Removal of ECG artifacts from EEG using a modified independent component analysis approach.

In this paper, we introduce a new automatic method for electrocardiogram (ECG) artifact elimination from the electroencephalogram (EEG) or the electrooculogram (EOG). It is based on a modification of the independent component analysis (ICA) algorithm which gives promising results while only using a single-channel EEG (or EOG) and the ECG. To check the effectiveness of our approach, we compared its correction rate with those obtained by ensemble average subtraction (EAS) and adaptive filtering (AF). For this purpose, we applied these algorithms to 10 excerpts of polysomnographic sleep recordings containing ECG artifacts and other typical artifacts (e.g. movement, sweat, respiration, etc.). Two hundred successive interference peaks were examined in each excerpt to compute correction rates. We found that our modified ICA was the most robust to various waveforms of cardiac interference and to the presence of others artifacts, with a correction rate of 91.0%, against 83.5% for EAS and 83.1% for AF.

Automatic sleep spindle detection in patients with sleep disorders.

In this paper, we present a new automatic method for sleep spindle detection. It consist of a generalisation of the Schimicek's method that takes more types of artefacts into account and uses variable thresholds regarding the statistical properties of the signal. Validity of our process is examined on the basis of visual spindle scoring performed by an expert. Results obtained are compared to those obtained by Schimicek's method. For a specificity of 90%, we obtain a sensitivity of 76.9% while Schimicek's method has a sensitivity of 70.4%. Moreover an increase of the area under the ROC curve is observed and confirms that the detection process is improved.

Brain glucose metabolism in borderline personality disorder.

We searched for regional cerebral metabolic disturbances in patients with borderline personality disorder (BPD). Ten inpatients with BPD, no current DSM-IIIR Axis I diagnosis and free of any psychotropic substances, were compared with 15 age-matched control subjects using positron emission tomography with 2-deoxy-2-[18F]fluoro-D-glucose and semiquantitative analysis of regional glucose metabolic activity. We found relative hypometabolism in patients with borderline personality disorder at the level of the premotor and prefrontal cortical areas, the anterior part of the cingulate cortex and the thalamic, caudate and lenticular nuclei. This study shows significant cerebral metabolic disturbances in patients with borderline personality disorder. These metabolic disturbances, which are similar to some of those described in other psychiatric entities, may help to understand the characteristic clinical aspects of this disorder.

Regional glucose metabolism and histopathology of gliomas. A study based on positron emission tomography-guided stereotactic biopsy.

BACKGROUND: Positron emission tomography (PET) with 18F-2-fluoro-2-deoxy-D-glucose (FDG) is widely applied to the study of gliomas. The histology of most gliomas is regionally heterogeneous. The relationship between histologic features and glucose metabolism evaluated by PET with FDG may therefore vary within the limits of the tumor. PET with FDG integrated in the planning of stereotactic brain biopsy allows precise comparison between local FDG uptake and histology. Using this approach, the authors investigated whether glucose metabolism of gliomas is related to anaplasia, and whether PET with FDG detects metabolic heterogeneity that parallels histologic heterogeneity of gliomas. METHODS: A total of 161 biopsy samples collected from 20 PET-guided procedures performed in patients with gliomas (8 low grade astrocytomas, 8 anaplastic astrocytomas, 1 anaplastic oligoastrocytoma, and 3 glioblastomas) were analyzed for the presence or absence of 8 histologic features. Stereotactic coordinates were used to calculate the metabolic rate of glucose (MRGlu) in the region of each biopsy sample. Gray and white matter MRGlu were used to define four metabolic grades that were compared with local histology. RESULTS: The difference in MRGlu expressed as micromoles per 100 g per minute was highly significant between anaplastic and nonanaplastic samples; the median +/- quartile deviation was 23 +/- 16 in anaplastic samples and 18 +/- 5 in nonanaplastic samples (P < 0.005). Even more significant differences were found when MRGlu was normalized to the cortex or to the white matter. Metabolic grades were different in anaplastic and nonanaplastic samples (P < 0.0001). Approximately 75% of samples metabolically graded 3 or 4 demonstrated signs of anaplasia, compared with 10% of samples graded 0 or 1. CONCLUSIONS: FDG uptake in gliomas is anatomically heterogeneous and is regionally related to the presence of anaplasia.

Sleep EEG analysis by linear prediction: frequency changes of slow-wave activity within NREM and REM sleep episodes in healthy men.

The linear prediction method was applied to obtain a power spectra estimate of sleep EEG in 10 healthy young men. In order to analyze frequency changes of the slow-wave activity (EEG power in the delta band, 0.05-2.88 Hz), the delta mean frequency was computed for each 20-second sleep epoch. A mean delta mean frequency was calculated for each sleep stage in each individual. Our observations indicate that the delta mean frequency decreases during NREM periods and increases mainly at the onset of the REM episodes. This finding, in parallel with the detailed analysis of slow-wave power variations, leads to an additional description of sleep characteristics during transitions between the NREM-REM sleep episodes.

Basal ganglia and frontal lobe glucose metabolism. A reproducibility positron emission tomography study.

Positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (FDG) is frequently used to study the metabolic correlates of movement and mental disorders. These studies generally focus on changes in the frontal cortex and the basal ganglia. The reproducibility of glucose metabolism estimates in these structures was tested in 13 normal subjects studied at rest using a standard and simple protocol. A reproducible dorsoventral metabolic gradient was demonstrated in the frontal cortex. Such a gradient was not present in the basal ganglia when the upper region of interest in the caudate nucleus, where the lower metabolic rate of glucose was probably attributable to partial volume effects, was not considered. Absolute values of glucose metabolic rates varied by 6.4 to 12.5% in the frontal cortex and by 6.8 to 14.7% in the basal ganglia. Variations in normalized values in the basal ganglia ranged from 4.0 to 8.6%. The number of subjects required to detect statistical differences in group comparison or in test-retest studies was calculated for different anticipated levels of change. With the variability detected in this experiment, less than 10 subjects were expected to be sufficient to detect a 15% change in most regions and in both types of studies.

Use of positron emission tomography (PET) in stereotactic conditions for brain biopsy.

In order to take advantage of the metabolic information provided by positron emission tomography (PET) in cases of brain tumour, we have developed a technique to integrate PET images routinely in the planning of stereotactic brain biopsy. We used stereotactic PET with [18F]-labelled fluorodeoxyglucose (PET-FDG) in 38 patients undergoing brain biopsy. To evaluate the contribution of PET-FDG in guiding brain biopsy, we analyzed the diagnosis provided by the 78 stereotactic trajectories obtained in these patients. We found that stereotactic PET-FDG seemed to provide more information in cases of anaplastic astrocytomas and glioblastomas than in low-grade gliomas. Our results also show that biopsy trajectories performed in areas where increased FDG uptake is found within the lesion boundaries always provide interpretable specimens; this was not the case for trajectories guided by CT only. Therefore, the routine integration PET-FDG in the planning of stereotactic brain biopsy may lead to a reduction in sampling. Recently, we also tested consecutive stereotactic PET with [11C]-labelled methionine (PET-Met) and PET-FDG. This technique allowed us to compare accurately the tumoural glucose metabolism and protein synthesis. Our results suggest that stereotactic PET may increase the diagnostic yield of brain biopsy and may improve the understanding of PET in neuro-oncology.

Temporal glucose metabolism in borderline personality disorder.

The pathophysiology of borderline personality disorder (BPD) is obscure. Underlying organic factors such as epilepsy are suspected because clinical characteristics of the syndrome are similar to some manifestations of patients with complex partial seizures (CPS). Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) reveals hypometabolism in the area surrounding epileptic foci. To test the epilepsy hypothesis in BPD, we have explored 10 patients with BPD and compared them with 15 control subjects using PET with FDG. We conclude that PET provides no metabolic indication of temporal lobe epilepsy in BPD.

[Cerebral lesions following convulsive partial status epilepticus. Clinical, neuroradiologic and PET study of a case]. / Lésions cérébrales séquellaires d'un etat de mal épileptique partiel convulsivant. Etude clinique, neuroradiologique et par TEP d'un cas.

An 11-year-old girl developed signs of intracranial hypertension after status epilepticus with convulsive movements of her right upper limb. Computerized tomography revealed left hemispheric hypodensity with mass effect, attributed to vasogenic edema. Intracranial hypertension was controlled under intracranial pressure monitoring and clinical status slowly improved. The patient was aphasic and right hemiplegic when she recovered consciousness but she remarkably recovered from her neurological deficits during the following two years despite neuroradiological evolution demonstrating extensive destruction of the left cortex and white matter. Two positron emission tomography (PET) scans were performed respectively six weeks and eight months after status epilepticus, and both demonstrated profound left hemispheric hypometabolism except in the lenticular nucleus and a restricted area of motor/premotor cortex. On the other hand, glucose metabolism in the right hemisphere was heterogeneously increased on the second PET when compared with the first PET. We concluded that, in this case, clinical recovery might have implicated functional reorganization arising from the intact hemisphere.

Positron emission tomography and histopathology in Creutzfeldt-Jakob disease.

We studied a 62-year-old man with Creutzfeldt-Jakob disease (CJD), using positron emission tomography (PET) and (18F)-2-fluoro-2-deoxy-D-glucose (FDG). Glucose metabolism was heterogeneously decreased throughout the brain. At autopsy, regional distributions of spongiosis, astrogliosis, and neuronal loss correlated with premortem regional metabolic deficits. These results suggest that PET with FDG may provide metabolic regional markers for CJD neuropathology.

Reversible striatal hypermetabolism in a case of Sydenham's chorea.

We studied a 10-year-old girl with Sydenham's chorea (SC) using positron emission tomography (PET) with fluorodeoxyglucose (FDG). Choreic movements involved the head and the left side of her body. PET showed increased glucose metabolism in the right caudate nucleus and putamen. Three months after complete recovery, striatal glucose metabolism had returned to normal in the caudate nucleus. In the right putamen, glucose metabolism had decreased compared to that in the first study but remained elevated compared to that of normal young adults. We propose that the transient striatal hypermetabolism may have been due to increased afferent inputs to the striatum as a consequence of striatal or subthalamic nucleus dysfunction.

Brain glucose metabolism and dopamine D2 receptor analysis in a patient with hemiparkinsonism-hemiatrophy syndrome.

We report findings on brain glucose metabolism and dopamine D2 receptors generated by positron emission tomography (PET) in a 67-year-old woman with right hemiparkinsonism-hemiatrophy syndrome (HP-HA). PET with [18F]-fluorodeoxyglucose (FDG) showed marked glucose metabolism asymmetry. There were significant reductions in glucose uptake at the level of the basal ganglia and, to lesser extent, in the fronto-parietal cortex contralateral to the clinically involved side. These changes were different from those found in a patient with hemi-Parkinson's disease who was scanned under similar conditions. Because the patient with HP-HA had only minimal response to levodopa therapy, we evaluated post-synaptic dopaminergic structures using PET with [18F]-fluoroethylspiperone (FESP). No striatal binding asymmetry was found in FESP/PET, which suggests a sparing of striatal dopamine D2 receptors. The changes in FDG uptake which we found were in brain areas relevant to the clinical features of HP-HA syndrome. In addition, our study provides evidence that FDG/PET may help to differentiate HP-HA syndrome from hemi-Parkinson's disease. In most instances, since HP-HA is associated with a more benign clinical course than Parkinson's disease, this distinction is of clinical important.

Positron emission tomography-guided stereotactic brain biopsy.

We describe a technique that allows target definition for stereotactic brain biopsy using coordinates calculated on stereotactic positron emission tomographic (PET) images. In this study, PET images were obtained using [18F]-labeled fluorodeoxyglucose, a marker for glucose metabolism. The difference between PET-calculated and actual stereotactic coordinates of simulated targets is within PET spatial resolution. Combined computed tomography- and PET-guided stereotactic biopsies were performed in 11 patients with brain tumors. In this report, we describe two representative patients who underwent stereotactic brain biopsy using the present technique. Because of the complementary role of PET and computed tomography, their integration in multimodality planning might optimize the target selection for stereotactic brain biopsies.

Computer-aided sleep staging in clinical environment.

In the present paper we will comment on how we have been implementing computer-aided sleep staging (CAS) in the Department of Psychiatry, Erasmus Hospital (Free University of Brussels). Major features of our CAS include real-time stage estimation, full report and hypnogram available in the morning, and evolution of state variables throughout the night (e.g. electroencephalographic spectral characteristics, eye movement density, myographic activity). Parallel, we report an extensive validation study of this system on 50 subjects divided in two groups of 25 patients with psychiatric diseases, and 25 normal subjects.

Automated sleep scoring: a comparative reliability study of two algorithms.

In the present study, deterministic and stochastic sleep staging (DSS and SSS) methods were compared with expert visual analysis in order to provide reliability estimates under strict conditions of comparison. Thirty polygraphic records (15 controls, 15 patients) have been investigated, including artefacts and doubtful periods. Average agreement rates of both methods compared to expert visual scoring were very similar, although a few specifics occasionally appeared for partial sleep stages. The comparison of more than 40,000 sleep decisions (on 20 sec epochs) yielded 75% absolute reliability for normal controls and 70% for pathological cases. However, if the agreement rate obtained for routine visual scoring (82%) in our sleep laboratory is considered as satisfactory, our system is then 90% satisfactory. Finally, complementary aspects outlined in the two automatic scoring systems suggested the development of a unique algorithm on the basis of these methods. Keeping in mind the size of the test sample and the strict procedure of comparison, the two automated staging systems described in this study can be used with reasonable confidence for large scale investigations of sleep in man.