Review articleThe filum terminale internum and externum: A comprehensive review

•Variations of the conus has implications when performing invasive procedure.•Tethered cord syndrome (TCS) is associated with pathology of the filum terminale.•In diagnosing TCS, the filum is often defined as greater than 2 mm in diameter.•The preferred surgical approach to untether the spinal cord is a S1 laminectomy.

Introduction: The filum terminale has oven been overlooked in the literature probably due to its small size and historical lack of research on its true morphology. However, this structure's roll in the tethered cord syndrome has become more apparent. Therefore, the current comprehensive review seemed timely. Methods: Using standard search engines, the history, embryology, anatomy, pathology and surgery of the filum terminale were reviewed. Conclusions: It is only recently that the true anatomy and pathological involvement of the filum terminale in the tethered cord syndrome have been elucidated.