Prognostic value of the pulse pressure amplitudes, time to reach the plateau and the slope obtained in the lumbar infusion test for the study of idiophatic normal pressure hydrocephalus.

BACKGROUND AND OBJECTIVE

To study the prognostic value of the resistance to the cerebrospinal fluid outflow (Rout) obtained in the lumbar infusion test in idiopathic normal pressure hydrocephalus (iNPH), as well as the pulse pressure amplitudes in the different periods of the test and other new variables extracted by Neuropicture® software.

MATERIAL AND METHODS

Patients with 'probable iNPH' who underwent a lumbar infusion test were retrospectively revised. The positive predictive values (PPV) of the cutoff point of the best prognostic accuracy of the Rout, the basal pulse pressure amplitude (AMPo), the pulse pressure amplitude during the first 10 min (AMP), the plateau pulse pressure amplitude (AMPmes), the Rout pulse pressure amplitude (AMP), the time to reach the plateau (T), and the slope until reaching the plateau were determined. Patients were categorized either as responders or non-responders.

RESULTS

The study included 64 responders patients and 16 non-responders patients. The PPV of Rout > 15 mmHg/mL/min was 91.7%; AMPo > 2.34 mmHg: 91.3%; AMP > 4.34 mmHg: 83.3%; AMPmes > 12.44 mmHg: 84.6%; AMP > 6.34 mmHg: 85%; T < 634 s: 86.7%; p > 0.040 mmHg/s: 96.3%.

CONCLUSIONS

Rout is a valid criterion to indicate a ventricular shunt. Pulse pressure amplitudes in the different periods of the lumbar infusion test, in addition to T and P, are other variables whose positivity is indicative of shunt response and should be considered in the diagnostic protocol of the iNPH.