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Biomedical subjects

S Seri

Publications and source records attributed to S Seri.

At least 19 recordsLinked to original sources
PubMed2001

The clinical value of electroencephalogram/magnetic resonance imaging co-registration and three-dimensional reconstruction in the surgical treatment of epileptogenic lesions.

With the rapid developments in image processing, new clinical applications of manipulation and three-dimensional (3-D) reconstruction of neuro-imaging are evolving. Combination with other non-invasive techniques aimed at localising electric sources in the brain is of particular interest. These techniques rely on the recording of brain electrical activity and/or the associated magnetic fields from multiple areas on the scalp. Data obtained from an electroencephalogram (EEG) or from magnetoencephalography (MEG) can be fused in 3-D arrangement with anatomical [magnetic resonance imaging/computerised tomography (MRI/CT)] and/or metabolic [positron emission tomography (PET)] data. Such techniques highlight information on the functional correlates of anatomical or space-occupying lesions and their role in the localisation of related symptomatic epilepsy. In the present study we report on methodological issues and preliminary clinical data on spectral EEG/MRI co-registration procedures, offering two examples of children presenting with hemispheric lesions, one frontal tumour and one temporal arterio-venous malformation. The EEG was acquired from 32/64 electrode location. The electrode position and that of four reference points were measured with a dual sensor Polhemus 3D Isotrak digitiser. Sources of EEG activity were determined in 3-D space with the inverse solution method low resolution electromagnetic tomography (LORETA), providing for each frequency component, the topographic distribution of active electrical sources. The positions of the reference points were also measured on MRI, and co-registration of EEG and MRI was achieved using a transformation algorithm. The reconstructed 3-D images of co-registered EEG/MRI clearly demonstrate the relationship between the space-occupying lesion and the epileptic activity. Preliminary results show that in all the patients it was possible to identify with a remarkable accuracy the 3-D topographic relationship between lesion and cortical areas showing localised abnormalities on the EEG. The present method could further enhance the understanding of the effect of resective treatment of structural lesions on brain functioning. The new combined images can be used in combination with image-guided surgery equipment to modify effective surgical resection.

Brain↗
PubMed2001

Melatonin as a sleep inductor for electroencephalogram recordings in children.

OBJECTIVE: To determine the efficacy of melatonin in obtaining sleep electroencephalograms in children. METHODS: Melatonin was used in 68 unselected children referred to the neurophysiology department for sleep electroencephalogram (EEG). A group of 68 children matched for age and sex who underwent EEGs after sleep deprivation in the same period was used as control. Sleep latency, as well as latency from stage 1 to stages 2, 3 and 4 were measured. RESULTS: No difference in the number of children who went to sleep was seen. No significant difference is the macrostructure of sleep was seen, other than a reduced sleep latency for the melatonin group (P<0.01). CONCLUSION: The study suggests that melatonin can reliably be used for obtaining sleep EEGs in children. Its use seems to provide a good alternative to pharmacological sedation and a complementary method to sleep deprivation.

Child↗
PubMed2001

Idiopathic central pontine myelinolysis in childhood.

Central pontine myelinolysis (CPM) is rare in childhood with only a few cases reported in world literature. We report a 7-year-old male who presented with acute ataxia, swallowing difficulties, dysarthria, and radiological features consistent with the disorder. He improved remarkably with oral prednisolone therapy and was almost back to normal by 2 weeks. A review of the literature is also included.

Anti-Inflammatory Agents↗
PubMed1999

Dynamic contrast-enhanced MRI of Implanted VX2 tumors in rabbit muscle: comparison of Gd-DTPA and NMS60.

We studied the dynamics of injected contrast enhancement in implanted VX2 tumors in rabbit thigh muscle. We compared two contrast agents Gd-DTPA and NMS60, a novel gadolinium containing trimer of molecular weight 2.1 kd. T1-weighted spin echo images were acquired preinjection and at 5-60 min after i.v. injection of 0.1 mmol/kg of agent. Dynamic T1-weighted SPGR images (1.9 s/image) were acquired during the bolus injection. Male NZW rabbits (n = 13) were implanted with approximately 2 x 10(6) VX2 tumor cells and grew tumors of 28+/-27 mL over 12 to 21 days. NMS60 showed significantly greater peak enhancement in muscle, tumor rim, and core compared to DTPA in both T1-weighted and SPGR images. NMS60 also showed delayed peak enhancement in the dynamic scans (compared to Gd-DTPA) and significantly reduced leakage rate constant into the extravascular space for tumor rim (K21 = 5.1 min(-1) vs. 11.5 min(-1) based on a 2 compartment kinetic model). The intermediate weight contrast agent NMS60 offers greater tumor enhancement than Gd-DTPA and may offer improved regional differentiation on the basis of vascular permeability in tumors.

Animals↗
PubMed1999

Autism in tuberous sclerosis: evoked potential evidence for a deficit in auditory sensory processing.

OBJECTIVE: Autism is a frequent manifestation of tuberous sclerosis complex (TSC) being reported in up to 60% of the patients. Its presence is in association with cortical and subcortical lesions involving the temporal lobes. This study was designed to shed light on the functional mechanisms linking anatomical lesions of TSC and behavioural phenotype by investigating scalp recorded event related potentials to auditory stimuli. METHODS: Fourteen children with TSC, seven of which fulfilled the DSM IV criteria for autistic disorder were selected for this study. All of the subjects underwent high resolution MRI, EEG, brainstem auditory evoked potentials, cognitive and behavioural evaluation. Electrical evoked responses to two different pitches, presented with different probability (80% 1000 Hz, 20% 1500 Hz) were recorded from 21 scalp electrodes in the autistic and non-autistic subgroups, to assess central auditory processing and automatic memory. RESULTS: The first component of the long latency auditory response (N1) had a significantly prolonged latency with lower amplitude in all of the patients with autistic behaviour who, contrary to non-autistics had MRI lesions involving one or both temporal lobes. A mismatch negativity was detected in all subjects and had a longer latency in subjects with autistic behaviour. CONCLUSIONS: To our knowledge this is the first electrophysiological evidence of a deficit in auditory information processing and automatic memory in TSC patients with autistic behaviour.

Auditory Perception↗
PubMed1999

The acceptability of sleep-deprived electroencephalograms.

The aim of this study was to ascertain the acceptability of sleep-deprived EEGs to parents and their young child. Fifty unselected children having a sleep-deprived EEG were recruited. Data were collected from a sleep diary, a parent questionnaire and the request form of the EEG. Data collected covered developmental, learning and behavioural problems and the acceptability of the sleep-deprived EEG. There were 29 males (58%) in the study group. The average age was 8.6 years (range 2-17 years). Fifty percent of parents found it difficult to keep their child awake at night and 30% of parents found it difficult to wake their child in the morning. Fifty-four percent of parents reported their child had difficult behaviour on the day of the EEG. None had seizures provoked by sleep deprivation.

Adolescent↗
PubMed1998

Spike-induced interference in auditory sensory processing in Landau-Kleffner syndrome.

OBJECTIVES: Landau-Kleffner Syndrome (LKS) is an epileptic syndrome characterised by a deficit in language comprehension and production, paroxysmal epileptiform activity in the posterior temporal leads, and by the inconsistent presence of epileptic fits. Its interest lies in the fact that it stands as a model for the study of interference of epileptiform activity on cognitive function, although the pathophysiology of the decline in language skills that follows its onset has not yet been clarified. METHODS: We have recorded spike-triggered auditory evoked responses in a group of 6 children with LKS, to investigate whether the occurrence of individual EEG paroxysms is able per se to induce a decline in the response of the auditory cortex. RESULTS: Results have indicated that left hemisphere spikes are associated with a greater reduction in amplitude and an increase in latency of the NI, than spikes occurring in the right hemisphere. No stable change in the evoked response has been detected outside of the EEG paroxysm. CONCLUSIONS: We postulate EEG interictal activity is able to induce impairment in processing auditory information and that this may play a role in the pathogenesis of language deficit in LKS.

Auditory Cortex↗
PubMed1998

Frontal lobe epilepsy associated with tuberous sclerosis: electroencephalographic-magnetic resonance image fusioning.

We studied the topographic relationships between cortical and subcortical lesions shown on magnetic resonance images (MRI) and sources of epileptiform activity in a series of nine children with intractable epilepsy and tuberous sclerosis complex. Although video-electroencephalographic (EEG) monitoring was suggestive of a frontal seizure onset, interictal EEG was, in seven of nine cases, in the form of apparently bisynchronous discharges. In all cases, the use of a short time lag estimation procedure based on a nonlinear correlation function between surface recorded EEG signals allowed the detection of a lateralized onset of EEG paroxysmal activity. Furthermore, a computerized method based on a source localization EEG-MRI image fusioning procedure, has revealed a topographic concordance between well-defined frontal cortical lesions shown on MRI and site of onset of paroxysmal discharges. Lennox-like EEG patterns frequently reported in children with tuberous sclerosis complex could be the result of the tendency of frontal tubers to induce secondary bilateral synchrony, with implications in the medical and eventually surgical management of the often drug-resistant associated seizures.

Child↗
PubMed1997

Extracranial localization of intracranial interictal epileptiform activity using LORETA (low resolution electromagnetic tomography).

Besides the standard clinical methods of EEG waveshape analysis, mathematical models for reconstruction of dipolar sources from the digitized surface EEG have been introduced in epilepsy research. Although useful for localizing focal sources, these methods are inadequate for analyzing widespread epileptiform activity. A recently introduced alternative method called LORETA (low resolution electromagnetic tomography, Pascual-Marqui et al., 1994), directly computes the current distribution throughout the full brain volume, assuming that neighboring neuronal populations are simultaneously and synchronously activated. In mathematical terms the method selects the smoothest of all possible 3-dimensional current distributions, inherently introducing a certain amount of dispersion. In 7 patients, undergoing simultaneous EEG recording from 10 intracranial (subdural) and 22 extracranial electrodes, 111 subdural discharges (61 subtemporal and 50 lateral temporal) were identified. The exact time point of maximal intracranial activity was automatically identified, and the LORETA solution at that timepoint was computed from the surface EEG. Statistical comparison revealed significantly higher LORETA current density in the area corresponding to the subdurally recorded spike compared to other areas, and a more anterior and more medial LORETA location for subtemporal compared to lateral temporal spikes. This study indicates that the LORETA technique may become a useful method to localize electrical activity in the brain.

Adolescent↗
PubMed1996

Trace element content in human milk during lactation of preterm newborns.

The present study has been finalized to perform the content of Zn, Cu, Cr, Se, Mn, F, Mo, Ni, and B in the preterm human milk over 21 d of lactation. Trace element (TE) contents were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-MS), and median concentrations of Zn, Cu, Cr, Se, Mn, and F observed in preterm milk did not demonstrate significant differences in comparison to levels shown in term milk. A statistical significant difference (p < 0.05) has been found among Mo, Ni, and B content in preterm milk for every stage of lactation. TE content of infant blood founded concentrations of Mo in preterm babies significantly (p < 0.01) lower than in term offsprings. Similar values of other TE content were obtained in blood of preterm and term newborns. These findings point to the need for a considerable reassessment of the existing dietary recommendation for Mo content in infant feeding.

Adult↗
PubMed1996

Magnetic resonance imaging of cold injury-induced brain edema in rats.

The chronological changes of blood-brain barrier disruption, and diffusion and absorption of edema fluid were investigated in rats with cold-induced brain injury (vasogenic edema) using magnetic resonance imaging. Contrast medium was administered intravenously at 3 and 24 hours after lesioning as a tracer of edema fluid. Serial T1-weighted multiple-slice images were obtained for 180 minutes after contrast administration. Disruption of the blood-brain barrier was more prominent at 24 hours after lesioning than at 3 hours. Contrast medium leaked from the periphery of the injury and gradually diffused to the center of the lesion. Contrast medium diffused into the corpus callosum and the ventricular system (cerebrospinal fluid). Disruption of the blood-brain barrier induced by cold injury was most prominent at the periphery of the vasogenic edema. Edema fluid subsequently extended into the center of the lesion and was also absorbed by the ventricular system. Magnetic resonance imaging is a useful method to assess the efficacy of therapy for vasogenic edema.

Animals↗
PubMed1994

Computerized electroencephalographic assessment of congenital brain infarction.

We studied 12 children (8 female and 4 male) aged 2.2-14.3 years, whose computed tomographic (CT) examination had shown evidence of malacic and/or porencephalic outcomes of early vascular brain infarction. Topographic spectral electroencephalographic (EEG) analysis was performed in all patients in the awake state. The following spectral EEG variables were studied: topography, absolute and relative power of delta, theta, alpha, beta bands, overall power, and peak alpha frequency asymmetries. The results of topographic spectral EEG analysis were compared with the localization and nature of lesions as detected by CT scans. Depending on the nature of the lesions, we were able to identify two different spectral patterns. Porencephalic cysts were characterized by an increase in delta and theta bands in the areas surrounding the lesion sites, as identified by CT. Spectral EEG patterns of malacic outcomes resulted in a focal increase in theta and delta band power, corresponding to the topography of lesions. Moreover, in 9/12 subjects an asymmetry of alpha rhythm in occipital leads was found homolaterally to the lesion sites, associated with a decrease in power, without any CT evidence of an occipital lesion.

Adolescent↗
PubMed1994

Quantitative EEG modifications during the Cold Water Pressor Test: hemispheric and hand differences.

In a study designed to investigate the neurophysiological correlates of the Cold Water Pressor Test, a standardized experimental model of tonic pain, spectral EEGs were examined during the test in 15 young right-handed adults. Each subject performed a "cold water" and a "warm water" session. The subject immersed in cold water (0 degree C) either the right or the left hand alone, in a randomized way. EEG activity was recorded for an initial 3 min baseline and for the first and second minute epochs after immersion. A further EEG recording was obtained after a 30-min rest. Pain intensity was measured with a visual analogue scale. The EEG recordings showed several patterns of cortical activation during the test. Alpha 2 desynchronization was more evident on the contralateral parietal electrodes of the stimulated hand and lasted longer over all the right hemisphere. Delta activity increased bilaterally, predominantly in the frontal leads. Stimulation of the left hand resulted in a higher delta increase during the second minute after immersion.

Adult↗
PubMed1993

Computerized EEG topography in childhood migraine between and during attacks.

Topographic EEG mapping was performed in 58 migrainous children (mean age: 12.9 years; 39 without, 19 with aura) between attacks. Ten children were also recorded during an attack with visual aura. Between attacks there were no significant differences between migraineurs and age-matched controls. During visual aura a decrease in occipital alpha power contralateral to the affected hemifield was found in all patients. This was followed by a bilateral frontal increase in delta power, and, during the headache, by an increased delta activity in posterior-temporal and occipital electrode sites. The possible brain mechanisms underlying these EEG changes are discussed.

Adolescent↗