RFA vs Medial Branch Block: Complete Coding Workflow for CPT 64490–64495 & 64633–64636

To clearly understand how these two procedures differ in both clinical purpose and coding approach, here’s a side-by-side comparison:

Quick Insight:

MBB answers the question “Is this the source of pain?”

RFA answers “How do we treat it long-term?”

Accurate coding for both Medial Branch Blocks (MBB) and Radiofrequency Ablation (RFA) depends on one key concept: facet joint levels.

Each facet joint is formed between two adjacent vertebrae. For example:

• L4–L5 = one facet joint (one level)
• C5–C6 = one facet joint (one level)

Even though multiple nerves are involved, this still counts as one level for coding purposes.

Two medial branch nerves supply each facet joint:

• One from the same level
• One from the level above

Example:

The L4–L5 facet joint is innervated by:

• L3 medial branch nerve
• L4 medial branch nerve

So, during a procedure:

The physician may inject or ablate two nerves

But for coding → it is still ONE level

Physicians often document procedures like this:

“Injected L3, L4 medial branches”

“Ablation performed at L3, L4, L5 medial branches”

This can confuse coders into thinking multiple levels were treated.

Correct interpretation:

L3 + L4 medial branches = L4–L5 joint (1 level)

L3 + L4 + L5 medial branches = 2 joints (L3–L4 and L4–L5)

Think of it like this:

2 nerves = 1 joint = 1 level

4 nerves = 2 joints = 2 levels

Always translate documentation from:

“Nerve-based language” → into “joint-based coding”

This single habit can significantly improve:

• Coding accuracy
• Claim acceptance rates
• Audit readiness

If you understand facet joint anatomy, you eliminate 80% of coding errors in MBB and RFA.

Once you understand how to count facet joint levels, the next step is selecting the correct CPT codes based on procedure type and spinal region.

Cervical / Thoracic Region

Lumbar / Sacral Region

Cervical / Thoracic Region

Lumbar / Sacral Region

• Use one base code per region (first level)
• Use add-on codes for each additional level
• Do not report more than 3 levels per region (payer dependent)
• Always ensure levels are counted correctly before assigning codes

Identify the procedure (MBB vs RFA) → determine the region → count levels → assign base + add-on codes.

To ensure accurate and compliant coding for MBB and RFA, follow this structured workflow:

Start by reviewing the operative note.

Ask:

Is this a diagnostic injection? → MBB

Is this nerve destruction? → RFA

Keywords:

MBB: “injection,” “diagnostic block,” “anesthetic”

RFA: “ablation,” “lesioning,” “radiofrequency”

This determines your base CPT code.

This is the most critical step.

Example:

L3–L4 and L4–L5 = 2 levels

C4–C5 only = 1 level

Do NOT count:

• Number of injections
• Number of nerves
• Number of needles

Use base code for first level

Add add-on codes for each additional level

Procedure:

L3–L4 and L4–L5 facet joints

Coding:

64493 – First level

+64494 – Second level

Procedure:

C4–C5, C5–C6, C6–C7

Coding:

64633 – First level

+64634 ×2 – Additional levels

Laterality is essential for correct reimbursement.

Options:

RT – Right side

LT – Left side

50 – Bilateral (payer dependent)

Important Note:

Many payers prefer:

Separate line items (RT and LT)

instead of modifier 50

For MBB

For RFA

Here’s how it works in real practice:

• Patient presents with chronic back/neck pain
• Physician performs MBB (64490–64495)
• Relief is measured
• If successful → proceed to RFA (64633–64636)

• 2 successful MBBs (payer dependent)
• ≥50–80% pain relief
• Consistent pain pattern

Procedure:

L4–L5 medial branch block

Code:

64493

Procedure:

L3–L4 and L4–L5 on both sides

Coding Option 1:

64493 RT

64493 LT

+64494 RT

+64494 LT

Procedure:

C3–C4, C4–C5, C5–C6

Code:

64633

+64634 ×2

If documentation lists:

“Injected L3, L4, L5 medial branches”

You must interpret:

L3–L4 and L4–L5 joints = 2 levels

Even with a clear workflow, certain mistakes frequently lead to denials, underpayments, or audits. Avoiding these can significantly improve claim accuracy.

• Counting needles instead of facet joint levels
• Counting the number of nerves treated
• Misinterpreting multiple injections as multiple levels

• Misreading documentation like “L3, L4, L5 medial branches”
• Failing to convert nerves into joint levels

• Not using RT/LT for unilateral procedures
• Incorrect use of modifier 50

• Reporting both procedures on the same level, same day
• Most payers do not allow this

• Missing pain relief %
• No prior MBB before RFA
• Unclear medical necessity

• Billing more than 3 levels per region
• Often flagged by payers

To better understand what leads to rejected claims, check out our guide on Mistakes Causing Claim Denials in Medical Billing.

Optimizing revenue for MBB and RFA procedures requires a combination of accurate coding, strong documentation, and payer-specific awareness. Small process improvements can significantly impact reimbursement.

• Incorrect level counting leads to underbilling or overbilling
• Always verify levels against operative notes before submission

• Apply RT/LT consistently for unilateral procedures
• Follow payer preference for bilateral billing (50 vs separate lines)

• Clearly document the pain relief percentage after MBB
• Include prior MBB results before RFA
• Ensure levels and regions are explicitly stated

• Check requirements for number of diagnostic blocks
• Confirm relief percentage thresholds (e.g., 50% vs 80%)
• Stay updated on payer-specific policies

• Identify patterns (e.g., missing modifiers, insufficient documentation)
• Adjust workflows based on common denial reasons

• Do not bill unsupported levels
• Avoid combining procedures incorrectly
• Ensure all codes align with documentation

For more strategies on improving reimbursement and reducing denials, explore our guide on Medical Billing Tips to Maximize Revenue.

Most payers allow billing for up to 3 levels per spinal region (cervical/thoracic or lumbar/sacral). Billing beyond this may trigger denials or require additional justification.

In most cases, no. Payers typically do not allow billing MBB and RFA for the same level on the same day, as MBB is a diagnostic step required before RFA.

This depends on the payer:

Medicare (commonly): Requires 2 successful MBBs

Commercial payers: May allow 1 or 2

Always verify payer-specific guidelines.

A successful MBB usually requires:

• 50%–80% pain relief
• Relief consistent with the duration of the anesthetic used

This must be clearly documented.

Yes, but it depends on payer preference:

Some accept modifier 50

Others require RT and LT on separate line items

Always code based on facet joint levels, not the number of nerves treated.

Accurate coding for MBB and RFA relies on precise facet joint level identification, correct CPT code selection, and strong supporting documentation. Getting these elements right minimizes denials and ensures consistent reimbursement.

Partner with Summit RCM for expert medical coding services tailored to complex procedures like MBB and RFA. Our team enhances coding accuracy, ensures compliance, reduces denials, and optimizes reimbursements so you can focus on patient care while maximizing revenue.

Contact Summit RCM today to streamline your medical billing and boost performance.