title: Supplementary Tests in Idiopathic Normal Pressure Hydrocephalus: A Single-Center Experience with a Combined Lumbar Infusion Test and Tap Test.
abstract: BACKGROUND
  The lumbar infusion test (LIT) and tap test (TT) have previously been described for the diagnosis and selection of appropriate surgical candidates in idiopathic normal pressure hydrocephalus (iNPH).
  
  
  METHODS
  We retrospectively reviewed 81 consecutive patients with a clinical diagnosis of iNPH selected for supplementary testing. Clinical evaluation was scored with the Japanese Grading Scale for Normal Pressure Hydrocephalus, the Global Deterioration Score, and the modified Rankin Scale (mRS). The test protocol included a cerebrospinal fluid pressure monitoring (PMi), an LIT, and a TT. Patients were selected for surgery if outflow resistance was ≥14 mm Hg/mL/minute or if a clinical improvement was recorded after TT.
  
  
  RESULTS
  Sixty-eight patients were selected for ventriculoperitoneal shunting; 72.8% had a positive PMi or LIT, 74.1% had a positive TT, and 63.0% were positive to both tests. Complications were all transient. Clinical evaluation at 12 months after shunting showed a global improvement in 60 patients (88.2%). Overall, 75.0% of patients had no significant disability (mRS score, 1 and 2), 20.6% had an mRS score of 3 or 4, and 4.4% had severe disability after surgery. The positive predictive value of PMi/LIT, TT, or both combined was similar (89.8, 90.0, and 88.2%); however, 21.7% of patients who improved after surgery were selected with either a positive LIT or TT alone.
  
  
  CONCLUSIONS
  LIT and TT are complementary and they can easily be combined in sequence with a low complication rate and high probability of selecting patients with iNPH who may benefit from ventriculoperitoneal shunt surgery.
authors.affiliation: Department of Pathophysiology and Organ Transplantation, University of Milan, Milan, Italy; Department of Neurosurgery, Fondazione IRCCS Cà Granda, Ospedale Maggiore Policlinico, Milan, Italy. Electronic address: fabran@gmail.com.
authors.forename: Fabio
authors.initials: F
authors.lastname: Raneri
authors.affiliation: Department of Pathophysiology and Organ Transplantation, University of Milan, Milan, Italy; Department of Neurology, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Maria Angela Samis
authors.initials: MAS
authors.lastname: Zella
authors.affiliation: Department of Pathophysiology and Organ Transplantation, University of Milan, Milan, Italy; Department of Neurosurgery, Fondazione IRCCS Cà Granda, Ospedale Maggiore Policlinico, Milan, Italy. Electronic address: andrea.dicristofori@gmail.com.
authors.forename: Andrea
authors.initials: A
authors.lastname: Di Cristofori
authors.affiliation: Department of Neurosurgery, Fondazione IRCCS Cà Granda, Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Zarino
authors.affiliation: Department of Neurosurgery, Fondazione IRCCS Cà Granda, Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Pluderi
authors.affiliation: Department of Pathophysiology and Organ Transplantation, University of Milan, Milan, Italy; Department of Neurosurgery, Ospedale Classificato "MoriggiaPelascini", Gravedona, Como, Italy.
authors.forename: Diego
authors.initials: D
authors.lastname: Spagnoli
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002557:Cerebrospinal Fluid Shunts / Q000379:methods*; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000175:diagnosis* / Q000628:therapy*; D060186:Infusions, Spinal / Q000379:methods*; D008365:Manometry / Q000379:methods*; D008875:Middle Aged; D018579:Patient Selection; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013129:Spinal Puncture / Q000379:methods*; D016896:Treatment Outcome
keywords: CSF tap test; Lumbar infusion test; Normal pressure hydrocephalus; VP shunt surgery