Comparing the injectate spread and nerve involvement between different injectate volumes for ultrasound-guided greater occipital nerve block at the C2 level: a cadaveric evaluation

Figures & data

Figure 1 (A) Schematic diagram showing the probe position and needle direction for greater occipital nerve block. (B) Ultrasound image demonstrating needle placement and dye spread of GON block.

Abbreviations: GON, greater occipital nerve; SP, spinous process; OCI, obliquus capitis inferior; TON, third occipital nerve.

Table 1 Comparison of dye staining between ultrasound-guided GON block with 1 mL and 5 mL of dye solution

Anatomical structures	1 mL dye (n=5)	5 mL dye (n=5)
Nerves
suboccipital nerve	1 (20%)	5 (100%)
gon	5 (100%)	5 (100%)
Third occipital nerve	3 (60%)	5 (100%)
Muscles
Obliquus capitis inferior	5 (100%)	5 (100%)
Rectus capitis major	2 (40%)	5 (100%)
Rectus capitis minor	1 (20%)	4 (80%)
Obliquus capitis superior	0 (0%)	5 (100%)
semispinalis capitis	5 (100%)	5 (100%)
semispinalis cervicis	0 (0%)	1 (20%)
splenius capitis	0 (0%)	1 (20%)
Longissimus capitis	0 (0%)	1 (20%)
Trapezius	0 (0%)	1 (20%)

Abbreviation: GON, greater occipital nerve.

Figure 2 Comparison of the dye-spreading patterns between GON block using 1 mL (left) and 5 mL (right) of dye solution.

Abbreviations: GON, greater occipital nerve; TON, third occipital nerve; OCI, obliquus capitis inferior.

Figure 3 Suboccipital region after GON block using 5 mL of dye solution.

Note: The red asterisk indicates the suboccipital triangle.
Abbreviations: GON, greater occipital nerve; TON, third occipital nerve; OCI, obliquus capitis inferior; OCS, obliquus capitis superior; RCM, rectus capitis posterior major; SP, spinous process; TP, transverse process.