title: Validation of a noninvasive test routinely used in otology for the diagnosis of cerebrospinal fluid shunt malfunction in patients with normal pressure hydrocephalus.
abstract: OBJECTIVE
  Ventriculoperitoneal shunting is the first-line treatment for normal pressure hydrocephalus. Noninvasive auditory tests based on recorded otoacoustic emissions were assessed, as currently used for universal neonatal hearing screenings, for the diagnosis of cerebrospinal fluid shunt malfunction. The test was designed based on previous works, which demonstrated that an intracranial pressure change induces a proportional, characteristic, otoacoustic-emission phase shift.
  
  
  METHODS
  Forty-four patients with normal pressure hydrocephalus (23 idiopathic and 21 secondary cases) were included in this prospective observational study. The male:female sex ratio was 1.44, the age range was 21-87 years (mean age 64.3 years), and the range of the follow-up period was 1-3 years (mean 20 months). Patients were implanted with a Sophy SU8 adjustable-pressure valve as the ventriculoperitoneal shunt. The phase shifts of otoacoustic emissions in response to body tilt were measured preoperatively, immediately postoperatively, and at 3-6 months, 7-15 months, 16-24 months, and more than 24 months postoperatively. Three groups were enrolled: Group 1, 19 patients who required no valve opening-pressure adjustment; Group 2, 18 patients who required valve opening-pressure adjustments; and Group 3, 7 patients who required valve replacement.
  
  
  RESULTS
  In Group 1, phase shift, which was positive before surgery, became steadily negative after surgery and during the follow-up. In Group 2, phase shift, which was positive before surgery, became negative immediately after surgery and increasingly negative after a decrease in the valve-opening pressure. In Group 3, phase shift was positive in 6 cases and slightly negative in 1 case before revision, but after revision phase shift became significantly negative in all cases.
  
  
  CONCLUSIONS
  Otoacoustic emissions noninvasively reflect cerebrospinal fluid shunt function and are impacted by valve-opening pressure adjustments. Otoacoustic emissions consistently diagnosed shunt malfunction and predicted the need for surgical revision. The authors' diagnostic test, which can be repeated without risk or discomfort by an unskilled operator, may address the crucial need of detecting valve dysfunction in patients with poor clinical outcome after shunt surgery.
authors: Service de Neurochirurgie, Hôpital Gabriel Montpied, Centre Hospitalier Universitaire de Clermont-Ferrand;|Equipe IGCNC, EA 7282, ISIT, UMR 6284, CNRS, Université d'Auvergne;
authors: Laurent
authors: L
authors: Sakka
authors: Laboratoire de Biophysique Sensorielle, Faculté de Médecine, Université d'Auvergne; and.
authors: Alexandre
authors: A
authors: Chomicki
authors: Service de Neuroradiologie, Hôpital Gabriel Montpied, Centre Hospitalier Universitaire de Clermont-Ferrand;
authors: Jean
authors: J
authors: Gabrillargues
authors: Service de Neurochirurgie, Hôpital Gabriel Montpied, Centre Hospitalier Universitaire de Clermont-Ferrand;|Equipe IGCNC, EA 7282, ISIT, UMR 6284, CNRS, Université d'Auvergne;
authors: Toufic
authors: T
authors: Khalil
authors: Service de Neurochirurgie, Hôpital Gabriel Montpied, Centre Hospitalier Universitaire de Clermont-Ferrand;|Equipe IGCNC, EA 7282, ISIT, UMR 6284, CNRS, Université d'Auvergne;
authors: Jean
authors: J
authors: Chazal
authors: Laboratoire de Biophysique Sensorielle, Faculté de Médecine, Université d'Auvergne; and.|Biophysique Médicale, Centre Jean Perrin, Clermont-Ferrand, France.
authors: Paul
authors: P
authors: Avan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002557:Cerebrospinal Fluid Shunts / Q000592:standards*; D004868:Equipment Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000628:therapy*; D007427:Intracranial Pressure; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods; D017084:Otoacoustic Emissions, Spontaneous; D011187:Posture; D011446:Prospective Studies; D012086:Reoperation / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D016896:Treatment Outcome; D017287:Ventriculoperitoneal Shunt / Q000592:standards
keywords: ICP = intracranial pressure; NPH = normal pressure hydrocephalus; OAE = otoacoustic emission; body tilt; normal pressure hydrocephalus; otoacoustic emissions; shunt malfunction; ventriculoperitoneal shunt