A phenol solution can be injected into a muscle that has too much tightness or uncontrolled movement. Phenol blocks the nerve pathways through which the muscle receives messages. The human body will automatically develop a new nerve pathway to replace it, but that process takes six to twelve months. During that time, the affected muscle will have less tone, in other words, it will not be so tight. 

The nerve that needs to be blocked is located by stimulating it with a mild electrical impulse from a small battery-operated box. This allows the doctor to place the phenol solution directly on the nerve. The process of finding the nerve may take about 10 to 30 minutes. 

You will see a change in muscle tone as soon as the procedure is complete. When high muscle tone has been present for a long time there may be a contracture or fixed position of the joint closest to the muscle. Your doctor might recommend a cast or a splint to help stretch the joint and muscles. 

Possible side effects from phenol injections may include soreness at the injection sites, nerve pain, swelling, or numbness. All of these effects are temporary when they occur, but some take longer than others to go away. Use of Tylenol or Motrin and ice packs may be helpful. When an extremity has swelling it should be elevated as much as possible. Any effects that last more than a day or two should be reported to your doctor. It is also helpful to rest the extremity temporarily, and then gradually resume normal activities. Because the immediate effect of the phenol on muscle tone may change strength and coordination, caution should be taken in all regular activities until your body recognizes and adapts to these changes. 

Questions or Problems

Contact Telehealth Nursing at 651-229-3890 if you see any of the following:

  • Fever over 101.5 F
  • Throat irritation
  • Severe pain

This information is for educational purposes only. It is not intended to replace the advice of your health care providers. If you have any questions, talk with your doctor or others on your health care team.