title: The role of intraoperative micro-Doppler ultrasound in verifying proper clip placement in intracranial aneurysm surgery.
abstract: BACKGROUND
  Aneurysmal subarachnoid hemorrhage constitutes a clinical entity associated with high mortality and morbidity. It is widely accepted that improper clip placement may have as a result of incomplete aneurysm occlusion and/or partial or complete obstruction of an adjacent vessel. Various modalities, including intraoperative or postoperative digital subtracting angiography, near-infrared indocyanine green angiography, micro-Doppler ultrasonography (MDU), and neurophysiological studies, have been utilized for verifying proper clip placement. The aim of our study was to review the role of MDU during aneurysmal surgery.
  
  
  METHODS
  A literature search was performed using any possible combination of the following terms: "aneurysm," "brain," "cerebral," "clip," "clipping," "clip malpositioning," "clip repositioning," "clip suboptimal positioning," "Doppler," "intracranial," "microsurgery," "micro-Doppler," "residual neck," "ultrasonography," "ultrasound," and "vessel occlusion". Additionally, reference lists from the retrieved articles were reviewed for identifying any additional articles. Case reports and miniseries were excluded.
  
  
  RESULTS
  A total of 19 series employing intraoperative MDU during aneurysmal microsurgery were retrieved. All studies demonstrated that MDU accuracy is extremely high. The highest reported false-positive rate of MDU was 2 %, while the false-negative rate was reported as high as 1.6 %. It has been demonstrated that the presence of subarachnoid hemorrhage, specific anatomic locations, and large size may predispose to improper clip placement. Intraoperative MDU's technical limitations and weaknesses are adequately identified, in order to minimize the possibility of any misinterpretations.
  
  
  CONCLUSIONS
  Intraoperative MDU constitutes a safe, accurate, and low cost imaging modality for evaluating blood flow and for verifying proper clip placement during microsurgical clipping.
authors.affiliation: Department of Neurosurgery, University Hospital of Larisa, Biopolis, 41110 Larissa, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Siasios
authors.forename: Eftychia Z
authors.initials: EZ
authors.lastname: Kapsalaki
authors.forename: Kostas N
authors.initials: KN
authors.lastname: Fountas
mesh_terms: D004453:Echoencephalography / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000601:surgery*; D008297:Male; D019635:Neurosurgical Procedures / Q000295:instrumentation / Q000706:statistics & numerical data*; D015995:Prevalence; D019919:Prosthesis Implantation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods / Q000706:statistics & numerical data*; D013525:Surgical Instruments / Q000706:statistics & numerical data*; D016896:Treatment Outcome; D018608:Ultrasonography, Doppler / Q000706:statistics & numerical data*; D014656:Vascular Surgical Procedures / Q000295:instrumentation / Q000706:statistics & numerical data