title: Ultrastructural study of the filum terminale and its elastic fibers.
abstract: OBJECTIVE
  The filum terminale (FT) is a fibrovascular band involved in the pathophysiology of tethered cord syndrome (TCS). Its morphological and ultrastructural properties remain largely unknown even though they are thought to play a role in the generation of TCS in adult patients with normal level conus medullaris.
  
  
  METHODS
  Twenty fresh adult human cadavers had their fila measured and removed. Transversal and longitudinal sections of the proximal, middle, and distal thirds of FT were submitted to light microscopy analysis with four different techniques. Five fila were selected for longitudinal and transversal scanning electron microscopy analysis.
  
  
  RESULTS
  The bulk of the FT is composed of 5- to 20-microm thick longitudinal bundles of Type 1 collagen separated by 3- to 10-microm intervals, although capillaries and other elements may be present. A delicate (0.05-1.5 microm) meshwork of predominantly Type 3 collagen transversal fibers connects these bundles. Abundant longitudinally oriented elastic and elaunin fibers are found inside collagen bundles. A complex tridimensional structure is evidenced on electron microscopy.
  
  
  CONCLUSIONS
  The longitudinal arrangement of collagen bundles and the impressive amount of elastic and elaunin fibers should elicit considerable elastic properties to the FT. An altered elasticity mechanism has been proposed for TCS; further studies are needed with TCS patients to define whether the collagen structure, Type 1/Type 3 proportion, or elastic fiber content are altered, which could lead to new histopathological definitions of TCS, helping neurosurgeons in the difficult management of TCS patients with normal level conus medullaris.
authors.affiliation: VQM Laboratory, Department of Anatomy, Instituto de Ciencias Biomedicas, and Liga de Neurocirurgia, Faculdade de Medicina, da Universidade de São Paulo, São Paulo, Brazil. rbvfontes@yahoo.com.br
authors.forename: Ricardo B V
authors.initials: RB
authors.lastname: Fontes
authors.forename: Felippe
authors.initials: F
authors.lastname: Saad
authors.forename: Matheus S
authors.initials: MS
authors.lastname: Soares
authors.forename: Flavia
authors.initials: F
authors.lastname: de Oliveira
authors.forename: Fernando C G
authors.initials: FC
authors.lastname: Pinto
authors.forename: Edson A
authors.initials: EA
authors.lastname: Liberti
mesh_terms: D000328:Adult; D002420:Cauda Equina / Q000473:pathology / Q000648:ultrastructure*; D004547:Elastic Tissue / Q000473:pathology / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009436:Neural Tube Defects / Q000175:diagnosis / Q000648:ultrastructure