Biomedical subjects

Andrew R Wilkinson

Publications and source records attributed to Andrew R Wilkinson.

15 recordsLinked to original sources

PubMed2006

Brainstem auditory evoked response in neonatal neurology.

Over the last three decades, the brainstem auditory evoked response (BAER) has been used to assess functional integrity and development of the auditory system and the brain in conditions that affect the brainstem auditory pathway. As a non-invasive objective test, BAER is particularly suitable in very young or sick infants. It is the major tool to detect hearing impairment in high-risk infants, and a component in universal hearing screening. BAER is also a valuable adjunct to detect neurological impairment in many developmental disorders and functional abnormalities in a range of neurological diseases. The maximum length sequence (MLS) technique has recently been incorporated into neonatal BAER study. Recent results indicate that the MLS has the potential to improve the diagnostic value of BAER in some clinical situations, although the wider utility of this relative new technique remains to be further explored.

Auditory Pathways↗

PubMed2006

Brain-stem auditory function in very preterm infants with chronic lung disease: delayed neural conduction.

OBJECTIVE: To examine brain-stem auditory function at term in very preterm infants who suffered chronic lung disease (CLD). METHODS: Brain-stem auditory evoked response (BAER) was recorded at term with clicks in 25 very preterm infants with CLD and no concomitant other major perinatal problems. RESULTS: Compared to those in normal term controls, BAER wave V latency and I-V and III-V interpeak intervals in the CLD infants increased significantly (ANOVA P<0.01-0.001). III-V/I-III interval ratio also increased significantly (P<0.01). The latencies of waves I and III did not differ significantly from the controls. However, no abnormalities were found in BAER wave amplitudes. These BAER findings, obtained at 21/s clicks, were also seen at the rates 51 and 91/s, although the increase in III-V interval tended to be more significant. Click rate-dependent changes in BAER variables in the CLD infants were generally similar to the controls, with slight differences. CONCLUSIONS: BAER components, mainly reflecting central auditory function, increased significantly. The increase in wave V latency and I-V interval is due to the increase in III-V interval. SIGNIFICANCE: Neural conduction in the more central portion of the brain-stem auditory pathway is delayed and thus brain-stem auditory function is impaired in CLD infants.

Acoustic Stimulation↗

PubMed2006

Changes in BAER amplitudes after perinatal asphyxia during the neonatal period in term infants.

We recorded serially brainstem auditory evoked response (BAER) during the neonatal period in term infants who suffered perinatal asphyxia. The amplitudes of BAER components was analysed at 40 dB above BAER threshold of each subject who had a threshold<or=25 dB nHL. No apparent changes in the amplitudes of waves I and III during the first 5 days after birth. The two wave amplitudes were slightly reduced thereafter. On day 30, the amplitudes were slightly smaller than in normal controls. No statistical significant differences were found in the two amplitudes between the infants after asphyxia and the controls on any days studied. In contrast, wave V amplitude showed a trend of reduction during the whole neonatal period. The amplitude was reduced slightly on the first day after birth, but reduced further on day 3 (ANOVA, P<0.01). Thereafter, the reduction persisted without any significant change. On day 30, wave V amplitude remained significantly smaller than in the controls (P<0.001). Compared to the controls, V/I amplitude ratio was slightly smaller during the neonatal period, but V/III amplitude ratio was significantly smaller on most of the days studied (P<0.05-0.01). The persistent reduction of wave V amplitude suggests a sustained neuronal damage of the auditory brainstem in infants after perinatal asphyxia.

Acoustic Stimulation↗

PubMed2006

Does peripheral auditory threshold correlate with brainstem auditory function at term in preterm infants?

CONCLUSION: Peripheral auditory threshold does not correlate with brainstem auditory function in preterm infants. Infants with peripheral auditory abnormality seem not to be necessarily more prone to brainstem auditory abnormality than those without the elevation, although further studies are needed in a larger number of subjects. OBJECTIVE: To investigate whether peripheral auditory threshold correlates with brainstem auditory function in preterm infants and shed light on whether preterm infants with threshold elevation are prone to central auditory abnormality. PATIENTS AND METHODS: Brainstem auditory evoked response (BAER) was recorded with clicks at term in preterm infants (gestation 28-36 weeks). Analysis of correlation was made between BAER threshold and various BAER components. BAER data were compared between preterm infants with thresholds < or = 20 dB nHL (n = 113) and those > 20 dB (n = 32). RESULTS: Although BAER threshold correlated significantly with BAER wave latencies and amplitudes, the threshold did not correlate significantly with I-V, I-III and III-V intervals. No significant differences were found between preterm infants with BAER thresholds < or = 20 dB and those > 20 dB in I-V, I-III intervals, although III-V was longer in the infants with thresholds > 20 dB nHL (p < 0.05).

Audiometry, Evoked Response↗

PubMed2006

Distortion product otoacoustic emissions in term infants with a low Apgar score.

CONCLUSION: Term infants with a low Apgar score have cochlear impairment, mainly at the frequencies 1-3 kHz. Compared with infants with both a low Apgar score and hypoxic-ischaemic encephalopathy we reported before, the impairment is less severe. OBJECTIVE: To detect any peripheral impairment of cochlear origin in infants with a low Apgar score. SUBJECTS AND METHODS: Fifty-four term infants with a low Apgar score at 1 and/or 5 min but without clinical signs of hypoxic-ischaemic encephalopathy were recruited. Distortion product otoacoustic emissions (DPOAEs) were recorded with the f2 primary tone at 10 frequencies (0.5-10 kHz) on days 3-5 and 1 month after birth. RESULTS: On days 3-5 DPOAE pass rates at most frequencies tended to be decreased, and were significant lower than those in normal term controls at 1, 2, 3, 5, 6 and 10 kHz (chi2=4.49-40.31, p<0.05-0.005). The greatest difference occurred at 1 kHz; 18.5% failed the DPOAE test and this was significantly higher than in the controls (4.3%, chi2=7.65, p<0.01). At 1 month the DPOAE pass rate at most frequencies did not show any significant improvement. The overall failure rate (14.8%) did not differ significantly from that on days 3-5.

Apgar Score↗

PubMed2006

Brainstem auditory evoked response at term in preterm infants after perinatal hypoxia-ischaemia.

AIM: To examine brainstem auditory function in preterm infants after perinatal hypoxia-ischaemia (HI). METHODS: Brainstem auditory evoked response (BAER) was studied at 37-42 wk postconceptional age in preterm infants who suffered perinatal HI, and were compared with those in preterm and term infants without any major perinatal problems. RESULTS: None of the latencies of waves I, III and V in the BAER in preterm infants after perinatal HI differed significantly from those in preterm and term controls. There were also no significant differences in the I-V and I-III interpeak intervals between preterm infants after HI and the controls. However, III-V interval in infants after HI tended to increase, and was significantly longer than in term controls (p<0.01), although it did not differ significantly from that in preterm controls. Similarly, the III-V/I-III interval ratio was greater than in term controls (p<0.05), but was similar to that in preterm controls. All amplitude variables did not differ significantly from the controls. CONCLUSION: BAER in preterm infants after perinatal HI did not differ significantly from that in preterm infants without perinatal problems, but differed slightly from that in normal term infants. The prolonged III-V interval as compared with the term controls suggests a minor impairment in central auditory function.

Evoked Potentials, Auditory, Brain Stem↗

PubMed2006

Neonatal auditory function and depressed Apgar score: correlation of brainstem auditory response with Apgar score.

AIM: To examine the relationship between neonatal auditory function and Apgar score in term infants with depressed Apgar scores. METHODS: Brainstem auditory evoked response (BAER) was recorded on day 3 after birth in term infants who had Apgar scores < or = 7 at 1 and/or 5 min. Half of the infants also had Apgar scores at 10 min, with 17 < or = 7. RESULTS: No BAER variables correlated significantly with 1-min Apgar score. However, wave III and V latencies, and I-V, I-III and III-V intervals correlated significantly and negatively with 5-min Apgar score (p < 0.05-0.01). These BAER variables were significantly longer in infants with 5-min Apgar scores < or = 7 than those > 7. Wave V latency and all intervals also correlated negatively with 10-min Apgar score (p < 0.05-0.01). Compared to normal controls, all latencies were prolonged in infants with depressed Apgar scores (all p < 0.05-0.01). All intervals were also prolonged in those with 5-min scores < or = 7 (p<0.05-0.01). Similar results were found when defining the depression of Apgar score as < or = 6. CONCLUSION: A depressed 5- and/or 10-min Apgar score is an indicator associated with neonatal auditory, mainly central, impairment. Apgar score < or = 7 or 6 at 1 min alone is unlikely to be associated with central impairment.

Apgar Score↗

PubMed2005

Brainstem auditory-evoked responses in full-term newborn infants with temporary low Apgar score.

CONCLUSIONS: No abnormalities, with the exception of maturational changes, in BAER were found during the neonatal period. The results suggest that a temporary low Apgar score is not accompanied by any significant auditory impairment. OBJECTIVE: To examine brainstem auditory function in newborn infants with a temporary low Apgar score but no clinical signs of hypoxic-ischaemic encephalopathy (HIE). MATERIAL AND METHODS: The subjects were 36 full-term infants with Apgar scores of < or =7 at 1 and/or 5 min and > or =8 at 10 min but without HIE. The brainstem auditory-evoked response (BAER) was serially recorded at click rates of 21, 51 and 91/s on Days 1, 3, 5, 7 and 30 after birth. RESULTS: On Day 1 and Days 3-5, the latencies of waves I, III and V tended to increase slightly at all click rates but did not differ significantly from normal control values. Thereafter, all latencies tended to decrease, reaching control values on Day 30. The I-V interval was similar to the control values at all click rates during the first 5 days, tended to decrease from Day 7 and did not differ from the control values on Day 30. There were no significant changes in BAER wave amplitudes at any of the click rates on any day.

Apgar Score↗

PubMed2005

Brainstem auditory function at term in preterm babies with and without perinatal complications.

Functional integrity of the auditory brainstem was studied at term in babies born at 30-36 wk of gestation using maximum length sequence brainstem auditory evoked response (MLS BAER). Compared with normal term babies, preterm babies who had perinatal complications showed a tendency of an increase in wave V latency and I-V and III-V intervals at all 91-910/s clicks, with statistical significance at higher rates. Wave V latency and I-V interval increased significantly at 455/s and 910/s. III-V interval increased at all click rates, which was more significant at higher rates. III-V/I-III interval ratio increased at most rates. Waves III and V amplitudes reduced significantly mainly at 455/s and 910/s. In preterm babies who had no perinatal complications, there were no major MLS BAER abnormalities except an increase in III-V interval at 91-910/s. By comparison, the preterm babies with perinatal complications had a significant increase in wave V latency, I-V and III-V intervals, and III-V/I-III interval ratio at 455/s and 910/s clicks. These results suggest that although there are no major abnormalities in brainstem auditory function in preterm babies without perinatal complications, the auditory brainstem, mainly the more central part, in preterm babies with perinatal complications is impaired, which becomes more apparent at very high stimulus rates. We conclude that preterm babies with perinatal complications are at high risk of central auditory impairment.

Brain Stem↗

PubMed2004

Brain-stem auditory impairment during the neonatal period in term infants after asphyxia: dynamic changes in brain-stem auditory evoked response to clicks of different rates.

OBJECTIVE: To explore dynamic changes in brain-stem auditory electrophysiology during the neonatal period in term infants after perinatal asphyxia. METHODS: Sixty-eight term newborn infants who suffered asphyxia were studied on days 1, 3, 5, 7, 14 and 30 after birth. Brain-stem auditory evoked response (BAER) was recorded with clicks, delivered at 21, 51 and 91 s(-1) and > or =40 dB above BAER threshold of each subject. RESULTS: During the neonatal period wave I latency in the infants after asphyxia increased slightly while later BAER components changed more significantly. On the first day after birth wave III and V latencies and I-V and III-V intervals increased significantly at all rates of clicks (ANOVA P<0.01-0.001). On day 3, the latencies and intervals increased further. III-V/I-III interval ratio increased at 51 and 91 s(-1), suggesting a relatively more significant increase in III-V interval than in I-III interval at higher rates. Thereafter, wave III and V latencies and all intervals decreased progressively, although these BAER variables were still significantly longer than in normal controls on days 5 and 7 (P<0.05-0.001) On day 30, all latencies and intervals approached near normal values, with a slight increase in wave V latency and I-V and III-V intervals at 51 and 91 s(-1). CONCLUSIONS: Perinatal asphyxia has a major effect on central auditory function, resulting in acute impairment. The impairment progresses during the first 3 days and then tends towards recovery. By 1 month the impaired auditory function has largely returned to normal. Significant increase in click rates can moderately improve the detection of auditory impairment. SIGNIFICANCE: After perinatal asphyxia early detection of hypoxic-ischaemic damage to the central auditory system and initialisation of neuroprotective and therapeutic measures during the first hours after birth are critical to prevent or reduce deterioration of central impairment.

Acoustic Stimulation↗

PubMed2004

Differential changes in peripheral and central components of the brain stem auditory evoked potentials during the neonatal period in term infants after perinatal hypoxia-ischemia.

To identify any differences in dynamic changes between peripheral and central hearing after perinatal hypoxia-ischemia, we studied 80 term infants during the neonatal period by serially recording brain stem auditory evoked potentials (BAEPs) at 60 dB normal hearing level. All BAEP wave latencies and the I-V interval increased significantly on day I (analysis of variance, all p < .001). Thereafter, the wave I latency decreased gradually with some variation. The wave V latency and the I-V interval increased further on day 3 and then decreased progressively. On day 30, neither the latencies nor the I-V interval differed significantly from those of normal controls, but the wave V latency and the I-V interval still tended to increase slightly. These results suggest that hearing is impaired shortly after hypoxia-ischemia. Peripheral hearing gradually recovers after day 1, whereas central impairment progresses during the first 3 days and then starts to recover. We conclude that peripheral impairment recovers sooner than central impairment after perinatal hypoxia-ischemia.

Asphyxia Neonatorum↗

PubMed2004

Fetal infants: the fate of 4172 infants with birth weights of 401 to 500 grams--the Vermont Oxford Network experience (1996-2000).

OBJECTIVE: Improvement in the survival of extremely low birth weight infants requires that we evaluate the limits of our care and assess the impact of treatment on a population of infants who previously rarely survived. METHODS: A review was conducted of demographic and clinical data of infants who had birth weight 401 to 500 g and were entered in the Vermont Oxford Network Database between 1996 and 2000. RESULTS: A total of 4172 infants who weighed 401-500 g (mean gestational age: 23.3 +/- 2.1 weeks) were born at 346 participating centers. Overall, 17% survived until discharge. A total of 2186 (52%) died in the delivery room (DR), and 1986 (48%) were admitted to a neonatal intensive care unit (NICU). Compared with infants who died in the DR, infants who survived the DR and were admitted to the NICU were more likely to be female (58% vs 49%), to be small for gestational age (56% vs 11%), to have received prenatal steroids (61% vs 12%), and to have been delivered by cesarean section (55% vs 5%). Thirty-six percent of NICU admissions survived to discharge. Mean gestational age of the 690 NICU survivors was 25.3 +/- 2.0 weeks. These survivors experienced significant morbidity in the NICU. CONCLUSIONS: An appreciable number of these marginally viable fetal infants survive. They experienced a high rate of serious morbidities while in the NICU. There is very little information about long-term outcomes, as the medical and developmental status of few of these infants has been followed carefully. Parents should be made aware of the high incidence of serious problems, and concerted efforts should be made to follow the status of these infants.

Databases, Factual↗

PubMed2003

Time course of brainstem pathophysiology during first month in term infants after perinatal asphyxia, revealed by MLS BAER latencies and intervals.

Dynamic changes in electrophysiology of brainstem auditory neurons during the first month after birth were studied in 51 term infants after perinatal asphyxia using maximum length sequence brainstem auditory evoked responses. The responses were recorded on d 1, 3, 5, 7, 10, 15, and 30 after birth. On d 1, wave III and V latencies and all interpeak intervals increased significantly at all repetition rates of clicks used (91-910/s), especially the higher rates (ANOVA, p < 0.05-0.0001). On d 3, all these latencies and intervals increased further and differed more significantly from the normal control subjects. Thereafter, the latencies and intervals decreased progressively. On d 7, wave V latency and all intervals still differed significantly from the control subjects. These dynamic changes were more significant at higher rates of clicks than at lower rates. On d 10 and 15, all intervals decreased significantly. On d 30, all wave latencies decreased to the values in the normal control subjects on the same day. The intervals also approached normal values, although the III-V and I-V intervals still increased slightly. These results indicate that hypoxic-ischemic brain damage persists during the first week, with a peak on d 3, and recovers progressively thereafter. By 1 mo, the damage has largely returned to normal. Maximum length sequence brainstem auditory evoked responses results correlated well with the stage of hypoxic-ischemic encephalopathy during the first week. The present study revealed a general time course of brainstem pathophysiology after asphyxia, although there were individual variations. Our findings can be used as a reference to monitor cerebral function and help judge the value of neuroprotective or therapeutic interventions. The first week, particularly the first 3 d, is a critical period of hypoxic-ischemic brain damage, and early intervention may prevent or reduce deterioration of the damage.

Asphyxia↗

PubMed2002

Maternal morbidity and pregnancy outcome in a cohort of mothers transferred out of perinatal centres during a national census.

OBJECTIVE: To record the maternal morbidity and pregnancy outcome in this cohort. DESIGN: Retrospective data collection from a prospectively defined cohort. SETTING: The 37 largest perinatal centres in the UK. POPULATION: 258 in utero transfers recorded during a three-month census (1/4/99-30/6/99). METHODS: A questionnaire regarding the outcome of each mother was sent to the perinatal centre and receiving hospital. RESULTS: Data were returned on 242/258 (94%) mothers. Fifty-eight percent were transferred out of their perinatal centre in preterm labour and 38% had coexisting disease necessitating early delivery. The median gestational age at transfer was 32 weeks (range 23-41). Sixty-one percent delivered at the receiving hospital; 12% were transferred on to a third hospital and 29% ultimately returned to deliver at the original perinatal centre. Fifty-two percent of mothers received postnatal care in hospitals other than those defined as a major perinatal centre. One mother delivered during transfer and a further nine within one hour of arrival. One mother received intensive care after delivery and later died, a further 7% required high dependency care postnatally. Data were available on 273/333 (82%) babies. The median gestational age at delivery was 34 weeks (range 24-41). Six infants were stillborn and 187/264 (71%) infants were admitted to a neonatal unit. CONCLUSIONS: This study has documented the maternal morbidity, potential risks and pregnancy outcome of a cohort of mothers transferred out of the largest perinatal centres in the UK because of a shortage of neonatal cots. A national standard for the delivery of high risk perinatal services is needed to uphold good clinical practice guidelines in the care of high risk mothers and their infants.

Bed Occupancy↗

PubMed2002

Auditory neural responses to click stimuli of different rates in the brainstem of very preterm babies at term.

Auditory neural responses to acoustic stimuli of different rates were studied by analyzing changes in brainstem auditory evoked responses (BAER) with increasing repetition rate of clicks, or rate-dependent changes, in 62 very preterm babies (gestation 24-32 wk). None had perinatal asphyxia or major complications at the time of testing (37-42 wk postconceptional age) to exclude their possible effects on the recorded BAER. As the rate of clicks was increased from 21/s to 51/s and 91/s, I-V interpeak interval in these babies increased similarly to that in normal term neonates. The rate-dependent change decreased significantly in I-III interval, but increased significantly in III-V intervals and III-V/I-III interval ratio (all p < 0.01). At all three rates of clicks, the I-V interval, the most commonly used BAER variable, tended to increase slightly but did not differ significantly from the term neonates. The I-III interval decreased significantly at higher click rates (ANOVA p < 0.05 at 51/s and < 0.001 at 91/s), whereas the III-V interval and III-V/I-III interval ratio increased significantly at all 21/s, 51/s, and particularly 91/s (p < 0.01-0.001). No abnormalities were found in wave V amplitude at any rates. These results suggest that very preterm babies have an advanced peripheral development of the brainstem auditory pathway but a retarded central development or central impairment. A nearly normal I-V interval does not exclude a possible abnormality in its subcomponents (I-III and III-V intervals). In babies who have a normal BAER at a conventionally used low rate of clicks, we cannot exclude an abnormal BAER at higher rates.

Acoustic Stimulation↗