Intrathecal Baclofen: The Baclofen Pump
Baclofen (Lioresol®) is a medication introduced in the late 1960s as a treatment for spasticity. The medication is also commonly used to treat select cases of dystonia. Baclofen in the spinal fluid around the brain and spinal cord supplements the body’s supply of a chemical neurotransmitter called GABA, which relaxes muscle movement. The drug may be given orally, but very high doses must often be used to ensure that the drug saturates the blood stream and reaches the spinal fluid. High doses of oral baclofen may cause intolerable side effects such as muscle weakness and fatigue. A surgically implanted baclofen pump delivers baclofen directly to the spinal fluid, and only very small doses are needed. (The term intrathecal means in the spinal fluid.)
Intrathecal baclofen therapy is a non-destructive, adjustable, and reversible treatment. Several hundred dystonia patients have been treated with intrathecal baclofen. It has been used for children and adults with generalized dystonia (both primary and secondary) and hemidystonia who respond to oral baclofen. Many persons treated with intrathecal baclofen have a combination of dystonia and cerebral palsy. Intrathecal baclofen may be used to treat dystonia affecting the upper and lower limbs.
In order to determine if an individual is eligible for intrathecal baclofen, he/she will undergo a screening test to observe the body’s response to baclofen. A response to the oral drug may necessitate a screening test to observe the body’s response to a small dose injected directly into the spinal fluid. The medication is injected using a standard lumbar puncture. The screening test procedure involves injection of the medication followed by several hours of observation. Relaxation of the muscles indicates that an implanted baclofen pump will likely be effective. The effects of the screening test are temporary and may last several hours after the injection. If a patient does not respond at all to the screening test, a second test using the same procedure may be tried the next day or at a later date.
Some physicians use a continuous intrathecal infusion of baclofen as a screening method, since more patients respond to continuous infusion than to single injection screening doses. In the infusion technique, a small catheter is inserted into the spinal fluid and is connected to an external pump that infuses baclofen in increasing doses over two to three days.
Starting intrathecal baclofen therapy involves surgically implanting a pacemaker-like device into the abdomen. The device is usually placed either to the right or left of the belly button, beneath the skin and fat of the abdomen. The pump is connected to a thin tube that is tunneled around the side of the body to the back. A small needle introduces the tube to the spinal canal. Once the surgical incisions are closed, the pump is adjusted by a remote computerized device to deliver the amount of medication appropriate for the individual. The procedure takes one to two hours, and hospital stay may range from four to seven days. Modest improvement of symptoms may be noticeable before the individual is discharged from the hospital, and it make take six months or more to achieve the full extent of benefit.
Regular maintenance is a key component of intrathecal baclofen therapy. Regular exams and physical therapy may be a component of postoperative care. Pumps must be refilled every one to four months in the physician’s office as a straightforward outpatient procedure. The pump is refilled by inserting a thin needle through the skin, into the pump. The frequency of refilling the pump depends on the dose required. If necessary, the doctor may adjust the delivery rate of the pump at the time of the refill by remote control. The pump battery needs to be replaced about every seven years.
Baclofen in the spinal fluid relaxes muscles throughout the body, and appears especially effective for targeting dystonia in both the upper and lower half of the body. Intrathecal baclofen may be more effective for treating secondary dystonia than for primary dystonia.
Studies have shown that intrathecal baclofen can dramatically improve symptoms and quality of life. Some centers have reported significant improvement in as much as 85% of patients. However, like any surgery, the procedure is not without risks. Hardware complications may also arise including infection and catheter breakage and disconnection. In a small percentage of cases, patients may lose effect within the first year of therapy or experience a worsening of symptoms. The most common side effects are constipation, decreased muscle control, and drowsiness.