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Biomedical subjects

L M Dubowitz

Publications and source records attributed to L M Dubowitz.

At least 73 records · Page 4Linked to original sources
PubMed1985

Hearing threshold in preterm and term infants by auditory brainstem response.

Hearing thresholds were established in preterm and term newborn infants by auditory brainstem responses in the first week of life. The presence of wave V was the criterion for threshold sensitivity in infants considered neurologically optimal on the basis of stringent clinical criteria and sequential ultrasound examination. The hearing threshold was found to be at 40 dB in preterm infants between 28 and 34 weeks gestational age, at 30 dB in infants between 35 and 38 weeks, and below 20 dB in term infants. This study confirms that the thresholds of newborn infants diminish with increasing age, and there is no apparent difference whether maturation occurs inside or outside the uterus. The data should provide a baseline for objective and quantitative assessment of hearing loss early in the neonatal period.

Audiometry, Evoked Response↗
PubMed1985

Maturation of the visual evoked response and its correlation with visual acuity in preterm infants.

Visual evoked responses (VERs) were elicited in 70 infants with postmenstrual ages between 30 and 39 weeks. On the basis of neurological and ultrasound examinations, 30 of the infants were classed as neurologically normal and 40 as abnormal: 26 of the latter had periventricular haemorrhage. Initially the VER consisted of a negative deflection only, and the appearance of a positive wave immediately preceding the negative deflection was taken to indicate maturation of the VER. Maturation was significantly delayed in the neurologically abnormal infants, and the delay was related to the degree of neurological insult. The visual acuity of 32 infants was estimated within seven days of the VER recording. There was a correlation of 79 per cent between the VER and the data for visual acuity.

Birth Weight↗
PubMed1985

Predictors for survival and normal neurodevelopmental outcome of infants weighing less than 1001 grams at birth.

Between 1979 and 1981, 67 infants weighing 1000 g or less at birth were admitted to the Hammersmith Hospital Neonatal Intensive Care Unit. 29 survived the neonatal period. Low acidosis score, without a metabolic component, was the most powerful predictor of survival. Other factors were gestational age, five-minute Apgar score, the need for ventilatory support, hypoxia, hypercapnia, pneumothorax, hypotension and the presence of a larger PVH. Of the 24 survivors followed up to three years of age, 11 were optimal, nine had some neurodevelopmental deficits and three had moderate functional handicap. Only one child has cerebral palsy and global mental retardation. Five-minute Apgar score and the presence of PDA correlated with normal outcome. None of the 20 obstetrical factors examined appeared to influence either survival or neurological outcome.

Child Development↗
PubMed1985

Developmental sequence of periventricular leukomalacia. Correlation of ultrasound, clinical, and nuclear magnetic resonance functions.

The evolution of severe periventricular leukomalacia was followed by ultrasonography in three newborn infants, and the subsequent myelination of the brain was assessed by nuclear magnetic resonance imaging. Four stages of periventricular leukomalacia could be identified by ultrasonography; (1) initial congestion, followed by (2) relative normalisation, (3) development of cysts, and (4) resolution of cysts but development of ventricular enlargement. All infants exhibited abnormal neurological signs from 36 weeks conceptual age and had unequivocal signs of cerebral palsy by 6 to 9 months of age. One infant became cortically blind but the other two seemed to have normal vision. Nuclear magnetic resonance imaging showed some abnormality of the ventricular system and delayed myelination in all three infants. The delay was most noticeable in the opticothalamic region, which was also the site of the most extensive lesions observed on ultrasonography. Progress in myelination was observed in the infants where a repeat scan was performed.

Brain Diseases↗
PubMed1985

Nuclear magnetic resonance imaging in the diagnosis and follow-up of neonatal cerebral injury.

NMR scanning is feasible in the newborn period, and is capable of diagnosing most of the problems in this age group, but its general application presents a number of difficulties at present. It cannot be transported to the bedside. Adequate monitoring of ill patients is difficult, and scanning takes a relatively long time. The neonatal brain has an extremely high water content, and NMR scanning procedures require adaptation to apply to these conditions. NMR imaging, however, has already proved extremely useful in the follow-up of neonatal insults. Repeated scanning is possible after closure of the fontanelle without subjecting the infant to ionizing radiation. The scans are able to demonstrate not only the anatomic changes associated with the various lesions, but also how these might affect myelination. Development of better coils and more suitable scanning sequences for neonates and infants are needed to improve image quality and establish the normal range of T1 and T2 values and the normal range of myelination at various ages. Further studies will also establish whether the changes in myelination primarily reflect the pathologic processes occurring in the tissues, such as the amount of gliosis, or are a marker of functional involvement.

Brain↗
PubMed1985

Relationship of serum bilirubin levels to ototoxicity and deafness in high-risk low-birth-weight infants.

During a 4-year period, 12 premature infants, all less than 34 weeks of gestation and all with a bilirubin level above 240 mumol/L (14 mg/dL) were determined to have bilateral sensorineural deafness. In order to to investigate how far the hyperbilirubinemia or any a associated factor might have been a causative factor, all infants of 34 weeks of gestation or less who had a serum bilirubin level above 240 mumol/L were investigated. For a period of 4 years, 99 infants meeting these criteria were classified as high risk or low risk on the basis of perinatal risk factors. Eight of the 22 high-risk infants with birth weight less than 1,500 g, but only two of 43 high-risk infants with birth weight greater than 1,500 g were deaf (P less than .05). The deaf infants were also matched with infants of normal hearing who had similar bilirubin levels and the same number of adverse perinatal factors. The mean duration of hyperbilirubinemia was significantly longer in the deaf infants (P less than .02), and they appeared to have a greater number of acidotic episodes while they were hyperbilirubinemic. These findings suggest that in healthy preterm infants with birth weight greater than 1,500 g, high bilirubin levels carry little risk, whereas a serum bilirubin level greater than 240 mumol/L in high-risk preterm infants with birth weight of 1,500 g or less is associated with a high risk of deafness.

Bilirubin↗
PubMed1984

Visual evoked responses to light emitting diode (LED) photostimulation in newborn infants.

The use of a Xenon discharge stroboscope to elicit VERs in a neonatal intensive care unit has several disadvantages. To overcome these a photostimulator has been developed which consists of an array of 25 red light emitting diodes (LEDs). The LEDs are driven by pulses of fixed length and current and the output intensity is controlled by the pulse repetition rate. Such a photostimulator is compact and can be hand-held inside a cot or incubator. Using this method VERs have been recorded in healthy full-term and pre-term infants which are comparable in wave form and latency to those elicited by a stroboscope.

Electroencephalography↗
PubMed1984

Follow-up of pre-term infants: is correction of the developmental quotient for prematurity helpful?

Developmental quotients, measured on the Griffiths' scales, of 114 preterm infants of less than 34 wk gestation are compared with abnormal neurological findings at 1 yr of cerebral palsy, dystonia, and motor delay. The developmental quotient (DQ) uncorrected for prematurity more readily distinguishes the abnormal infant than the corrected DQ. It is recommended that while developmental follow-up still uses scales originally standardised on older preterm and full-term infants the uncorrected developmental quotient is also used. Ideally normative data on the preterm infant should be compiled as a basis for assessing development in these infants.

Cerebral Palsy↗
PubMed1984

Correlation of neurologic assessment in the preterm newborn infant with outcome at 1 year.

A prospective study was undertaken of the outcome at 1 year in 129 preterm infants of less than 34 weeks gestation (range 27 to 34 weeks) who underwent detailed neurologic assessment and ultrasound scanning in the neonatal period and again at 40 weeks postmenstrual age, and an independent neurodevelopmental assessment at 12 months chronologic age. Of the 129 infants, 37 (29%) had ultrasound evidence of periventricular hemorrhage. At 40 weeks postmenstrual age the infants were classified as neurologically normal, abnormal, or borderline on the basis of the neurologic examination. Of the 62 infants considered normal at 40 weeks, 57 (91%) were assessed as normal at one year, compared to only 14 (35%) of the 39 infants considered abnormal (P less than 0.001). Ten (85%) of the 12 normal infants with associated periventricular hemorrhage were normal at 1 year, compared to 47 (94%) of the 50 normal infants without periventricular hemorrhage, whereas 5 (25%) of 20 abnormal infants with associated periventricular hemorrhage and 9 (47%) of the 19 without periventricular hemorrhage were normal at 1 year. There was no direct correlation in individual cases between the severity of neurologic deficit and the presence or severity of periventricular hemorrhage. Infants with a cluster of abnormal signs were more likely to have later dystonia or cerebral palsy than those with marked hypotonia but no other abnormality.

Cerebral Hemorrhage↗
PubMed1984

The maturation of the auditory brainstem response compared to peripheral nerve conduction velocity in preterm and full-term infants.

The maturation of the auditory brainstem response in preterm and full-term infants is compared with that of nerve conduction velocity. There is a linear relationship between wave I latency, the peripheral component of the response, and nerve conduction velocity, but the negative correlation is not high. A poor negative correlation exists between the I-V interval, an index of brainstem transmission, and nerve conduction velocity. The factors governing the maturation of central transmission along the auditory pathway in the brainstem are not related to myelination of peripheral nerves. Abnormal nerve conduction velocities are not related to any particular abnormal brainstem response in a stable external environment.

Auditory Pathways↗
PubMed1983

The maturation of visual acuity in neurologically normal and abnormal newborn infants.

The maturation of visual acuity was studied in 162 neurologically normal and 96 neurologically abnormal newborn infants. Ninety-five percent of the neurologically normal infants developed an acuity of 80 min arc by 35 weeks postmenstrual age (PMA) but only 50% developed an acuity of 40 min arc by 40 weeks PMA. Neurologically abnormal infants, and in particular those with periventricular haemorrhage (PVH), had a delay in the development of acuity. There was a close correlation between the development of 80 min arc acuity and the appearance of the first positivity of the flash visually evoked potential (VEP).

Cerebral Hemorrhage↗
PubMed1983

Use of nerve conduction velocity to determine gestational age in infants at risk and in very-low-birth-weight infants.

Nerve conduction velocity was used to measure gestational age in at risk and very-low-birth-weight neonates. The method gave highly significant correlations with gestational estimates by the Dubowitz score and with confirmed maternal dates; 86% of the estimates agreed within two weeks with confirmed maternal dates. The method is valid in babies 30 weeks old or younger and is reproducible after the first postnatal week. There was no difference in babies small for gestational age. The technique was estimated to predict gestation with a standard deviation of +/- 1.14 weeks.

Gestational Age↗
PubMed1983

Auditory brainstem responses in neurologically abnormal infants.

Abnormal auditory brainstem responses (ABR) were recorded in 33 of 59 infants with neurological abnormality in the newborn period compared with a 5 per cent incidence in infants who were neurologically optimal. Abnormality of ABR was most common in infants with intraventricular hemorrhage (17/21) but showed no correlation to size of hemorrhage. Abnormal ABRs were also frequent in infants with apnoeic syndrome (5/8) and in infants with abnormal tone patterns in the absence of intraventricular hemorrhage (7/13). All the infants with birth asphyxia had normal ABRs. Although some infants with midbrain signs had abnormal ABRs, the degree of abnormality did not correlate with the severity of clinical signs. ABR may be a useful adjunct in assessing function in neurologically abnormal infants and in confirming early major hearing deficit. Further studies should show whether the abnormal ABR reflects a primary neurological defect or is secondary to recognisable neurological lesions such as intraventricular hemorrhage. Follow-up studies are also needed to establish whether infants who are clinically abnormal and have abnormal ABR will have a worse prognosis than those without associated abnormality in ABR.

Apnea↗
PubMed1983

Intraventricular haemorrhage in a preterm neonate: discordance between clinical course and ultrasound scan.

A 30-week-gestation preterm infant developed bilateral periventricular haemorrhage with massive right sided parenchymal extension and subsequent porencephaly; yet his subsequent development was unexpectedly good, with a developmental quotient in the normal range and only mild motor delay. He showed no asymmetry of motor function until 10 weeks of age, and the signs were still mild at one year of age.

Cerebral Hemorrhage↗
PubMed1982

A comparison of neurological function in growth-retarded and appropriate-sized full-term newborn infants in two ethnic groups.

A comparative neurological study was undertaken of growth-retarded or small-for-dates (SFD) and appropriately grown (AFD) full-term infants in a Cape Coloured and a White (London, UK) population. There were no associated complications of pregnancy or labour. Consistent differences were found between SFD and AFD infants in both ethnic groups. In the SFD infants there was an increase in visual and auditory orientation, alertness, startle reflexes, tremors and tone, and some reduction in habituation. The difference between our results and those of earlier authors can probably be accounted for by factor such as use of drugs in labour, perinatal events and different causes of growth retardation, all of which may influence neurological behaviour.

Black or African American↗
PubMed1982

Neurological and neurobehavioural differences between preterm infants at term and full-term newborn infants.

A detailed neurological and neurobehavioural examination was done in 80 preterm infants of 27 to 35 weeks gestation in the first week of life and again at 40 weeks postmenstrual age, and in 40 appropriately-sized full-term infants on the first and fifth days of life. There were several consistent differences between the preterm infants reaching term and the newborn full-term infants. The preterm infants reaching 40 weeks showed less flexion in their posture, and less arm traction, arm recoil and leg recoil than the full-term infants on day 1, although this difference was less apparent by day 5. The preterm infants appeared not to develop the flexor tone of the full-term newborn. The preterm infants demonstrated better visual and auditory orientation and alertness than the full-term infants. The significance of these findings, both for initial neonatal examinations and for subsequent assessments, is evaluated.

Arousal↗