Pathological evaluation of the filum terminale tissue after surgical excision.

Purpose: Tethered cord syndrome (TCS) is an important disease and can produce progressive neurological symptoms. Studies about the filum terminale (FT) have drawn attention to the importance of histopathological investigation of this structure. The most interesting of these subtypes is the FT that incorporates peripheral nerve fibers (PNF). Our study aimed to analyze the frequency of PNF in the FT of 40 cases diagnosed with TCS.

Methods: We performed a retrospective histopathological investigation of FT excised during surgery of patients with TCS who underwent de-tethering. Neurologic and other types of postoperative complications were also revised.

Results: Analysis of the samples showed six dominant histopathological subtypes in the FT: fibroadipose tissues including peripheral nerve bundles (n = 14, 37 %), fibroadipose tissue (n = 10, 25 %), fibrous or adipose tissue (n = 7, 17 %), glial tissues including peripheral nerve sections (n = 4, 10 %), and ependymal and glial tissues (n = 4, 10 %). None of the patients presented with neurologic postoperative complications.

Conclusion: Embryologic studies revealed that it is common to encounter different histological subtypes of FT pathology. However, the presence of peripheral nerve cells in the FT is important for neurosurgical practice due to the risk of sectioning a functional structure during surgery. In our analysis, we demonstrated the high frequency of PNF in FT pathology. However, since none of the patients showed any symptoms of neurologic deterioration, we considered that these fibers were probably not functional. Our findings emphasize the importance of neuromonitoring in TCS surgery. Although we consider that most of the fibers are probably not functional, neuromonitoring after surgery may prevent serious complications.