What is ICD-10 code G36.8?

G36.8 is the ICD-10-CM diagnosis code for Other specified acute disseminated demyelination. Other rare forms of sudden-onset inflammation affecting multiple areas of the brain and spinal cord, causing demyelination and neurological symptoms. It belongs to the ICD-10-CM chapter for diseases of the nervous system (g00-g99). G36.8 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. G36.8 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. G36.8 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. G36.8 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does G36.8 map to under V28?

G36.8 maps to CMS-HCC V28 HCC 198 (Multiple Sclerosis). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM G36.8: Other specified acute

G36.8 maps to CMS-HCC V28 198. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · free HCC coding tools

ICD-10-CM Code View

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Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupG36.8Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Demyelinating diseases of the central nervous system (G35-G37)

G36.8

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Other specified acute disseminated demyelination

Other rare forms of sudden-onset inflammation affecting multiple areas of the brain and spinal cord, causing demyelination and neurological symptoms.

Buddy Insight

Other specified acute disseminated demyelination captures rare forms of sudden-onset central nervous system demyelination that do not fit other G36 categories.

CMS-HCC V28

Mapped

HCC 198

Multiple Sclerosis

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

Mapped

HCC 77

Multiple Sclerosis

Code-level coefficient reference

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

G36Other acute disseminated demyelination

G36.8Other specified acute disseminated demyelination

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for G36.8 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for G36.8 in this effective period.

Related Child Codes

Official

G36.0Neuromyelitis optica [Devic]

G36.1Acute and subacute hemorrhagic leukoencephalitis [Hurst]

G36.9Acute disseminated demyelination, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for G36.8 in this effective period.

Excludes 1

Official

postinfectious encephalitis and encephalomyelitis NOS (G04.01)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for G36.8 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for G36.8 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for G36.8 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation specifying the type of acute disseminated demyelination

Neuroimaging (MRI) showing acute demyelinating lesions in multiple CNS areas

Documentation of acute onset timeline (days to weeks)

Evidence that NMO (G36.0) and hemorrhagic leukoencephalitis (G36.1) have been excluded

MEAT Support

HCC Buddy guidance

Documentation specifying the type of acute disseminated demyelination

Neuroimaging (MRI) showing acute demyelinating lesions in multiple CNS areas

Documentation of acute onset timeline (days to weeks)

Evidence that NMO (G36.0) and hemorrhagic leukoencephalitis (G36.1) have been excluded

Audit Caution

HCC Buddy guidance

Using G36.9 (unspecified) when the provider has documented a specific type of acute demyelination

Confusing acute disseminated demyelination with a first attack of multiple sclerosis

Not following up to reclassify the diagnosis if the condition evolves into a chronic demyelinating disease

Failing to document the specific subtype, making the 'other specified' designation unsupportable on audit

Common Mistakes

HCC Buddy guidance

G36.0 — Neuromyelitis optica; specific disease with AQP4 antibodies

G36.1 — Acute hemorrhagic leukoencephalitis; has hemorrhagic component

G36.9 — Acute disseminated demyelination, unspecified; use only when the specific type cannot be determined

G35 — Multiple sclerosis; chronic relapsing condition, not acute disseminated

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 G36.8 an HCC code?

Yes. G36.8 (Other specified acute disseminated demyelination) maps to HCC 198, Multiple Sclerosis under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.647. 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: G36.8 is billable and maps to V28 HCC 198, Multiple Sclerosis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: G36.8
Description: Other specified acute disseminated demyelination
HCC (V28): HCC 198 — Multiple Sclerosis
RAF reference coefficient: 0.647
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 198, Multiple Sclerosis

0.647

ESRDHCC 77, Multiple Sclerosis

Not separately weighted

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 G36.8 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for G36.8

For G36.8 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 G36.8 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

G36.8 is the ICD-10-CM diagnosis code for other specified acute disseminated demyelination. Other rare forms of sudden-onset inflammation affecting multiple areas of the brain and spinal cord, causing demyelination and neurological symptoms. G36.8 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering demyelinating diseases of the central nervous system (g35-g37).

Under the CMS-HCC V28 risk adjustment model, G36.8 maps to Multiple Sclerosis (HCC 198) with a source-labeled community, non-dual, aged reference coefficient of 0.647. No V24 mapping is shown for G36.8; use the applicable model and payment year when reviewing the V28 mapping. 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. 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.

Use this code only after excluding G36.0 and G36.1; document the specific type of acute disseminated demyelination. Because G36.8 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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 G36.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only after excluding G36.0 and G36.1; document the specific type of acute disseminated demyelination
•Provide clinical details about affected CNS regions and acute presentation timeline

Clinical Significance

Other specified acute disseminated demyelination captures rare forms of sudden-onset central nervous system demyelination that do not fit other G36 categories. These conditions cause acute neurological dysfunction and require urgent diagnostic evaluation and treatment. Accurate coding ensures proper recognition of these complex neurological emergencies for risk adjustment.

Documentation Requirements

✓Documentation specifying the type of acute disseminated demyelination
✓Neuroimaging (MRI) showing acute demyelinating lesions in multiple CNS areas
✓Documentation of acute onset timeline (days to weeks)
✓Evidence that NMO (G36.0) and hemorrhagic leukoencephalitis (G36.1) have been excluded
✓Treatment documentation (corticosteroids, plasma exchange, or IVIG)
✓Follow-up plan to determine if condition is monophasic or relapsing

Commonly Confused Codes

•G36.0: Neuromyelitis optica; specific disease with AQP4 antibodies
•G36.1: Acute hemorrhagic leukoencephalitis; has hemorrhagic component
•G36.9: Acute disseminated demyelination, unspecified; use only when the specific type cannot be determined
•G35: Multiple sclerosis; chronic relapsing condition, not acute disseminated
•G04.00: Acute disseminated encephalitis and encephalomyelitis; may overlap clinically