Intrathecal Baclofen In the Treatment of Adult Spasticity

Joseph C. Hsieh, M.D., M.B.A., M.P.H.; Richard D. Penn, M.D.

Disclosures

Neurosurg Focus. 2006;21(2) 

In This Article

Surgical Process

Although it is usually well tolerated, implantation of an intrathecal catheter and baclofen pump represents an invasive surgical procedure that must be fully evaluated before it is undertaken. Care must be taken in patient selection, surgical implantation, and postoperative management.

Adequate patient assessment for ITB pump implantation is necessary to determine if surgical intervention is a viable option. Screening requires a complete physical ex am ination and neurological assessment, including a thorough history of spasticity and prior treatment regimens. Common ratings of spasticity include the following: 1) the Ashworth Scale (scores 1–5) for assessment of muscle tone in lower extremities (including hip abduction, hip flexion, knee flexion, and ankle dorsiflexion) and upper extremities (including shoulder abduction, elbow extension, elbow flexion, and wrist extension); 2) the Penn Spasm Frequency Scale (scores 0–4) for quantification of spontaneous sustained flexor and extensor muscle spasms per hour; and 3) the Reflex Scale (scores 0–5) for categorization of deep tendon reflexes at the biceps, patella, and Achilles tendon.

One set of reasonable criteria for inclusion in an ITB trial includes the following items: 1) severe chronic spastic hypertonia in the lower extremities lasting at least 6 months, with Ashworth scores of at least 3 in an affected extremity, or a Penn Spasm frequency score of at least 2 during screening; 2) failure to respond to maximum recommended doses of antispasmodic medications, including baclofen and possibly diazepam, clonidine, tizanidine, or dantrolene sodium.

As part of surgical screening, patients should demonstrate a positive clinical response to an ITB injection bo lus. Screening involves a 50-mg bolus injection of bac lofen diluted to 50 mg/ml into the intrathecal space by barbotage over a period of not less than 1 minute. The pa tient is then observed over a period of 4 to 8 hours. A positive response consists of a significant decrease in mus cle tone, frequency of spasms, or severity of spasms. Pa tients with suboptimal responses may be rescreened after a rest period of 24 hours with 75 mg baclofen (100 mg if necessary). Higher intrathecal doses are rarely if ever indicated. Some patients have clear, classic signs and symptoms of spasticity that have always been known to respond. In such cases, the ITB screening test may be omitted at the discretion of the physician.

The implantation of an intrathecal baclofen pump and catheter is a relatively straightforward surgical procedure. The continuous-infusion pump and spinal catheter systems are usually inserted after induction of general anesthesia with the patient placed in the lateral position after receiving appropriate perioperative antibiotic drugs. In trathecal catheter placement is best performed with the aid of fluoroscopic guidance by using a percutaneous technique, in which a 14- or 15-gauge Tuohy needle is introduced into an appropriate lower lumbar interspace to avoid the conus. We have found that an insertion slightly lateral to the spinous process with oblique advancement in the in tra thecal space reduces the risk of positional catheter oc clu sion or tearing by normal spine flexion and extension.

The catheter is then threaded into the upper lumbar or lower thoracic region. Care should be taken not to torque or pivot the Tuohy needle while threading the catheter, because this may lead to shearing of the catheter into the intrathecal space. Similarly, the catheter should never be withdrawn without simultaneous needle withdrawal, because this also predisposes the catheter to shearing. The catheter tip should be advanced adequately to prevent migration of the device from the intrathecal space. Con versely, overly aggressive advancement predisposes to a higher cervical and brainstem dose of baclofen in the setting of bulk rostral CSF flow. Although higher catheter tip placement may be indicated in upper-extremity spasticity, we have found T9–L1 to be an appropriate catheter tip lev el in the majority of cases. Intrathecal catheters may be secured to lumbar fascia without occluding the catheter itself by a simple purse-string suture in the tissue around the Tuohy needle prior to removal. Basic care should be taken with catheter tunneling.

Placement of the continuous-infusion pump itself is a matter of choice. The standard placement has been within the lower abdominal wall in a suprafascial pocket no more than 1 inch from the surface of the skin for ease of refilling. Consideration must be made for patient comfort be cause the pump may abut either the lower ribs or iliac crest in a mobile patient capable of assuming a seated posi tion. A small lipectomy may be necessary in obese pa tients to sim plify routine postoperative pump filling. Post operative care may include supine positioning for several hours post implantation to reduce the risk of postoperative head ache and CSF leakage.

Optimal pump programming depends on the patient, and dosing ultimately depends on the severity and location of symptoms, catheter position, and the patient's sensitivity to baclofen. According to our experience, the initial continuous-administration daily dose is usually ap prox i mately twice the effective trial bolus dose. Further adjustments may be made after evaluation of the response profile of the patient. Optimal dosing may usually be attained with constant-flow pump titration in two to six adjustments over a period of 1 to 6 months. The most critical time is the initial stabilization period, with dose adjustments made at subsequent refills. Recent 1-year mean daily doses reported in the literature have ranged from 175 to 477 mg/day.[2,37]

It is necessary to remember that dosing depends not only on spasticity relief but also on overall patient satisfaction. Therefore, baclofen dosing is rarely as simple as optimizing performance based on spasticity scales. Indeed, Van Schaeybroeck, et al.,[36] reported a blind dose-reduction test conducted in patients with CP that demonstrated subjective functional deterioration in five but increased Ashworth Scale scores in only two patients, sug gesting that spasticity is only a single component of the benefit to patients from ITB. Several authors have suggested that subjective functional evaluations are influenced dramatically by baclofen-related reduction in spasticity-related pain.[1] Other complicating factors in optimal dosing are the complexity of the clinical syndromes (especially in supraspinal spasticity conditions like CP) and fluctuating external influences on the patient's condition.

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