. 2019 Jul 25;16:21. doi: 10.1186/s12987-019-0142-9

Table 1.

Use and Interpretation of prognostic or diagnostic tests in KUH iNPH protocol

Prognostic or diagnostic test	Performance	Interpretation	Action
Tap test	Gait task: Walking 10 meters, rotating and returning to the starting point (20 m in total). Repeated twice prior and twice after the CSF removal by lumbar puncture CSF drainage: 20–40 ml of CSF is removed by lumbar puncture in a sitting position. Patient rests 1 h in supine position before the repetition of the gait task Evaluation: Examining the gait in a standardized manner. The average gait speed (meters/second), the number and the length of steps prior to and after CSF removal are calculated	Positive^a if there is at least 20% improvement in average gait speed. Negative if less	If positive, patient is referred for CSF shunt treatment, if the patient is willing, and if there are no contraindications Negative test does not exclude favorable CSF shunt treatment outcome. Such patients are referred to the infusion test if willing
Infusion test	CSF outflow resistance via lumbar catheter by measuring changes in ICP caused by continuous or pulsatile infusion of Ringer solution	Positive^b if: Outflow resistance is ≥ 12 mmHg/(ml/min). Negative if not	If positive, patient is likely to suffer from iNPH, and thus may benefit from CSF shunt treatment. If test is negative, patient is unlikely to have iNPH, but some iNPH patients may have normal findings
Continuous measurement of ICP	24 h, intraventricular measurement of ICP	Positive if: (a) a basal intracranial pressure is above 10 mmHg or (b) the presence of any A waves or (c) more than 30% B waves during the monitoring	If positive, patient is likely to suffer from iNPH, and thus may benefit from CSF shunt treatment. If test is negative, patient is unlikely to have iNPH, but some iNPH patients may have normal findings

Prognostic or diagnostic test

Performance

Interpretation

Action

Tap test

Gait task: Walking 10 meters, rotating and returning to the starting point (20 m in total). Repeated twice prior and twice after the CSF removal by lumbar puncture

CSF drainage: 20–40 ml of CSF is removed by lumbar puncture in a sitting position. Patient rests 1 h in supine position before the repetition of the gait task

Evaluation: Examining the gait in a standardized manner. The average gait speed (meters/second), the number and the length of steps prior to and after CSF removal are calculated

Positive^a if there is at least 20% improvement in average gait speed. Negative if less

If positive, patient is referred for CSF shunt treatment, if the patient is willing, and if there are no contraindications

Negative test does not exclude favorable CSF shunt treatment outcome. Such patients are referred to the infusion test if willing

Infusion test

CSF outflow resistance via lumbar catheter by measuring changes in ICP caused by continuous or pulsatile infusion of Ringer solution

Positive^b if: Outflow resistance is ≥ 12 mmHg/(ml/min). Negative if not

If positive, patient is likely to suffer from iNPH, and thus may benefit from CSF shunt treatment. If test is negative, patient is unlikely to have iNPH, but some iNPH patients may have normal findings

Continuous measurement of ICP

24 h, intraventricular measurement of ICP

Positive if: (a) a basal intracranial pressure is above 10 mmHg or (b) the presence of any A waves or (c) more than 30% B waves during the monitoring

CSF Cerebrospinal fluid, iNPH idiopathic normal pressure hydrocephalus, KUH Kuopio University Hospital, ICP intracranial pressure, ml milliliter, min minute, mmHg millimeter of mercury

^aThere are no uniform guidelines how to measure and what is the minimal clinically significant gait improvement after CSF removal

^bStricter outflow resistance limits exist (13, 19, 20)