title: Spectral analysis of intracranial pressure: Is it helpful in the assessment of shunt functioning in-vivo?
abstract: OBJECTIVE
  Shunt failure is common in hydrocephalic patients. The cerebrospinal fluid (CSF) infusion test enables the assessment of CSF absorption capacity, which is represented by the resistance to CSF outflow (ROUT) However, shunt failure may not only affect the CSF absorption capacity but also the intracranial compliance or compensatory properties. Spectral analysis of the ICP signal obtained during the infusion test may enable the comprehensive assessment of the overall deterioration caused by shunt failure.
  
  
  METHODS
  A total of 121 hydrocephalic shunted patients underwent the infusion test with continuous intracranial pressure (ICP) and arterial blood pressure (ABP) recording. The maximum amplitudes of three major frequency bandwidths (0.2-2.6, 2.6-4.0 and 4.0-15 Hz, respectively) were calculated from the ICP. Statistical analyses were conducted to identify factors significantly associated with shunt failure, to construct an index (i.e., the shunt response parameter, SRP) for detecting shunt failure, and to define thresholds for ROUT and SRP.
  
  
  RESULTS
  The ROUT threshold for detecting shunt failure was 7.59 mmHg/ml/min, and this threshold showed an accuracy of 82.64%. All spectral parameters were found to be significantly associated with shunt patency (p<0.05). The SRP exhibited significantly better accuracy than ROUT in detecting shunt failure (91.74%).
  
  
  CONCLUSIONS
  The hydrodynamic assessment of shunted patients enhanced by spectral analysis during the infusion test detected shunt failure with high accuracy. Although further validation is needed, the SRP exhibited promising results.
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Seoul, South Korea; Department of Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom. Electronic address: dongjookim@gmail.com.
authors.forename: Dong-Joo
authors.initials: DJ
authors.lastname: Kim
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Seoul, South Korea.
authors.forename: Hakseung
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Seoul, South Korea.
authors.forename: Eun-Jin
authors.initials: EJ
authors.lastname: Jeong
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Seoul, South Korea.
authors.forename: Hack-Jin
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University, Seoul, South Korea.
authors.forename: Yunsik
authors.initials: Y
authors.lastname: Son
authors.affiliation: Department of Neurology, Korea University College of Medicine, Seoul, South Korea.
authors.forename: Byung-Jo
authors.initials: BJ
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Zofia
authors.initials: Z
authors.lastname: Czosnyka
mesh_terms: D001921:Brain / Q000601:surgery*; D002557:Cerebrospinal Fluid Shunts / Q000379:methods; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000134:cerebrospinal fluid* / Q000601:surgery*; D007427:Intracranial Pressure / Q000502:physiology*; D019736:Prostheses and Implants; D016896:Treatment Outcome
keywords: Cerebrospinal fluid; Hydrocephalus; Infusion test; Shunt; Waveform analysis