G35.D

🧠 ICD-10-CM G35.D — Multiple Sclerosis, Unspecified

Billable Code Confirmed — FY2026 New Code

ICD-10-CM G35.D is a valid, billable ICD-10-CM code new for FY2026, effective October 1, 2025. It is the designated billable code for multiple sclerosis when the subtype and activity level are not documented in the medical record after a good-faith query attempt.

CRITICAL FY2026 Change — G35 Is No Longer Billable

• ❌ G35 — Now a non-billable parent code as of October 1, 2025
• ✅ G35.D — New billable code for MS, unspecified subtype/activity

Any claim submitted with standalone G35 after October 1, 2025 is invalid and will reject or deny. G35.D is the correct replacement for all MS encounters where subtype and activity level are genuinely not documented. Do not use G35 alone under any circumstances in FY2026.

G35.D Is the Last Resort — Always Query First

ICD-10 CM G35.D should only be assigned after a good-faith effort to identify MS subtype and activity from the medical record or via CDI query. The FY2026 expansion exists specifically to capture clinical distinctions that carry therapeutic, prognostic, and risk-adjustment significance. If the physician documents ANY subtype — use that code. ICD-10 CM G35.D is appropriate only when the record is genuinely silent on both subtype and activity after query.

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.

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🔍 Code Description

ICD-10 CM G35.D classifies multiple sclerosis, unspecified — a chronic, immune-mediated demyelinating disease of the central nervous system in which the subtype (relapsing-remitting, primary progressive, or secondary progressive) and/or activity status (active vs. non-active) have not been documented in the medical record. It is the FY2026 replacement for the previously standalone billable code G35.

Multiple sclerosis is characterized by demyelination and axonal injury throughout the CNS — brain, spinal cord, and optic nerves — producing plaques of inflammation and scarring at multiple sites. Clinical manifestations are highly variable depending on lesion location, ranging from optic neuritis and sensory disturbances to motor weakness, spasticity, cerebellar ataxia, bladder dysfunction, and cognitive impairment.

The FY2026 restructuring of the G35 category reflects the clinical reality that MS subtype profoundly affects treatment selection, prognosis, and payer authorization. G35.D exists as a catch-all for encounters where this granularity is genuinely unavailable — it is not a preferred default. At every encounter coded with G35.D, a CDI query opportunity exists to upgrade to G35.A, G35.B0-G35.B2, or G35.C0-G35.C2.

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🌳 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
│ ├── G35.B1 — Active Primary Progressive MS ✅ 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 ◀ THIS CODE ✅ Billable

Upgrade Path — Always Preferred Over G35.D

If ANY of the following is documented, a more specific code is required:

• Relapsing-remitting (RRMS) → G35.A
• Primary progressive (PPMS), activity unspecified → G35.B0
• Active primary progressive → G35.B1
• Non-active primary progressive → G35.B2
• Secondary progressive (SPMS), activity unspecified → G35.C0
• Active secondary progressive → G35.C1
• Non-active secondary progressive → G35.C2

Reserve G35.D strictly for when the record is silent on both subtype AND activity level after a query attempt.

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✅ Includes

The following clinical terms map to G35.D when MS subtype and activity level are not documented:

• Multiple sclerosis NOS
• Multiple sclerosis, type unspecified
• Disseminated sclerosis NOS
• Generalized multiple sclerosis
• Multiple sclerosis of brain stem (type unspecified)
• Multiple sclerosis of cord (type unspecified)
• All encounters previously coded to standalone G35 that lacked subtype documentation, carried over after October 1, 2025

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❌ Excludes

Excludes 1 — Cannot Be Coded Simultaneously with G35.D

Code	Description	Note
G37.9	Demyelinating disease of central nervous system, unspecified	Mutually exclusive — G37.9 is the code for unspecified demyelinating disease that is NOT MS; if MS is confirmed, do not additionally assign G37.9

Excludes 1 — G37.9 Is the Trap for Unspecified Demyelinating Disease

G37.9 is an Excludes 1 entry within the G35 category per the FY2026 tabular. If the diagnosis is confirmed as multiple sclerosis — even unspecified subtype — assign G35.D only. G37.9 is appropriate only when the demyelinating disease cannot be further characterized as MS, NMO, or another specific entity. Do not code both.

Excludes 2 — May Be Coded in Addition if Separately Present

Code	Description	Note
G36.0	Neuromyelitis optica (Devic disease)	Excludes 2 — distinct AQP4-IgG-mediated demyelinating disease; may code alongside G35.D only if both conditions are separately confirmed and documented

NMO vs. MS — Distinct Diagnoses, Distinct Codes

G36.0 (neuromyelitis optica / Devic disease) is a separate demyelinating condition with distinct pathophysiology, serology (AQP4-IgG or MOG-IgG positive), and treatment paradigm. Do not use G35.D for NMO — assign G36.0 when that is the documented diagnosis. Excludes 2 means both may be coded if a patient has both conditions separately confirmed, but NMO alone never receives G35.D.

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📋 Clinical Overview

The FY2026 MS Code Expansion — Why It Happened

Prior to FY2026, all of multiple sclerosis collapsed into a single billable code — G35. The FY2026 expansion aligns ICD-10 CM M with the clinical reality neurologists have documented for decades: MS subtype (RRMS, PPMS, SPMS) and disease activity (active vs. non-active) are clinically fundamental distinctions that drive FDA-approved DMT selection, payer authorization, and prognostic stratification. The new structure directly reflects the 2013 MS Phenotype Descriptions published by the International Advisory Committee on Clinical Trials of MS.

FY2026 Code	MS Subtype	Activity	Key Clinical Notes
G35.A	Relapsing-remitting	Active by definition	Most common subtype (~85% at diagnosis); relapses + remissions; all relapse-specific DMTs authorized here
G35.B0	Primary progressive	Unspecified	Gradual worsening from symptom onset, no discrete relapses; activity unspecified — query
G35.B1	Primary progressive	Active	New T1 Gd+ lesion or clinical relapse in PPMS context
G35.B2	Primary progressive	Non-active	Stable PPMS — no new MRI lesion activity
G35.C0	Secondary progressive	Unspecified	Began as RRMS, now worsening without clear relapses; activity unspecified — query
G35.C1	Secondary progressive	Active	New MRI activity or clinical relapse superimposed on SPMS progression
G35.C2	Secondary progressive	Non-active	Steadily worsening SPMS without new MRI activity
G35.D	Unspecified	Unspecified	Only when both subtype and activity are undocumented after query — THIS CODE

CDI Query Trigger — MS Subtype and Activity Level

If the physician documents only “multiple sclerosis” without specifying subtype or activity, a CDI query is warranted at every inpatient encounter. The distinction between G35.A, G35.B0- G35.B2, and G35.C0-G35.C2 requires physician documentation and carries meaningful HCC, clinical, and authorization significance. G35.D is the appropriate default only after the query has been exhausted or the record is genuinely silent.

Pathophysiology

Multiple sclerosis is a chronic autoimmune demyelinating disease in which autoreactive T-lymphocytes and B-cells breach the blood-brain barrier and attack the myelin sheath surrounding CNS axons. The resulting demyelinating plaques — areas of inflammation, myelin loss, and reactive gliosis (sclerosis) — disrupt saltatory conduction along myelinated axons, producing the clinical deficits characteristic of MS.

Plaques form throughout the CNS but have predilection sites: the periventricular white matter, corpus callosum (Dawson’s fingers on MRI sagittal FLAIR), corticospinal tracts (motor), posterior columns (sensory, proprioception), cerebellar pathways (coordination), optic nerves (vision), and spinal cord. The location of active plaques determines the clinical presentation at any given relapse or progressive phase. Over time, axonal loss — beyond demyelination alone — drives irreversible disability accumulation independent of relapse activity.

Clinical Presentation

Patients coded to G35.D may present with any manifestation of MS across any disease course. Common inpatient presentations include:

• Acute relapse / exacerbation — new or worsening neurological deficit lasting >24 hours; treated with IV corticosteroids (Solu-Medrol)
• Motor deficits — limb weakness, hemiparesis, paraparesis; spasticity (see M62.838 or R25.2 1 per documentation specificity)
• Sensory disturbances — paresthesias, numbness, Lhermitte’s sign (electric shock sensation with neck flexion)
• Optic neuritis — painful vision loss, typically unilateral; relative afferent pupillary defect (RAPD); coded additionally as H46.x
• Cerebellar / brainstem symptoms — ataxia, dysarthria, diplopia, internuclear ophthalmoplegia (INO), vertigo
• Bladder and bowel dysfunction — neurogenic bladder (N31.x), urinary retention, incontinence — extremely common; always query and code
• Cognitive impairment — processing speed, memory, executive function
• Fatigue — one of the most disabling MS symptoms; often underdocumented

Documentation Requirements

For precise code assignment within the G35 family — and to minimize default to G35.D — physician documentation should include:

1. MS subtype — relapsing-remitting, primary progressive, or secondary progressive; established from clinical history and MRI pattern
2. Activity status — active (new MRI lesion activity or clinical relapse within the monitoring period) vs. non-active
3. Current disease status — in relapse, in remission, progressing
4. Specific neurological deficits — motor, sensory, cerebellar, visual, bladder — each supports additional ICD-10-CM code assignment
5. Disease-modifying therapy — current DMT and any changes; relevant for medical necessity and payer authorization
6. Disability level (EDSS or equivalent) — supports severity documentation

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💰 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.D maps to CMS-HCC v28: HCC 198 (Multiple Sclerosis) and RxHCC v08: HCC 159 — inherited from the prior standalone G35 mapping, which carried the same HCC 198 assignment. Verify the new G35.x subcategory codes against the current CMS crosswalk as FY2026 mapping confirmation is pending in some payer systems.

MS Complications Often Carry Independent HCC Weight

At every G35.D encounter, review and ensure complete coding of all documented MS-related complications and comorbidities:

• paraplegia / quadriplegia (G82.x) — HCC-mapped
• Hemiplegia / hemiparesis (G81.x) — HCC-mapped
• Neurogenic bladder (N31.x) — review HCC mapping
• Dysphagia (R13.1x) — may be MCC tier at DRG level
• Aspiration pneumonia (J69.0) — MCC — very high DRG impact
• Pressure ulcers (L89.x stage 3/4) — MCC
• Malnutrition (E43, E44.x) — MCC/CC tier
• Sepsis (A41.x) — MCC

Do not leave risk-adjustable complications undercoded. All conditions meeting UHDDS criteria for “other diagnoses” must be reported.

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🏥 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.

CC/MCC Capture Is Critical for MS Admissions

MS patients frequently present with significant comorbidities and complications that qualify as CCs or MCCs — UTI (N39.0), aspiration pneumonia (J69.0), pressure injuries (L89.x stage 3/4), malnutrition (E43), and sepsis (A41.x). Each qualifying CC/MCC elevates the DRG from 060 → 059 → 058 with meaningful reimbursement impact. Complete diagnosis capture is both a compliance obligation and a financial imperative.

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🔗 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 — header only
G35.A	Relapsing-remitting MS ✅	RRMS documented — most common subtype
G35.B0	Primary progressive MS, unspecified ✅	PPMS documented; activity not specified
G35.B1	Active primary progressive MS ✅	PPMS with new MRI Gd+ lesion or clinical relapse
G35.B2	Non-active primary progressive MS ✅	Stable PPMS; no new MRI lesion activity documented
G35.C0	Secondary progressive MS, unspecified ✅	SPMS documented; 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 documented
G35.D	Multiple sclerosis, unspecified ✅	Both subtype AND activity undocumented — THIS CODE

Commonly Associated Additional Diagnosis Codes

Code	Description	Coding Relevance
M62.838	Other muscle spasm	MS-related spasm at non-back, non-calf site — code additionally when documented
R25.2	Cramp and spasm	Symptom-level documentation only — mutually exclusive with M62.838; use M62.838 when disorder is established
N31.9	Neuromuscular dysfunction of bladder, unspecified	Neurogenic bladder in MS — extremely common; always query and code
H46.10	Optic neuritis, unspecified	MS presenting with optic neuritis — code additionally when documented
R13.10	Dysphagia, unspecified	MS brainstem lesion — dysphagia a common complication; may be MCC
G81.10	Flaccid hemiplegia, unspecified side	MS motor deficit — code additionally when documented
G82.20	Paraplegia, unspecified	MS spinal cord involvement with bilateral leg paralysis
J69.0	Aspiration pneumonia	MCC — complication of MS dysphagia; highest DRG impact
F06.30	Mood disorder due to known physiological condition	MS-related depression — high prevalence; code when documented
G36.0	Neuromyelitis optica (Devic disease)	Excludes 2 — may coexist if separately confirmed and documented
G37.9	Demyelinating disease of CNS, unspecified	Excludes 1 — mutually exclusive with G35.D; do not code both

Differential Demyelinating Codes

Code	Description	Coding Relevance
G36.0	Neuromyelitis optica (Devic’s)	AQP4-IgG positive; distinct from MS — do not use G35.D for NMO
G36.1	Acute and subacute hemorrhagic leukoencephalitis	Rare; distinct entity
G37.3	Acute transverse myelitis in demyelinating disease	May coexist with or precede MS diagnosis
H46.10	Optic neuritis, unspecified	Frequently the presenting symptom of MS; code additionally

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🛠️ Commonly Associated CPT Codes

Outpatient and Physician Setting Context

The CPT codes below are associated with MS evaluation, infusion management, neurological monitoring, and MS-related 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	Complex MS management — DMT adjustments, relapse assessment, MDM complexity
99214	Office visit, established patient, moderate complexity	Routine follow-up MS visit with medication management
96413	Chemotherapy administration, IV infusion, up to 1 hour	IV methylprednisolone (Solu-Medrol) for acute MS relapse — first hour
96415	Chemotherapy administration, IV infusion, each additional hour	Additional hour(s) of IV methylprednisolone infusion
96360	IV infusion, hydration, initial 31-90 minutes	Pre/post hydration with corticosteroid infusion
95930	Visual evoked potential (VEP) testing	Optic nerve conduction — screens for subclinical optic neuritis in MS
95925	Short-latency somatosensory evoked potential (SSEP)	Evaluates posterior column sensory pathway integrity
95885	Needle EMG, each extremity, limited	Evaluates for coexisting peripheral neuropathy vs. central MS deficit
70553	MRI brain without and with contrast	Standard MS surveillance MRI — gadolinium enhancement identifies active plaques
72157	MRI thoracic spine without and with contrast	Thoracic cord MS lesion assessment
72158	MRI lumbar spine without and with contrast	Conus/cauda equina MS involvement
96116	Neurobehavioral status exam, first hour	Cognitive assessment for MS-related cognitive impairment

NCCI Bundling Considerations

NCCI PTP Edits — Verify Before Billing

• 96413 (infusion) billed same DOS as E/M: Modifier -25 required on the E/M when the E/M is separately documented and medically necessary beyond the pre/post infusion assessment.
• 95930 (VEP) and 95925 (SSEP) same DOS: both are separate studies — confirm each has independent medical necessity documentation; review NCCI PTP edit status.
• 70553 (brain MRI) and 72157/72158 (spine MRI) same DOS: typically separately payable; verify LCD/NCD coverage requirements for multi-region MRI on the same date.

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🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)

When G35.D 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)	0 (Central Nervous System)	0 (Introduction)	Intrathecal medication administration (e.g., baclofen pump fill, intrathecal corticosteroid)
3 (Administration)	3 (Peripheral Vein)	0 (Introduction)	IV infusion of therapeutic substance (methylprednisolone, natalizumab, ocrelizumab)
0 (Medical & Surgical)	0 (Central Nervous System)	H (Insertion)	Intrathecal baclofen pump implantation for MS spasticity management
B (Imaging)	0 (Central Nervous System)	3 (MRI)	Brain MRI (B030ZZZ series) — structural and lesion characterization

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💊 Coding Scenarios and Examples

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Scenario 1 — MS, Subtype Undocumented, Carried Over from Pre-FY2026 Record (Outpatient)

Clinical Vignette: A 48-year-old female presents to neurology for routine follow-up. Her chart reflects a prior diagnosis of “multiple sclerosis” coded as G35 on all prior encounters through September 2025. The physician’s current note documents “multiple sclerosis — stable, continue current DMT.” No subtype is specified in the current note. Prior records in the chart reference RRMS from the initial diagnosis 8 years ago.

CPT Codes (Outpatient):

• 99214 — Office visit, established patient, moderate complexity

ICD-10-CM:

• ⚠️ Query first — prior chart documentation references RRMS from initial diagnosis; if confirmed by physician, use G35.A
• G35.D — Multiple sclerosis, unspecified (only if query yields no subtype confirmation from the current encounter provider)

Prior Chart Entries Are Not Sufficient — Current Encounter Documentation Governs

Coders cannot unilaterally apply G35.A based on older records without the current treating physician confirming the diagnosis in the current encounter documentation. A CDI query is the appropriate pathway. If the physician responds confirming RRMS → G35.A. If the physician does not respond or the subtype remains undocumented → G35.D with a documented query attempt on file.

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Scenario 2 — MS, Acute Relapse, Subtype Not Documented (Inpatient)

Clinical Vignette: A 35-year-old male is admitted with acute onset bilateral lower extremity weakness and urinary retention over 48 hours. MRI spine reveals new T2 hyperintense lesion at T6-T7 with gadolinium enhancement. Neurology consult documents: “Multiple sclerosis — acute relapse. IV Solu-Medrol initiated.” No MS subtype is specified in any note during the admission. Neurogenic bladder documented.

Principal Diagnosis:

• G35.D — Multiple sclerosis, unspecified (subtype not documented after query — MS driving admission; sequences as principal)

Additional Diagnoses:

• N31.9 — Neuromuscular dysfunction of bladder, unspecified (neurogenic bladder — document separately; supports clinical picture)
• G82.20 — Paraplegia, unspecified (if bilateral lower extremity paralysis meets documented severity threshold)

MS-DRG Assignment:

• DRG 059 — Multiple Sclerosis and Cerebellar Ataxia with CC (if N31.9 or G82.20 qualifies as CC; confirm CC/MCC tier)
• DRG 058 — with MCC if higher-tier complication documented

CDI Query Opportunity — Active Lesion Strongly Suggests G35.A or G35.B1/C1

The gadolinium-enhancing lesion on MRI is a hallmark of active disease. A CDI query asking the neurologist to specify MS subtype and confirm active vs. non-active status could upgrade G35.D to G35.A (if RRMS) or G35.B1/G35.C1 (if progressive with active lesion). Do not infer activity from imaging alone — physician documentation is required.

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Scenario 3 — MS, Aspiration Pneumonia Complication (Inpatient MCC)

Clinical Vignette: A 62-year-old female with known MS is admitted with aspiration pneumonia secondary to dysphagia from brainstem MS lesions. Physician documents “multiple sclerosis with brainstem involvement — aspiration pneumonia.” MS subtype not documented.

Principal Diagnosis:

• G35.D — Multiple sclerosis, unspecified (MS driving admission)

Additional Diagnoses:

• J69.0 — Aspiration pneumonia (MCC — elevates DRG to 058)
• R13.10 — Dysphagia, unspecified (brainstem MS complication)

MS-DRG Assignment:

• DRG 058 — Multiple Sclerosis and Cerebellar Ataxia with MCC (J69.0 is MCC — maximum DRG weight for MS grouping)

Aspiration Pneumonia Is MCC — Never Miss This

J69.0 (aspiration pneumonia) is a Major Complication/Comorbidity and moves the MS encounter from DRG 060 or 059 straight to DRG 058. In MS patients with documented brainstem disease and dysphagia, aspiration pneumonia is a predictable, clinically significant complication. Complete documentation and coding of J69.0 is both clinically accurate and the difference between the lowest and highest MS DRG weight.

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Scenario 4 — Newly Diagnosed MS, Subtype Established at Discharge (Inpatient)

Clinical Vignette: A 28-year-old female is admitted with new-onset bilateral optic neuritis and right arm numbness. MRI brain and spine reveal multiple periventricular white matter lesions and a right cervical cord lesion, consistent with MS. CSF oligoclonal bands positive. Neurology discharge summary: “Newly diagnosed relapsing-remitting multiple sclerosis. Initiating dimethyl fumarate at discharge.”

Principal Diagnosis:

• G35.A — Relapsing-remitting multiple sclerosis (subtype documented at discharge — G35.A is correct; do NOT use G35.D when RRMS is confirmed in the record)

Additional Diagnoses:

• H46.10 — Optic neuritis, unspecified (bilateral optic neuritis as presenting symptom — code additionally)

G35.D Is Not Needed When Subtype Is Documented

This scenario illustrates the upgrade: physician documents RRMS at discharge → G35.A is the correct and only MS code. G35.D is not assigned alongside G35.A — one code captures the MS diagnosis at the appropriate specificity level. G35.D would only apply here if the discharge summary had not specified the subtype.

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⚠️ Coding Pitfalls and Tips

	Pitfall or Tip
❌	Do not submit G35 alone after October 1, 2025 — it is a non-billable parent code and will reject; minimum valid code is G35.D for unspecified MS
❌	Do not default to G35.D without a CDI query attempt — subtype and activity documentation may exist elsewhere in the record or can be obtained via query
❌	Do not assign G35.D simultaneously with G37.9 — Excludes 1; mutually exclusive
❌	Do not use G35.D for NMO / Devic disease — assign G36.0; NMO is a distinct condition with distinct pathophysiology and treatment
❌	Do not infer MS subtype or activity from imaging alone — gadolinium enhancement suggests active disease but physician documentation is required for G35.B1 or G35.C1 assignment
✅	Query every G35.D in the inpatient setting — ask neurologist/attending to document subtype (RRMS, PPMS, SPMS) and current activity status
✅	G35.D carries CMS-HCC v28: HCC 198 / RxHCC v08: HCC 159 — confirm mapping on current CMS crosswalk for new FY2026 subcategory codes
✅	Capture all MS complications as additional diagnoses — neurogenic bladder (N31.x), dysphagia (R13.1x), aspiration pneumonia (J69.0), hemiplegia (G81.x) — these drive DRG tier and RAF
✅	J69.0 (aspiration pneumonia) is MCC and moves MS encounter to DRG 058 — never miss this complication in MS patients with brainstem disease
✅	G35.D sequences as principal when MS is the reason for admission and no more specific subtype is documented; groups to MDC 01 / DRG 058-060
✅	Sweep for HCC-bearing complications at every G35.D encounter — paraplegia, hemiplegia, malnutrition, pressure ulcers carry independent RAF weight

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📚 Sources

1. CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. Tabular List — G35.D; G35 parent code restructure and new G35.A-G35.D subcategory structure effective October 1, 2025; Excludes 1/Excludes 2 notations.

2. CMS. FY2026 Addendum B — ICD-10-CM New, Revised, and Deleted Diagnosis Codes. G35A, G35B0-B2, G35C0-C2, G35D added; G35 deleted as billable code.

3. 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.

4. CMS. IPPS Final Rule FY2026 — MS-DRG Definitions Manual v43. MDC 01 logic tables — DRG 058/059/060 Multiple Sclerosis and Cerebellar Ataxia.

5. CMS. ICD-10-PCS Reference Manual FY2026. Section 0 (Medical & Surgical), Body System 0 (CNS); Section 3 (Administration).

6. Lublin FD, et al. Defining the clinical course of multiple sclerosis: The 2013 revisions. Neurology. 2014;83(3):278-286. (Clinical basis for RRMS/PPMS/SPMS/activity distinctions reflected in FY2026 codes.)

7. AMA. CPT Professional Edition 2026. Neurology and Neuromuscular Procedures (95800-96020); Evaluation and Management guidelines; Infusion/Injection subsection.

8. CMS. NCCI Policy Manual for Medicare Services, current version. Neurology chapter and general correct coding principles.