Background: Filum Disease (FD) is a proposed diagnostic entity in which anomalous traction by an abnormally tense filum terminale is hypothesized as the common mechanical origin of Arnold-Chiari Type I Syndrome (ACIS), Idiopathic Syringomyelia (IS), and Idiopathic Scoliosis (ISc). Whether FD carries a hereditary basis remains unexplored in the literature.

Objective: To gather preliminary evidence bearing on the possible hereditary nature of FD, through bibliographic review and analysis of familial cases from a single institutional cohort.

Methods: A narrative review of genetic and hereditary studies on ACIS, IS, and ISc was performed. Separately, 33 familial groups were identified retrospectively from 950 patients diagnosed with FD at the ICSEB between 1993– 2015, each with at least two affected members, including two monozygotic twin pairs.

Results: Existing genetic literature on the component conditions of FD suggests polygenic inheritance with variable penetrance, with chromosomal regions 9, 15, and 16 most frequently implicated — though no consensus exists. Co- occurrence with Klippel-Feil, von Recklinghausen's neurofibromatosis, IgE syndrome, and Ehlers-Danlos syndrome adds circumstantial support. Within the institutional cohort, the observed familial clustering and the differing phenotypic expression between monozygotic twins — syringomyelia predominance in one versus scoliosis in the other — are consistent with, though not conclusive of, a polygenic hereditary component.

Conclusions: The available evidence is suggestive of a hereditary basis for FD, most plausibly polygenic and autosomal. These observations support further investigation, and if confirmed, would have practical implications for genetic counseling of affected families. Genetic research into FD should prioritize filum terminale anomalies over posterior fossa malformations as the primary etiological target.

Miguel B. Royo Salvador, born in 1950 in Zaragoza (Spain), graduated in Medicine and Surgery from the University of Barcelona’s School of Medicine in 1974. He specialized in Neurosurgery and Neurology in 1978 and earned his doctorate ‘cum laude’ from the Autonomous University of Barcelona in 1993. With over forty years of research, he has studied the etiological connection of conditions like Arnold Chiari I syndrome, idiopathic Syringomyelia, and idiopathic Scoliosis. As head of the Institut Chiari & Syringomyelia & Scoliosis de Barcelona, he promotes the Filum System through research, clinical practice, international conferences, and specialist training.