Comparison of Noninvasive Measurements of Intracranial with Tap Test Results in Patients with Idiopathic Normal...

Normal pressure hydrocephalus is a disease directly related to the change in intracranial compliance and consequent repercussions in the brain parenchyma. Invasive monitoring of such parameters proves to be reliable especially for prognosis in neurocritical patients; however, it is not applicable in an outpatient service setting. The present study describes the comparison between the tap test results and the parameters obtained with a non-invasive sensor for monitoring intracranial compliance in patients with suspected NPH.

Twenty-eight patients were evaluated before and after lumbar puncture of 50mL of CSF (the tap test), comprising clinical assessment, magnetic resonance imaging, physical therapy assessment using the Timed Up and Go test, Dynamic Gait Index, BERG test, neuropsychological assessment, and recording of non-invasive intracranial compliance data using the Brain4care^® device in three different positions (lying, sitting, and standing) for 5 min each. The tap test results were compared to the Time to Peak and P2/P1 ratio parameters obtained by the device.

The group that had a positive Tap test result presented a median P2/P1 ratio greater than 1.0, suggesting a change in intracranial compliance. In addition, there was also a significant difference between patients with positive, negative, and inconclusive results, especially in the lying position.

A non-invasive intracranial compliance device when used with the patient lying down and standing up obtained parameters that suggest correspondence with the result of the tap test.