The Time Course of Onset and Peak Effects of Phenol Neurolysis.

OBJECTIVE

The aim of this study was to explore the time course of onset and peak effects of phenol neurolysis.

DESIGN

This is a retrospective chart review. Eleven patients with elbow flexor spasticity after brain injury were enrolled. The resting angle of the elbow joint was measured before and after the injection and up to 6 wks of follow-up.

RESULTS

Phenol injection was performed to 13 musculocutaneous nerves under ultrasound and electrical stimulation guidance. The resting elbow angles were 84.4° ± 25.8° (before injection), 116.6° ± 20.9° (immediately after injection), 121.2° ± 21.4° (2 hrs after injection), 127.2° ± 19.7° (24 hrs after injection), 145.4° ± 11.8° (7 days after injection), 145.5° ± 10.4° (14 days after injection), and 150.3° ± 12.2° (6 wks after injection; N = 7). The mean resting angle was statistically different among the time points from preinjection to 14 days after (F2.625, 31.505 = 36.805, P < 0.01). Post hoc tests revealed that significant improvements existed immediately after and 7 days after the injection (P < 0.01 for both). The effects seemed to reach its peak in 7 days. The effect sizes immediately and 7 days after the injection were 1.37 and 3.04, respectively. The immediate effect accounted for approximately 60% of the maximal effect.

CONCLUSIONS

Phenol neurolysis has an immediate effect on spasticity reduction and reaches its peak effect around 1 wk after injection.