Postoperative pain management following posterior cervical spine (PCS) surgery remains a significant clinical challenge. Unlike lumbar or thoracic procedures, cervical spine surgery introduces unique risks when performing regional anesthesia, as inadvertent spread of local anesthetics can affect the brachial plexus or phrenic nerve, potentially causing upper extremity weakness or respiratory complications.

The ideal block for PCS should provide effective analgesia by targeting the dorsal rami of cervical spinal nerves while avoiding spread to the ventral rami, epidural space, or phrenic nerve.

Ultrasound-guided cervical paraspinal interfascial plane (CPIP) blocks represent a group of techniques designed for this purpose. Among them, the cervical cervicis plane (CCeP) block—first described as an interfascial injection between the semispinalis capitis and semispinalis cervicis muscles—has been increasingly used for PCS surgery. Early clinical studies suggest it reduces postoperative opioid consumption, lowers pain scores for up to 48 hours, and may facilitate earlier mobilization.

However, the detailed anatomical spread of injectate within the CCeP layer has not been fully characterized. Conflicting cadaveric findings have raised questions about whether the CCeP block consistently reaches higher cervical dorsal rami (C1–C3) when performed at lower levels (C5).

To address these uncertainties, researchers from Chiang Mai University and Westchester Medical Center performed a cadaveric dye study to systematically evaluate CCeP spread at the C2 and C5 levels, investigating potential anatomical barriers and unintended spread to adjacent structures.

Study objective and methods

The primary objective was to assess the spread pattern of methylene blue dye injected into the CCeP plane at two distinct cervical levels (C2 and C5). Specifically, the study aimed to determine:

• Which dorsal rami were consistently stained.
• Whether the injectate spreads to the ventral rami, multifidus muscle, retrolaminar region, brachial plexus, or phrenic nerve.
• The impact of different injection volumes on craniocaudal spread.
• Whether an anatomical barrier exists at the C2–C3 level.

Methodology

• Design: Cadaveric observational study.
• Setting: Department of Anatomy, Chiang Mai University, Thailand.
• Sample: 20 fresh frozen cadavers (75% male, mean age 72 years). Cadavers with prior neck injury were excluded.
• Randomization: Injection side (left/right) was randomly assigned.
• Block technique: Ultrasound-guided in-plane, lateral-to-medial approach.
  • At C2: Needle placed between semispinalis capitis and obliquus capitis inferior.
  • At C5: Needle placed between semispinalis capitis and semispinalis cervicis.
• Injectate: 0.1% methylene blue dye.
• Volumes:
  • C2 group: 5 mL (n=7), 10 mL (n=3).
  • C5 group: 10 mL (n=7), 20 mL (n=3).
• Outcome measures: Craniocaudal dye spread, dorsal rami staining, contralateral spread, and unintended spread to deeper structures.
• Dissection: Performed 1 hour after injection by anatomists to evaluate the dye distribution.

Key findings

1. Spread at the C2 level

5 mL injections:

• Consistent staining of C2 and C3 dorsal rami.
• Limited craniocaudal spread (C1–C5).
• No contralateral staining.

10 mL injections:

• Broader spread (C1–C6).
• 100% staining of C2 and C3; additional staining at C1, C4, C5, and C6 in some specimens.
• Consistent contralateral staining of the C2 dorsal ramus.

Misplaced injections at C3: Two cases inadvertently deposited at the spinous/articular process of C3, leading to staining from C2–C7.

2. Spread at the C5 level

10 mL injections:

• Staining from C3–C5 consistently; sometimes reaching C6–C7.
• No contralateral spread.

20 mL injections:

• Extensive spread from C2–T2.
• Reliable staining of C3–C6 dorsal rami, with occasional extension to C7.
• Still no contralateral spread.

3. No spread to unintended targets

At both C2 and C5 levels, regardless of volume, no dye was found in the:

• Multifidus muscle.
• Retrolaminar region.
• Ventral rami.
• Epidural space.
• Brachial plexus or phrenic nerve.

This strongly supports the selective targeting of the dorsal rami by the CCeP block.

4. Anatomical barrier at C2–C3

Findings suggest a functional barrier to cranial spread at the C2 level. Low-volume C2 injections did not extend beyond C3, but high-volume injections overcame this boundary, reaching C1–C6. This aligns with prior imaging studies questioning the continuity of the CCeP plane.

Conclusion

This cadaveric study demonstrates that the ultrasound-guided CCeP block reliably stains cervical dorsal rami without affecting ventral rami, epidural structures, or the brachial plexus. The block can be tailored to surgical needs:

• C2 injections for upper cervical coverage.
• C5 injections for lower cervical and upper thoracic coverage.

A functional anatomical barrier exists at C2, but higher injection volumes can overcome it.

By offering selective analgesia without motor or respiratory compromise, the CCeP block could play an important role in enhanced recovery after posterior cervical spine surgery.

Future research

The authors highlight several directions:

• Randomized clinical trials in surgical patients to confirm analgesic efficacy and opioid-sparing benefits.
• Functional outcomes such as ambulation, respiratory function, and intraoperative neuromonitoring signal quality.
• Comparative studies of CCeP block versus cervical erector spinae and paravertebral blocks.
• Optimal dosing and volume studies to balance spread with safety.
• Anatomical investigations into the C2–C3 barrier to refine block placement strategies.

Clinical implications

This study provides strong anatomical evidence that the CCeP block delivers reliable coverage of the dorsal rami while sparing the ventral rami and other critical structures, offering a clear safety advantage over alternatives such as cervical erector spinae or paravertebral blocks. Clinically, the choice of injection site can be tailored to surgical needs: C2-level injections are best suited for upper cervical procedures such as Chiari decompression, whereas C5-level injections provide broader coverage from C3 to C7, ideal for multi-level posterior cervical surgeries. Injectate volume is also important—10 mL ensures a clinically relevant spread, while 20 mL at C5 can extend analgesia into the upper thoracic region, which is useful for long incisions. By avoiding brachial plexus, phrenic nerve, and epidural involvement, the CCeP block emerges as a motor-sparing, targeted option that aligns with enhanced recovery goals in posterior cervical spine surgery.

Clinical pearls

• 10 mL at C2 → reliable staining of C2–C3 dorsal rami; contralateral spread possible.
• 10–20 mL at C5 → coverage of C3–C7; 20 mL may extend to T2.
• No spread to ventral rami, brachial plexus, phrenic nerve, or epidural space.
• Safe for preserving respiratory function and intraoperative neuromonitoring.

Practical tip: Use 10 mL at C2 for upper cervical surgery (e.g., Chiari decompression). For multilevel C3–C7 surgery, 10–20 mL at C5 provides broader coverage.

For more detailed information, refer to the full article in RAPM. 

Leurcharusmee P. et al. Ultrasound-guided cervical cervicis plane (CCeP) block: a cadaver study. Reg Anesth Pain Med. Published online August 11, 2025.

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