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Biomedical subjects

S G Boyd

Publications and source records attributed to S G Boyd.

At least 19 recordsLinked to original sources
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↗
PubMed1990

The cerebral function analysing monitor in paediatric medical intensive care: applications and limitations.

Practical guidelines for continuous single channel EEG monitoring using the Cerebral Function Analysing Monitor (CFAM) have been outlined based on experience of 54 critically ill comatose and/or paralysed sedated children monitored for up to 9 days during the acute phase of illness. Fall in amplitude and slowing of frequency following either a cerebral insult or barbiturate administration as well as paroxysmal events were readily recognisable in the CFAM traces. Such changes could be used to (1) identify effects of cerebral insults (acute or cumulative), (2) recognise unstable patients exquisitely sensitive to aspects of standard care and (3) evaluate seizure control. Despite these useful contributions to clinical care, significant limitations were apparent. It is recommended that CFAM monitoring should be combined with serial conventional EEG recording in order to check the appropriateness of the cortical areas being monitored, the quality and type of signal being processed as well as the significance of the 1 or 2 channel CFAM findings in relation to global cerebral function.

Adolescent↗
PubMed1990

Myelination patterns on magnetic resonance of children with developmental delay.

Magnetic resonance (MR) imaging was performed in 30 children with unexplained developmental delay who had associated neurological abnormalities such as seizures, spasticity, hypotonia, ataxia or poor vision. No child had a history of regression, preterm birth or neonatal cerebral injury. CT scans were performed before MR in all cases and were either normal or showed only mild atrophy. At least two MR sequences were obtained for all patients. Nine children had delayed or absent myelination on MR, one had patchy white-matter abnormalities, and in one patient myelination was topographically normal, but of inappropriately low signal intensity. MR was abnormal in six of seven children who had abnormal brainstem auditory evoked potentials (BAEP), and was normal in nine of 11 patients who had a normal BAEP. MR may have a useful rôle in demonstrating abnormal white-matter maturation in children with unexplained neurodevelopmental delay, particularly when abnormalities are found on BAEP studies.

Brain↗
PubMed1989

EEG monitoring of prolonged thiopentone administration for intractable seizures and status epilepticus in infants and young children.

Thiopentone anaesthesia was used in the treatment of seizures in 19 infants and young children. Nine had a pre-existing seizure disorder without acute cerebral injury and 10 had status epilepticus secondary to an acute cerebral illness. Clinical details, drug levels and findings from serial multichannel electroencephalograms (EEG) and continuous 1 to 2 channel signal processed EEGs using a Cerebral Function Analysing Monitor (CFAM) were reviewed to evaluate the contribution of these techniques to clinical management. Initial EEGs showed discharges that were not generalised in 16/19 patients. This necessitated the use of 7 different montages for continuous monitoring. Three different CFAM patterns representing particular EEG paroxysmal findings were seen. Acute seizure control was achieved in all 19 patients. All patients with a pre-existing seizure disorder survived, although 4/10 with an acute cerebral illness died. During treatment, patterns of burst-suppression to electrocerebral silence (ECS) were eventually seen in 16/19 patients and repeat EEGs demonstrated concordant multi-channel findings in 8/8. Although increasing thiopentone levels (13 patients) correlated with deeper suppression of cortical electrical activity, there was marked inter-patient variability. Inotropic support was not required during the period of treatment even when ECS was induced. In young children a combination of multi-channel EEG and continuous 1 to 2 channel monitoring has advantages over either method used alone. In individual patients on-line monitoring can be easily incorporated in a protocol of controlled cortical suppression and drug titration for seizure control.

Child, Preschool↗
PubMed1989

Rett syndrome: an EEG study in 52 girls.

EEG studies have been carried out on 52 girls with Rett syndrome, the majority of records being taken between two and 7 years of age. Discharges were a common feature, occurring in 43 patients, and did not appear to be related to the onset of seizures. The discharges, consisting of sharp waves or spikes, were characteristically most prominent around the middle third of the head, often occurring asymmetrically and could be infrequent or almost continuous. They were usually enhanced by light sleep and were seen only during sleep in 15 EEGs taken in 13 patients, most of whom were under four years of age. These EEG features when present may help confirm the diagnosis of Rett syndrome in the appropriate clinical setting and in particular are quite distinct from the usual EEG patterns seen in Angelman (Happy Puppet) syndrome.

Adolescent↗
PubMed1989

Clinical neurophysiological assessment of children with sacral anomalies.

Clinical neurophysiological investigations were carried out in 8 children with various forms of sacral dysplasia. No EMG activity was found in leg muscles in two children with complete sacral agenesis, even though pelvic floor activity was preserved in one of these. The external anal sphincter and puborectalis were examined in all cases, and it was easy to demonstrate neuropathic changes in individual motor unit potentials by attenuation of their low frequency components. There was only a loose association between any pelvic floor neuropathy and the level of the bony defect in the sacrum, confirming recent reports. Trans-cutaneous stimulation of the spinal nerve roots in the lumbar canal was carried out in four children. Unilateral slowed conduction in L5 roots corresponded with the clinical signs in one patient, and absent innervation of leg muscles was confirmed in the two children with complete agenesis. Normal L1-L4 conduction times were found in a child with no clinical signs. Early assessment of children with sacral anomalies is important in order to prevent secondary complications. Clinical neurophysiological investigations are useful in delineating the different patterns of neurological involvement, especially in the pelvic floor, and the results complement those obtained with imaging techniques.

Anal Canal↗
PubMed1989

Effects of halothane on motor evoked potential recorded in the extradural space.

We studied the effects of supplementing nitrous oxide-oxygen anaesthesia with halothane (1 MAC end-tidal concentration) on the motor evoked potential recorded in the extradural space of eight patients before corrective surgery for idiopathic adolescent scoliosis. The motor cortex was stimulated electrically through the scalp. An additional eight patients in whom anaesthesia was supplemented with an infusion of propofol acted as a control group. Halothane had no significant effect on the amplitude or latency of the motor evoked potential. We conclude that halothane is unlikely to alter the interpretation of motor evoked potentials recorded extradurally during scoliosis surgery.

Adolescent↗
PubMed1988

The EEG in early diagnosis of the Angelman (happy puppet) syndrome.

An EEG study has been carried out on 19 children (including siblings in 3 families) with clinical features of Angelman syndrome. The age at time of the first EEG ranged from 11 months to 11 years with the majority under 5 years. Six children had no history of seizures at the time of the first EEG. One or more of the following EEG abnormalities were seen in all patients: 1. Persistent rhythmic 4-6/s activities reaching more than 200 microV not associated with drowsiness. 2. Prolonged runs of rhythmic 2-3/s activity (200-500 microV) often more prominent anteriorly, sometimes associated with discharges (ill-defined spike/wave complexes). 3. Spikes mixed with 3-4/s components usually more than 200 microV mainly posteriorly and facilitated by, or only seen with, eye closure. Two and sometimes three of these EEG features could be present in the same record particularly at a young age. The appearance of discharges mixed with slow components on eye closure was the commonest finding seen at some stage in 17 patients (aged from 11 months to over 12 years). The EEG features of Angelman syndrome appear to be sufficiently characteristic to help identify patients at an early age before the clinical features become obvious and at a time when genetic counselling may be particularly important.

Adolescent↗
PubMed1987

Progressive neuronal degeneration of childhood with liver disease. Computed tomographic features.

The clinical, electrophysiological and neuroradiological features of thirteen patients suffering from progressive neuronal degeneration of childhood with liver failure are presented. The disease commonly presents very early in life with progressive mental retardation, followed by intractable epilepsy, and should be suspected clinically especially if there is a family history of similar disorder in a sibling. On computed tomography there are low density regions, particularly in the occipital and posterior temporal lobes, involving both cortex and white matter, combined with or followed by progressive atrophy. Typical EEG findings may be confirmatory.

Age Factors↗
PubMed1987

Progressive neuronal degeneration of childhood (PNDC) with liver disease.

Thirteen children with progressive neuronal degeneration and liver disease are reported. Clinical features included developmental delay after a normal initial period with later onset of intractable epilepsy. The EEG showed an unusual but characteristic pattern, and visual evoked responses (VER) were abnormal. Rapidly progressive cerebral atrophy was seen on computerized axial tomography (CAT). Inheritance was consistent with an autosomal recessive trait. Pathological findings were neuronal degeneration and spongy change of the cerebral cortex. The calcarine cortex was more severely affected than other areas. Hepatic lesions included severe fatty change and cirrhosis. In six patients liver disease was detected before the onset of epilepsy and exposure to anticonvulsants. Two others were reported to have died from sodium valproate (SV) toxicity, but both had abnormal liver enzymes before treatment with SV, and in both the neuropathological findings were indicative of PNDC. During life, PNDC may be indicated by the characteristic clinical course, abnormal liver function tests, and abnormalities of EEG, VER, and CAT.

Brain↗