title: Impact of changes in intraoperative somatosensory evoked potentials on stroke rates after clipping of intracranial aneurysms.
abstract: BACKGROUND
  Somatosensory evoked potential (SSEP) monitoring is used during intracranial aneurysm surgery to track the effects of anesthesia, surgical manipulation, and temporary clipping.
  
  
  OBJECTIVE
  To present the outcomes of 663 consecutive patients (691 cases) treated surgically for intracranial aneurysms who underwent intraoperative SSEP monitoring and to analyze the sensitivity and specificity of significant SSEP changes in predicting postoperative stroke.
  
  
  METHODS
  Of 691 surgeries analyzed, 403 (391 anterior circulation, 12 posterior circulation) were unruptured aneurysms and 288 (277 anterior, 11 posterior) were ruptured. Postoperatively, symptomatic patients underwent computed tomography imaging. Positive predictive value, negative predictive value, sensitivity, and specificity were calculated with a Fisher exact test (2-tailed P value).
  
  
  RESULTS
  Changes in SSEP occurred in 45 of 691 cases (6.5%): 16 of 403 (4.0%) in unruptured aneurysms and 29 of 288 (10%) in ruptured aneurysms. In unruptured aneurysms, reversible SSEP changes were associated with a 20% stroke rate, but irreversible changes were associated with an 80% stroke rate. In ruptured aneurysms, however, reversible changes were associated with a 12% stroke rate, and irreversible changes were associated with a 42% stroke rate. The overall accuracy of SSEP changes in predicting postoperative stroke was as follows: positive predictive value, 30%; negative predictive value, 94%; sensitivity, 25%; and specificity, 95%.
  
  
  CONCLUSIONS
  Intraoperative SSEP changes are more reliable in unruptured aneurysm cases than in ruptured cases. Whereas irreversible changes in unruptured cases were associated with an 80% stroke rate, such changes in ruptured cases did not have any adverse ischemic sequelae in 58% of patients. This information is helpful during the intraoperative assessment of reported SSEP changes.
authors: The Johns Hopkins University School of Medicine, Department of Neurosurgery, Baltimore, Maryland, USA.
authors: Robert T
authors: RT
authors: Wicks
authors: Gustavo
authors: G
authors: Pradilla
authors: Shaan M
authors: SM
authors: Raza
authors: Uri
authors: U
authors: Hadelsberg
authors: Alexander L
authors: AL
authors: Coon
authors: Judy
authors: J
authors: Huang
authors: Rafael J
authors: RJ
authors: Tamargo
mesh_terms: D017542:Aneurysm, Ruptured / Q000175:diagnosis* / Q000453:epidemiology / Q000601:surgery*; D015897:Comorbidity; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000175:diagnosis* / Q000453:epidemiology / Q000601:surgery*; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000706:statistics & numerical data*; D019635:Neurosurgical Procedures; D015995:Prevalence; D011379:Prognosis; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity; D020521:Stroke / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control*; D016896:Treatment Outcome; D014656:Vascular Surgical Procedures