Spasticity

Intrathecal Baclofen™ (ITB)

Intrathecal baclofen therapy (ITB Therapy) consists of long-term delivery of baclofen to the intrathecal space. This treatment can be very effective for patients with severe spasticity, particularly for those patients whose conditions are not sufficiently managed by oral baclofen and other oral medications. Lack of substantial therapeutic benefit from oral baclofen, a mainstay of drug therapy, can result from an inadequate penetration of the blood-brain barrier by the drug. Since unacceptable CNS effects often occur when high doses of baclofen are taken orally, the therapeutic effect usually can't be improved by increasing the dose.

Sedation, somnolence, ataxia and respiratory and cardiovascular depression are the drug's CNS depressant properties.

The SynchroMed® Infusion System provides direct, pattern-controlled delivery of baclofen to its target via an implanted, programmable pump. This precise delivery yields better spasticity reduction at lower doses: doses 100 times the intrathecal dose are needed to produce similar benefits if baclofen is taken orally. Thus, adverse effects associated with high dosages of oral baclofen are minimized.

The SynchroMed® pump is a small titanium disk that is about three inches in diameter, and one inch thick. It contains a refillable reservoir for the liquid baclofen as well as a computer chip that regulates the battery-operated pump. A telemetric wand programs the dose of baclofen to be received. A flexible silicone catheter serves as the pathway through which the baclofen flows to the intrathecal space. To prevent an accidental depletion of baclofen, the pump contains a programmable alarm that sounds when the reservoir needs to be refilled, the battery is low, or the pump is not delivering the baclofen.

ITB Therapy can be used to treat severe spasticity in patients with conditions such as spinal cord injury, stroke, multiple sclerosis, cerebral palsy, or brain injury.

Benefits
Benefits of ITB Therapy typically include reduced tone, spasms, and pain, and increased mobility. In addition, many patients, caregivers, family members and physicians have reported striking improvements in movement and self-care. Other benefits may include improved speech, sleep quality, bladder control, and self-image.

The efficacy of ITB Therapy in controlling spasticity typically allows patients to decrease and often discontinue other spasticity medications.

Treating Patients with ITB Therapy
The use of ITB Therapy as a treatment for spasticity requires a four-phase approach: patient selection, screening, implantation, and dose adjustment and maintenance.

Patient Selection
Candidates for ITB Therapy have disabling spasticity unresponsive to conservative pharmacotherapy or intolerable side effects at therapeutic doses. Pharmacotherapy should include, but need not be limited to, a trial of oral baclofen. (See Special Patient Considerations and FAQ for more information). There appears to be consensus among physicians on a post-ITB Therapy target Ashworth score of approximately 2 for the majority of patients.

Screening
The screening process for ITB Therapy requires the administration of an intrathecal test dose of baclofen (typically with 50 mcg, usually not to exceed 100 mcg), via lumbar puncture. Peak effect of the drug usually occurs within four hours. Patients who respond positively to the test dose can be considered for chronic ITB Therapy.

During screening, patients must be monitored closely in a fully equipped and staffed setting, due to the rare risk of life-threatening side effects.

Implantation of pump
The pump implantation requires two incisions: one in the lower abdomen to make a subcutaneous (SQ) pocket for the pump, and another, smaller, incision in the lumbar region for catheter insertion. Exact placement of the pump differs with each patient, but it is generally implanted near the waistline, about one inch below the skin.

implanted, programmable pump

The surgeon inserts the catheter into the intrathecal space using a spinal introducer. An intra-operation myelogram is often used to confirm catheter placement. The distal end of the catheter loops around the torso and connects to the pump which is sutured to the SQ pocket. The tip of the catheter rests between the first and second lumbar vertebrae. The procedure typically lasts about 1 hour.

Once the pump is implanted, it is often not perceived as a distinct part of the body, although the outlines of the pump can be seen through the skin.

Dose Adjustment
The dose delivered by the pump is adjusted using the programmer and telemetry wand. This system is non-invasive and affords flexibility in individualizing doses. The telemetric wand is held over a patient's pump; the patient can remain fully clothed. The initial total daily dose of intrathecal baclofen after implantation may be up to double the screening dose that resulted in a beneficial response. If, however, the efficacy of the screening dose was maintained for more than 8 hours or the patient became lethargic during screening, it is recommended that the initial daily dose not exceed the screening dose.

computer wand

Dose increases should not be made until 24 hours after surgery. Doses for adult patients with spasticity of spinal cord origin may be increased by 10 to 20 percent increments no more than once every 24 hours until the desired clinical effect is achieved. Physicians treating adult patients with spasticity of cerebral origin and all pediatric patients should increase dosages more conservatively. After the first 24 hours, dosages can be increased by 5 to 15 percent, no more than once every 24 hours until the desired clinical effect is achieved. However, in most clinical situations for all indications, there is no urgency to increase dose rapidly and, therefore, a more cautious titration schedule is recommended.

The programmer has the capability to provide flexible dosing schedules. About 60 days following surgery or when a stable dose program has been established, the fine-tuning of the dose delivery may begin. For example, the pump may be programmed to deliver a 5 to 20 percent increase at night for patients who have difficulty sleeping due to spasticity. To achieve a clinical effect such as this requires a lead time of approximately two hours (e.g., for a therapeutic benefit to occur at 10 pm, an increase in dose delivery should begin at 8 pm).

Maintenance doses of intrathecal baclofen for spasticity of spinal cord origin range from 12 mcg to 2,003 mcg/day with most patients requiring 300 mcg to 800 mcg/day. Patients with spasticity of cerebral origin receive doses ranging from 22 mcg to 1,400 mcg/day. For most patients, doses of 90 mcg to 703 mcg/day result in therapeutic benefits. For children under 12, the average daily dose is 274 mcg/day, with a range of 24 mcg to 1199 mcg/day. Doses for children over 12 are the same as for adults. The daily dose may be increased if greater therapeutic benefits are needed, or reduced to alleviate side effects. Dose reduction should always be performed in a stepwise fashion. Sudden withdrawal of intrathecal baclofen can result in cardiovascular instability, fever, rash, and requires emergency treatment.

If an increase in daily dose does not result in a substantive clinical effect, pump function and catheter patency can be checked.

Pump Refilling and Maintenance
The pump's reservoir must be refilled every 4 to 12 weeks, depending on the daily dose. To avoid depletion of the reservoir, which can lead to a marked return of spasticity (often with itching) and other side effects, patients should be scheduled regularly and well in advance for their refills.

The pump hardware can last 4 to 6 years, depending upon the battery life, and is generally replaced within 4 to 5 years.

To refill a pump reservoir, the pump is reprogrammed, emptied, and a new supply of baclofen is injected. A non-coring, 22-gauge, Huber-type needle is used to reach the reservoir of the pump through its silicone septum. Refilling the pump requires one needle stick. The procedure lasts about 20 minutes.

Supplies needed to refill a pump include vials of baclofen, sterile gloves, drapes with holes for the pump, betadine, alcohol and gauze swabs, templates for the shape of the pump, needles, tubing, syringes, microport filters and manometers. These supplies are provided by Medtronic, Inc. in refill kits.

Possible Side Effects and Risks
As with any surgical procedure, the implantation of the pump exposes a patient to a risk of infection and general anesthesia. There is also the risk of spinal fluid leakage.

Side effects such as drowsiness, nausea, headache, muscle weakness and light-headedness can stem from the pump delivering an inappropriate dosage of baclofen. These side effects are resolved by assessing the pump and adjusting the dose. Physicians generally start patients on low doses of baclofen with to avoid possible side effects.

Additionally, the pump itself can malfunction, and the catheter can become kinked or fractured. A large and sudden escalation in dose requirement, for example, suggests a catheter complication. In cases such as these, surgical intervention may be necessary. In cases where an overdose is possible, the patient should be brought immediately to the hospital for evaluation.