Search PubMed⌕ Search

Biomedical subjects

L M Dubowitz

Publications and source records attributed to L M Dubowitz.

At least 55 records · Page 3Linked to original sources

Further technical development in magnetic resonance imaging of the brain in children.

Further technical developments implemented in magnetic resonance imaging (MRI) of the brain in children are described. These include the use of longer data collection periods, T2-dependent field echoes, susceptibility mapping, short inversion time inversion recovery sequences, very long echo time spin-echo sequences, and phase mapping techniques to detect tissue perfusion. These techniques are illustrated in selected cases and have increased the range of options available in MR examinations of children.

Brain↗

Outcome of infants shunted for post-haemorrhagic ventricular dilatation.

Between April 1980 and March 1986, 19 infants underwent cerebrospinal fluid (CSF) shunting procedures for post-haemorrhagic ventricular dilatation at the Hammersmith Hospital, London. A total of 58 shunt-related procedures have been performed on these children. The major perioperative complication was seizure activity (eight children). Postoperative complications included infection (12 shunts) and blockage (29 shunts). Prophylactic antibiotics failed to prevent shunt infection. The likelihood of the first shunt failing was significantly reduced by greater weight of the infant and lower CSF protein at surgery. Long-term outcome was poor: three have died and another four are quadriplegic with severe mental retardation. Only four children are developmentally normal. These outcomes cannot be related to the shunt surgery or its complications, but correlate best with pre-operative parenchymal brain-lesions, as shown on ultrasound scans.

Cerebral Hemorrhage↗

Predictive value of early continuous electroencephalogram monitoring in ventilated preterm infants with intraventricular hemorrhage.

The contribution of early continuous four-channel EEG monitoring to the evaluation of intraventricular hemorrhage in acutely ill preterm infants mechanically ventilated for acute respiratory distress was assessed in a prospective study of 54 infants of less than 34 weeks' gestation. Early abnormal EEG results correlated significantly with later outcome. They often preceded ultrasound evidence of hemorrhage and provided prognostically significant functional correlation with the grade of hemorrhage. Continuous EEG monitoring allows collection of significant data with minimal interference and could contribute to clinical management of high-risk preterm infants.

Cerebral Hemorrhage↗

Localized cerebral infarction in the premature infant: an ultrasound diagnosis correlated with computed tomography and magnetic resonance imaging.

Findings on cranial ultrasonography strongly suggested the diagnosis of a localized infarct in four premature infants. CT was performed to differentiate between hemorrhagic and nonhemorrhagic lesions, and magnetic resonance imaging was used to obtain information about the late effect of the lesions. The clinical findings, imaging findings, and later outcome in these premature infants were compared with the existing knowledge of this type of lesion in the full-term infant. A localized infarct appears to carry a good prognosis in the premature infant and should be differentiated from other types of lesions, such as periventricular leukomalacia or parenchymal hemorrhage, which are more common in the premature infant and carry a worse prognosis.

Brain↗

Relationship of serum bilirubin levels and hearing impairment in newborn infants.

A comparison has been made between 39 infants with a birthweight of 1500 g or less and a bilirubinlevel of 240 mumol/l or above, born between January 1980 and December 1983 and 19 infants with the same criteria, born between January 1984 and December 1985. Eight of the 22 high risk and two of the 17 low risk infants were diagnosed to have sensorineural deafness (SND) during the first period and this was strongly associated with the duration of the hyperbilirubinaemia. During the second period, more active intervention for hyperbilirubinaemia led to an increased number of exchange transfusions and a marked drop in the mean duration of hyperbilirubinaemia (less than 240 mumol/l). None of the very low birth weight (VLBW) infants born in the second period have developed SND. To investigate the independent effect of hyperbilirubinaemia on hearing, six low risk infants with bilirubin levels less than 320 mumol/l were studied by serial auditory brainstem responses (ABR). Impairment of the ABRs was found in four infants, with further deterioration with the persistence of high bilirubin levels in two. Although recovery of hearing thresholds was noted in all infants with impaired ABRs, an absence of wave I was noted in three infants at 6 months of age, which could indicate damage to the auditory nerve-cochlear complex. These findings suggest that hyperbilirubinaemia in itself can have an adverse effect on hearing and that careful management of hyperbilirubinaemia may reduce the incidence of sensorineural deafness.

Deafness↗

Neurological, electrophysiological and MRI abnormalities in infants with extensive cystic leukomalacia.

Twenty infants, diagnosed by cranial ultrasound as having extensive cystic leukomalacia, had visual evoked responses (VER) and electroencephalograms (EEG) in the neonatal period and MRI scans later in infancy. The early ultrasound findings and results from the electrophysiological tests were correlated with later MRI findings and functional abilities. In infants with periventricular leukomalacia (PVL), the cysts were usually no longer visible by ultrasonography, beyond 40 weeks postmenstrual age (PMA), but later MRI scans showed a consistent pattern of delayed myelination around the irregularly dilated occipital horns of the lateral ventricles. VER's were present in the neonatal period and vision was maintained, although all infants developed a marked squint. EEG's were either normal or abnormal initially, but improvement was noted within several weeks. In those with subcortical or mixed lesions, cysts were noted to persist beyond 40 weeks PMA. Later MRI scans showed very poor myelination, with poor progress on subsequent scans and cortical atrophy. VER's were absent and all infants later became cortically blind. EEG's were severely abnormal and recovery was very poor. The infants with PVL developed spastic diplegia with moderate developmental delay, while those with mixed or subcortical lesions developed quadriplegia with severe mental retardation. An integrated approach, consisting of ultrasound imaging and electrophysiological recordings in the neonatal period and MRI imaging later in infancy, may provide a more reliable prediction of the pattern of later deficits.

Brain↗

Continuous four-channel EEG monitoring in the evaluation of echodense ultrasound lesions and cystic leucomalacia.

Continuous monitoring by electroencephalography (EEG) was performed in 31 preterm infants with echodense ultrasound lesions using the Oxford Medilog four channel recorder. In 12 infants these densities preceded cyst formation, eight in the periventricular and four in the subcortical region. In the 19 other infants the densities resolved. The most severe EEG depression occurred in the four infants with subcortical cysts, who also had the poorest outcome. Six of eight infants with periventricular lesions had lesser degrees of abnormality though all infants had moderate to severe handicap at follow up. Similar abnormalities were seen on EEG recording in three infants in whom the densities resolved without cyst formation and these infants also had an abnormal outcome. An abnormal EEG recording provides a sensitive early guide to the severity and prognosis of these lesions, even before they can be seen on ultrasonography.

Brain Ischemia↗

Visual function in the newborn infant: is it cortically mediated?

Reasonably normal visual behaviour was observed in premature infants in the neonatal period up to about 48 weeks' postmenstrual age even when there was gross destruction of the cortex in the occipital region. Symmetrical visual evoked responses could be elicited at this time even when asymmetrical lesions of the occipital cortex had been demonstrated on ultrasound scan; the visual evoked response became asymmetrical later, around the age of 2 months. A visual evoked response, albeit of abnormal waveform, was recorded in an infant with complete absence of the visual cortex. These findings suggest that early visual function, both behavioural and electrophysiological, is not dependent on the cortex but appears to be mediated through subcortical pathways.

Abnormalities, Multiple↗

The visual evoked potential in neonates with occipital lesions and holoprosencephaly.

Visual evoked potentials (VEPs) were studied in 4 preterm and 2 fullterm infants in whom unilateral lesions of the occipital cortex were demonstrable on cranial ultrasonography. In the neonatal period, symmetrical responses were recorded from the two hemispheres, and the VEPs only became asymmetrical at the age of 2-3 months. Evoked responses to flash stimulation were also recorded initially in an infant with complete holoprosencephaly. These findings, together with previous reports on the maturation of the VEPs in the neonatal period, suggest that the early evoked response may be subcortical rather than cortical in origin.

Brain↗

Magnetic resonance imaging of the brain in children.

Differences between MRI of the brain in children and adults are discussed. These include the need for sedation, greater difficulties in obtaining normal controls and substantial differences in pulse sequences due to changes in T1 and T2 with age. The common features in the major pathological entities are presented and the need to relate them to physiological changes is emphasized.

Brain↗

High-resolution magnetic resonance imaging of the brain in children.

Magnetic resonance image quality in infants and children has been improved by the use of spherical receiver coils and age-adjusted sequences allowing use of a high-resolution (256 X 256) image reconstruction matrix, provided adequate immobilisation is maintained. This increased resolution provides more satisfactory demonstration of the cortical mantle and details of sulci, as well as pathological processes such as periventricular oedema, infarction and tumours.

Brain↗

Late onset cystic leucomalacia.

The ultrasound findings of eight premature infants who developed extensive cystic leucomalacia after the first two weeks of life are reported. Ultrasound examinations should be considered after any clinical deterioration in preterm infants up to 40 weeks' postmenstrual age to avoid missing cases of extensive cystic leucomalacia.

Brain Diseases↗

Low serum thyroxine concentrations and neural maturation in preterm infants.

The effect of hypothyroxinaemia on postnatal progression of the motor nerve conduction velocity was studied in 33 very low birthweight infants. Serum concentrations of thyroid stimulating hormone, triiodothyronine, and thyroxine were determined at birth and at ages 3, 7, and 21 days. Nerve conduction velocity was measured in the first week of life, on day 21, and at 40 weeks' postmenstrual age. Seven infants maintained their thyroxine concentration above 60 nmol/l (4.67 micrograms/100 ml) throughout the study. Three of these infants needed mechanical ventilation and one had an intraventricular haemorrhage. Twenty six infants developed hypothyroxinaemia (thyroxine less than 60 nmol/l). The nerve conduction velocity was delayed in 13 infants, two on day 21 and 11 at 40 weeks' postmenstrual age. The delay was equivalent to 1.9-4.4 weeks. All these infants belonged to the group with depressed thyroxine concentrations. The delay in progression in nerve conduction velocity was associated with prolonged hypothyroxinaemia, especially in those infants who also required ventilation. Further studies are in progress to study the effect of thyroid hormone on the nerve conduction velocity in preterm infants.

Aging↗

Predictive value of cranial ultrasound in the newborn baby: a reappraisal.

During a 36-month period 435 babies of 34 weeks' gestation or less were regularly scanned with ultrasound. A large periventricular/intraventricular haemorrhage developed in 40 babies, and extensive cystic leucomalacia developed in 10. The neurodevelopmental outcome and the frequency of handicap in these 2 groups were compared. 9 of the 18 survivors with a large haemorrhage were found to be completely normal and only 2 showed a major handicap. However, severe cerebral palsy with mental retardation developed in all the survivors with extensive cystic leucomalacia, and 4 of the 7 babies were also cortically blind. These findings suggest that the size of the haemorrhage is not a good predictor of outcome, but that severe cystic leucomalacia is associated with a very poor prognosis.

Brain↗