Voxel-based analysis of Tc-99m ECD brain perfusion SPECT in patients with normal pressure hydrocephalus

Association of right precuneus compression with apathy in idiopathic normal pressure hydrocephalus: a pilot study

Apathy is frequently observed in idiopathic normal pressure hydrocephalus (iNPH) and worsens cognitive impairment and gait disturbance. In this study, we evaluated the regions associated with apathy in iNPH using statistical imaging analysis on the whole brain, both in terms of cerebral blood flow and gray matter volume. Twenty-seven patients with iNPH were assigned to two groups based on their scores on the neuropsychiatric inventory items related to apathy; 18 patients were assigned to the group with apathy (iNPH + APA) and 9 to the group without apathy (iNPH - APA). The magnetic resonance images and cerebral blood flow single-photon emission computed tomography data of the two groups were compared using statistical parametric mapping 12. The regional gray matter volume of the right precuneus was significantly larger in the iNPH + APA group than in the iNPH - APA group, but the regional cerebral blood flow in any region of the brain was not significantly different between the two groups. These results suggested that the larger gray matter volume, which is thought to reflect gray matter compression, in the precuneus might be involved in apathy in iNPH.

Apathy and right caudate perfusion in idiopathic normal pressure hydrocephalus: A case-control study

OBJECTIVES

Apathy is prevalent in patients with idiopathic normal pressure hydrocephalus (iNPH), a treatable disorder resulting from ventricular enlargement. We assessed the relationship between apathy and regional cerebral blood flow (rCBF) in patients with iNPH.

METHODS

Before lumbo-peritoneal shunt surgery (LPS), 56 iNPH patients were evaluated on apathy and dysphoria subscales of the Neuropsychiatric inventory (NPI), and were divided into two groups according to NPI apathy score: 15 without apathy (iNPH-APA) and 41 with apathy (iNPH+APA). Among iNPH+APA, 29 patients were evaluated for apathy and dysphoria 3 months after LPS, and were divided into two groups on the basis of the change in NPI apathy score: 13 with improvement (iNPH+ImpAPA) and 16 without improvement in apathy (iNPH-ImpAPA). N-isopropyl-p-iodoamphetamine single photon emission computed tomography using the autoradiography method was performed before and after LPS, and rCBF was calculated in 22 regions of interest in the frontal cortex, basal ganglia, and limbic system.

RESULTS

In iNPH+APA, rCBF in the right caudate nuclei before LPS was significantly lower than that in iNPH-APA (P = 0.004; two-sample t test). Between iNPH-ImpAPA and iNPH+ImpAPA, a significant group-by-shunt interaction was observed for rCBF in only the right caudate nuclei (F_{1, 28}  = 11.75, P = 0.002; two-way repeated-measures analysis of variance), with increased rCBF in iNPH+ImpAPA but not in iNPH-ImpAPA. The significant group-by-shunt interaction persisted if change in NPI dysphoria scores was used as a covariate (F_{1, 27}  = 8.33, P = 0.008).

CONCLUSIONS

Our findings suggest that right caudate dysfunction might cause apathy in iNPH patients.

Association of cerebrospinal fluid tap-related oscillatory activity and shunt outcome in idiopathic normal-pressure hydrocephalus

BACKGROUND

Idiopathic normal-pressure hydrocephalus (iNPH) is a neuropsychiatric syndrome characterized by the clinical triad of gait disturbance, urinary dysfunction, and cognitive impairment. The aim of the present study was to find specific EEG patterns associated with shunt response in iNPH.

METHODS

Twenty five iNPH patients (10 shunt responders and 15 non-responders) were enrolled in this study. We performed current source density (CSD) analysis in several frequency bands (delta: 2-4 Hz, theta: 4-8 Hz, alpha: 8-13 Hz, beta: 13-30 Hz, gamma: 30-60 Hz) using exact Low Resolution Brain Electromagnetic Tomography (eLORETA). CSD distribution was compared between shunt responders and non-responders for each frequency band before and after CSF tap test.

RESULTS

Shunt responders showed increased gamma CSD in the left temporal cortex before CSF tapping relative to non-responders. However, after CSF tapping, shunt response was associated with significantly higher CSDs in several frequency bands, specifically theta, alpha, beta and gamma, involving mainly the frontal and temporal areas. Using eLORETA analysis, we were able to identify cortical oscillatory activity before and after CSF tap test related to clinical recovery due to shunt operation in iNPH.

CONCLUSION

Our findings support and extend the results of previous studies examining the effects of CSF tap test and shunt operation in patients with iNPH, possibly indicating electrophysiological features of shunt response in this disease. These findings warrant future studies to use EEG for prediction of shunt response in iNPH.

Dynamic state of water molecular displacement of the brain during the cardiac cycle in idiopathic normal pressure hydrocephalus

The predictive accuracy of iNPH diagnoses could be increased using a combination of supplemental tests for iNPH. To evaluate the dynamic state of water displacement during the cardiac cycle in idiopathic normal pressure hydrocephalus (iNPH), we determined the change in water displacement using q-space analysis of diffusion magnetic resonance image. ECG-triggered single-shot diffusion echo planar imaging was used. Water displacement was obtained from the displacement probability profile calculated by Fourier transform of the signal decay fitted as a function of the reciprocal spatial vector q. Then maximum minus minimum displacement (delta-displacement), of all cardiac phase images was calculated. We assessed the delta-displacement in white matter in patients with iNPH and atrophic ventricular dilation (atrophic VD), and in healthy volunteers (control group). Delta-displacement in iNPH was significantly higher than those in the atrophic VD and control. This shows that water molecules of the white matter in iNPH are easily fluctuated by volume loading of the cranium during the cardiac cycle, due to the decrease in intracranial compliance. There was no significant correlation between delta-displacement and displacement. The delta-displacement and the displacement do not necessarily yield the same kind of information. Delta-displacement demonstrated to obtain biophysical information about fluctuation. This analysis may be helpful in the understanding physiology and pathological condition in iNPH and the assisting in the diagnosis.

Global cerebral hypoperfusion in preclinical stage of idiopathic normal pressure hydrocephalus

In patients with idiopathic normal pressure hydrocephalus (iNPH), ventriculomegaly and narrowed subarachnoid spaces at the high convexity appear in magnetic resonance (MR) images before the occurrence of objective symptoms. In addition, quantitative regional cerebral blood flow (rCBF) has been reported to be reduced in iNPH patients with objective symptoms. To determine whether reduced rCBF is responsible for the appearance of symptoms, we compared rCBF in patients with suspected iNPH with no objective triad symptoms (NOS), iNPH patients with apparent objective triad symptoms (AOS) and normal control subjects (NC). Regional CBF was quantified in 35 Regions-of-interest (ROIs) by 123I-IMP single photon emission computed tomography (SPECT) using the autoradiography (ARG) method. Multiple comparisons showed that, in all brain regions examined except for in the frontal white matter, rCBF in the NOS group was significantly lower than that in the NC group, but in all brain regions, not significantly different from that of the AOS group. These results suggest that factors other than rCBF in the resting state are responsible for the occurrence of objective symptoms of iNPH.