Auditory brainstem response screening for hearing loss in high risk neonates.

The present paper reports the findings of a 7 year study evaluating the use of the auditory brainstem response (ABR) as the basis of a hearing screening procedure in a group of newborns at increased risk of hearing impairment. A Special Care Baby Unit (SCBU) population of 417 infants with diverse clinical backgrounds and treatment histories was tested for hearing impairment at birth using ABR audiometry. Some 332 passed the original screen at 30 dBnHL test level in both ears. Of the failure group, 18 did not survive and 32 had some degree of hearing impairment confirmed, nine of which were sensorineural in origin. An increased incidence of persistent middle ear disease was also noted in the failure group. A detailed operational analysis demonstrates that provided appropriate pass/fail criteria are adopted, the ABR technique offers excellent sensitivity and specificity for the detection of significant hearing loss in the test population. Furthermore, the study establishes that implementation of an ABR-based screening programme could reduce the average age at detection of permanent hearing loss by 7 months. A cost assessment shows that the introduction of such a targetted screening procedure could be done at a reasonable outlay.

The post-concussional state: neurophysiological aspects.

BACKGROUND: Twenty-six young men admitted to an Accident and Emergency Department for observation following a minor closed head injury (post-traumatic amnesia (PTA) less than 12 hours) were investigated within 24 hours of admission (day 0) and followed up at 10 days, 6 weeks and 1 year after the trauma. METHOD: Investigations at day 0 included physical examination, completion of post-concussional symptom and stress-arousal checklists, computerised EEG (CEEG) and auditory brainstem evoked potential (BAEP) recordings. These were repeated at ten days and six weeks. At 12 months follow-up, the Present State Examination (PSE) was carried out and a further post-concussional symptom checklist completed. RESULTS: Post-concussional symptomatology declined progressively from day 0 but half had residual symptoms at 1 year. Seventy-two per cent ran an acute course with recovery by 6 weeks, 8% chronic unremitting course and 20% initially improved but had an exacerbation of symptoms between 6 weeks and 12 months. The CEEG alpha-theta ratios decreased significantly between days 0 and 10, reaching a baseline thereafter. Measures of CEEG recovery from all channels correlated with symptom counts at six weeks; the slower the recovery the greater the symptoms. A relative delay in left temporal recovery was associated with residual psychiatric morbidity (PSE ID scores) at 12 months. Prolonged central brainstem conduction times occurred in 27% of patients at day 0. These correlated positively with PTA and degree of psychiatric morbidity (PSE ID scores) at 12 months. CONCLUSIONS: Symptom chronicity was accompanied by continuing brainstem dysfunction, while the degree of transient cortical dysfunction appeared to have a direct influence in the intensity of early organic symptom reaction to the trauma. Levels of perceived stress at the time of the injury, or afterwards, were not related to symptom formation.

Effects of rilmenidine and clonidine on the electroencephalogram, saccadic eye movements, and psychomotor function.

Rilmenidine is a novel oxazoline derivative that is effective in the treatment of hypertension. Studies in animals have indicated that rilmenidine may reduce blood pressure without the associated central alpha 2 side effects of clonidine. The aim of this double-blind, crossover, placebo-controlled study was to evaluate the hypotensive and central sedative effects of single oral doses of rilmenidine (1 or 2 mg), clonidine (150 or 300 micrograms), and lorazepam (2.5 mg) in 12 healthy male volunteers. Drug effects were assessed with a test battery composed of resting electroencephalogram, auditory evoked responses (AERs), saccadic eye movements, psychomotor performance, and subjective ratings as well as blood pressure and heart rate. Rilmenidine and clonidine produced similar dose-dependent reductions in blood pressure without an effect on heart rate. Saccadic eye movements were not significantly impaired after rilmenidine (1 mg) treatment in contrast to after clonidine (150 micrograms) treatment. Peak saccadic velocity was impaired by all drugs except rilmenidine (1 mg), which was indistinguishable from placebo. The electroencephalographic spectral analysis also demonstrated greater sedation with lorazepam than with the other drugs and greater vigilance with placebo and rilmenidine (1 mg) than with lorazepam. AERs showed a differentiation in sedative effects between lorazepam and clonidine (300 micrograms) relative to placebo, rilmenidine (1 mg), and clonidine (150 micrograms). These results are consistent with the hypothesis that at lower doses, rilmenidine may act preferentially through imidazoline receptors, whereas at higher doses, alpha 2-adrenoceptors may become activated.

Prevalence and associated features of epilepsy in adults with Down's syndrome.

The aim of this study was to establish the prevalence of epilepsy in persons with Down's syndrome aged 19 years and over. A total of 191 adults with Down's syndrome were identified, giving a prevalence of 0.76/1000 (95% CI 0.75 to 0.77). Of these, 18 had epilepsy, giving a prevalence of 9.4% (95% CI 5.3% to 13.5%). The prevalence of epilepsy increased with age, reaching 46% in those over 50. The neurophysiological (EEG) findings of the epilepsy group were compared with those of a control group of Down's syndrome adults without epilepsy. Paroxysmal abnormalities consistent with a diagnosis of epilepsy were found in 80% of the epilepsy group, compared with only 13% of controls (P < 0.001). Epilepsy of late onset was associated with diffuse EEG abnormalities and clinical evidence of dementia. The age distribution and EEG findings suggest two independent processes in the causation of epilepsy: late-onset epilepsy associated with clinical evidence of dementia, and early-onset epilepsy in the absence of dementia.

Central conduction time in childhood autism.

To investigate the integrity of the brain-stem in 20 mentally handicapped children who met the Rutter criteria for autism, brain-stem auditory evoked potentials were obtained for a range of stimulus intensities. Central conduction times (CCTs) were calculated for the Wave I-Wave V interval of the brain-stem potentials. In children under 14 years of age CCTs were normal. In children 14 years of age and over, three of four girls and eight of nine boys had CCTs exceeding normal limits when compared with a group of controls of normal intelligence, matched for age and sex. CCTs recorded from a group of non-autistic mentally handicapped children were within normal limits. The age distribution are consistent with a maturational defect in myelination within the brain-stem in autism, a defect which may have a much wider anatomical distribution throughout cortical and subcortical structures.

Reliability and effectiveness of screening for hearing loss in high risk neonates.

OBJECTIVE: To establish the reliability and effectiveness of screening for hearing loss by brainstem auditory evoked potential testing in high risk neonates. DESIGN: Seven year investigation of newborn babies admitted to a special care baby unit and monitored through a regional children's audiology unit. SETTING: Special care baby unit and children's audiology department, Belfast. SUBJECTS: 405 neonates admitted to the baby unit, during 1 October 1982 to 31 March 1987. MAIN OUTCOME MEASURES: Presence of hearing impairment, type and severity of hearing impairment, mortality. RESULTS: 85 children failed the screening test, 62 of whom were followed up. Five children had severe bilateral sensorineural impairment and 12 had conductive impairment requiring surgical intervention. A further 18 had severe neurological disorder detected. The sensitivity of screening was 100% and specificity was 88%. If the procedure was introduced into routine clinical practice the mean age at diagnosis for all children with severe perinatal hearing impairment would be 11 (median 1) months. The mean age at diagnosis with the health visitor screening service was 23 (19) months (difference 10 months, 95% confidence interval 6 to 16 months; p < 0.0001). CONCLUSION: Screening for hearing loss in high risk neonates is highly reliable and cost effective. It also provides valuable neurophysiological information. Routine testing of these infants would result in over half of all children with severe bilateral perinatal sensorineural hearing impairment being identified by 2 months of age. This would make an important contribution to the habilitation of this socially, emotionally, and educationally vulnerable group.

Variation in power spectral analysis of the EEG with gestational age.

Power spectral analysis (PSA) of the EEG was studied in healthy term and preterm neonates to establish the normal range with gestational age. Sixty healthy newborn infants from 26 to 41 weeks' gestation had PSA performed at 3 days of age. Five main frequency bands were studied: delta 1 (1 Hz or less), delta 2 (2-3 Hz), theta, alpha, and beta. A significant correlation was shown between absolute power in delta 1 and delta 2 with gestational age. Relative power of each frequency band, calculated as a percentage of the total power in each channel, also correlated with gestational age. A significant quadratic relationship between absolute power in the beta range and gestational age is described for the first time.

The psychobiology of minor head injury.

Twenty-six consecutive admissions to an accident and emergency unit with minor head injury were examined. This was defined as a head injury warranting brief in-patient overnight stay but with a post-traumatic amnesia of less than 12 hours. Each patient had a neurological examination, a post-traumatic symptom check list completed, EEG power spectra analysis and auditory brain stem-evoked potential recordings, and a four-choice reaction-time measurement. These assessments were repeated six weeks later. Six months after the head injury a symptom check list was completed and four-choice reaction time measured again. Post-traumatic symptoms are persistent in half of all patients at six weeks and six months follow-up. The EEG power spectra showed a significant change in theta power between the first recording and the second one at six weeks, with relative reduction being noted. Approximately half of all patients had significant delays in brain stem conduction time at day 0. There was a trend towards a decrease in brain stem conduction time at six weeks, though in almost half the brain stem conduction time still remained abnormal at six weeks. Head-injured patients had prolonged choice reaction times at day 0 with serial improvement between then and six months, though the values at six weeks were still significantly longer than healthy controls. It is suggested that these findings reflect both cortical and brain stem damage following minor head injury, the brain stem damage being more persistent. There appear to be three patterns of recovery, half recovering within six weeks, a minority persisting over six months with persisting brain stem dysfunction and less than a third showing an exacerbation of symptoms with no evidence of brain stem dysfunction, the exacerbation being possibly a consequence of psychological and social factors.

Spectral edge frequency of the EEG in healthy neonates and variation with behavioural state.

Spectral edge frequency (SEF) of the EEG was studied in 51 healthy neonates to assess its value as a measure of cerebral maturation. SEF was calculated as the frequency below which 95% of the power in the power spectrum resides. Summated SEF (sSEF) of 4 EEG channels correlated significantly with gestational age (r = 0.83). sSEF varied with behavioural state and with EEG derivation. Intra- and interindividual variability were both greater in preterm compared to term babies. We conclude that SEF is a useful measure of cerebral maturation in the newborn and may have a role in studying stressed newborns.

A steroid stupor in a surgical ward.

In the development and management of a steroid-induced stupor, in a 17-year-old man, the dose and route of administration of steroid medication were felt to be important aetiological factors. A co-ordinated plan of management involving the physician, surgeon and psychiatrist is needed in such cases.

A neurophysiological study of children with reading, writing and spelling difficulties.

Recordings of early and late auditory evoked potentials and spectral analysis of scalp EEGs of 14 eight- and nine-year-old boys with difficulties in reading, writing and spelling were compared with those of 18 matched controls. The recordings of the poor readers lacked the normal asymmetry of central conduction time and wave amplitude in the early (brainstem) auditory evoked potentials, and late (cortical) evoked potential components were reduced in amplitude. Spontaneous EEG activity was significantly increased in power in all spectral bands, and this activity was less responsive to changes in sensory stimulation. These observations provide evidence for disturbed early and late auditory processing and altered cortical function. Correlations with behavioural measures considered to be indices of reading, writing and spelling ability support the view that the electrophysiological differences in the group of poor readers reflect a disturbance in the mechanisms subserving the acquisition of written language. These differences are consistent with a primary disturbance of selective attention, which may contribute to a less efficient cognitive strategy for the acquisition of reading skills.

Topographical brain electrical activity mapping on an IBM-compatible personal computer.

A new system for computing brain electrical activity maps on a standard IBM-compatible computer has been developed. The EEG is recorded using a CED1401 intelligent laboratory interface and stored in the computer; colour coded maps are generated using software developed in Turbo PASCAL and displayed on the EGA graphics screen. An acceptable computation time of 1.2 s for a 64 x 64 map displayed as a 128 x 128 pixel image has been achieved by incorporating assembly language routines and a maths coprocessor. The system may be readily upgraded as improved hardware becomes available and further software can be added. In addition to triggering auditory, visual and somatosensory stimulators, it provides the potential for the generation of complex stimuli for cognitive experiments by means of mass RAM and digital-to-analogue converters.

Effects of nitrous oxide on auditory cortical evoked potentials and subjective thresholds.

This study has examined the effects of inhaled nitrous oxide on the N1 and P2 components of the cortical auditory evoked potentials (AEP) in the latency interval 80-300 ms after the stimulus. The amplitudes, latencies and thresholds of the AEP were measured at a range of end-tidal nitrous oxide concentrations (0%, 10%, 20%, 40%) in 10 subjects with normal hearing. Systematic decreases in amplitude and latency were observed with an increase in threshold. A study of the effect of stimulus intensity on AEP amplitude showed that the amplitude change with nitrous oxide was accounted for largely by systematic increase in evoked potential threshold. Subjective pure tone thresholds were not affected by the concentrations of nitrous oxide used, indicating that the AEP changes were independent of subjective hearing level.

Multidisciplinary teaching in a formal medical ethics course for clinical students.

A successful feature of the 4th-year curriculum in the Medical Faculty of the Queen's University, Belfast has been the development of interdisciplinary teaching in a three-week joint course to which several clinical departments contribute...Co-ordinated teaching of topics of common interest in small groups included, until the academic year 1987/88, a three-hour session on medical ethics. In the spring of 1987 the authors approached the Department of Philosophy at Queen's; subsequently proposals for a formal multidiscipinary course in medical ethics for 4th-year clinical students in the Medical Faculty, for the academic year 1987/88, were approved by the Education Committee of the Medical Faculty.