What is ICD-10 code B02.21?

B02.21 is the ICD-10-CM diagnosis code for Postherpetic geniculate ganglionitis. Nerve pain and inflammation affecting the geniculate ganglion (a nerve cluster in the facial nerve) occurring after a shingles infection. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). B02.21 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. B02.21 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. B02.21 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. B02.21 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.

What is the V28 vs V24 difference for B02.21?

B02.21 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards B02.21 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

What should coders know when reporting B02.21?

This is a specific postherpetic complication affecting the facial nerve pathway Document the timing and severity of pain to support medical necessity for treatment

B02.21: Postherpetic geniculate ganglionitis — ICD-10

ICD-10-CM Code View

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Code lookupB02.21Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Viral infections characterized by skin and mucous membrane lesions (B00-B09)

B02.21

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

Postherpetic geniculate ganglionitis

Nerve pain and inflammation affecting the geniculate ganglion (a nerve cluster in the facial nerve) occurring after a shingles infection.

Buddy Insight

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Not risk-adjusted for this model/period.

RAF 0

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Not risk-adjusted for this model/period.

RAF 0

RXHCC

Mapped

HCC 168

Trigeminal and Postherpetic N...

RAF 0.0

Code Trumping

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Code Book Path

Official

B02Zoster [herpes zoster]

B02.2Zoster with other nervous system involvement

B02.21Postherpetic geniculate ganglionitis

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for B02.21 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for B02.21 in this effective period.

Related Child Codes

Official

B02.22Postherpetic trigeminal neuralgia

B02.23Postherpetic polyneuropathy

B02.24Postherpetic myelitis

B02.29Other postherpetic nervous system involvement

Includes

Official

ICD-10-CM does not list Includes notes for B02.21 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for B02.21 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for B02.21 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for B02.21 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for B02.21 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

History of herpes zoster affecting the ear or facial region

Clinical findings: facial nerve palsy, vesicles on ear/external auditory canal, hearing loss, vertigo

Timing: symptoms persist after resolution of the acute shingles episode

Pain assessment: character, severity, distribution along facial nerve pathway

MEAT Support

HCC Buddy guidance

History of herpes zoster affecting the ear or facial region

Clinical findings: facial nerve palsy, vesicles on ear/external auditory canal, hearing loss, vertigo

Timing: symptoms persist after resolution of the acute shingles episode

Pain assessment: character, severity, distribution along facial nerve pathway

Audit Caution

HCC Buddy guidance

Coding Bell palsy (G51.0) when facial paralysis is actually due to postherpetic geniculate ganglionitis — the shingles etiology changes the code

Confusing geniculate ganglionitis with trigeminal neuralgia — different nerves with different distributions

Not documenting the temporal relationship between the shingles episode and the ongoing ganglionitis

Missing associated complications like sensorineural hearing loss that should be coded separately

Common Mistakes

HCC Buddy guidance

B02.22 (Postherpetic trigeminal neuralgia) — Affects the trigeminal nerve (face sensation), not the facial nerve (motor function/hearing); different nerve pathways

G51.0 (Bell palsy) — Idiopathic facial paralysis; geniculate ganglionitis has a known herpes zoster etiology with vesicles

B02.29 (Other postherpetic nervous system involvement) — Use B02.21 when the geniculate ganglion is specifically affected

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is B02.21 an HCC code?

No. B02.21 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

HCC Category Mapping

RxHCCHCC 168, Trigeminal and Postherpetic Neuralgia

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work B02.21 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for B02.21

For B02.21to 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 B02.21 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

B02.21 is the ICD-10-CM diagnosis code for postherpetic geniculate ganglionitis. Nerve pain and inflammation affecting the geniculate ganglion (a nerve cluster in the facial nerve) occurring after a shingles infection. B02.21 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering viral infections characterized by skin and mucous membrane lesions (b00-b09).

B02.21 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

This code does not map to a CMS-HCC V28 payment category. Capture depends on documentation that supports the diagnosis; verify the HCC assignment against the current CMS mapping for the applicable payment year. Coders reviewing B02.21 should check whether additional documentation would support a more specific child code in the same hierarchy that does map to a payment HCC, capturing the correct specificity is the highest-impact RAF improvement available within accurate coding.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for B02.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This is a specific postherpetic complication affecting the facial nerve pathway
•Document the timing and severity of pain to support medical necessity for treatment

Clinical Significance

Postherpetic geniculate ganglionitis is a complication of herpes zoster involving the facial nerve's geniculate ganglion, which can cause Ramsay Hunt syndrome with facial paralysis, hearing loss, and severe pain. This condition reflects ongoing nerve damage after shingles resolution and often requires prolonged pain management.

Documentation Requirements

✓History of herpes zoster affecting the ear or facial region
✓Clinical findings: facial nerve palsy, vesicles on ear/external auditory canal, hearing loss, vertigo
✓Timing: symptoms persist after resolution of the acute shingles episode
✓Pain assessment: character, severity, distribution along facial nerve pathway
✓Audiometric testing results if hearing loss is present

Commonly Confused Codes

•B02.22 (Postherpetic trigeminal neuralgia): Affects the trigeminal nerve (face sensation), not the facial nerve (motor function/hearing); different nerve pathways
•G51.0 (Bell palsy): Idiopathic facial paralysis; geniculate ganglionitis has a known herpes zoster etiology with vesicles
•B02.29 (Other postherpetic nervous system involvement): Use B02.21 when the geniculate ganglion is specifically affected