title: Cranial computed tomography before lumbar puncture: a prospective clinical evaluation.
abstract: OBJECTIVE
  To prospectively identify which patients can safely undergo lumbar puncture (LP) without screening cranial computed tomography (CT).
  
  
  METHODS
  Emergency department physicians examined patients before CT. Examiners recorded the presence or absence of 10 clinical findings and answered 8 additional questions. The criterion standard was noncontrast cranial CT interpreted by staff radiologists. Clinical findings were prospectively compared with those of CT.
  
  
  RESULTS
  One hundred thirteen consecutive adults with the urgent need for LP (median age, 42 years) were studied. Fifteen percent of patients meeting entrance criteria had new CT-documented lesions, with 2.7% having lesions that contraindicated LP. Sensitivity, specificity, and likelihood ratios (LRs) were measured for the clinical findings. Three statistically significant predictors of new intracranial lesions were identified: altered mentation (positive LR, 2.2; 95% confidence interval [CI], 1.5-3.2), focal neurologic examination (positive LR, 4.3; 95% CI, 1.9-10), and papilledema (positive LR, 11.1; 95% CI, 1.1-115). No single item adequately predicted the absence of CT abnormalities, but the clinical screening items in aggregate significantly predicted the results (negative LR, 0; upper 95% confidence limit, 0.6). The overall clinical impression had the highest predictive value in identifying patients with CT-defined contraindications to LP (positive LR, 18.8; 95% CI, 4.8-43).
  
  
  CONCLUSIONS
  Because of the low prevalence of lesions that contraindicate LP, screening cranial CT solely to establish the safety of performing an LP typically provides limited additional information. Physicians can use their overall clinical impression and 3 clinical predictors to identify patients with the greatest risk of having intracranial lesions that may contraindicate LP.
authors.affiliation: Department of Medicine, Duke University, Durham, NC, USA. agopal@u.washington.edu
authors.forename: A K
authors.initials: AK
authors.lastname: Gopal
authors.forename: J D
authors.initials: JD
authors.lastname: Whitehouse
authors.forename: D L
authors.initials: DL
authors.lastname: Simel
authors.forename: G R
authors.initials: GR
authors.lastname: Corey
mesh_terms: D000328:Adult; D001927:Brain Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology; D000075202:Contraindications; D004638:Emergency Treatment; D006801:Humans; D010808:Physical Examination; D011237:Predictive Value of Tests; D011446:Prospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012886:Skull / Q000000981:diagnostic imaging*; D013129:Spinal Puncture; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data