ICD-10 code G08: Intracranial and intraspinal phlebitis

Key Takeaways

ICD-10 code G08 is a billable diagnosis code for intracranial and intraspinal phlebitis and thrombophlebitis, classified under Chapter 6 (Diseases of the Nervous System).

G08 covers septic forms only: the five inclusion terms all specify septic embolism, phlebitis, endophlebitis, thrombophlebitis, or thrombosis of intracranial or intraspinal venous sinuses.

G08’s excludes notes are mostly Type 1: I67.6 (nonpyogenic intracranial thrombosis) and the obstetric codes are Excludes1 and cannot be reported with G08. G95.1 (nonpyogenic intraspinal phlebitis) is the only Type 2 Excludes and may be reported alongside G08 when both conditions coexist.

Pabau’s claims management software and structured patient records support accurate G08 documentation and cleaner claims submission for neurology and hospital-based coders.

ICD-10 code G08 is a valid, billable ICD-10-CM diagnosis code for intracranial and intraspinal phlebitis and thrombophlebitis. It belongs to Chapter 6 of ICD-10-CM, which covers Diseases of the Nervous System (G00-G99), within the block G00-G09 (Inflammatory diseases of the central nervous system).

The condition describes inflammation of veins (phlebitis) or inflammation with concurrent thrombosis (thrombophlebitis) affecting the venous structures inside the skull or spinal canal. These venous structures include the dural venous sinuses (superior sagittal sinus, transverse sinus, sigmoid sinus, cavernous sinus) and intraspinal veins. When infection drives the thrombotic process, the condition is classified here under G08.

Clinical significance

Septic intracranial thrombophlebitis most commonly arises as a complication of facial infections, sinusitis, otitis media, or mastoiditis. Cavernous sinus thrombosis is the most recognized presentation, typically secondary to facial cellulitis or dental abscess.

Superior sagittal sinus thrombosis and transverse sinus thrombosis may occur in the context of meningitis or bacteremia. The common feature across all G08 presentations is the septic (infectious) etiology, which separates them from non-pyogenic venous thromboses coded elsewhere in ICD-10-CM.

Billable status and code hierarchy for G08

G08 is a billable/specific ICD-10-CM code. It can be used on claims to indicate a diagnosis for reimbursement purposes. According to the Centers for Medicare and Medicaid Services (CMS), G08 is current for fiscal year 2026 with no pending revisions.

G08 does not have any child or subcategory codes. It is a terminal code within the G00-G09 block, meaning no additional specificity digits are available under this heading in ICD-10-CM.

Inclusion terms for G08

The ICD-10-CM tabular list specifies five inclusion terms under G08. All five share the qualifier “septic,” confirming that G08 applies exclusively to infectious presentations. Non-infectious (non-pyogenic) venous thrombosis of the intracranial or intraspinal system maps to different codes covered in the Excludes section below.

• Septic embolism of intracranial or intraspinal venous sinuses and veins
• Septic endophlebitis of intracranial or intraspinal venous sinuses and veins
• Septic phlebitis of intracranial or intraspinal venous sinuses and veins
• Septic thrombophlebitis of intracranial or intraspinal venous sinuses and veins
• Septic thrombosis of intracranial or intraspinal venous sinuses and veins

Synonyms reported in the coding literature for G08 include cavernous sinus syndrome, cavernous sinus thrombosis, cerebral venous thrombosis (septic), dural venous sinus thrombosis (without infarction, septic), and cerebral venous sinus thrombosis (CVST) in the setting of infection. Coders should confirm the clinician’s documentation specifies a septic or infectious etiology before assigning G08.

Excludes notes for G08: When to use G95.1 and I67.6

G08 carries both Type 1 and Type 2 Excludes notes, and the distinction is critical for accurate coding. A Type 1 Excludes note (Excludes1) means the excluded code can never be reported with G08, because the two conditions are mutually exclusive. A Type 2 Excludes note (Excludes2) means the excluded condition is not part of G08 but the two codes may be reported together when both conditions genuinely coexist in the same encounter.

The excludes codes for G08 are listed below alongside the clinical scenarios where each applies. Note that I67.6 and the obstetric codes are Type 1 (never coded with G08), while G95.1 is the only Type 2 Excludes.

The septic-versus-non-pyogenic distinction is the primary axis for code selection in intracranial venous thrombosis. Payer edits and clinical documentation improvement (CDI) queries most frequently arise at this axis. When the medical record is ambiguous, a physician query is the appropriate next step, not a coder assumption.

Obstetric context excludes

G08 also carries Type 1 Excludes notes for venous embolism and thrombosis complicating abortion, ectopic or molar pregnancy (O00-O07, O08.7) and thrombosis complicating pregnancy, childbirth, and the puerperium (O22.5, O87.3). Because these are Type 1 Excludes, G08 is not reported alongside them. When intracranial venous thrombosis occurs in an obstetric context, the appropriate obstetric complication code from the O-chapter is assigned instead of G08.

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Pabau helps neurology and hospital-based practices capture the septic versus non-pyogenic distinction at the point of care, supporting cleaner G08 claims and fewer CDI queries.

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ICD-9 crosswalk and code history

ICD-10 code G08 converts directly to ICD-9-CM code 325 (Phlebitis and thrombophlebitis of intracranial venous sinuses) via CMS General Equivalence Mappings. The conversion is a one-to-one forward and backward map, meaning there is no ambiguity in the crosswalk for legacy data reconciliation or longitudinal claims analysis.

Practices transitioning historical billing data or responding to retrospective payer audits covering pre-October 2015 encounters should use ICD-9 code 325 as the equivalent code. Note that G08 captures only the septic form of intracranial venous thrombosis; non-pyogenic cerebral venous sinus thrombosis is coded to I67.6 or I63.6, so administrative-data analyses of CVST typically span all three codes. Code identities can be cross-checked against ICD List, and for current FY 2026 code validation, use the CDC/NCHS ICD-10-CM web tool.

Related ICD-10 diagnosis codes

Coders working with G08 regularly encounter the related codes below. Distinguishing these codes correctly at the encounter level reduces retrospective audits and supports appropriate DRG assignment for inpatient claims.

• G95.1 – Vascular myelopathies (includes nonpyogenic intraspinal phlebitis and thrombophlebitis)
• I63.6 – Cerebral infarction due to cerebral venous thrombosis, non-pyogenic
• I67.6 – Nonpyogenic thrombosis of intracranial venous system
• G00-G09 – Block: Inflammatory diseases of the central nervous system (parent block for G08)
• A32.12 – Listerial meningitis and meningoencephalitis (when Listeria is the causative organism for septic thrombosis)
• B37.5 – Candidal meningitis (fungal septic thrombosis context)
• Z87.39 – Personal history of other conditions of the nervous system (relevant for follow-up encounters after G08 treatment)

Documentation requirements for accurate G08 coding

When cerebral venous sinus thrombosis leads to infarction in a non-pyogenic context, I63.6 takes over from G08 as the primary code. When the thrombosis is non-pyogenic and does not cause infarction, I67.6 applies. G08 remains the correct primary code when the thrombosis is documented as septic, infectious, or pyogenic, regardless of whether infarction has occurred.

Coding G08 accurately depends on clinical documentation that explicitly supports the septic etiology. The table below summarizes the key documentation elements CDI specialists and coders should look for in the medical record before assigning this code.

Practices using patient intake software and structured clinical templates can embed these documentation prompts directly into the neurology encounter workflow. Capturing the septic-versus-non-pyogenic distinction at the point of care eliminates the most common retrospective query. Medical records management systems that flag missing documentation fields before a note is finalized reduce coding rework across high-complexity neurological presentations like G08.

For practices managing medical forms documentation workflows, integrating a standardized neurology assessment form that includes septic etiology checkboxes, affected venous structures, and imaging findings significantly lowers the CDI query rate on G08 encounters.

Coding workflow guidance for G08 in neurology and hospital settings

Hospital coders and neurology billing teams encounter G08 most often in the context of inpatient admissions for complicated sinusitis, head and neck infections, or septicemia with neurological sequelae. The coding decision tree below reflects the most common scenarios.

1. Confirm septic etiology. Check attending notes, ID consult, and lab/culture data for evidence of infection. No infection documented: do not assign G08.
2. Identify the affected structure. Cavernous sinus, superior sagittal sinus, transverse sinus, sigmoid sinus, or intraspinal veins. Document the structure in the record.
3. Check for infarction. If infarction is documented alongside the venous thrombosis, code the infarction to its specific code; note that I63.6 applies only to non-pyogenic venous infarction, so confirm the documented etiology before assigning it.
4. Rule out obstetric context. Confirm the patient is not pregnant or within the puerperium period. Obstetric context routes coding to the O-chapter with G08 as secondary.
5. Identify the causative organism. Assign an additional B95-B97 code for bacterial, viral, or fungal agents when the organism is confirmed.
6. Sequence principal diagnosis. In most inpatient admissions, the underlying infection (e.g. sinusitis, otitis media) will be the principal diagnosis with G08 as a secondary complication code, unless the thrombosis was the condition that occasioned the admission.

Neurology practices using claims management software with built-in code validation can flag G08 submissions that lack a secondary infectious organism code or that omit imaging confirmation from the record. This catches the most common denial triggers before the claim leaves the practice. Our guide on EHR integration workflows covers how practice management platforms can connect coding validation to clinical documentation in real time.

For practices covering broader neurological and psychiatric presentations, understanding how Chapter 6 codes interact with adjacent chapters is foundational. The mental health EMR guidance covers cross-chapter coding scenarios where neurological conditions intersect with psychiatric presentations, a common comorbidity pattern in complex CNS infections.

Coding context: G08 and the ICD-10-CM Chapter 6 framework

G08 sits within the G00-G09 block alongside meningitis codes (G00-G03), encephalitis codes (G04-G05), and intracranial and intraspinal abscess codes (G06-G07). This block captures the infectious and inflammatory conditions of the CNS that require the most precise documentation to code correctly, because each code in the block has specific causal or pathological criteria that determine code assignment.

The WHO ICD-10 browser provides the international classification context for G08. In the U.S., the ICD-10-CM adaptation maintained by CMS and NCHS is the operative version, with G08’s definition and excludes notes derived from the official tabular list. Practices using the AAPC Codify ICD-10-CM lookup can cross-reference G08 with related codes in real time during chart review.

The same documentation discipline applies across diagnostic chapters. For a contrasting example outside the nervous-system chapter, our reference on the ICD-10 code for autistic disorder shows how explicit clinical documentation drives correct code assignment. The underlying principle is consistent: Clinical documentation must explicitly name the condition meeting the code’s definitional criteria.

For practices managing HIPAA-compliant clinical documentation, ensuring that neurology encounter notes containing G08 include all required elements before finalization is both a coding accuracy requirement and a compliance obligation. Incomplete records that later require physician queries create documentation gaps that can attract payer attention during retrospective audits.

Conclusion

Accurate coding of intracranial and intraspinal venous thrombosis hinges on a single clinical question: Was the cause septic or non-pyogenic? When the answer is septic, ICD-10 code G08 is the correct, billable code. When it is non-pyogenic, coders must choose between I67.6 (without infarction) and I63.6 (with infarction); I67.6 is a Type 1 Excludes from G08, meaning the two are never reported together.

Pabau’s claims management software helps neurology and hospital-based practices embed documentation prompts directly into the clinical workflow, reducing CDI queries on complex codes like G08. To see how Pabau supports accurate neurological coding and documentation, book a demo.

Continue your research

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