Intrathecal phenol is a nerve blocker that has been used for more than 60 years to treat severe muscle stiffness. It is recommended for people with MS who have failed to respond to all oral medications and other treatments. Phenol is administered in an oily formulation into the spinal column at the lower end of the spine. A puncture of the lumbar, or lower back, gets the formulation to the intrathecal, or spinal canal. Doctors use a local anesthetic for the procedure. How does intrathecal phenol work? Phenol stops the spasticity by preventing the lower motor neurons from sending signals to the muscles of the lower limbs, helping to relax those muscles. The effect of intrathecal phenol is permanent, so it should be used only in those with spasticity who have no feeling and no control of their legs, bowel or bladder function. Intrathecal phenol treatment Intrathecal phenol’s effects show up a few minutes after treatment and may last from one to several years. The treatment can be repeated every three to six months if symptoms recur. Since phenol is an invasive treatment, a patient needs to stay in a hospital for a few days for observation. After phenol is injected, medical staff position the patient in a way that directs the medicine toward the target nerves for about an hour. After that, the patient’s position is altered. Note: Multiple Sclerosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.