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Biomedical subjects

S G Boyd

Publications and source records attributed to S G Boyd.

At least 37 records · Page 2Linked to original sources
PubMed1996

Hypoxaemia and cardiorespiratory changes during epileptic seizures in young children.

In order to measure epileptic seizure(ES)-induced hypoxaemia and explore its relation to other physiological changes, 53 seizures were documented in 10 children (aged 1 week to 5 years) during continuous recordings of breathing, ECG, oxygenation and EEG. Hypoxaemia was demonstrated in 42 ESs with an arterial oxygen saturation (SaO2) below baseline for a median duration of 100s and < or = 60% for 17s, despite resuscitation. There were pauses in breathing movements in 45 seizures, but only 35 of these were hypoxaemic; pauses of comparable severity occurred in the 10 seizures without hypoxaemia. In seven seizures there was hypoxaemia without pauses in breathing movements, although continued nasal airflow was not demonstrable. Sinus tachycardia occurred in 35 seizures and T-wave changes in 20, but no sinister arrhythmias were observed.

Arrhythmias, Cardiac↗
PubMed1995

Cortical dysgenesis: serial EEG findings in children and adults.

Cortical dysgenesis (CD) is becoming increasingly recognised as a cause of epilepsy in otherwise cryptogenic cases. We describe the serial EEG findings in 22 patients with focal/localised CD. The EEGs covered a minimum period of 5 years in each case (median = 13 years, range: 5-30 years), beginning in childhood. Median age at seizure onset was 3 years (range: 3 weeks-10 years, n = 21). The EEG was normal in the one patient, a 6 year old, who did not have epilepsy. Background rhythms appropriate for age were preserved in the majority of patients (18/22). Slow activity localised to the area of CD was seen in 11 patients; in 3 patients, this did not appear until the second decade of life. Epileptiform discharges were seen in at least one EEG in 20 patients: these were continuous or near-continuous (6 patients) or occurred recurrently in short runs (6 patients). In 6 patients, these discharges appeared only after the second decade of life and in 11 patients, they became more widespread over time. In the remaining patients, the EEG changes did not evolve. Sleep failed to produce new abnormalities (n = 15). None of the patients showed EEG features characteristic of lissencephaly or evolution to the Lennox-Gastaut syndrome. Even in this selected cohort of patients who had undergone serial clinical EEGs, the EEG abnormalities in focal/localised CD appeared relatively stable and showed only moderate changes over time. CD must be included in the differential diagnosis of any patient who presents with localised slow activity on EEG.

Adolescent↗
PubMed1995

Children with intractable focal epilepsy: ictal and interictal 99TcM HMPAO single photon emission computed tomography.

Fourteen children with intractable complex partial seizures underwent ictal and interictal 99TcM HMPAO single photon emission computed tomography (SPECT) scans. Abnormalities concordant with clinical and/or EEG localisation were present in 13 of 14 ictal and/or interictal scans. Focal hyperperfusion was seen at the seizure focus on ictal scans and focal hypoperfusion was seen on interictal scans. The timing of the injection in relation to the start of the seizure was crucial for reliable localisation. While recognisable patterns of regional cerebral blood flow (rCBF) were seen on either interictal or ictal scans, marked changes in the patterns of rCBF between the ictal study and interictal study provided the most reliable information about seizure localisation. Using both ictal and interictal studies, 99TcM HMPAO SPECT may provide data about both the seizure origin and its relationship to structurally abnormal regions of the brain.

Adolescent↗
PubMed1995

Selective epileptic gait disorder.

Two children with an unusual gait disorder, one combined with acquired aphasia, in association with focal epilepsy are reported. Both children also showed paroxysmal "dystonic" phenomena, and a clear therapeutic response to corticosteroids. This newly described condition widens the range of discrete, recoverable defects of cerebral function that are associated with epilepsy in the developing nervous system and suggests that the site of action is at a functionally combined bilateral motor/sensory level of the cerebral cortex.

Aphasia↗
PubMed1995

Differential effect of maturation on insulin- vs. contraction-stimulated glucose transport in Zucker rats.

Insulin-stimulated glucose transport has been shown to decline during maturation in lean rats. To determine whether this maturation-induced decrease occurred in the muscle of obese rats and whether the contraction-stimulated pathway for glucose transport was similarly affected, glucose transport rates were measured in insulin- and electrically stimulated skeletal muscle during hindlimb perfusion of 10- and 29-wk-old lean and obese male Zucker rats. Glucose transporter (GLUT-4) protein was also measured. Insulin-stimulated glucose transport rates were significantly decreased (36-56%) in 29-wk compared with 10-wk-old lean rats. There was no maturation-related decrease in GLUT-4. Insulin-mediated glucose transport was unaltered by maturation in skeletal muscle of obese rats. Differential effects of maturation on lean and obese rats caused the effect of obesity on maximally insulin-stimulated glucose transport to be much greater in 10- than 29-wk-old animals. Maturation had no effect on contraction-stimulated glucose transport rates in either lean or obese animals. The combined effect of maximal insulin plus contraction was not altered with maturity in lean animals but was significantly increased in 29- compared with 10-wk-old obese rats. Absence of a change in GLUT-4 content together with uncompromised contraction-stimulated glucose transport suggests that the maturation-induced decrease in insulin-stimulated glucose transport in lean rats is due to a defect in the insulin signaling pathway.

Aging↗
PubMed1994

Epileptic seizure-induced hypoxemia in infants with apparent life-threatening events.

OBJECTIVE: To describe the physiologic changes that occur during epileptic seizure (ES)-induced apparent life-threatening events (ALTE) and to provide an explanation for the mechanism whereby the hypoxemia characterizing these events occurred. PATIENTS AND DESIGN: Six infants were retrospectively selected from a group of 17 because they had ALTE documented on physiologic recordings where the first change in signals was in the electroencephalogram (EEG). The 17 infants had clinical features suggestive of partial seizures (but normal standard EEGs) and were from a sample of 172 infants with recurrent ALTE. All 17 infants underwent continuous recordings of breathing, electrocardiogram (ECG), oxygenation, and EEG, but only in 6 was an ES-induced ALTE recorded and the physiologic changes described. RESULTS: Twenty-three ALTE were documented in six infants. Events commenced with an abnormality in the EEG, followed by a decrease in SaO2 after a median interval of 27 seconds (range 2 to 147). Despite resuscitation, the median duration of severe hypoxemia (SaO2 < or = 60%) was 40 seconds (range 8 to 74). In 18 events (five infants) there was a median of four apneic pauses (range 1 to 9) preceding the decrease in SaO2 by a median duration of 24 seconds (range 3 to 48). The longest apneic pause per event lasted a median of 19 seconds (range 8 to 47). Breathing movements continued in five events (four infants), and expiratory airflow in one. Sinus tachycardia was found in 19 of the 23 events (six infants), but there were no cardiac arrhythmias. CONCLUSIONS: ES in infants can manifest as ALTE and be accompanied by potentially life-threatening episodes of severe hypoxemia and apnea, despite a normal EEG between events.

Apnea↗
PubMed1993

EEG features of cortical dysplasia in children.

Two distinctive electroencephalographic abnormalities, very high amplitude rhythmic activity or prominent fast activity, have been described in children with extensive cortical dysplasia. Cases with cortical dysplasia identified on computerised tomography or magnetic resonance imaging, or a characteristic EEG were selected. One hundred and forty electroencephalograms from 94 cases were reviewed and related to the imaging findings. An EEG with very high amplitude rhythmic activity was found to have high specificity for severe cortical dysplasia but low sensitivity (< 50% cases). Abnormal fast activity was not specific and was seen with very diverse pathologies. The EEG features of most cases with localised cortical dysplasia were very variable. The EEG could be normal even when the cortical dysplasia was extensive.

Cerebral Cortex↗
PubMed1993

Early detection of abnormalities in partial epilepsy using magnetic resonance.

The incidence of brain abnormalities determined by magnetic resonance in 30 consecutive children presenting with intractable complex partial seizures is reported. Images were optimised to visualise the hippocampus and cortical grey matter. Abnormalities of the hippocampus or temporal lobe were seen in all 19 children with clinical features of temporal lobe epilepsy and in six of the seven children with clinically unlocalised epilepsy. By contrast, in the four children with a clinical diagnosis of extratemporal epilepsy, no temporal or hippocampal abnormalities were seen. Generalised cortical abnormalities of uncertain significance were found in a total of 14 children from all groups. The identification of focal brain abnormalities using optimised magnetic resonance imaging enables early non-invasive assessment of children with intractable seizure disorders and the identification of patients for whom epilepsy surgery may be appropriate. It may also lead to a better understanding of the structural basis of intractable epilepsy, and thereby contribute to early treatment decisions.

Adolescent↗
PubMed1993

Effect of hyperkalemia on myocardial depression by verapamil in isolated hearts.

Verapamil can produce depression of left ventricular function, delayed atrioventricular conduction, and hypotension, which can be potentiated by hyperkalemia. We sought to investigate a direct cardiac interaction between verapamil and hyperkalemia. Studies utilized isolated guinea pig hearts (Langendorff) paced at 250 beats/min. Hearts were randomly assigned to perfusion (Krebs-Henseleit buffer) with potassium concentrations ([K]+) of 1.5, 3, 6 and 9 mmol/l. Infusion of verapamil at rates of 0.2 to 60 micrograms/min (approximately 3 x 10(-8) to 10(-5) mol/l) produced concentration-dependent reduction of isovolumic left ventricular developed pressure. As [K]+ increased, concentration response curves showed parallel shifts to the left. The ED50 for reduction of left ventricular developed pressure significantly decreased: 8.2 +/- 3.7, 2.9 +/- 1.4, 1.2 +/- 0.7, 0.6 +/- 0.2 micrograms/min (mean +/- SD), respectively. Nifedipine and diltiazem were also studied in hearts perfused with 3 and 9 nmol/l [K]+. Infusion of nifedipine 0.003-1 microgram/min (approximately 10(-9) to 3 x 10(-7) mol/l) produced concentration-dependent reduction of left ventricular developed pressure but the ED50 was not affected by [K]+: 0.06 +/- 0.03 and 0.05 +/- 0.04 microgram/min, respectively. Nifedipine vehicle was without effect at the infusion rates tested. Infusion of diltiazem 2-200 micrograms/min (approximately 3 x 10(-7) to 3 x 10(-5) mol/l) also produced concentration-dependent reduction of left ventricular developed pressure. The ED50 for diltiazem-induced reduction of left ventricular developed pressure was significantly reduced by elevated [K]+: 20.1 +/- 6.7 and 3.5 +/- 0.9 micrograms/min with 3 and 9 mmol/l [K]+, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Alexander's disease: clues to diagnosis.

The clinical, radiologic, neurophysiologic, and pathologic findings in 10 children with histologically proven Alexander's disease are described, and the presence of two broad clinical subgroups is confirmed. Macrocephaly, regression, and seizures are found in the infantile form, whereas bulbar signs predominate the so-called juvenile form. None of the clinical or neurophysiologic findings is pathognomonic, and radiologic features suggesting the diagnosis are not present in all cases. However, the combination of abnormalities may suggest the diagnosis and justify histologic confirmation.

Cerebral Cortex↗
PubMed1992

Effects of isoflurane anaesthesia on the median nerve somatosensory evoked potential in children.

Evoked potentials are used to determine the integrity of neural pathways during neurosurgical and orthopaedic procedures, but the extent to which they may be altered by anaesthetic agents has not been studied systematically in children. In this study we have recorded median nerve somatosensory evoked potentials (mnSSEP) in children during isoflurane anaesthesia to determine if there are changes similar to those seen in adults. We studied 10 patients using standardized anaesthetic and clinical neurophysiological techniques. Control mnSSEP were obtained with 70% nitrous oxide in oxygen and isoflurane was then administered at 0.25, 0.50 and 0.75 MAC. The latencies and amplitudes of the mnSSEP were subjected to repeated measures analysis of the variance (ANOVA) and linear regression. There were statistically significant increases in N20, P22 latencies and central conduction time (P < 0.001) and reductions in amplitude of the N20-P22 complex (P < 0.03) with increasing end-tidal isoflurane concentrations. These results are similar to the findings in adults.

Anesthesia, Inhalation↗
PubMed1992

Sequential measurement of the median nerve somatosensory evoked potential during isoflurane anaesthesia in children.

We have used sequential measurements of median nerve somatosensory evoked potentials (mnSSEP) in 10 children to estimate the equilibration time of an inhalation anaesthetic agent between alveolar gas, arterial blood and brain. MnSSEP were obtained sequentially every 90-180 s. After control measurements in the absence of isoflurane, the end-tidal concentration was increased stepwise (0.25, 0.5 and 0.75 MAC). Each isoflurane concentration was maintained for 15 min. The point at which the N20 latency reached stability was determined; the mean time between reaching a stable end-tidal isoflurane concentration and this point varied between 5 min 16 s and 7 min 37 s. This technique may be useful in circumstances in which a "steady state" of anaesthesia is important, such as in the determination of MAC or during intraoperative monitoring of evoked potentials.

Anesthesia, Inhalation↗
PubMed1991

Intractable seizures from infancy can be associated with dentato-olivary dysplasia.

Five children with severe developmental delay had intractable fits of various types but tonic, often extensor, seizures were prominent from an early stage. Onset was in the neonatal period in 4 cases. EEGs were severely abnormal and showed a "burst-suppression" pattern in the first months of life. There were no metabolic or consistent neuroradiological abnormalities. A distinctive form of dentato-olivary dysplasia was found in all cases. Inferior olives were hook-shaped, coarse and lacking undulations, while dentate nuclei showed a compact arrangement of interconnected islands. The clinico-pathological findings form a novel nosological entity.

Apgar Score↗
PubMed1991

The clinical significance of seizures in critically ill young infants requiring intensive care.

The aetiology, severity of systemic and biochemical abnormalities, seizure duration, EEGs and CT scans have been reviewed in previously normal young infants with an acute critical illness occurring after the first week of life; none of whom had birth asphyxia. Findings were related to outcome in an attempt to evaluate the significance of seizures during the acute phase of severe illness. In three years seizures occurred in 54/251 (22%) young infants requiring ventilatory support. In these patients the acute illness was most commonly infection and encephalitis/encephalopathy. Twenty-one died, 24 had good or moderate outcome and 9 poor outcome (follow-up 6-27 months). The outcome was not directly related to diagnosis, but to systemic and biochemical changes, the most important being severe hypotension (40/54). After correction of these factors, in survivors, increasing number of days over which seizures occurred during the acute phase of illness was related to worsening outcome (tau(c) = 0.66, p less than 0.0001). In many of these patients one of three abnormal low density changes (generalized, boundary zone and focal) were seen on CT scan and were not uncommonly associated with focal/multifocal clonic seizures and characteristic type, distribution and evolution of EEG discharge. In the 45 patients with EEGs from presentation, severity of encephalopathy assessed by predominant background EEG activity was most closely related to outcome, irrespective of aetiology and seizures. There was a significant relationship between graded severity of background EEG activities and outcome both in the initial and serial recordings (tauB = 0.70, p less than 0.0001 and 0.75, p less than 0.0001 respectively). Seizures are a common occurrence in the previously well young infant with an acute critical illness necessitating intensive care. Prompt recognition and treatment may influence outcome in patients with a potentially reversible encephalopathy. However, in many patients seizures reflect severe, often multifactorial cerebral insult with variable morphological changes, EEG patterns and clinical outcome.

Anticonvulsants↗
PubMed1991

EEG features and their evolution in the acute phase of haemorrhagic shock and encephalopathy syndrome.

Serial EEGs have been carried out during the acute phase of haemorrhagic shock and encephalopathy syndrome (HS&E) in 22 infants and children aged 3 months to 14 years. Most patients presented with fits and coma and all had shock with bleeding and disseminated intravascular coagulation (DIC). The initial EEG showed prolonged runs of often rhythmic discharges which fluctuated in amount and amplitude with varying distribution and morphology ("electrical storms"). Over a period of days the "electrical storms" gradually decreased leaving only low amplitude EEG activities or evolving to electrocerebral silence (7 cases). Fifteen patients died and all five children with multifocal "electrical storms" who survived showed gross neurological handicap. The rather distinctive EEG pattern is unusual in the context of an acute encephalopathy outside the neonatal period although similar "electrical storms" may be seen in a less extreme form in infants and children with other conditions associated with DIC. This EEG pattern presumably reflects changes in the cerebral microcirculation which in HS&E are usually relentlessly progressive and associated with devastating cortical damage.

Adolescent↗
PubMed1991

EEG findings in hypomelanosis of Ito.

The EEG findings in 15 children with Hypomelanosis of Ito have been reviewed and related to the clinical and CT scan data. Although no consistent electroclinical associations were found in the group as a whole, there was some association between the presence of abnormal rhythmic EEG activity and the radiological appearances of neuronal migration defects. In addition, the possibility is raised that there may be a distinctive sub-group of children with Ito's syndrome who present with an early onset of intractable seizures and who have a neuronal migration defect.

Adolescent↗