Abstract Background: To identify a group of patients with fibromyalgia (FM) and filum disease (FD)/neuro-cranio-vertebral syndrome (NCVS). To analyse the clinical and radiological similarities and differences between groups. To evaluate the clinical results in the FM group after sectioning of the filum terminale (SFT) with the Filum System (FS) Method. To propose an aetiopathological mechanism for FM by applying the FD/NCVS theory. Methods: A retrospective study of 394 patients diagnosed with FD/NCVS. From this sample, two subsamples were created: patients with FM (n=25) and patients without FM (n=369). The incidence of signs and symptoms were compared between groups. The FM group underwent SFT, and the evolution of signs and symptoms were assessed 8 hours, 1 month, and 1 year post-procedure. Results: 55% of the signs and symptoms assessed were present in similar proportions in both samples. There were also similar radiological findings between groups. There was a significant improvement ( p <0.05) in many of the signs and symptoms in the FM group after the sectioning of the filum terminale. There were also radiological signs present in similar proportions, including descent of the cerebellar tonsils, multiple discopathy and syringomyelia. Conclusions: The overlap of signs and symptoms suggests that the underlying cause for central sensitization may be due to FD in a subgroup of FM patients. Patients with FM experience an amelioration of signs and symptoms after SFT. We propose that doctors approach FM cases with an extensive neurological exam that includes complete imaging to facilitate possible diagnosis of FD/NCVS and subsequent treatment.