Histology and intramuscular pressure in spastic muscle

A prospective study was performed to delineate the pathologic processes occurring in the degradation of muscle function with the onset of spasticity. Sixteen adult patients with spasticity secondary to traumatic brain injury (TBI) were evaluated clinically and histologically. Short-term patients showed even distribution of mild, moderate, and severe spasticity, while moderate spasticity predominated in the chronic group. Motor control was predominately selective with pattern overlay in both groups. Muscles with spasticity of less than 6 months duration showed nonspecific histologic changes. Muscles with spasticity of duration longer than 1 year demonstrated neurogenic atrophy, some also showed signs of denervation followed by reinnervation. No evidence of compartment syndrome was found in the spastic muscles studied. Transient high elevation of intramuscular pressure was noted in some patients during muscle stretch or activity. Muscles that become spastic following TBI demonstrate neurogenic degeneration, generally apparent greater than 1 year after the injury. Prior to this, spastic muscles demonstrate nonspecific atrophic changes.