title: Utility of intraoperative ultrasound for tumors of the cauda equina.
abstract: METHODS
  A retrospective chart review of patients with tumors of the cauda equina was performed.
  
  
  OBJECTIVE
  To assess the role of intraoperative ultrasound for detecting tumor migration and modifying the approach to cauda equina tumors.
  
  
  BACKGROUND
  Rostral migration of cauda equina tumors relative to preoperative imaging is well described. The utility of intraoperative ultrasound to identify tumor migration and to modify the surgical approach was analyzed.
  
  
  METHODS
  The medical records of nine consecutive patients undergoing biopsy or resection of a cauda equina tumor diagnosed by magnetic resonance imaging at the authors' institution from January 1994 through December 2000 were reviewed. Four patients with tumors of the cauda equina underwent transdural sonography of the intraspinal compartment after initial laminectomy and before durotomy.
  
  
  RESULTS
  In three patients, the findings on intraoperative ultrasound showed rostral migration of the lesion with respect to the preoperative magnetic resonance imaging, necessitating additional laminectomy and modifying the site of durotomy. One tumor had migrated rostrally one full bony vertebral segment, whereas two tumors each had migrated one half of a bony vertebral segment. Pathology examination in the three patients whose lesions had migrated rostrally demonstrated a schwannoma in every case. In one patient, intraoperative ultrasound showed no lesion migration with respect to the preoperative magnetic resonance imaging, and no modifications to the surgical approach were needed. Pathology examination of this patient demonstrated an ependymoma.
  
  
  CONCLUSIONS
  Intraoperative ultrasound was useful in documenting rostral migration of cauda equina tumors, and facilitated appropriate laminectomy and durotomy. The technique may be particularly valuable for schwannomas of the cauda equina, which seem to have a greater potential for rostral migration.
authors.affiliation: Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, USA. friedman.jonathan@mayo.edu
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Friedman
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Wetjen
authors.forename: John L D
authors.initials: JL
authors.lastname: Atkinson
mesh_terms: D000230:Adenocarcinoma / Q000556:secondary / Q000601:surgery / Q000648:ultrastructure*; D000328:Adult; D002420:Cauda Equina / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D004806:Ependymoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D007796:Laminectomy; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D019635:Neurosurgical Procedures / Q000295:instrumentation; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013120:Spinal Cord Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D013997:Time Factors; D018084:Ultrasonography, Interventional