clinical Presentation
Patients coded to G35.B1 present with the progressive myelopathic picture of PPMS alongside evidence of active inflammatory disease:
- Progressive gait disturbance — the cardinal PPMS feature; worsening leg stiffness, foot drop, balance impairment on a continuous trajectory
- New or acutely worsening neurological deficit — may represent a superimposed relapse in active PPMS; >24-hour discrete episode with objective deficit on exam
- Spastic paraparesis / paraplegia — lower extremity spasticity and weakness; G82.20 or G82.10 codeable when severity documented
- Neurogenic bladder — urinary urgency, frequency, retention; N31.9 when documented; near-universal in PPMS
- MRI surveillance findings prompting visit — new Gd+ or T2 lesion detected on scheduled monitoring MRI leading to clinical reassessment
- Fatigue, cognitive impairment, pain — common across all PPMS stages
Documentation Requirements
For accurate assignment of G35.B1 — and to distinguish from G35.B0 and G35.B2 — physician documentation must include:
- MS subtype — “primary progressive MS” or “PPMS” explicitly stated
- Activity status — confirmed active — physician must document: “active,” “new Gd+ lesion,” “new T2 lesion,” or “clinical relapse”
- MRI findings interpreted by the neurologist — not just a radiology report; the physician’s clinical note must reference the active finding
- Current DMT — ocrelizumab documentation directly supported by G35.B1 assignment; supports prior authorization alignment
- Disability level and functional status — documents severity, supports CC/MCC coding of complications
💰 HCC Risk Adjustment (CMS-HCC v28)
| Field | Detail |
|---|---|
| CMS-HCC Model Version | v28 (2024-2025 Implementation) |
| HCC Assignment | ✅ HCC 198 — Multiple Sclerosis |
| HCC Category | HCC 198 |
| RAF Coefficient | Verify current coefficient against CMS v28 publication |
| RxHCC Assignment | RxHCC v08: HCC 159 |
G35.B1 maps to CMS-HCC v28: HCC 198 (Multiple Sclerosis) and RxHCC v08: HCC 159. Verify the FY2026 G35.x subcategory code mapping against the current CMS crosswalk, as the new codes were added effective 10/1/2025 and mapping confirmation should be reviewed in your payer system.
Active PPMS Complications Carry Independent HCC Weight
At every G35.B1 encounter, review and ensure complete coding of:
- Paraplegia / quadriplegia (G82.x) — HCC-mapped
- Hemiplegia / hemiparesis (G81.x) — HCC-mapped
- Neurogenic bladder (N31.x) — review HCC mapping
- Aspiration pneumonia (J69.0) — MCC — very high DRG impact
- Pressure ulcers (L89.x stage 3/4) — MCC; common in non-ambulatory PPMS
- Malnutrition (E43, E44.x) — MCC/CC tier
- Sepsis (A41.x) — MCC
Do not leave risk-adjustable complications undercoded.
🏥 MS-DRG Assignment
MDC 01 — Diseases and Disorders of the Nervous System
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 058 | Multiple Sclerosis and Cerebellar Ataxia with MCC | ~1.50-1.90 |
| DRG 059 | Multiple Sclerosis and Cerebellar Ataxia with CC | ~1.00-1.30 |
| DRG 060 | Multiple Sclerosis and Cerebellar Ataxia without CC/MCC | ~0.70-0.90 |
*Approximate. Verify against IPPS FY2026 Final Rule tables.
Active PPMS Admissions Frequently Qualify for DRG 058
Active PPMS admissions involve patients with advanced disability who are often admitted with concurrent complications. J69.0 (aspiration pneumonia — MCC), A41.x (sepsis — MCC), L89.x stage 3/4 (pressure ulcer — MCC), and E43 (malnutrition — MCC) each move the encounter to DRG 058. Do not accept DRG 060 without a full record sweep for qualifying complications.
🔗 Related ICD-10-CM Codes
The Complete FY2026 MS Code Family
| Code | Description | Use When |
|---|---|---|
| G35 | Multiple sclerosis ❌ NON-BILLABLE PARENT | Never submit after 10/1/2025 |
| G35.A | Relapsing-remitting MS ✅ | RRMS documented |
| G35.B0 | Primary progressive MS, unspecified ✅ | PPMS; activity not documented — see G35.B0 |
| G35.B1 | Active primary progressive MS ✅ | PPMS with confirmed active disease — THIS CODE |
| G35.B2 | Non-active primary progressive MS ✅ | Stable PPMS; no new MRI activity confirmed |
| G35.C0 | Secondary progressive MS, unspecified ✅ | SPMS; activity not specified |
| G35.C1 | Active secondary progressive MS ✅ | SPMS with new MRI activity or superimposed relapse |
| G35.C2 | Non-active secondary progressive MS ✅ | Stable SPMS; no new activity |
| G35.D | Multiple sclerosis, unspecified ✅ | Both subtype AND activity undocumented |
Commonly Associated Additional Diagnosis Codes
| Code | Description | Coding Relevance |
|---|---|---|
| G82.20 | Paraplegia, unspecified | PPMS spinal cord involvement — code when lower extremity paralysis documented |
| G82.10 | Paraparesis, unspecified | Incomplete lower extremity motor dysfunction in PPMS |
| N31.9 | Neuromuscular dysfunction of bladder, unspecified | Neurogenic bladder — near-universal in PPMS; always query and code |
| M62.838 | Other muscle spasm | PPMS-related spasm at non-back, non-calf site — code additionally when documented |
| H46.10 | Optic neuritis, unspecified | May occur as superimposed relapse in active PPMS |
| R13.10 | Dysphagia, unspecified | Brainstem/cerebellar PPMS involvement — may be MCC tier |
| J69.0 | Aspiration pneumonia | MCC — complication of PPMS dysphagia; highest DRG impact |
| L89.x | Pressure ulcer (stage-specific) | Stage 3/4 = MCC; common in non-ambulatory PPMS patients |
| N39.0 | Urinary tract infection | Common complication of neurogenic bladder — CC tier |
| F06.30 | Mood disorder due to known physiological condition | MS-related depression; code when documented |
| G35.B0 | Primary progressive MS, unspecified | Downgrade target — use when activity becomes undocumented on subsequent encounters |
Differential and Related Codes
| Code | Description | Coding Relevance |
|---|---|---|
| G35.D | Multiple sclerosis, unspecified | Use when subtype AND activity are both undocumented — broader |
| G36.0 | Neuromyelitis optica (Devic’s) | Distinct from active PPMS — do not use G35.B1 for NMO |
| G37.3 | Acute transverse myelitis in demyelinating disease | May coexist or precede PPMS diagnosis |
🛠️ Commonly Associated CPT Codes
Outpatient and Physician Setting Context
The CPT codes below are associated with active PPMS evaluation, infusion management, neurological monitoring, and complication management in outpatient and physician fee schedule settings. In the inpatient setting, ICD-10-PCS procedure codes govern procedural reporting.
| CPT Code | Description | Clinical Application |
|---|---|---|
| 99215 | Office visit, established patient, high complexity | Active PPMS management — DMT authorization, new MRI lesion discussion, relapse assessment |
| 99214 | Office visit, established patient, moderate complexity | Ongoing PPMS follow-up with active disease monitoring |
| 96413 | Chemotherapy administration, IV infusion, up to 1 hour | IV ocrelizumab (Ocrevus) — primary DMT for active PPMS; first hour |
| 96415 | Chemotherapy administration, IV infusion, each additional hour | Additional hour(s) of ocrelizumab infusion |
| 96360 | IV infusion, hydration, initial 31-90 minutes | Pre/post hydration with ocrelizumab infusion |
| 95930 | Visual evoked potential (VEP) testing | Optic pathway surveillance; superimposed optic neuritis in active PPMS |
| 95925 | Short-latency somatosensory evoked potential (SSEP) | Posterior column pathway assessment — primary PPMS involvement area |
| 70553 | MRI brain without and with contrast | Active PPMS surveillance — gadolinium enhancement confirms active lesion |
| 72157 | MRI thoracic spine without and with contrast | Thoracic cord active lesion detection — primary PPMS target |
| 97110 | Therapeutic exercise | PT for PPMS gait impairment and strength maintenance |
| 51726 | Complex cystometrogram | Urodynamic testing for neurogenic bladder in PPMS |
NCCI Bundling Considerations
NCCI PTP Edits — Verify Before Billing
- 96413 (ocrelizumab infusion) billed same DOS as E/M: Modifier -25 required on the E/M when separately documented.
- 70553 (brain MRI) and 72157 (thoracic spine MRI) same DOS: typically separately payable; verify LCD/NCD multi-region coverage.
- 95930 (VEP) and 95925 (SSEP) same DOS: confirm separate medical necessity documentation for each; review NCCI PTP edit status.
🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)
When G35.B1 is an inpatient diagnosis and a procedure is performed, the following ICD-10-PCS sections and root operations are relevant. Full PCS codes require completion of all seven characters — consult the PCS tables for the applicable fiscal year.
| PCS Section | Body System | Root Operation | Clinical Application |
|---|---|---|---|
| 0 (Medical & Surgical) | 0 (Central Nervous System) | 9 (Drainage) | Lumbar puncture (CSF analysis) — Body Part U (Spinal Canal), Approach 3 (Percutaneous), Qualifier X (Diagnostic) |
| 3 (Administration) | 3 (Peripheral Vein) | 0 (Introduction) | IV infusion of therapeutic substance (ocrelizumab, methylprednisolone for superimposed relapse) |
| 0 (Medical & Surgical) | 0 (Central Nervous System) | H (Insertion) | Intrathecal baclofen pump implantation for PPMS spasticity management |
| 3 (Administration) | 0 (Central Nervous System) | 0 (Introduction) | Intrathecal baclofen pump refill/dose adjustment |
| B (Imaging) | 0 (Central Nervous System) | 3 (MRI) | Brain and spinal cord MRI with contrast — Gd+ lesion detection confirming active disease |
💊 Coding Scenarios and Examples
Scenario 1 — Active PPMS, New Gd+ Lesion on Surveillance MRI (Outpatient)
Clinical Vignette: A 54-year-old male with known PPMS presents for his 6-month neurology follow-up. Surveillance MRI brain performed prior to visit. Neurologist reviews MRI and documents in the visit note: “MRI shows one new gadolinium-enhancing lesion in the right cerebellar peduncle compared to prior study 6 months ago. Primary progressive MS — currently active. Will proceed with ocrelizumab infusion series.”
CPT Codes (Outpatient):
- 99215 — Office visit, established patient, high complexity (new MRI lesion requiring DMT decision — high MDM complexity)
ICD-10-CM:
- G35.B1 — Active primary progressive MS (physician explicitly documents “currently active” and references new Gd+ lesion — G35.B1 is correct and required)
This Is the Ideal G35.B1 Documentation Scenario
The neurologist did exactly what is needed — interpreted the MRI finding AND stated activity status in the clinical note. No CDI query required. G35.B1 is assigned with confidence. This documentation also directly supports ocrelizumab prior authorization alignment.
Scenario 2 — Active PPMS, Superimposed Relapse, Inpatient
Clinical Vignette: A 49-year-old female with known primary progressive MS is admitted for acute new right arm weakness and dysarthria developing over 36 hours. MRI brain shows new T2 hyperintense lesion in the left internal capsule with gadolinium enhancement. Neurology documents: “Primary progressive MS with superimposed acute relapse — active disease. Initiating IV methylprednisolone 1g daily x 3 days.”
Principal Diagnosis:
- G35.B1 — Active primary progressive MS (PPMS with confirmed active disease — physician documents superimposed relapse and active disease; sequences as principal)
Additional Diagnoses:
- G81.10 — Flaccid hemiplegia, unspecified side (right arm weakness documented — code if severity threshold met per physician documentation)
- R47.81 — Dysarthria (documented speech impairment — code additionally)
MS-DRG Assignment:
- DRG 059 — Multiple Sclerosis and Cerebellar Ataxia with CC (if G81.10 qualifies as CC — confirm CC/MCC tier)
- DRG 058 — with MCC if higher-tier complication also present
Superimposed Relapse in PPMS — Correct Code Is Still G35.B1
Some coders question whether a relapse in a PPMS patient shifts the code to G35.A (RRMS). It does not. The disease subtype is determined by the overall clinical course — PPMS is progressive from onset with no early relapses. A relapse superimposed on an established PPMS course does not reclassify the patient as RRMS. The physician documents the subtype; the activity modifier changes to “active” → G35.B1 is correct.
Scenario 3 — Active PPMS, Ocrelizumab Infusion Encounter (Outpatient Infusion)
Clinical Vignette: A 58-year-old male with active PPMS presents for his second ocrelizumab infusion. Prior authorization was obtained based on documented active disease (new T2 lesion on last MRI). The infusion center note documents: “Active primary progressive MS — scheduled Ocrevus infusion per neurology plan.”
CPT Codes:
- 96413 — IV infusion, chemotherapy, first hour (ocrelizumab)
- 96415 — IV infusion, each additional hour
- 96360 — Hydration infusion, initial 31-90 minutes (pre-medication hydration if separately documented)
ICD-10-CM:
- G35.B1 — Active primary progressive MS (explicitly documented in infusion center note — correct)
Modifier -25 on E/M If Billed Same Day as Infusion
If the neurologist performs a separate E/M at the same infusion encounter (beyond pre/post infusion assessment), modifier -25 is required on the E/M code. The infusion itself does not include a separately billable E/M without that modifier.
Scenario 4 — Radiology Shows Gd+ But Physician Hasn’t Documented Activity Yet (Inpatient)
Clinical Vignette: A 53-year-old female with PPMS is admitted for urinary sepsis. During the admission, MRI brain is performed and radiology reports one new Gd+ lesion. The attending internal medicine physician’s notes reference PPMS but do not address the MRI activity finding. No neurology consult is obtained. Discharge summary documents “primary progressive MS” without activity status.
Principal Diagnosis:
- (Urinary sepsis — sequences as principal per reason for admission)
Additional Diagnoses:
- G35.B0 — Primary progressive MS, unspecified (Gd+ is in radiology report ONLY — the attending did not document active PPMS; coder cannot assign G35.B1 from radiology report alone; G35.B0 is correct)
This Is the Most Important Compliance Scenario for G35.B1
Do not assign G35.B1 based solely on a radiology report. The radiologist’s finding of a Gd+ lesion is not physician documentation of active PPMS. A CDI query to the attending or a neurology consult request is the correct pathway. If no physician documents active disease status before bill drop → G35.B0 is the correct code. Assigning G35.B1 without physician activity documentation is a compliance violation.
⚠️ Coding Pitfalls and Tips
| Pitfall or Tip | |
|---|---|
| ❌ | Do not submit G35 or G35.B alone — both are non-billable after 10/1/2025; minimum valid PPMS code is G35.B0 for unspecified activity |
| ❌ | Do not assign G35.B1 from a radiology report alone — physician documentation of active disease status is required; radiology interpretation without clinical documentation = G35.B0 + CDI query |
| ❌ | Do not assign G35.B1 alongside G35.B0 or G35.B2 — mutually exclusive; only one G35.B code per encounter |
| ❌ | Do not reclassify PPMS as RRMS because of a superimposed relapse — a relapse in a PPMS patient → G35.B1, not G35.A; subtype is the overall disease course, not a single episode |
| ❌ | Do not assign G35.B1 simultaneously with G37.9 — Excludes 1; mutually exclusive |
| ✅ | G35.B1 requires explicit physician documentation of active disease — “active,” “new Gd+ lesion,” “new T2 lesion,” or “clinical relapse” must appear in physician note, consult, or discharge summary |
| ✅ | G35.B1 directly supports ocrelizumab prior authorization — accurate assignment aligns the medical record with the DMT authorization request |
| ✅ | G35.B1 carries CMS-HCC v28: HCC 198 / RxHCC v08: HCC 159 — confirm mapping on current CMS crosswalk |
| ✅ | Capture all PPMS complications — neurogenic bladder (N31.x), paraplegia (G82.x), aspiration pneumonia (J69.0), pressure ulcers (L89.x) drive DRG tier and RAF |
| ✅ | J69.0 is MCC — moves active PPMS admission to DRG 058; never miss in non-ambulatory patients with documented dysphagia |
| ✅ | Query before bill drop when Gd+ lesion is in the radiology report but physician hasn’t addressed activity status — one clarifying sentence upgrades G35.B0 to G35.B1 |
📚 Sources
-
CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. Tabular List — G35.B1; G35.B subcategory structure; Excludes 1/Excludes 2 notations at G35 category level.
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CMS. FY2026 Addendum B — ICD-10-CM New, Revised, and Deleted Diagnosis Codes. G35B1 added; G35 deleted as billable code.
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CMS. 2025-2026 Medicare Advantage Risk Adjustment — CMS-HCC Model v28 ICD-10-CM Mappings. G35 family: CMS-HCC v28 HCC 198 (Multiple Sclerosis); RxHCC v08 HCC 159.
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CMS. IPPS Final Rule FY2026 — MS-DRG Definitions Manual v43. MDC 01 logic tables — DRG 058/059/060 Multiple Sclerosis and Cerebellar Ataxia.
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CMS. ICD-10-PCS Reference Manual FY2026. Section 0 (Medical & Surgical), Body System 0 (CNS); Section 3 (Administration).
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Lublin FD, et al. Defining the clinical course of multiple sclerosis: The 2013 revisions. Neurology. 2014;83(3):278-286. (Clinical basis for activity distinction in PPMS — “active” vs. “non-active” modifiers directly reflected in G35.B1 vs. G35.B2.)
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Montalban X, et al. Ocrelizumab versus placebo in primary progressive multiple sclerosis. N Engl J Med. 2017;376(3):209-220. (ORATORIO trial — clinical and regulatory basis for ocrelizumab authorization in active PPMS; supports G35.B1 DMT alignment.)
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AMA. CPT Professional Edition 2026. Neurology and Neuromuscular Procedures (95800-96020); Evaluation and Management guidelines; Infusion/Injection subsection.
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CMS. NCCI Policy Manual for Medicare Services, current version. Neurology chapter and general correct coding principles.