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At least 595 records · Page 33Linked to original sources
PubMed1996

Electro-encephalography spectral analysis of heroin addicts compared with abstainers and normal controls.

UNLABELLED: Previous studies have shown that opiates slow the EEG and, in high doses, reduce the threshold of seizure activity. The present work looks at computerized EEG analyses (in the Fast Fourier Transform-FFT-method) of heroin addicts, recent abstainers and normal controls, with the aim of comparison and delineation of group characteristics. Examinations of 60 taped EEG recordings were performed: 20 subjects were current heroin users, 20 were recent abstainers and 20 were normal controls. Statistical analysis was performed for the relative frequency of wave bands. To amplify the known findings of slowing in heroin users, specific ratios were calculated: the alpha ratio (namely, the 8.0-9.5 Hz to 9.5-12.0 Hz ratio) and the delta to low alpha ratio. The specificity and sensitivity of the FFT method were evaluated through the use of discriminant analysis. The EEG was also recorded on conventional paper and evaluated by a neurologist. RESULTS: The addicts had a higher alpha ratio. The abstainers had a slowing of their alpha waves, a high incidence of delta waves and a delta to low alpha ratio that was relatively high. As a function of time from the beginning of abstinence, this ratio decreased. Abstainers for more than 80 days and controls had identical EEGs. The FFT method had 50% sensitivity for the addicts and 70% for the abstainers, while the specificity was 55%. In contrast, the neurologist's reading of the EEG had a very low sensitivity (25% for the addicts, 30% for the abstainers and 20% for the controls) and a 70% specificity.

Adult↗
PubMed2004

Can CT predict the level of CSF block in tuberculous hydrocephalus?

INTRODUCTION: Treatment of obstructive hydrocephalus in children with tuberculous meningitis (TBM) depends on the level of the cerebrospinal fluid (CSF) block. Air-encephalography is regarded as the gold standard for differentiating communicating and non-communicating hydrocephalus. Since air-encephalography involves a lumbar puncture, it carries the risk of cerebral herniation. AIM. The aim of this study was to determine whether communicating and non-communicating hydrocephalus in TBM can be differentiated by means of cranial computerised tomography (CT). METHODS: A number of CT indices were measured in 50 children with communicating and 34 children with non-communicating hydrocephalus according to air-encephalographic findings. RESULTS: The only CT finding that correlated with the type of hydrocephalus was the shape of the third ventricle. Significantly more children with non-communicating hydrocephalus had a rounded third ventricle than those with communicating hydrocephalus. CONCLUSION: CT is therefore not useful in determining the level of CSF block in TBM. Air-encephalography remains the most reliable way of determining the level of CSF obstruction.

Cerebrospinal Fluid↗
PubMed1979

Neuroradiological aspects of suprasella germinoma.

The plain skull roentgenography, angiography, air encephalography or positive contrast medium ventriculography and computed tomography (CT) of twelve cases of suprasella germinoma were reviewed. In over half of the cases, plain skull roentgenography and angiography showed some abnormalities suggesting a suprasella mass. CT was found to be the most appropriate for routine examination. And air encephalography or positive contrast medium ventriculography offered decisive information.

Adolescent↗
PubMed1979

Metrizamide cisternography and computed tomography for the investigation of pituitary lesions.

Metrizamide cisternography and computed tomography (CT) have been performed on 22 patients suspected of having pituitary or suprasellar lesions, using a low dose of metrizamide. These patients would otherwise have been subjected to air encephalography. The technique is described and the results are presented. The lesions demonstrated included empty sellae and suprasellar extensions of pituitary tumours. We also identified those patients in whom there was no suprasellar extension of a pituitary tumour. The diagnostic information required was obtained in all cases by a combination of the two techniques and air encephalography was avoided in all but one case. The side effects were mild and no serious complications were encountered. We consider this combination of methods to be very useful for the investigation of pituitary lesions.

Humans↗
PubMed1992

The early development of neurosonology: I. Echoencephalography in adults.

The discovery of Midline Echoencephalography is usually attributed to Leksell in 1956. While this was the first time that the examination had been used clinically, it had been preceded by work in England where the echo from the midline of the head appears first to have been demonstrated but its clinical usefulness not recognised. The clinical need for such an examination was so great that, until 1968, more papers were published about echoencephalography than any other medical ultrasonic technique. It only slowly became appreciated how subjective was the technique which, for highest accuracy, had to be performed by a skilled neurologist or neurosurgeon with an intimate knowledge of the patient's cerebral status. The development of more objective automatic techniques, which did not involve the expenditure of a skilled clinician's time, was vociferously opposed by established echoencephalographers who appeared to believe that the demonstration that the examination depended, for accuracy, upon clinical bias by both operator and interpreter, reflected upon their honesty. It was demonstrated that it was the gross attenuation of the acoustic beam by scattering while propagating through the diploic layer of the skull that was responsible for the very variable displays made by echoencephalography. It was for the same reason that two-dimensional B-mode examinations were equally unsatisfactory and none of the ingenious attempts to overcome the obscuring effect of the skull have, after 35 years, been successful. It is only when the skull is removed that the techniques of transdural and intracerebral ultrasonic encephalography can provide useful images from the brain within the skull. It was fortuitous that the realization that ultrasonic encephalography in adults was largely useless coincided with the development of more sophisticated radiological and magnetic techniques which were much more successful in imaging the brain.

Echoencephalography↗
PubMed2003

The spatiotemporal dynamics of the face inversion effect: a magneto- and electro-encephalographic study.

The neurophysiological basis of the face inversion effect was studied with magneto- and electro-encephalography in 10 normal subjects. Spatiotemporal analyses using dipole modeling was performed on combined evoked magneto and electro-encephalography data to hemifield presentation of upright and inverted faces and objects. Inferior temporal cortex, i.e. fusiform gyrus, and lateral temporal cortex near the superior temporal sulcus were activated simultaneously, but independently, at 140-200 ms post-stimulus to upright and inverted unfamiliar faces. Right hemisphere inferior temporal cortex and lateral temporal cortex were active in all subjects, and in the left hemisphere in half the subjects. Latencies to inverted relative to upright faces were longer in the right hemisphere, and shorter in the left hemisphere. For right hemifield stimulation ipsilateral activation delay was around 18-19 ms for both upright and inverted faces and was calculated from all 10 subjects. For left hemifield stimulation, and the data from 7 of 10 subjects, it was 22 and 29 ms to upright and inverted faces, respectively. In sum, the methods used in this study did not identify clear differences in anatomical location of activated regions to upright and inverted faces. We believe, however, that the differences in processing upright versus inverted faces are attributable to temporal processing differences rather than to processing of information by different brain regions.

Adult↗
PubMed2001

Neuromagnetic source localization of auditory evoked fields and intracerebral evoked potentials: a comparison of data in the same patients.

OBJECTIVE: To compare the localizations of different neural sources (a) obtained from intracerebral evoked responses and (b) calculated from surface auditory evoked field responses recorded in the same subjects. Our aim was to evaluate the resolving power of a source localization method currently used in our laboratory, which is based on a recent spatio-temporal algorithm used in magneto-encephalography (MEG). METHODS: Auditory evoked responses were studied in 4 patients with medically intractable epilepsy. These responses were recorded from depth electrodes implanted in the auditory cortex for pre-surgical evaluation (stereo-electro-encephalography (SEEG)), as well as from surface captors (for MEG) placed on the scalp after removal of the depth electrodes. Auditory stimuli were clicks and short tone bursts with different frequencies. RESULTS: All middle-latency components (from 13 to 70 ms post-stimulus onset) were recorded and localized (via SEEG) along Heschl's gyrus (HG). MEG reliably localized Pam and P1m in the same area of HG that intracerebral recordings localized them in. No significant delay between SEEG and MEG latencies was observed. Both methods suggest that N1 is generated from different sources in the intermediate and lateral parts of the HG and in the planum temporale (PT). The source of P2 (PT and/or Area 22) remains unclear and was in one case, localized in different regions according to the method used. This latter component may therefore also be generated by different sources. CONCLUSIONS: The results suggest that both techniques are useful and may be used together in a complementary fashion. Intracerebral recordings allow the researcher to validate and interpret surface recordings.

Acoustic Stimulation↗
PubMed2001

Language and brain: what is up? What is coming up?

The classical aphasiological model of brain/language relationships is nowadays complemented by independent results from functional neuroimaging studies using techniques such as Positron Emission Tomography, functional Magnetic Resonance Imaging, or Event-Related Electro-Encephalography and Magneto-Encephalography mapping. Although brain mapping of language is still hampered by many methodological pitfalls, these methods now appear reliable and provide a renewed description of the temporal spatial dynamics of neural ensembles subserving language functions. Moreover, neuroimaging techniques should also shed a new light on remaining difficult issues such as neural and functional plasticity in developmental or post-lesional contexts.

Aphasia↗
PubMed1975

An assessment of the accuracy of computerized transverse axial scanning (EMI scanner) in the diagnosis of intracranial tumour. A review of 366 patients.

The computerized transverse axial (CTA) scans of 366 patients with intracranial tumours and 267 patients without tumours, but with similar presenting features, were analyzed. In all cases the definitive diagnosis was established either by histological or neurological methods. Most tumours were found to be of low tissue density, but a gradation from low through normal to a high density appearance was recognized. Tissue density enhancement with sodium iothalamate was achieved in 63-9% of supratentorial and 62-4% of infratentorial tumours, and usually allowed a more accurate determination to be made of the boundary between the tumour and the surrounding oedema. The accuracy of the CTA scanner as a screening technique was found to be 96%, this being superior to either clinical evaluation or rectilinear isotope scanning. When assessed on the basis of structural abnormalities demonstrated in the same groups of patients, the CTA scans enabled a diagnosis to be made or a lesion excluded in 92-3% of the patients, a figure which bears comparison with arteriography and pneumo-encephalography. It is anticipated that the simplicity and superior sensitivity of the system should decrease the necessity for invasive techniques such as angiography and pneumo-encephalography in the future.

Adenoma↗
PubMed1976

Radiology for detecting brain tumor recurrences.

Angiography, 99Tcm-pertechnetate scintigraphy and encephalography are compared in their efficacy in the detection of tumor recurrences in 45 patients following brain tumor resection. No single method is always preferable and the best way of detecting a particular tumor recurrence is based on the location and nature of the primary tumor. Scintigraphy is the method of choice for performing routine postoperative follow-up. In cerebral hemisphere tumors angiography may be replaced by brain scanning which is a lesser procedure for the patient and does not necessitate hospitalisation. Encephalography is the examination favoured for detecting recurrences near the base of the skull. Angiography is the best method for demonstrating recurrences near the surface in the region of craniotomy and is essential before reoperation.

Adult↗
PubMed1977

Cranial chordomas.

The clinical and radiological features of 44 cranial chordomas are recorded. Classical features of a mid-line partially calcified tumour, destroying the clivus and causing a soft tissue mass in the sphenoid sinus or nasopharynx were present in about half of the cases. The high incidence of unilateral bone erosion which occurred in nearly a third of the cases, the diagnosti1c significance of erosion of the tip of the clivus and odontoid peg and the not infrequent sclerotic bone reaction to the tumour, are stressed. Increased uptake of 99Tcm occurred in the five cases in which gamma encephalography was performed. Computed transmission tomography was valuable not only in showing the intracranial extension of the tumours and changes in the ventricular system, but also in outlining the extent of the mass within the skull base. Chordomas tend to displace the dura before transgressing it so that the subarachnoid space is usually patent adjacent to quite large tumours allowing the margins of any intracranial or spinal extension to be outlined at encephalography or myelography. Displacements of basal vessels are helpful in confirmation of the site and extent of the tumour. Narrowing of arteries by compression is not frequent but encasement is rare. Pathological circulation which has not been considered to be a feature of chordomas was shown in six cases.

Adolescent↗
PubMed1976

Carbohydrates as potential diagnostic tracers for brain tumors.

Currently available diagnostic tracers for brain tumors are not specific. Tumor-specific tracers would improve the detection of brain tumors by gamma encephalography. Glucose is an important substrate for tumor metabolism and is known to be taken up in large amounts. The authors have studied five labeled carbohydrates in an attempt to find a tumor-specific tracer: three were tritiated (L-galactose-1-3H, L-fucose-3H, and 4,6-dideoxy-xylo-hexose-3H) and two were radioiodinated (methyl-6-125I-6-deoxy-D-glucoside and 6-125I-6-deoxy-D-glucose). The uptake of these tracers by a transplantable mouse ependymoblastoma after intravenous injection was determined by liquid and well scintillation counting. The highest tumor-to-brain ratio was 7.1 to 1 for the tritiated tracers and 6.2 to 1 for the radioiodinated tracers. Although these ratios are not high enough for gamma encephalography, one of the iodinated tracers may be useful for enhancement of contrast in computerized axial tomography.

Animals↗
PubMedDate not supplied

[Magnetoencephalography: a new functional diagnostic technique for the neurosciences].

INTRODUCTION AND OBJECTIVES: We present a review on the technical, methodological and clinical advances in the functional study of the brain by means of magneto-encephalography. We look back the milestones of its historical development, through the work of the major research groups on this field and through our group's works and database (including doctoral thesis). Discussion on the neurophysiological and biomagnetism basis is provided as well as description of technical developments in superconducting detectors (SQUID, Superconducting Quantum Interference Device), signal processing, enhancement of noise-signal ratio and dipole modeling. DEVELOPMENT: The need for brain functional studies has led to newer imaging procedures (functional magnetic resonance, PET, SPECT, etc.). Their spatial and temporal resolution and invasivity are compared to that of magneto-encephalography. Current equipment, up to 306 whole-head channels, may accurately detect cortical and subcortical activity. Apart from the physiological activity, it may be applied to a number of conditions: epilepsy (ictal, interictal and presurgical); dementia, movement disorders, stroke, eloquent cortex delimitation prior to tumour or lesion resection; learning disabilities and foetal studies. CONCLUSIONS: Magnetoencephalography provides with an excellent temporal, very good spatial resolution, acquires in real-time, without references and minimal interference. It entails a great advance in the diagnostic approach in neurosciences.

Brain↗