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ICD-10-CM B01.12: Varicella myelitis

B01.12 is the billable ICD-10-CM code for varicella myelitis, in category B01 (Varicella [chickenpox]) of the Viral infections characterized by skin and mucous membrane lesions section. As a principal diagnosis it groups to MS-DRG 023 Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator, MS-DRG 024 Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis without MCC, MS-DRG 097 Non-Bacterial Infection of Nervous System Except Viral Meningitis with MCC (MDC 01 MDC 01: Diseases and Disorders of the Nervous System). It maps to HCC 182 (Spinal Cord Disorders/Injuries) in CMS-HCC V28. As a secondary diagnosis it is an MCC, excluded with 31 principal diagnoses. 1 LCD billing and coding article lists it as covered.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
B01.12
billable FY2027 ICD-10-CM code
Category
B01 Varicella [chickenpox]
Chapter
1: Certain infectious and parasitic diseases (A00-B99)
CC/MCC (MS-DRG v44)
MCC
CMS-HCC V28
HCC 182
POA reporting
Required

Tabular list notes for B01.12

The tabular list has no notes on B01.12 itself; the notes below apply from its parent headings.

Inherited from B01.1 (Varicella encephalitis, myelitis and encephalomyelitis)

Inclusion terms
  • Postchickenpox encephalitis, myelitis and encephalomyelitis

MS-DRG grouping when B01.12 is the principal diagnosis

MS-DRG v44 groups for B01.12 as principal diagnosis
MDCMS-DRGs
01 MDC 01: Diseases and Disorders of the Nervous System023024097098099

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for B01.12 shows the full grouping logic.

CC/MCC status and inpatient edits

As a secondary diagnosis, B01.12 is an MCC under MS-DRG v44, unless the principal diagnosis is one of the 31 codes in its exclusion list. Check B01.12 against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.

CMS-HCC V28 risk adjustment

In the PY2027 mapping, B01.12 maps to HCC 182 (Spinal Cord Disorders/Injuries). The HCC lookup shows the RAF weight and the hierarchy.

LCD billing and coding articles that list B01.12

1 current Medicare billing and coding article lists B01.12 among the diagnoses that support medical necessity for the services they cover.

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Frequently asked questions

What does ICD-10-CM B01.12 mean?

B01.12 means varicella myelitis. It is one of 7 billable codes under B01, varicella [chickenpox].

Which MS-DRG does B01.12 group to?

As the principal diagnosis, B01.12 groups to MS-DRG 023 Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator, MS-DRG 024 Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis without MCC, MS-DRG 097 Non-Bacterial Infection of Nervous System Except Viral Meningitis with MCC (MDC 01 MDC 01: Diseases and Disorders of the Nervous System) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Does B01.12 map to an HCC?

Yes: HCC 182, Spinal Cord Disorders/Injuries, in the PY2027 CMS-HCC V28 mapping.

Is B01.12 a CC or MCC?

B01.12 is an MCC under MS-DRG v44; 31 principal diagnoses exclude it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.