Electromyographic and tomographic muscle changes after botulinum toxin administration through either 3 or 8 injection points in patients with large midline ventral hernias: a superiority study

In this superiority study, the primary endpoint was to evaluate whether muscle changes in amplitude, thickness and length are superior when administering botulinum toxin to external and internal oblique muscles using small volumes through 8 injection points compared to large volumes through 3 injection points in patients with large midline ventral hernias. A secondary endpoint was to assess new symptoms developed after injections.

Between March 2023 and July 2025, 31 patients with large midline ventral hernias underwent pre-habilitation with botulinum toxin injected to the external and internal oblique muscles. In each patient, a dose of 100 units of botulinum toxin was administered on the right side through 3 injection points using a volume of 48 cc, and the same dose was administered on the left side through 8 injection points using a volume of 16 cc. Muscle amplitude, thickness and length on each side were compared before and 4 weeks after injection using the Wilcoxon signed-ranked test for matched pairs. The changes seen between sides were compared using the Wilcoxon signed-ranked test and adjusted with the Benjamini–Hochberg false discovery rate method.

Muscle amplitude decreased 52% on the 8-injection point side (from 275 µV to 121 µV; p = 0.003) and 50% on the 3-injection point side (from 259 µV to 129 µV vs.; p = 0.01) (95% CI between sides [-0.14, 0.27]; p = 0.14). Muscle thickness was reduced by 31% on the 8-injection point side (from 28 mm to 18 mm; p = 0.002) and 28% on the 3-injection point side (from 28 mm to 18 mm; p = 0.004) (95% CI between sides [-0.06, 0.09]; p = 0.89). Muscle length increased 26% on the 8-injection point side (from 113 mm to 154 mm; p = 0.001) and 15% on the 3-injection point side (from 124 mm to 139 mm; p = 0.003) (95% CI between sides [-0.13, 0.04]; p = 0.61). No new symptoms were recorded after botulinum toxin injections.

In a group of patients with large midline ventral hernias, the degree of change in muscle amplitude, thickness and length was not superior when botulinum toxin was administered using small volumes through 8 injection points compared to large volumes through 3 injection points.