Objective Techniques for Evaluating Response to Intrathecal Baclofen Therapy Medication

Past Studies

“Spasticity” is a term used to describe a condition that causes muscles to be stiff and resist stretch. As a result of injury to the brain, spastic muscles are overactive and unable to “relax” or “stretch out.” Because of this, individuals with spasticity may not be able to straighten out or bend their arm or leg joints, even if they had the strength to do the task. For instance, the muscles necessary to straighten the arm may actually be working, but if the muscles that bend the arm are spastic, they can be so powerful that individuals cannot overcome the force generated by the spastic muscles and are unable to strengthen their arms. When spasticity limits an individual’s body movements, it can decrease abilities and lead to medical problems such as pain, sleep disturbances, and skin conditions. Also, if spasticity remains severe for a long enough period of time, permanent changes can occur to the muscles and associated joints, leading to deformity.

Spasticity can be treated and relieved for some individuals. Some treatments include therapeutic stretching, medications that relax muscles, injected medications that weaken or paralyze selective muscles, and surgery. Individuals can work with occupational and physical therapists to strengthen movements and improve coordination. Improved body movement abilities can enable individuals to take care of themselves, do more activities on their own, and experience less associated medical problems.

Baclofen is one of the medications used to treat spasticity. Baclofen can be delivered continuously and directly to the fluid surrounding the spinal cord by using a small pump placed surgically under the skin of the abdomen. This is called “Intrathecal Baclofen Therapy.” Because using this method allows medication to be delivered directly to the spinal cord, a much lower dose is required with much less distributed to the whole body. The medication’s negative side effects can be greatly lessened as a result. Intrathecal Baclofen Therapy (ITB) can be very effective for persons with spasticity in large muscle groups or the type of spasticity that increases with movement. Finding the right dose of medication for some individuals can be challenging. Patients may find that changing the stiffness of the muscles may take getting used to, particularly if they have some ability to walk, and the series of adjustments may take weeks or months. Researchers have directly measured the effectiveness of ITB in research projects. The use of direct measurements in “daily clinical settings” has been limited.

This Study

This study consisted of a review of the published medical research related to the direct measurement of the effectiveness of ITB on the spinal cord and nerves involved with spasticity. The researchers focused on studies that measured how well ITB works by testing nerve and muscle reactions using techniques called the Hoffman Reflex (H-reflex), F-wave, and Flexion Withdrawal Reflex. The researchers also considered their own studies of ITB evaluation that included measurement of the H-reflex. Measurement with these techniques use equipment that are available in many neurologist and physiatrist offices. By examining and establishing what is known, the researchers hope to create a basis for determining if the ITB system is working properly, and to help adjust dosages of ITB for individuals that receive treatment in clinical settings.

It appears that assessment with the Hoffman Reflex and the Flexion Withdrawal Reflex may serve as an indicator of response to ITB, when used along with other clinical scales. The researchers found that the Hoffman Reflex appeared to be the best indicator of how well the ITB worked on the spinal cord and nerves involved with spasticity. Assessment with the F-wave does not appear to be as useful to indicate the effectiveness of ITB.

Who May Be Affected By These Findings

Individuals with brain injury and spasticity, health care providers, and researchers.

Caveats

It appears that assessment with the Hoffman Reflex is especially useful during the period shortly after the Intrathecal Pump is surgically implanted, during which time the dosage of medicine required for an individual is difficult to predict. It is also very helpful if a problem with the ITB system is suspected, such as breakage of the catheter that connects the pump to the spinal fluid, as the technique is very sensitive to the presence of baclofen in the nervous system.

Bottom Line

Assessments using the Hoffman Reflex and the Flexor Withdrawal Reflex, along with other clinical tests appear to be useful for determining response to dosage adjustment with Intrathecal Baclofen Therapy.

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