Localization of center of intramuscular nerve dense regions in adult anterior brachial muscles: a guide for botulinum toxin A injection to treat muscle spasticity

This study aimed to identify the location and depth of the center of intramuscular nerves dense regions (CINDRs) in anterior brachial muscles. Twelve adult cadavers were used. One side anterior brachial muscles were isolated and subjected to Sihler's staining to show intramuscular nerve dense regions. Then the data was used to localize CINDRs in situ on the same muscles of the contralateral side. The localization method involved dissection and exposure of CINDRs, barium sulfate labeling, body surface reference line design, spiral computed tomography scan, three-dimensional image reconstruction, and Syngo system measurements. The number of CINDRs in coracobrachialis, biceps brachii and brachialis muscle were 3, 2 and 2, respectively. The body surface coordinates for the three CINDRs in coracobrachialis muscle were at 24.22%, 18.89% and 8.15% on the horizontal reference line and 21.37%, 31.78% and 30.07% on the longitudinal reference line. For biceps brachii muscle, they were at 49.68% and 40.28% on the horizontal reference line and 56.60% and 67.63% on the longitudinal reference line. For brachialis muscle, they were at 48.34% and 52.45% on the horizontal reference line and 71.30% and 81.62% on the longitudinal reference line. On cross-sectional planes, the depths of these CINDRs were at 22.81%, 26.76% and 27.99% (coracobrachialis); 14.79% and 17.45% (biceps); 34.03% and 30.26% (brachialis) of section diameters through CINDRs. These results may help to guide the injection of botulinum toxin A for the treatment of spasticity in the anterior brachial muscles and improve treatment efficacy and efficiency.