Incidentally identified syringomyelia associated with Chiari I malformations: Is early interventional surgery necessary?

OBJECTIVE: The purpose of this study was to analyze clinical data and magne tic resonance imaging (MR[) findings for patients with asymptomatic, incide ntally identified syringomyelia associated with Chiari I malformations who were monitored for more than 10 years, and to clarify the natural history o f these lesions. METHODS: The clinical records of nine patients who had not been surgically treated and were regularly subjected to neurological and MRI examinations w ere analyzed. In MRI studies, the axial diameter of the syrinx at the wides t level, the longitudinal extent of the syrinx, and the extent of tonsillar herniation into the spinal canal were analyzed. As a control, MRI findings for 11 patients with symptomatic syringomyelia associated with Chiari I ma lformations who had been surgically treated were also analyzed, and these M RI parameters were statistically compared between the asymptomatic and symp tomatic groups. RESULTS: One patient underwent surgery, because of neurological changes, 7 years after the first visit. None of the remaining patients demonstrated an y neurological change during the follow-up period (11.2 +/- 0.7 yr), and al l of them have been faring well without surgery. No statistically significa nt differences in MRI findings between the asymptomatic and symptomatic gro ups were observed. CONCLUSION: The long-term clinical courses of patients with asymptomatic, i ncidentally identified syringomyelia associated with Chiari I malformations were observed to be benign. MRI parameters did not provide predictable val ues to recommend interventional surgery. Unless changes in neurological or MRI findings are detected, early interventional surgery is not necessary.