Source: Albright AL, Barry MJ, Shafron DH, et al. Intrathecal baclofen for generalized dystonia. Dev Med Child Neurol. 2001;43:652–657.This study from Children’s Hospital of Pittsburgh, Pennsylvania, reports on a large experience with intrathecal baclofen in the treatment of dystonia. Eighty-six patients (median age 13 years, range 3–42 years), mostly children with cerebral palsy, were offered a trial of intrathecal baclofen. Because dystonia is more difficult to assess than spasticity, most patients underwent dose-escalation trials conducted over the course of several days by means of a temporary spinal catheter. Responses were graded using a scale developed and validated by the authors.1, 2 More than 90% of patients had a favorable response to the trial, and 77 patients underwent implantation and have had at least 1 year of follow-up. Patient questionnaires indicated improved quality of life and ease of care in 86% and improvements in speech in 33%, swallowing in 26%, upper limb function in 34%, and lower limb function in 37%. The doses of baclofen needed to achieve these effects were notably greater than the doses ordinarily used to treat spasticity, and the spinal catheters were placed in the lower cervical region for these dystonia patients, as compared to thoracic sites for patients predominantly affected by spasticity. Surgical complications were noted in 38% of cases. Eighty-five percent of patients and families reported that intrathecal baclofen was “worth it.”Implantable pumps for continuous intrathecal drug infusion have had a major impact on the use of pharmacological agents whose benefits are mediated at a spinal level but whose side-effects are mediated at a cerebral level. Morphine and baclofen have been approved in this country for use in implantable pumps. Baclofen was first introduced for the management of spasticity of spinal origin.3 The initial beneficiaries were adults with spinal cord injury and demyelinating disease. Most spasticity in childhood, however, develops in the setting of cerebral palsy or traumatic encephalopathy, and because it is of cerebral origin it was not included in the initial FDA approval. A second round of clinical trials demonstrated benefit for spasticity caused by brain diseases in children,4, 5 and since 1994 this therapy has seen increasing implementation in the pediatric age group.Spasticity is easily understood from a physiological, clinical, and therapeutic standpoint. The physiological substrate of spasticity is the monosynaptic muscle stretch reflex arc, and its clinical manifestation is velocity-dependent resistance to passive movement: slow passive movements of a limb encounter little resistance, but rapid movements elicit a sudden increase in tone. Therapeutic interventions that interrupt the afferent or efferent limb of that arc or turn down the gain at the synapse successfully suppress spasticity. Baclofen, a synthetic GABA agonist, is thought to act by dampening spinal reflexes by enhancing presynaptic inhibition. In high enough doses intrathecal baclofen can abolish any degree of spasticity.Spasticity is only part of the spectrum of motoric disturbances that characterize cerebral palsy, traumatic encephalopathy, anoxic encephalopathy, or the heredo-degenerative encephalopathies of childhood. Another major contributor to disability in these conditions is dystonia. Dystonia is characterized by repetitive, involuntary, phasic increases in muscle tone that can occur spontaneously or in response to sensory stimulation or changes in emotional state. It can cause deformities of the appendicular or axial skeleton, and it can interfere with functions such as speech, swallowing, and even breathing. It is a frequent fellow-traveler with spasticity among more severely affected patients, but it does not respond readily to the usual medical and surgical treatments for spasticity. Many failures in the treatment of spasticity are, in fact, failures to distinguish spasticity from dystonia.Dystonia is quite common in cerebral palsy. It causes much disability and difficulty for patients and caretakers and until now there have been no effective treatments. The surgical complication rate seen in the above study seems high, but as the period of time covered saw significant improvements in hardware design and surgical technique,6 current complication rates may be somewhat lower. Between clinic visits for dose adjustments and pump refills and the occasional surgical complication, there must be no hesitation in acknowledging the burdens of intrathecal baclofen therapy; however, the overwhelming majority of families report that the benefits justify the burdens.
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Jun 14, 2024
Prateek Kumar Panda + 4
Open Access