Cerebrospinal fluid closing pressure-guided tap test for the diagnosis of idiopathic normal pressure hydrocephalus: A descriptive cross-sectional study

Standardizing the large-volume "tap test" for evaluating idiopathic normal pressure hydrocephalus: a systematic review

INTRODUCTION

Idiopathic normal pressure hydrocephalus (iNPH) is characterized by the clinical triad of gait, cognitive, and urinary dysfunction associated with ventriculomegaly on neuroimaging. Clinical evaluation before and after CSF removal via large volume lumbar puncture (the "tap test") is used to determine a patient's potential to benefit from shunt placement. Although clinical guidelines for iNPH exist, a standardized protocol detailing the procedural methodology of the tap test is lacking.

EVIDENCE ACQUISITION

Using PRISMA guidelines, a systematic review of PubMed and Embase identifying studies of the tap test in iNPH was performed, centered on four clinical questions (volume of CSF to remove, type of needle for lumbar puncture, which clinical assessments to utilize, and timing of assessments). A modified Delphi approach was then applied to develop a consensus standardized tap test protocol for the evaluation of idiopathic normal pressure hydrocephalus.

EVIDENCE SYNTHESIS

Two hundred twenty-two full-text articles encompassing a total of 80,322 participants with iNPH met eligibility and were reviewed. Variations in the tap test protocol resulted in minimal concordance among studies. A standardized protocol of the tap test was iteratively developed over a two-year period by members of the International Parkinson and Movement Disorders Society Normal Pressure Hydrocephalus Study Group until expert consensus was reached.

CONCLUSIONS

The literature shows significant variability in the procedural methodology of the tap test. The proposed protocol was subsequently developed to standardize clinical management, improve patient outcomes, and better align future research in idiopathic normal pressure hydrocephalus.

[Possibilities of dynamic phase contrast MRI of cerebrospinal fluid for performing a tap test in a patient with idiopathic normotensive hydrocephalus]

Idiopathic normotensive hydrocephalus (iNH) is a widespread disease in elderly patients. The effectiveness of iNG treatment and the subsequent quality of patients' lives directly depends on timely and early diagnosis. The criteria for diagnosing iNG that are used in neuroimaging can also be found in patients without clinical manifestations of this disease, and the widely used tap-test is an invasive technique with a rather low sensitivity. The need for early diagnosis and initiation of treatment before the development of irreversible damage to brain structures determines the relevance of the search for an accessible, minimally invasive, accurate and safe diagnostic method. The article presents a clinical observation of the use of phase-contrast MRI of cerebrospinal fluid (CSF) in a female patient with a positive response to the tap test with a quantitative analysis of changes in CSF flow parameters and ALVI and Evans indices depending on the time after CSF evacuation. Phase-contrast MRI of CSF with a quantitative assessment of CSF flow parameters in combination with an assessment of the ALVI index has the potential to increase the accuracy of diagnosing iNH and is of scientific interest for further research.