Abstract
Idiopathic normal pressure hydrocephalus (iNPH) is a neuropsychiatric disease characterized by gait disturbance, cognitive deterioration and urinary incontinence associated with excessive accumulation of cerebrospinal fluid (CSF) in the brain ventricles. These symptoms, in particular gait disturbance, can be potentially improved by shunt operation in the early stage of the disease, and the intervention associates with a worse outcome when performed late during the course of the disease. Despite the variable outcome of shunt operation, noninvasive presurgical prediction methods of shunt response have not been established yet. In the present study, we used normalized power variance (NPV), a sensitive measure of the instability of cortical electrical activity, to analyze cortical electrical activity derived from EEG data using exact-low-resolution-electromagnetic-tomography (eLORETA) in 15 shunt responders and 19 non-responders. We found that shunt responders showed significantly higher NPV values at high-convexity areas in beta frequency band than non-responders. In addition, using this difference, we could discriminate shunt responders from non-responders with leave-one-subject-out cross-validation accuracy of 67.6% (23/34) [positive predictive value of 61.1% (11/18) and negative predictive value of 75.0% (12/16)]. Our findings indicate that eLORETA-NPV can be a useful tool for noninvasive prediction of clinical response to shunt operation in patients with iNPH.
Highlights
Idiopathic normal pressure hydrocephalus is a neuropsychiatric disease characterized by gait disturbance, cognitive deterioration and urinary incontinence associated with excessive accumulation of cerebrospinal fluid (CSF) in the brain ventricles
Lumbar punction is an invasive procedure having some risks, including infection, bleeding and postural headache. It has the problem of low negative predictive value (18–50%) which means that patients that do not respond to the lumbar tapping (CSF tap negative patients) may show symptoms improvement if shunt operation is p erformed[10,11,12]
In a previous study using EEG and normalized power variance (NPV) analysis, a sensitive measure of the instability of cortical electrical a ctivity[19,30], we showed that shunt responders had significantly higher NPV at the right fronto-temporo-occipital electrodes (Fp2, T4 and O2) in beta frequency band compared to non-responders[29]
Summary
Idiopathic normal pressure hydrocephalus (iNPH) is a neuropsychiatric disease characterized by gait disturbance, cognitive deterioration and urinary incontinence associated with excessive accumulation of cerebrospinal fluid (CSF) in the brain ventricles. We used normalized power variance (NPV), a sensitive measure of the instability of cortical electrical activity, to analyze cortical electrical activity derived from EEG data using exact-low-resolution-electromagnetic-tomography (eLORETA) in 15 shunt responders and 19 non-responders. Brain imaging by Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) shows typical morphologic abnormalities such as ventriculomegaly, dilation of the Sylvian fissures and narrowing of the sulci and subarachnoid spaces over the high-convexity area of the brain, indicating excessive accumulation of cerebrospinal fluid (CSF) in the ventricles[1] This morphological feature was defined as disproportionately enlarged subarachnoid-space hydrocephalus (DESH) in Japanese diagnostic criteria for iNPH1. In a previous study using EEG and normalized power variance (NPV) analysis, a sensitive measure of the instability of cortical electrical a ctivity[19,30], we showed that shunt responders had significantly higher NPV at the right fronto-temporo-occipital electrodes (Fp2, T4 and O2) in beta frequency band compared to non-responders[29]. We decided to apply NPV analysis with eLORETA cortical electrical activity (eLORETA-NPV analysis), as it is able to detect differences in phase-instability of cortical electrical activity between shunt responders and non-responders
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