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Intrathecal Baclofen Therapy (ITB)

Intrathecal Baclofen Therapy (ITB) involves the long term delivery of Baclofen to the intrathecal space surrounding the spinal cord for the purposes of relieving severe spasticity. This delivery method of Baclofen is used when oral medication of the drug no longer manages the spasticity sufficiently, and the spasticity has an impact on the quality of life of the patient. Due to the direct point of delivery of the Baclofen using ITB, much smaller amounts can be used than would otherwise be taken orally.

The most common types of pump used are the Electronic Programmable Pumps, and the Gas Driven Pumps. Both these pumps are usually implanted under the skin on the front of the abdomen, and deliver the drug via a thin tube which is tunneled under the skin to the back of the spine, where the tip of the tubing is secured into the intrathecal space.

The electronic pumps such as the Medtronic SynchroMed pump, is a fully programmable battery operated pump with a battery life of around 7 years. The pump can be programmed to give an hourly dosage, a bolus, or a combination of drug administration as the patient requires. The programming is carried out by a qualified nurse, who uses a special hand held computer with a built in transmitter. Communication is two way, as the pump can send diagnostic information back to the computer such as fault diagnosis, and drug reservoir levels.

The gas driven pump is powered by a reservoir of pressurised gas, which places pressure on a flexible membrane on the side of the drug reservoir, thus forcing the Baclofen out through a precision valve, through the tubing and into the intrathecal space. As the pressure of the gas is fixed, and cannot be altered, the dosage delivered is controlled by the strength of the Baclofen used in the pump. As there are no batteries, once the pump is implanted, it will not need replacing.

Both the electronic and gas driven pumps are made from titanium, and are implanted on the abdomen under the skin, both pumps are connected to the intrathecal space via a thin silicone tube called a catheter.

Patient Benefits

The benefits of ITB to the patient are well documented, and typically reduce muscle spasms, tone and pain. This in turn increases mobility, independence, stamina, sleep and an overall increased quality of life.

In addition to the patient benefits, there is also a reduced workload for care by patient caregivers and family members.

Once the pump has been implanted and is functioning as required, oral medication for the relief of muscle spasms is stopped or reduced. Once oral medication is changed, the patient usually is more alert, and has more energy. This due to the sedation effects of oral drugs being removed.

Patient Selection Process

Patients wishing to be proposed for ITB usually have excessive spasticity, and will of not responded, or have had an adverse reaction to conventional oral medication. In order to classify spasticity, the surgeon will use a table called the "Ashworth Scale". Generally, for someone to be considered for a Baclofen pump, they will have a grading greater than 3 on the Ashworth Scale.

The Ashworth Scale (1964) is as follows:

1. No increase in tone.

2. Slight increase in tone, giving a "catch" when affected part(s) are moved in flexion or extension.

3. More marked increase in tone but affected part(s) are easily flexed.

4. Considerable increase in tone; passive movement is difficult.

5. Affected part(s) rigid in flexion or extension.


Initial Patient Testing

The initial test to see if a patient will benefit from ITB, requires the administration of an intrathecal test dose of Baclofen. This is usually done via a lumbar puncture, and the patient is then monitored for a reduction of spasticity. If a reduction of spasticity is observed, then the patient is usually considered for the implantation of a pump.

Pump Implantation and Surgery

The Baclofen pump is implanted under surgical conditions and requires two incisions. One incision is made in the lower abdomen, and a small pocket under the skin is created in which to place the pump. Another small incision is made in the lumbar region of the back, and a thin tube is tunneled under the skin around the side of the abdomen to join the pump. The tip of the tubing is placed into the intrathecal space using an spinal introducer, and positioned using an X-Ray Mylogram to ensure the correct placement of the catheter tip. The tip of the catheter usually rests between the 1st and 2nd lumbar vertebrae.

Dosage Adjustment

In a programmable pump, the dosage is adjusted by computer, and transmitted to the pump. In a gas driven pump, a perceived safe dosage is filled into the reservoir, and the patient is then monitored.

No further alterations are then made to the dosage for at least 24 hours, as it can take time for the drug to work it's way through the tubing and into the intrathecal space. If after this time the patient is still not responding to the Baclofen, the dosage of a electronic pump may be increased slightly, and the patient monitored. In the case of a gas driven pump, the dosage has to be changed by emptying the pump of Baclofen, and refilling it with a stronger dosage.

Refilling the Pump and Maintenance

Depending on the reservoir in the pump, and volume of drug administered, the pump will need refilling every 4 to 12 weeks. If the pump becomes empty, the patient will notice a return of muscle spasms, and itching of the skin.

To refill an electronic pump, the pump is scanned by the computer telemetry, emptied, refilled and reprogrammed. The pump is refilled by passing a needle through the skin and into the pump via a silicone port built into the pump. This procedure takes about 20 minutes.

To refill a gas pump, a needle is placed through the skin and into the pump, the pump is then emptied, and refilled. As there is no programming to do, this can be quicker than refilling the electronic pump.

In the electronic pump, the battery lasts around 7 years, at which point the pump is replaced. However, the tubing is not replaced, and can be left in place and used again.

The gas driven pump will effectively last the lifetime of the patient, as there are no batteries. The only limitation is the seal in the pump through which the needle passes.

Risks and Complications

As with all surgical procedures requiring general anesthesia, the patient is at risk of infection, and due to the surgery of the intrathecal space, there may also be some spinal fluid leakage.

Sometimes the dosage in the pump may be too high, and this can result in drowsiness, nausea, headache, muscle weakness and light-headedness. In these cases, the Baclofen dosage must be reduced using the methods explained earlier.

As the pump is an electro / mechanical device, it may become faulty and malfunction. Typical examples are of a flat battery, kinking of the tubing/catheter, disconnection of the catheter to the pump, and dislodging of the catheter tip in the intrathecal space.

If an overdose of Baclofen is suspected, the patient should be admitted to hospital for urgent evaluation. If a fault is suspected in the pump, medical or surgical intervention may be required.

Copyright 2004. Simon Roulstone.