This procedure involves the implantation of a small catheter into the spinal canal of the lower thoracic and upper lumbar spine. This allows for the regulated administration of medication directly into the thecal sac-the fluid filled sac that bathes and encloses the brain, spinal cord and nerves. Typically, when infusion of baclofen is considered, the patient undergoes a spinal tap to administer a small test dose thereby gauging the potential benefit of the medication. If a beneficial response is observed, the catheter is implanted. The rate of infusion is regulated by a pump that is implanted in the subcutaneous fat of the lower abdomen at the time of the surgery. This pump contains a reservoir for storage of the medication and must be refilled from time to time depending on the rate of administration; the pump must furthermore be replaced when its battery supply is exhausted.

This device may also be used to administer narcotic medications to treat cancer pain as well as chronic back pain secondary to degenerative conditions.