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G43.409 ICD-10-CM Code: Hemiplegic migraine, not intractable, without status migrainosus

G43.409 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · free HCC coding tools

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Code lookupG43.409

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Episodic and paroxysmal disorders (G40-G47)

G43.409

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

Hemiplegic migraine, not intractable, without status migrainosus

A rare type of migraine causing temporary weakness on one side of the body that responds to treatment and is not in a prolonged migraine state.

Buddy the Bee presenting code insight

Buddy Insight

Hemiplegic migraine is a rare and serious migraine subtype characterized by temporary motor weakness or paralysis on one side of the body, mimicking stroke presentation.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

N/A

—

Not mapped

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

N/A

—

Not mapped

ESRD/PACE

N/A

—

Not mapped

RXHCC

HCC 166

Code-level coefficient reference

Code Book Path

Official
G43.4Hemiplegic migraineG43.40Hemiplegic migraine, not intractableG43.409Hemiplegic migraine, not intractable, without status migrainosus

Inclusion Terms

Official
  • Hemiplegic migraine NOS
  • Familial migraineInherited from G43.4, G43.40
  • Sporadic migraineInherited from G43.4, G43.40
  • Hemiplegic migraine without refractory migraineInherited from G43.4, G43.40

Excludes 2

Official
  • certain conditions originating in the perinatal period (P04-P96)Inherited from G00-G99, G43
  • certain infectious and parasitic diseases (A00-B99)Inherited from G00-G99, G43
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from G00-G99, G43
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from G00-G99, G43
  • endocrine, nutritional and metabolic diseases (E00-E88)Inherited from G00-G99, G43
  • injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from G00-G99, G43
  • neoplasms (C00-D49)Inherited from G00-G99, G43
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from G00-G99, G43
  • headache NOS (R51.9)Inherited from G00-G99, G43
  • headache syndromes (G44.-)Inherited from G00-G99, G43

Related Codes

Official
G43.401Hemiplegic migraine, not intractable, with status migrainosus

Includes

Official

No Includes notes are included in this display for G43.409. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • lower half migraine (G44.00)Inherited from G43

Code First

Official

No Code First sequencing instructions are included in this display for G43.409. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)Inherited from G43

Code Also

Official

No Code Also instructions are included in this display for G43.409. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Documented unilateral motor weakness or hemiplegia during migraine episode
Neurological examination findings differentiating from stroke (reversibility, associated aura symptoms)
Characterization as not intractable (responsive to treatment) vs. intractable
Documentation of episode duration (status migrainosus = >72 hours; absence should be clear)

MEAT Support

HCC Buddy guidance
Documented unilateral motor weakness or hemiplegia during migraine episode
Neurological examination findings differentiating from stroke (reversibility, associated aura symptoms)
Characterization as not intractable (responsive to treatment) vs. intractable
Documentation of episode duration (status migrainosus = >72 hours; absence should be clear)

Audit Caution

HCC Buddy guidance
Failing to distinguish hemiplegic migraine from common migraine with aura — motor weakness is the defining feature
Not clarifying intractable vs. not intractable status; intractable means the migraine has failed to respond to treatment
Confusing status migrainosus (>72 hours) with a severe but shorter episode; duration must be documented
Coding stroke (I63.x) when presentation is actually hemiplegic migraine — always verify with imaging

Common Mistakes

HCC Buddy guidance
G43.001-G43.019 (Migraine without aura) — lacks the motor weakness/hemiplegia component that defines hemiplegic migraine
G43.101-G43.119 (Migraine with aura) — has sensory/visual aura but NOT motor weakness; hemiplegic migraine specifically requires motor involvement
I63.x (Cerebral infarction) — hemiplegic migraine mimics stroke but is reversible; requires imaging to differentiate
G43.601-G43.619 (Persistent migraine aura with cerebral infarction) — use when migraine aura symptoms persist AND imaging confirms infarction

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 G43.409 an HCC code?

G43.409 is not in the CMS-HCC V28 or V24 community payment model. G43.409 has a separate mapping under the Part D RxHCC model (HCC 166 (Migraine Headaches)); the applicable result needs member context.

Code
G43.409
Description
Hemiplegic migraine, not intractable, without status migrainosus
HCC (V28)
No CMS-HCC V28 mapping
RAF reference coefficient
—
Billable
Yes
Payment year
2026

HCC Category Mapping

RxHCCHCC 166, Migraine Headaches
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 G43.409 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for G43.409

For G43.409, 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

G43.409 is the ICD-10-CM diagnosis code for hemiplegic migraine, not intractable, without status migrainosus. A rare type of migraine causing temporary weakness on one side of the body that responds to treatment and is not in a prolonged migraine state. G43.409 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering episodic and paroxysmal disorders (g40-g47).

G43.409 has no mapping under the CMS-HCC V28 or V24 community payment models. G43.409 has a separate mapping under the Part D RxHCC model (HCC 166 (Migraine Headaches)); the applicable result needs member context. Do not assign V28 risk adjustment value from this page; verify the applicable model and payment year before using this code for risk adjustment.

Document the specific neurological deficits (weakness location and duration) clearly.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for G43.409 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Document the specific neurological deficits (weakness location and duration) clearly
  • •Hemiplegic migraine requires exclusion of other serious conditions like stroke

Clinical Significance

Hemiplegic migraine is a rare and serious migraine subtype characterized by temporary motor weakness or paralysis on one side of the body, mimicking stroke presentation. Accurate coding is critical because hemiplegic migraine requires distinct management protocols and may indicate increased cerebrovascular risk. This code maps to RxHCC 166 (Severe Head Injury) in the prescription drug risk adjustment model, impacting pharmacy cost predictions.

Documentation Requirements

  • ✓Documented unilateral motor weakness or hemiplegia during migraine episode
  • ✓Neurological examination findings differentiating from stroke (reversibility, associated aura symptoms)
  • ✓Characterization as not intractable (responsive to treatment) vs. intractable
  • ✓Documentation of episode duration (status migrainosus = >72 hours; absence should be clear)
  • ✓Family history of hemiplegic migraine if applicable (familial vs. sporadic subtype)
  • ✓Neuroimaging results (CT/MRI) to exclude cerebrovascular accident
  • ✓Current treatment plan and medication regimen

Commonly Confused Codes

  • •G43.001-G43.019 (Migraine without aura): lacks the motor weakness/hemiplegia component that defines hemiplegic migraine
  • •G43.101-G43.119 (Migraine with aura): has sensory/visual aura but NOT motor weakness; hemiplegic migraine specifically requires motor involvement
  • •I63.x (Cerebral infarction): hemiplegic migraine mimics stroke but is reversible; requires imaging to differentiate
  • •G43.601-G43.619 (Persistent migraine aura with cerebral infarction): use when migraine aura symptoms persist AND imaging confirms infarction
  • •G81.x (Hemiplegia/hemiparesis): sequela codes for established paralysis, not episodic migraine-related weakness

Child Codes

G43.401Hemiplegic migraine, not intractable, with status migrainosus
G43.409Hemiplegic migraine, not intractable, without status migrainosus

Code Hierarchy

└G43Migraine└G43.4Hemiplegic migraine└G43.40Hemiplegic migraine, not intractable└G43.409Hemiplegic migraine, not intractable, without status migrainosus
└G43.409Hemiplegic migraine, not intractable, without status migrainosus

Also searched as

  • G43 409
  • G43409

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