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Biomedical subjects

P F Weston

Publications and source records attributed to P F Weston.

11 recordsLinked to original sources

Somatosensory evoked potentials predict neurologic outcome in full-term neonates with asphyxia.

OBJECTIVE: To investigate the ability of somatosensory evoked potentials (SSEP) to predict neurologic outcome in term neonates with birth asphyxia. METHODOLOGY: Upper limb SSEP were performed on nine infants of 1-7 weeks of age who had perinatal asphyxia and an encephalopathy still present at 7 days of age. Comparison was made between the cranial ultrasound, electroencephalogram (EEG), SSEP and neurologic outcome at 9-36 months. RESULTS: Normal SSEP were found in four infants, all of whom were normal on neurologic follow up at 9-12 months. Neonatal EEG performed on two out of four of these infants were also normal, while cerebral oedema was seen on cranial ultrasound in three of the four studies. No SSEP response was seen initially in three infants, all of whom had adverse outcomes (one death, two with spastic diplegia). In contrast, their neonatal EEG had shown normal background rhythms, while two of the three cranial ultrasounds revealed oedema. For two infants the initial SSEP was absent over one hemisphere and just present over the other. Both children were abnormal on follow up at 10-12 months but did not have a hemiparesis. CONCLUSIONS: Upper limb SSEP appear more sensitive than EEG or cranial ultrasounds in predicting the short term neurologic outcome of neonates with asphyxia.

Asphyxia Neonatorum↗

Assessment of spinal cord blood flow and function in sheep after anterolateral cervical interbody fusion in the presence of cord damage.

The safety of an anterolateral cervical fusion, which facilitates stabilization without sacrifice of the anterior longitudinal ligament, recently has been brought into question. The purpose of this study was to assess the effect of an anterolateral cervical fusion on spinal cord blood flow and motor and sensory-evoked potentials in the presence of an incomplete spinal cord injury. In 12 sheep, a spinal cord injury was produced by the rapid inflation of an extradural balloon catheter; six of the animals had a cervical fusion. There was no significant difference in spinal cord blood flow or evoked potential responses obtained from the sheep that had an anterolateral cervical fusion, compared with the sheep that did not. Based on these results, it seems unlikely that this surgery has an adverse effect on recovery from spinal cord injury in the absence of operative mishap.

Animals↗

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↗

Auditory brainstem-evoked response in childhood brainstem glioma.

Auditory brainstem-evoked responses were recorded from 14 children with clinical and radiological evidence of brainstem glioma. Responses were abnormal in all cases. The findings were consistent with intrinsic brainstem lesions in all except one case with a glioma, which was shown to be located predominantly in the medulla oblongata. Seven of the children had more than one test and changes in the responses paralleled clinical changes in all except the case with glioma of the medulla. The usefulness of auditory brainstem-evoked responses as an aid in diagnosing and monitoring changes in brainstem gliomas is discussed.

Astrocytoma↗

Auditory brainstem evoked response as a hearing test in infants and children: a follow up study.

In recent years the auditory brainstem evoked response (BSER) has become an established aid in assessing hearing in unco-operative subjects. We have reviewed our experience with this technique in 293 infants and children aged less than 11 years. We have found that the threshold for click BSER correlates well with the average audiometric threshold in the 2-4 kHz range. We have had encouraging preliminary experience to support the claim by other workers that 500 Hz stimuli may be used to assess low tone auditory function. In interpreting results it is important to appreciate that hearing levels may fluctuate with disorders such as otitis media and occasionally in cases of meningitis. Caution is also advised in interpreting results in cases where central nervous system pathology capable of affecting auditory pathways is known to exist.

Audiometry↗

A slow wave auditory brainstem response to clicks in a case of high frequency hearing loss.

A slow component of the auditory brainstem response (BSER) to broad band clicks was revealed in a case of high frequency hearing loss. The latency, morphology, and threshold level characteristics of the response resembled those for the slow wave response (SWR) to 500 Hz tone pips. The SWR to clicks appeared to be initiated by the cochlear partition below 2 kHz and was unmasked by a hearing loss at 2 kHz and above. With click stimuli at intensities above the 2 kHz hearing thresholds, wave V dominated the response to clicks, thus supporting the evidence that wave V is initiated from the high frequency region of the cochlear partition. Caution is advised in interpreting threshold studies using click BSERs, as the SWR may be mistaken for a delayed wave V.

Acoustic Stimulation↗

Testing hearing with the brain-stem evoked response.

The brain-stem electroencephalograph (EEG)-evoked response (BSER) constitutes a reliable and objective method of testing hearing in infants, and in uncooperative, or retarded patients. The procedure is harmless and painless, and involves recording the EEG brain-stem responses to clicks presented by headphones. The patient may be sedated, or even anaesthetized, if necessary. Because of the equipment and time involved, the procedure is not recommended as a routine screening procedure, but constitutes a valuable adjunct to conventional audiological testing, especially in doubtful cases.

Adolescent↗

Two-dimensional echoencephalography in paediatric neurology.

Two-dimensional echoencephalography is a useful procedure in screening young infants for hydrocephalus and cerebral malformation. The procedure is noninvasive and easily repeated. The procedure is less reliable in detecting mass lesions except insofar as they disturb the anatomy of the ventricular system. The procedure can be considered as complementary to computerised axial tomography in the investigation of cerebral anatomy in paediatric neurology.

Brain↗

Does tolerance develop to low doses of d- and l-amphetamine on locomotor activity in rats?

An observational study of the behavioural effects of chronic regimens of d- and l-amphetamine was designed to investigate possible mechanisms underlying any parallel behavioural changes: (1) Accumulation of p-hydroxynorephedrine in noradrenergic nerve terminals; (2) Altered sensitivity of dopaminergic receptors. The study revealed that locomotor activity seen with low doses of both isomers (2.0 mg/kg d- and 6.0 mg/kg l-) decreased with chronic once daily treatment. However, this was accompanied by an increase in directed sniffing activity and the behaviour came to resemble that seen with higher doses of amphetamine (8.0 mg/kg d- and 16.0 mg/kg l-). Nonsignificant decreases in locomotor activity and increases in directed sniffing to apomorphine administration were observed during chronic amphetamine treatment. These findings suggest that (1) p-hydroxynorephedrine, a metabolite of d- but not 1- amphetamine, does not play an important role in these alterations in behaviour with chronic treatment and (2) the tolerance to amphetamine observed under these conditions is due to an increased, rather than decreased, sensitivity of the rats to amphetamine.

Amphetamine↗

Dose-related effects of central noradrenaline stimulation on behavioural arousal in rats.

The general activity of rats in an open field test situation was observed following the central administration of isotonic saline and 0.5 and 2.0 mug of noradrenaline into the locus coeruleus. A significant increase in activity was found following the 0.5 mug, but not the 2.0 mug dose. The results are consistent with other reports indicating that low doses of centrally administered noradrenaline produce behavioural arousal whereas higher doses may result in behavioural depression. In addition, these findings suggest that the noradrenergic neurons arising from the locus coeruleus may be important for the arousal status of rats.

Animals↗