ABSTRACT
The treatment of spasticity by the direct infusion of intrathecal baclofen (ITB), first proposed by Penn and Kroin in 1984, has met with significant success in treating patients with this condition [1]. To apply this therapy successfully, the surgeon must have a clear understanding of the definition of spasticity and the criteria with which to select appropriate patients. In a narrow physiological sense, spasticity may be defined as a motor disorder characterized by a velocity-dependent increase in muscle tone with exaggerated tendon jerks resulting from hyperexcitability of the stretch reflex [2]. The presence of spasticity can be thought of as pathognomonic of an upper motor lesion and is the result of both a facilitation and a disinhibition of the stretch reflex from a lack of input from descending cortical and spinal tracts [3]. The fact that it is defined as velocity dependent helps to distinguish it from other forms of rigidity, such as that caused by contractures, dystonias, or Parkinson’s disease. The condition of spasticity may result from many disease states originating in either the spine or the brain. Spasticity of spinal cord origin may occur with spinal cord injury, multiple sclerosis, spinal ischemia, spinal dysraphism, degenerative myelopathy, transverse myelitis, syringomyelia, spinal tumor, cervical spondylosis, and familial spastic paraparesis. Spasticity of cerebral origin may result from cerebral palsy, trau-
matic brain injury, cerebrovascular accident, anoxic injury, brain tumor, and metabolic diseases of the brain [4,5]. This list is by no means complete. The end result is that spasms, rigidity, and clonus interfere with the normal initiation and completion of a smooth movement and ultimately result in weakness with a loss of mobility and dexterity.
