Syringomyelia Associated with Tethered Cord Syndrome

Summary

The pathogenesis and dynamic pathophysiology of syringomyelia are not fully understood. Pathogenetically, syringomyelia is categorized as either a communicating syrinx (hydromyelia) or a noncommunicating syrinx. The latter category includes those caused by (1) contusion, (2) compression, (3) traction, (4) arachnoiditis, (5) tumors, and (6) ischemia. Syringomyelia located in the lumbosacral cord is likely derived from the same types of pathogenesis. The signs and symptoms of lumbosacral syringomyelia are similar to those of tethered cord syndrome (TCS), caused by the lesion being in the central portion of the spinal cord. Neurological deficits in these disorders are motor and sensory deficits in the lower limbs, incontinence, and musculoskeletal deformities. Syringomyelia associated with TCS is a unique combination and difficult to correlate because TCS is a metabolic functional disorder and syringomyelia is an anatomic functional criterion. The authors divided a series of syrinx patients into three groups: (1) those with lumbosacral syringomyelia associated with tethered spinal cord, in which the spinal cord is anchored by an inelastic filum; (2) those with low thoracic and lumbar syringomyelia associated with TCS, in which a lipoma, lipomyelomeningocele, or meningocele manqué is the mechanical cause of tethering; and (3) those with a syrinx in the lower thoracic and lumbosacral cord without evidence of a tethered cord. The syrinxes in the patients in all three groups were considered to be isolated from the fourth ventricle cord. The authors’ observations include: (1) The incidence of lumbosacral syrinx in tethered spinal cord patients is much lower than that in TCS patients; (2) The group 1 patients have milder neurological symptomatology than do the group 2 patients. The degree of improvement in the neurological conditions and physical activities are much greater in group 1 than in group 2 patients; (3) Group 3 patients tend to have more serious neurological deficits associated with hydrocephalus and severe musculoskeletal deformities. Based on these facts, the authors postulate that syrinxes should be drained in cases in which the signs and symptoms suggest that the neurological deficits are more significant than those for TCS alone.