Intrathecal Baclofen Infusion For Spasticity

Posted by Ilya Shnaydman, Drexel University College of Medicine Class of 2013:

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Spasticity is defined as a ‘stiffness’ or ‘tightness’ of muscle due to spasms, or increased muscular tone. It is usually due to a lack of inhibition, as seen in an upper motor neuron lesion affecting the brain or spinal cord. Examples of upper motor neuron lesions include stroke (cerebrovascular infarct), multiple sclerosis, traumatic brain injury and cerebral palsy.

Although the exact cause of spasticity is not know, it is theorized to be due to an imbalance between the excitatory and inhibitory input to a muscle group. Increased excitability leads to spasticity, whereas increased inhibition leads to a flaccid muscle.

IS2_cerebral_spasticityThis can be better understood by illustrating the popular ‘knee jerk reflex’. During this test, the examiner strikes the patellar ligament with a reflex hammer which stretches specialized sensory fibers called the muscle spindle. This produces a signal which travels to the spinal cord (specifically at the L4 level). From the spinal cord, another specialized nerve complex called the ‘alpha-motor neuron’ conducts an impulse back to the quadriceps femoris muscle which triggers the contraction (knee jerk).

IS2_preflexOne of the patients treated at Monmouth Medical Center by the Neurology Specialists of Monmouth County, TM (the patient’s name is hidden to preserve anonymity)  is a 65 year old male who suffers from a spinal cord infarct 15 years ago, which resulted in spasticity of his lower extremities (legs) just as described above. The right side has been affected more than the left.  He has difficulty walking, as his gait is very rigid, but does manage to get around using a cane.

For spasticity, medical treatment consists primarily of physical therapy and muscle relaxants such as baclofen, benzodiazepines, and even botulinum injections. When these methods have been exhausted and either do not work to the patient’s satisfaction or cause side effects, patient’s must turn to experts in the treatment of spasticity.

The patient’s multidisciplinary neuroscience physicians at Monmouth Medical center urged the patient to consider intrathecal baclofen to help the patient improve his gait and overall quality of life. By injecting baclofen directly into the spinal canal (where the spinal cord lays), his neurologists are able to give significantly lower doses of the medication (as it directly contacts the spinal cord) and prevent unwanted side effects.

IS2_ITB-pump-1-KHI-RCH
Baclofen is infused into the spinal canal via a programmable pump that is implanted beneath the skin (similar to a pacemaker). The pump’s batteries last about 10 years and most patients do not notice any discomfort from having the pump implanted. The baclofen is replenished by injecting it into the pump’s port (yellow arrow) with a small needle.

IS2_F3.large2Before undergoing surgery for placement of the baclofen pump, patients typically undergo a trial to see if the intrathecal baclofen will be beneficial to them. During this ‘trial’, baclofen is injected directly into the spinal canal during a spinal tap (lumbar puncture, or needle placed through the skin into the spinal canal). The patient is then observed over a few hours to see if they are a good candidate for the permanent intrathecal baclofen pump. During the trial, only a small dose of baclofen is used, so once the pump is placed and programmed, the patient can expect to see even more benefit from the therapy. After the pump has been placed it can be adjusted non-invasively using a magnet (similar to a pacemaker) and should be followed by a neurologist to adjust the dosage as needed.

Below you can see the effect of the baclofen trial (again with just a small dose) for our patient, TM

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