title: Pathomorphological description of the shunted portion of a filum terminale arteriovenous fistula.
abstract: BACKGROUND
  The clinical morphology of a filum terminale arteriovenous fistula (f-AVF) is well known; however, pathological details of the fistulized portion are unknown. Herein, we report the pathological findings of the f-AVF.
  
  
  METHODS
  Case report and literature review.
  
  
  OBJECTIVE
  To present a detailed pathological examination of the fistulized portion of the f-AVF.
  
  
  METHODS
  A 71-year-old man presented with gradually worsening bilateral foot paresthesias and anal dysesthesia. T2-weighted magnetic resonance imaging showed flow voids surrounding an edematous conus medullaris and cauda equina with spinal stenosis at L3-L4 and L4-L5. Spinal digital subtraction angiography demonstrated an f-AVF fed by the left T9 intercostal artery.
  
  
  RESULTS
  We performed laminotomies of L3 and L4 to open the dura mater and found a hypertrophic filum terminale. It was resected, leaving a length of 2 cm between the abnormal proximal end and normal distal end. The f-AVF completely disappeared after the surgery. On pathological examination, the filum terminale included two vessels at the proximal end and one at the distal end. At the proximal end, immunostaining showed one vessel that was definitively an artery with both an internal elastic membrane (IEM) and smooth muscle. The other was a vein and lacked an IEM. On the distal side, the collagen fibers gradually increased, the IEM partially disappeared from the arterial wall, and the vein became arterialized with a thin IEM. At the distal end the two vessels joined. Therefore, we speculated that the fistulized portion of the f-AVF was not a fistula point but had some lengths where the artery had characteristics of a vein and there was venous arterialization.
  
  
  CONCLUSIONS
  The filum arteriovenous shunting occurred at the portion where there was venous arterialization and the artery had the characteristics of a vein. Therefore, resecting the filum terminale requires more proximal from the normal distal end.
authors: Department of Neurological Surgery, Aichi Medical University Hospital, Karimata, Yazako, Nagakute City, Aichi, Japan. Electronic address: take7106@aichi-med-u.ac.jp.
authors: Mikinobu
authors: M
authors: Takeuchi
authors: Department of Neurological Surgery, Aichi Medical University Hospital, Karimata, Yazako, Nagakute City, Aichi, Japan.
authors: Aichi
authors: A
authors: Niwa
authors: Department of Neurological Surgery, Aichi Medical University Hospital, Karimata, Yazako, Nagakute City, Aichi, Japan.
authors: Naoki
authors: N
authors: Matsuo
authors: Department of Neurological Surgery, Aichi Medical University Hospital, Karimata, Yazako, Nagakute City, Aichi, Japan.
authors: Masahiro
authors: M
authors: Joko
authors: Department of Neurological Surgery, Aichi Medical University Hospital, Karimata, Yazako, Nagakute City, Aichi, Japan.
authors: Takahiro
authors: T
authors: Nakura
authors: Department of Neurological Surgery, Aichi Medical University Hospital, Karimata, Yazako, Nagakute City, Aichi, Japan.
authors: Masahiro
authors: M
authors: Aoyama
authors: Department of Pathology, Aichi Medical University Hospital, Karimata, Yazako, Nagakute City, Aichi, Japan.
authors: Toyoharu
authors: T
authors: Yokoi
authors: Department of Neurological Surgery, Aichi Medical University Hospital, Karimata, Yazako, Nagakute City, Aichi, Japan.
authors: Masakazu
authors: M
authors: Takayasu
mesh_terms: D000368:Aged; D015901:Angiography, Digital Subtraction; D001164:Arteriovenous Fistula / Q000473:pathology* / Q000601:surgery; D002420:Cauda Equina / Q000098:blood supply / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007796:Laminectomy / Q000379:methods; D008159:Lumbar Vertebrae / Q000601:surgery; D018810:Magnetic Resonance Angiography; D008297:Male; D011128:Polyradiculopathy / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D016896:Treatment Outcome
keywords: AVF; Arterialization; Artery with characteristics of a vein; Filum terminale arteriovenous fistula; Pathology; Shunt