University Hospitals

Spasticity is an abnormal increase in the resting muscle tone due to a brain or a spinal cord disease. It often leads to impairment of residual function in the afflicted limb along with stiffness, pain, discomfort, and limitation in the range of joint movement. It can predispose to skin breakdown, ulceration, and infection. It impedes personal hygiene and adds to caregiver burden. In addition, multiple involuntary movements can accompany spasticity including painful spasms and body jerks or shaking. The most common causes of spasticity include stroke, multiple sclerosis, brain or spinal cord injury, and cerebral palsy. Conventional treatment of spasticity includes a combination of stretching exercise, physical therapy, oral muscle relaxants, and targeted botulinum toxin injections to focal areas of spasticity.

Surgical implantation of an intrathecal baclofen pump is a newer neuromodulatory technique indicated for severe or treatment-refractory spasticity. In this technique, a catheter is surgically implanted under the coverings of the spinal cord often in the mid-back. The catheter is connected to a batteryoperated pump housed under the skin in the lower abdomen. The pump is periodically filled with liquid baclofen (a potent muscle relaxant) and can be programmed to continuously deliver baclofen directly to the spine. The delivery can follow a simple continuous mode or a flex mode incorporating additional boluses to serve individual patient needs and lifestyle. Most of the liquid baclofen gravitates in the lower part of the spine where the motor control centers of the lower extremities are located. Therefore, intrathecal baclofen usually results in a significant reduction in muscle tone and spasms of the lower extremities. Some benefit can also be achieved in the upper extremities though the benefit is often smaller compared to the lower extremities. The concentration of intrathecal baclofen needed to achieve meaningful tone reduction is much less compared to that of oral baclofen and is better tolerated by patients due to a lower rate of systemic and sedating side effects. Intrathecal baclofen pump has been studied and found beneficial in patients with post-stroke spasticity, multiple sclerosis, and traumatic central nervous system injuries. The pump can be replaced every 4 to 5 years via a simple outpatient procedure and can be connected to the existing catheter after each replacement. 

Proper case selection is key for favorable outcomes. Patients with only focal or mild spasticity are not the best candidates for this technique. Patients with predominant upper extremity spasticity and patients who need spasticity to compensate for lower extremity weakness while walking are also poor candidates. Patients with severe diffuse spasticity, non-ambulatory patients, and those with lower extremity spasticity but preserved strength are good candidates for intrathecal baclofen. Failure to respond to or poor tolerability to oral and injectable agents are common indications for intrathecal baclofen pump. Fortunately, it is possible to pretest the response to intrathecal baclofen via a direct injection prior to surgical implantation. This screening test is extremely important for proper case selection as it can predict the advantages and disadvantages of intrathecal baclofen on the individual level and can detect any unforeseen reactions.

“The goal of intrathecal baclofen pump refinement is to further improve the quality of life of neurological patients and minimize the use of systemic medications”

The possible side effects of this technique include lower extremity weakness, urine retention, hardware infection, and most importantly baclofen withdrawal. The latter is a life-threatening condition that can occur because of missed baclofen refill, catheter leak, pump malfunction, or programming errors. Baclofen withdrawal can lead to hyperexcitability of the nervous system resulting in seizures, spasms, and extreme elevations in blood pressure. This is a treatable condition but may require admission to an intensive care unit for stabilization.

Despite its benefits, intrathecal baclofen pump remains underutilized. Further research is needed to maximize benefit and minimize potential risks of this technique. The value of higher level implantation and data on optimizing the daily dose and programming modes are among the most pressing needs. Ultimately, the goal of intrathecal baclofen pump refinement is to further improve the quality of life of neurological patients and minimize the use of systemic medications.