Features of the Filum Terminale in Tethered Cord Syndrome with Focus on Pathology

Objective : Filum transection is one of the most commonly performed operative procedure in pediatric neurosurgery. However, the clinical and pathological features as well as the surgical indication are not well-established. This study aimed to analyze the characteristics of patients who underwent transection of the filum during the last 10 years in a single institute. Methods : A total of 82 patients underwent transection of the filum during the period. As a general rule, we performed the transection in patients who are symptomatic or have abnormality in the urologic or neuromuscular evaluations. There were exceptions as asymptomatic patients who only fit the definition of thickened filum (width greater than 2.0 mm or conus level below L3 vertebral body) were operated by parent's wish or surgeon's preference according to radiological findings, etc. Results : Seventy-six out of 82 patients had fibrous tissue in the pathologic specimen of filum. Interestingly, patients who had glial cells were more correlated with no preoperative syrinx, and no progression of syrinx even for those who did have syrinx initially. Also, larger percentage of symptomatic patients had peripheral nerve twigs than asymptomatic patients. No difference in conus level or thickness of filum was found between patients with or without preoperative syrinx. Significantly more patients with syrinx (56%) were chosen to be operated without any symptom or abnormality in study i.e., solely based on radiological findings than those without syrinx (21%). The surgical outcome for syrinx was favorable, as all but one patient had either improved or static syrinx. The exceptional case had increase in size due to the upward displacement of the proximal end of the cut filum. Conclusion : This study evaluated the pathological, clinical, radiological features of patients who underwent transection of the filum. Interesting correlations between pathological findings and clinical features were found. Excellent outcome regarding preoperative syrinx was also shown.