The Utility of Neuroimaging Parameters in Discriminating Patients of Normal-Pressure Hydrocephalus with Positive Cerebrospinal Fluid Tap Test Response from Healthy Controls

Abstract

Objective: To investigate the frequency of previously defined neuroimaging signs of normal pressure hydrocephalus in our NPH patient group with positive cerebrospinal fluid (CSF) tap test response. Methods: Twenty-two patients with probable NPH and 33 healthy control individuals were enrolled in this study. Previously defined 9 parameters including Evan’s index, narrow high convexity sulci, dilation of the Sylvian fissures, focally enlarged sulci, enlargement of the temporal horns, callosal angle, periventricular hyperintensities, bulging of the lateral ventricular roof, and disproportionately enlarged subarachnoid space hydrocephalus were evaluated on conventional magnetic resonance imaging. A total radiological score was formed in both groups. The total radiological score, scores, and frequency of each radiological parameters were compared between patient and healthy control groups. Results: The mean age of the patient group was 67.31 ± 7.27 (F/M ratio was 7/15), whereas it was 69.09 ± 4.89 (F/M ratio was 11/22) in healthy control group. The result of these analyses revealed that scores of all the radiological parameters, except callosal angle score, were found to be higher in NPH patient group. The parameters with the highest positive predictive values were narrow high convexity sulci, narrowing of callosal angle, and DESH (100%, 100%, and 100%, respectively). On the other hand, enlargement of temporal horns had the highest negative predictive value among all parameters (96%). Conclusion: The results of our study support the use of neuroimaging parameters as an alternative method for CSF tap test. We suggest that in the presence of narrow high convexity sulci and/or narrowing of callosal angle, the decision of shunt surgery may be made in patients with suspicion of NPH, without performing CSF tap test. Confirmation of these results, in the future, large-scale studies may certainly provide critical perspectives to be used in the clinical practice.

Callosal Angle Sub-Score of the Radscale in Patients with Idiopathic Normal Pressure Hydrocephalus Is Associated with Positive Tap Test Response

“…The same holds true for the individual sub-scores except for “callosal angle” sub-score, which was higher (meaning the angle is more acute) among tap test responders. This is in agreement with the findings of Onder et al (2020) supporting that callosal angle, is an imaging marker, that could be used in patients with high suspicion of iNPH as an alternative of tap test to decide if they should have shunt surgery [ 12 ]. Lotan et al in 2021 also suggested that callosal angle may be used as an imaging marker useful to predict tap test responsiveness [ 35 ].…”

“…Thus, brain imaging in patients with iNPH is essential to diagnosis. However, many of the individual imaging parameters described in various studies lack adequate sensitivity and specificity [ 12 ]. To this end, a structured scale for the overall evaluation of imaging data has been proposed by Kockum et al, in 2015 and 2018, the so-called Radscale [ 13 , 14 ].…”