title: The Sonographic Appearance of Spinal Fluid at Clinically Selected Interspaces in Sitting Versus Lateral Positions.
abstract: OBJECTIVE
  Our objective was to describe the sonographic appearance of fluid at clinically selected interspinous spaces and see if additional interspaces could be identified as suitable and safe targets for needle insertion. We also measured the reproducibility of fluid measurements and assessed for positional differences.
  
  
  METHODS
  A prospective convenience sample of infants younger than 3 months was enrolled in the pediatric emergency department. Excluded were clinically unstable infants or those with spinal dysraphism. Infants were first held in standard lateral lumbar puncture position. Pediatric emergency medicine (PEM) physicians marked infants' backs at the level they would insert a needle using the landmark palpation technique. A PEM sonologist imaged and measured the spinal fluid in 2 orthogonal planes at this marked level in lateral then sitting positions. Fluid measurements were repeated by a second blinded PEM sonologist.
  
  
  RESULTS
  Forty-six infants were enrolled. Ultrasound verified the presence of fluid at the marked level as determined by the landmark palpation technique in 98% of cases. Ultrasound identified additional suitable spaces 1 space higher (82%) and 2 spaces higher (41%). Intraclass correlation coefficient of all measurements was excellent (>0.85), with differences noted for sitting versus lateral position in mean area of fluid 0.34 mm versus 0.31 mm (difference, 0.03; 95% confidence interval [CI], 0.005-0.068), dorsal fluid pocket 0.23 mm versus 0.15 mm (difference, 0.08; 95% CI, 0.031-0.123), and nerve root-to-canal ratio 0.44 versus 0.51 (difference, 0.07; 95% CI, 0.004-0.117).
  
  
  CONCLUSIONS
  Ultrasound can verify the presence of fluid at interspaces determined by the landmark palpation technique and identify additional suitable spaces at higher levels. There were statistically greater fluid measurements in sitting versus lateral positions. These novel fluid measurements were shown to be reliable.
authors.affiliation: From the Division of Pediatric Emergency Medicine, Morgan Stanley Children's Hospital of NY Presbyterian, Columbia University Medical Center, New York, NY.
authors.forename: Yaffa M
authors.initials: YM
authors.lastname: Vitberg
authors.forename: Peggy
authors.initials: P
authors.lastname: Tseng
authors.forename: David O
authors.initials: DO
authors.lastname: Kessler
mesh_terms: D002555:Cerebrospinal Fluid / Q000000981:diagnostic imaging*; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D010173:Palpation / Q000379:methods; D056888:Patient Positioning / Q000379:methods*; D000070316:Pediatric Emergency Medicine; D011446:Prospective Studies; D015203:Reproducibility of Results; D013129:Spinal Puncture / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*