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Background The aim of this study was to investigate whether default mode network (DMN) connectivity and brain white matter integrity at baseline were associated with severe cognitive impairments at baseline and poor cognitive outcomes after shunt placement in patients with idiopathic normal pressure hydrocephalus (iNPH). Methods Twenty consecutive patients with iNPH whose symptoms were followed for 6 months after shunt placement and 10 healthy controls (HCs) were enrolled. DMN connectivity and brain white matter integrity at baseline in the patients with iNPH and HCs were detected by using resting-state functional magnetic resonance imaging (MRI) with independent component analysis and diffusion tensor imaging, respectively, and these MRI indexes were compared between the patients with iNPH and HCs. Performance on neuropsychological tests for memory and executive function and on the gait test was assessed in the patients with iNPH at baseline and 6 months after shunt placement. We divided the patients with iNPH into the relatively preserved and reduced DMN connectivity groups using the MRI indexes for DMN connectivity and brain white matter integrity, and the clinical measures were compared between the relatively preserved and reduced DMN connectivity groups. Results Mean DMN connectivity in the iNPH group was significantly lower than that in the HC group and was significantly positively correlated with Rey auditory verbal learning test (RAVLT) immediate recall scores and frontal assessment battery (FAB) scores. Mean fractional anisotropy of the whole-brain white matter skeleton in the iNPH group was significantly lower than that in the HC group. The reduced DMN connectivity group showed significantly worse performance on the RAVLT at baseline and significantly worse improvement in the RAVLT immediate recall and recognition scores and the FAB scores than the preserved DMN connectivity group. Moreover, the RAVLT recognition score highly discriminated patients with relatively preserved DMN connectivity from those with relatively reduced DMN connectivity. Conclusions Our findings indicated that iNPH patients with reduced DMN connectivity relative to the severity of brain white matter disruption have severe memory deficits at baseline and poorer cognitive outcomes after shunt placement. However, further larger-scale studies are needed to confirm these findings.

Background: The aim of this study was to investigate whether default mode network (DMN) connectivity and brain white matter integrity at baseline were associated with severe cognitive impairments at baseline and poor cognitive outcomes after shunt placement in patients with idiopathic normal pressure hydrocephalus (iNPH).Methods: Twenty consecutive patients with iNPH whose symptoms were followed for 6 months after shunt placement and 10 healthy controls (HCs) were enrolled. DMN connectivity and brain white matter integrity in patients with iNPH at baseline were detected by performing resting-state functional magnetic resonance imaging with independent component analysis and by using diffusion weighted imaging with tract-based spatial statistics, respectively. Performance on the neuropsychological tests for memory and executive functions and gait test was assessed in patients with iNPH at baseline and 6 months after shunt placement.Results: The mean DMN connectivity in the iNPH group was significantly reduced compared with that in the HC group and was significantly positively correlated with the scores of the Rey auditory verbal learning test (RAVLT) immediate recall and the frontal assessment battery (FAB). The mean fractional anisotropy of the whole-brain white matter skeleton in the iNPH group was significantly lower than that in the HC group. We divided the patients with iNPH into relatively preserved and reduced DMN connectivity groups using the indexes of DMN connectivity and white matter integrity. The reduced DMN connectivity group showed significantly worse performance on RAVLT at baseline and significantly worse improvement of RAVLT immediate recall and FAB scores compared with the preserved DMN connectivity group. Moreover, the RAVLT immediate score/the FAB score ratio highly distinguished the patients with relatively preserved DMN connectivity from those with relatively reduced DMN connectivity.Conclusions: Our findings indicated that iNPH patients with relatively reduced DMN connectivity in comparison to the severity of brain white matter involvement are associated with severe memory deficits at baseline and poorer cognitive outcomes after shunt placement. In addition, DMN connectivity/brain white matter integrity and RAVLT immediate score/FAB score ratios are useful predictors of poor cognitive outcomes after shunt placement.

Non-convulsive status epilepticus describes the syndrome of unexplained impaired consciousness in critically ill patients. Non-convulsive status epilepticus is very likely to lead to delayed diagnosis and poor outcomes because of the absence of convulsive symptoms. EEG is essential for the diagnosis of non-convulsive status epilepticus to establish the association between periodic discharges and rhythmic delta activity in addition to ictal epileptiform discharges according to the Salzburg criteria. Arterial spin labelling, a type of perfusion MRI, has been applied for rapid and non-invasive evaluation of the ictal state. Ictal cerebral cortical hyperperfusion is the most common finding to demonstrate focal onset seizures. Hyperperfusion of the thalamus on single photon emission computed tomography was found in patients with impaired awareness seizures. We hypothesized that thalamocortical hyperperfusion on arterial spin labelling identifies non-convulsive status epilepticus and such thalamic hyperperfusion specifically associates with periodic/rhythmic discharges producing impaired consciousness without convulsion. We identified 27 patients (17 females; age, 39–91 years) who underwent both arterial spin labelling and EEG within 24 h of suspected non-convulsive status epilepticus. We analysed 28 episodes of suspected non-convulsive status epilepticus and compared hyperperfusion on arterial spin labelling with periodic/rhythmic discharges. We evaluated 21 episodes as a positive diagnosis of non-convulsive status epilepticus according to the Salzburg criteria. We identified periodic discharges in 15 (12 lateralized and 3 bilateral independent) episodes and rhythmic delta activity in 13 (10 lateralized, 1 bilateral independent and 2 generalized) episodes. Arterial spin labelling showed thalamic hyperperfusion in 16 (11 unilateral and 5 bilateral) episodes and cerebral cortical hyperperfusion in 24 (20 unilateral and 4 bilateral) episodes. Thalamic hyperperfusion was significantly associated with non-convulsive status epilepticus (P = 0.0007; sensitivity, 76.2%; specificity, 100%), periodic discharges (P, Thalamocortical hyperperfusion on arterial spin labelling MRI could be a new biomarker of non-convulsive status epilepticus according to the Salzburg criteria in critically ill patients. This thalamic hyperperfusion might contribute to the periodic discharges and rhythmic delta activity associated with non-convulsive status epilepticus., Graphical Abstract Graphical Abstract

Background Cryptococcal meningoencephalitis (CM) causes cerebral infarction, typically, lacunar infarction in the basal ganglia. However, massive cerebral infarction leading to death is rare and its pathophysiology is unclear. We report a case of CM causing massive cerebellar infarction, which led to cerebral herniation and death. Case presentation A 56-year-old man who suffered from dizziness and gait disturbance for one month was admitted to our hospital and subsequently diagnosed with a cerebellar infarction. He had a past medical history of hepatitis type B virus infection and hepatic failure. Although the findings on magnetic resonance imaging (MRI) imitated an arterial infarction of the posterior inferior cerebellar artery, an accompanying irregular peripheral edema was observed. The ischemic lesion progressed, subsequently exerting a mass effect and leading to impaired consciousness. External and internal decompression surgeries were performed. Cryptococcus neoformans was confirmed in the surgical specimen, and the patient was diagnosed with CM. In addition, venule congestion in the parenchyma was observed with extensive fibrosis and compressed veins in the subarachnoid space. The patient died 26 days after admission. Autopsy revealed that pathological changes were localized in the cerebellum. Conclusion C. neoformans can induce extensive fibrosis of the subarachnoid space, which may compress small veins mechanically inducing venule congestion and massive cerebral infarction. In such cases, the clinical course can be severe and even rapidly fatal. An atypical pattern of infarction on MRI should alert clinicians to the possibility of C. neoformans infection.

Objective: Temporo-parietal theta activity (TPTA), often detected in hemispheres with internal carotid (ICA) or middle cerebral artery (MCA) occlusive lesions, is more clearly separated from occipital alpha activity by magnetoencephalography (MEG) than electroencephalography. The present study investigated whether TPTA is correlated with misery perfusion, a surgically correctable type of hemodynamic impairment. Methods: Awake MEG was measured in 56 patients with ICA or MCA occlusive lesions. Regional cerebral blood flow (rCBF) and regional cerebrovascular reactivity (rCVR) to acetazolamide were measured in the MCA territory by xenon-133 single-photon emission computed tomography. MEG was repeated in 10 patients after vascular reconstruction surgery. Results: Fourteen patients showed TPTA in the lesion hemisphere (n = 13) or bilaterally (n = 1). The presence of TPTA was significantly correlated with both reduced rCBF and reduced rCVR (P = 0.0009). After surgery, TPTA disappeared in 7 of the 10 studied patients. Conclusions: The presence of TPTA suggests misery perfusion, which is characterized by reduced rCBF and reduced rCVR. Significance: MEG can detect the presence of reversible and surgically remediable cerebral ischemia before the development of complete infarction.

Rhythmic theta activity detected by electroencephalography (EEG) may be correlated with cerebrovascular brain diseases. Magnetoencephalography (MEG) has higher sensitivity and spatial resolution than conventional scalp EEG, so may be a better method to detect theta rhythm in patients with internal carotid artery (ICA) occlusive disease. Simultaneous EEG and MEG were performed in the awake state in 48 patients with unilateral ( n = 42) or bilateral ( n = 6) stenotic lesions (more than 60% occlusion) of the ICA ( n = 47) or middle cerebral artery ( n = 7), and in 27 age-matched healthy normal subjects. No subject had severe neurological deficits. MEG detected the theta rhythm (6–8 Hz) in 14 of 48 patients: ipsilateral to the stenotic or occluded side in 13 hemispheres and bilaterally in one patient with unilateral lesion. The source of the MEG theta rhythm was estimated in the dorsolateral temporo-parietal area, regardless of the location of infarct foci or the stenotic portion of the ICA system. The temporo-parietal theta rhythm was separated from the occipital alpha rhythm by frequency and distribution in MEG. The theta rhythm was found in only two patients by EEG, as well as by MEG. MEG provided better separation of this theta rhythm from the occipital alpha rhythm. Neither MEG nor EEG detected this theta rhythm in the normal subjects. Unilateral temporo-parietal theta rhythm is correlated with the hemisphere with ICA occlusive disease. This rhythm may indicate mild or subclinical abnormalities in the ICA system. MEG is superior to EEG for the detection and localization of theta rhythm.

A 16-year-old girl suffering from intractable temporal lobe epilepsy presented with a pilocytic astrocytoma, which occurred in an area of nodular heterotopia located in the white matter of the temporal lobe. The pilocytic astrocytoma appeared to be covered by an area of gliosis, which contained numerous Rosenthal fibers, while in the lesion the pilocytic astrocytoma occupied a small area. The gliosis eventually became a tumor-like lesion. The white matter around the mass was composed of gliosis with nodular heterotopia. Temporal developmental malformation, which was a basic lesion of the patient, might therefore be a precursor lesion of pilocytic astrocytomas.

Pattern reversal stimulus is most frequently used for clinical application of visual evoked potentials (VEPs). Half-field stimulus has been employed to separate the left and right hemispheric responses. In the partial-field stimulus, however, subjects have to fix their eyes on a given point during the entire procedure; if the visual fixation is not strict, bilateral occipital responses may interfere with each other. In a clinical applications, therefore, the partial-field stimulus may not be suitable for inexperienced patients.

Auditory evoked potentials have been measured in patients with several temporal lobe diseases. The N100 responses disappear in patients with lesions on bilateral superior temporal gyrus[1]. However, separation of a unilateral abnormality in evoked potentials, is difficult due to the spearing effect by tissue layers with inhomogeneous electric conductivities. Activity on the normal hemisphere may interfere with abnormal activity on the diseased hemisphere. Magnetoencephalography (MEG) is known to be less influenced by the inhomogeneous head conductivity. We have found that the whole head MEG is especially suitable to identify differences in bilateral cerebral function [2–4].