title: Intracranial pressure modulates distortion product otoacoustic emissions: a proof-of-principle study.
abstract: BACKGROUND
  There is an important need to develop a noninvasive method for assessing intracranial pressure (ICP). We report a novel approach for monitoring ICP using cochlear-derived distortion product otoacoustic emissions (DPOAEs), which are affected by ICP.
  
  
  OBJECTIVE
  We hypothesized that changes in ICP may be reflected by altered DPOAE responses via an associated change in perilymphatic pressure.
  
  
  METHODS
  We measured the ICP and DPOAEs (magnitude and phase angle) during opening and closing in 20 patients undergoing lumbar puncture.
  
  
  RESULTS
  We collected data on 18 patients and grouped them based on small (<4 mm Hg), medium (5-11 mm Hg), or large (≥15 mm Hg) ICP changes. A permutation test was applied in each group to determine whether changes in DPOAEs differed from zero when ICP changed. We report significant changes in the DPOAE magnitudes and angles, respectively, for the group with the largest ICP changes and no changes for the group with the smallest changes; the group with medium changes had variable DPOAE changes.
  
  
  CONCLUSIONS
  We report, for the first time, systematic changes in DPOAE magnitudes and phase in response to acute ICP changes. Future studies are warranted to further develop this new approach.
  
  
  BACKGROUND
  DPOAE, distortion product otoacoustic emissionICP, intracranial pressureIIH, idiopathic intracranial hypertensionLP, lumbar punctureTBI, traumatic brain injury.
authors.affiliation: *Baylor College of Medicine, Department of Neurology, Houston, Texas; ‡Smith College, Department of Engineering, Northampton, Massachusetts; §Amherst College, Department of Mathematics and Statistics, Amherst, Massachusetts.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Bershad
authors.forename: Mian Z
authors.initials: MZ
authors.lastname: Urfy
authors.forename: Alina
authors.initials: A
authors.lastname: Pechacek
authors.forename: Mary
authors.initials: M
authors.lastname: McGrath
authors.forename: Eusebia
authors.initials: E
authors.lastname: Calvillo
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Horton
authors.forename: Susan E
authors.initials: SE
authors.lastname: Voss
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D011446:Prospective Studies; D015203:Reproducibility of Results; D013129:Spinal Puncture; D055815:Young Adult