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Biomedical subjects

C W Erwin

Publications and source records attributed to C W Erwin.

At least 19 recordsLinked to original sources
PubMed1992

Ambulatory polysomnography: technical aspects and normative values.

Ambulatory polysomnographic (APSG) assessment of sleep disorders is now possible, but the technique of APSG is sufficiently different from in-laboratory PSG that normative data from in-laboratory PSG may not apply to APSG. This paper reviews the technical aspects of APSG and presents normative APSG data from 20 older healthy males. Subjects underwent medical and psychiatric screening before completing APSG in their homes. Total sleep time and the rapid-eye-movement sleep latency (RL) were both shorter than those reported by others using traditional in-laboratory techniques. The shorter total sleep may be related to behaviors at home that impinge upon sleep. The shorter RL may be related to differences in calculation methods. Periodic limb movements were common in our subjects but did not contribute to sleep disturbance. We conclude that APSG is sufficiently different from traditional PSG as to warrant collection of a large normative data base.

Ambulatory Care↗
PubMed1992

Periodic limb movement variability in older DIMS patients across consecutive nights of home monitoring.

Older difficulty initiating and/or maintaining sleep (DIMS) patients who met criteria for periodic limb movement disorder (PLMD) were monitored for three consecutive nights in their homes using ambulatory polysomnography (PSG). Correlational analyses of the group data suggested little night-to-night variability in either movement indices or movement-related arousal indices for this sample. However, within-subjects comparisons suggested considerable variability in these indices and other sleep measures across nights. Nevertheless, for most subjects, the variability noted for these indices appeared to have little effect on PLMD severity classification or clinical treatment decisions derived from blind examinations of PSGs. Further, the initial PSG study generally led to a representative severity classification and clinical decision. Additional research is needed to determine the generalizability of these results to younger subjects, patients with complaints of excessive somnolence and other methods of home PSG monitoring.

Age Factors↗
PubMed1991

Sleep variability across consecutive nights of home monitoring in older mixed DIMS patients.

Twenty patients with difficulties initiating and maintaining sleep (DIMS) were monitored in their homes for three consecutive nights using ambulatory polysomnography (PSG). Following each night of monitoring, patients provided subjective ratings of sleep disturbance and tolerance of the PSG equipment. Friedman analyses of variance performed on the objective and subjective parameters showed that the sample, as a whole, evidenced no systematic first night effects (FNE) in response to monitoring. Inspection of the data from each individual subject, nevertheless, showed that half of the sample did experience multiple FNE. Further, several scales from the Minnesota Multiphasic Personality Inventory discriminated those patients who showed multiple FNE from those who did not. However, far more striking was the finding that clinically and statistically significant intrasubject variability across nights was observed for each sleep parameter measured. Given this finding, a single ambulatory PSG study may not fully convey the nature of the sleep disturbance experienced by the DIMS patient even when FNE are absent. We thus, recommend multiple ambulatory sleep studies for those clinical and research situations in which it is necessary to document patients' night-to-night sleep variability. In contrast, when the goal of the PSG study is that of determining a sleep diagnosis, a single ambulatory study, in combination with other clinical data, may be sufficient.

Aged↗
PubMed1990

Daytime functioning and nighttime sleep before, during, and after a 146-hour tennis match.

Two adult males (ages 31 and 35 years) were studied while they participated in a week-long marathon tennis match under conditions of extreme sleep restriction (4-5 h reductions per night). Polysomnographic monitoring was conducted on the two nights prior to the marathon, continuously throughout the match, and on two recovery nights. In addition, measures of daytime sleepiness, mood state, and cognitive performance were obtained during the course of the study. Despite undergoing marked sleep restriction, both players continued to obtain their usual (baseline) amounts of slow wave sleep throughout the marathon. Both players showed a gradually increasing tendency toward daytime dozing across the first few days of the marathon. This tendency decreased on the fifth day but increased again on the sixth day of the match. Also, both players showed a pre- to postmatch decline on some cognitive measures. However, the players differed markedly in their ratings of sleepiness, mood ratings, recovery sleep patterns, and endurance with respect to the demands of the match. Results appear to be consistent with previous laboratory studies in documenting the primacy of the "slow wave sleep drive." Given the marked differences observed between the players, research designed to identify factors that predict response to sleep loss seems to be warranted.

Adult↗
PubMed1989

Intraoperative brainstem auditory evoked potentials: significant decrease in postoperative morbidity.

Evoked potentials are commonly used for intraoperative monitoring of neural tissue under surgical threat despite the lack of unequivocal evidence demonstrating its effectiveness in preventing neural injury. This study retrospectively compares the auditory morbidity of posterior fossa microvascular decompressive surgery before and after the introduction of intraoperative brainstem auditory evoked potentials (BAEPs). All patients underwent a similar operative procedure performed by a single surgeon. The two groups were comparable with regards to age, sex, and indications for surgery. In the nonmonitored group, auditory morbidity had not declined with increasing experience of the surgeon. Ten of 152 patients (6.6%) suffered a profound hearing loss in the nonmonitored group. In the monitored group, none of 70 patients suffered a profound hearing loss. We attribute this significant decline (p = 0.02) in morbidity to the introduction of intraoperative BAEPs. We believe this to be the first demonstration of a significant decrease in operative morbidity directly associated with the use of intraoperative evoked potential monitoring.

Audiometry↗
PubMed1989

Two methods of scoring sleep with the Oxford Medilog 9000: comparison to conventional paper scoring.

This study evaluated two methods of scoring taped polysomnographic data directly on the Medilog 9000 scanner: (a) screen-by-screen scoring, and (b) rapid screen scoring. Sixteen overnight polysomnograms recorded on Medilog 9000 recorders were scored using the above two methods and were also printed on paper for conventional paper scoring. Interscorer agreement was 87.8% for paper scoring, 85.5% for screen-by-screen scoring, and 84.2% for rapid screen scoring. Comparison of screen-by-screen scoring with paper scoring revealed small absolute deviations and correlations of r greater than 0.90 for all sleep parameters, with the exception of brief (less than 2 min) awakenings (r = 0.69). Rapid screen scoring resulted in slightly lower correlations and greater deviations from paper scoring on several sleep parameters, but appeared acceptable for most clinical purposes and greatly reduced the required scoring time. Although some statistically significant differences between scoring methods were observed, the size of effect was small and of doubtful clinical importance. These findings suggest that polysomnographic data recorded on Medilog 9000 recorders can be reliably and accurately scored on the Medilog scanner, obviating the laborious task of printing the taped data on paper.

Adolescent↗
PubMed1989

Polysomnographic assessment of DIMS: empirical evaluation of its diagnostic value.

This investigation examined the diagnostic value of polysomnography (PSG) for evaluating disorders of initiating and maintaining sleep (DIMS). The sample consisted of 100 outpatients who presented to the Duke Sleep Disorders Center with a complaint of chronic insomnia. All patients were given comprehensive medical, psychiatric, behavioral, and ambulatory PSG evaluations. Sleep disorder diagnoses were assigned using the criteria of the Association of Sleep Disorders Centers. Overall, PSG yielded important diagnostic information in 65% of the sample: 34% were given a primary sleep disorder diagnosis that was heavily dependent on PSG data [periodic movements of sleep (PMS) = 25%, apnea = 3%, and subjective insomnia = 6%]; 15% were given a secondary diagnosis of one of these three disorders; and PSG ruled out suspected PMS in 9% and sleep apnea in 7% of the sample. Patients greater than 40 years of age had a significantly higher rate of positive PSG findings than younger patients. Using only the clinical exam, two experienced sleep clinicians were able to predict only 14 of 25 PMS cases and one of three cases of sleep apnea. Based on these data, we suggest using PSG routinely with older insomniacs and with younger patients who fail initial treatment.

Adult↗
PubMed1989

Effect of epidural lidocaine on spinal cord blood flow.

The effect of epidural lidocaine on spinal cord blood flow (SCBF) was measured in mongrel dogs. Spinal evoked potentials were used to measure spinal cord conduction and enabled us to time the measurement of SCBF associated with maximum reduction in latency and amplitude of spinal evoked potentials produced by instillation of 5 ml of 2% lidocaine in the epidural space. We used the radioactive microsphere technique to quantitate SCBF in the cervical, upper thoracic, lower thoracic, and lumbar regions of the spinal cord. A narcotic/relaxant technique was used to eliminate SCBF changes associated with other anesthetic agents. Other parameters known to affect SCBF were kept constant and within normal physiologic values. As compared with saline solution controls, there were significant decreases in SCBF in all the four areas of spinal cord in animals given epidural lidocaine, most marked in the lumbar area.

Anesthesia, Epidural↗
PubMed1988

Somatosensory evoked potentials in a patient with a cervical glioma and syrinx.

Short-latency somatosensory evoked potentials (SSEPs) were obtained in a 61-year-old patient with a cervical spinal cord glioma extending from C3 to C7. SSEPs in response to tibial nerve stimulation were normal; however, all components of the median nerve responses were markedly abnormal bilaterally (except for normal brachial plexus responses). This selective abnormality of median nerve SSEPs has not been reported previously in a patient with cervical cord tumor associated with a syrinx and illustrates the use of the SSEP in the anatomical localization of the lesion.

Astrocytoma↗
PubMed1988

Intraoperative monitoring of auditory and brain-stem function.

Extensive clinical experience has demonstrated that intraoperative brain stem auditory evoked potentials (BAEPs) are a reliable method of monitoring auditory and brain stem function during posterior fossa surgery. An intraoperative BAEP change identifies possible neurophysiologic compromise and allows adjustment of the surgical approach in an attempt to avoid permanent neurologic injury. The use of BAEPs intraoperatively has been associated with a significant decline in postoperative auditory morbidity. Supplementation of this technique with direct eighth nerve recordings and/or upper extremity somatosensory evoked potentials offers further improvement in identifying possible surgical threat to auditory or brain stem function.

Brain Diseases↗
PubMed1987

Effects of halothane and enflurane on far and near field somatosensory evoked potentials.

Somatosensory potentials evoked in response to median nerve stimulation were studied in 10 patients during surgery under general anaesthesia with halothane (five patients) or enflurane (five patients). Bipolar scalp responses (near field) and scalp to non-cephalic reference (far field) potentials were recorded before the induction of anaesthesia, and after 15 min stabilization at each of 0.5, 1.0, 1.5 and 2.0% end-tidal concentrations of anaesthetic agent. Both agents produced similar effects. The latency of the bipolar responses was increased and the amplitude decreased. The amplitude of the far field, subcortically generated, potentials measured from the scalp to non-cephalic electrodes did not decrease as much as the near field potential with increasing concentrations of volatile anaesthetic, although the latency of the potential recorded at the frontal electrode increased. At higher anaesthetic concentrations the virtual elimination of the near field potential caused the frontal and rolandic potentials to appear to be identical. Since far field somatosensory evoked potentials are preserved during deep anaesthesia, they should be considered for use when measurement of evoked responses is required for monitoring purposes.

Adult↗
PubMed1987

Somatosensory evoked potentials and the dorsal column myth.

Somatosensory evoked potentials (SEPs) are believed to travel primarily if not totally over the dorsal column (DC) system. The modalities of joint position sense and vibration are said to be mediated by the DCs. The authors cite classic and recent literature as well as their own work to reveal a lack of consistent agreement between clinical sensory (neurological examination) and electrophysiological (SEP) data regarding DC dysfunction. Documentation of this discrepancy is presented, and potential causes are examined. The authors conclude that, despite the classic tenets, there is not testable modality specific to the DC. Instead, there is likely a transmission of several proprioceptive modalities, not limited to the DC, that ascend variously in the spinal cord and are integrated at a higher level to produce somesthetic appreciation.

Animals↗
PubMed1986

Evoked potentials in choreoacanthocytosis.

Visual, brain-stem auditory and somatosensory evoked potentials were obtained in two patients with choreoacanthocytosis. Only minor SSEP amplitude reduction was found in one patient. Therefore evoked potentials were not helpful in identifying patients with symptoms of this disorder of up to 8 years duration.

Acanthocytes↗
PubMed1986

Abnormal sensory evoked potentials in amyotrophic lateral sclerosis.

We have reviewed sensory evoked potential (EP) findings in 17 patients with amyotrophic lateral sclerosis (ALS). Somatosensory EPs were abnormal in 7 of 16 patients after lower-extremity stimulation and in 2 of 16 patients after upper-extremity stimulation. Brainstem auditory EP abnormalities were found in 2 of 12 patients. No abnormalities were noted on pattern reversal visual EPs in 12 patients. Overall, 47% of all ALS patients studied had at least one EP abnormality. EP evidence of CNS sensory dysfunction in ALS is more frequent than that noted clinically or pathologically and offers further support to previous observations of sensory system involvement in ALS.

Adult↗
PubMed1986

Effects of buspirone and diazepam, alone and in combination with alcohol, on skilled performance and evoked potentials.

Effects of buspirone, 10 and 20 mg, and diazepam, 10 mg, on skilled performance and evoked responses, as well as their interactions with 0.8 g/kg of alcohol were investigated in 24 healthy men. Alcohol, 0.8 g/kg, caused the greatest performance impairment, followed closely by diazepam. Both doses of buspirone had lesser effects. Buspirone had primarily sedative effects which were short lasting, whereas diazepam impaired tracking and body balance in addition to being sedative. Both anxiolytics showed only slight additive interactions with the present dose of alcohol. A strong drug effect and a lesser but significant alcohol and a drug/alcohol interaction effect were seen on evoked potentials. Diazepam effects on evoked potentials were similar to alcohol, whereas buspirone in some instances appeared to reverse the alcohol effect. Pharmacokinetics of buspirone and diazepam were not significantly affected by concomitant administration of alcohol. The psychomotor side effect profile of a single anxiolytic dose of buspirone is preferable to a single 10-mg dose of diazepam.

Adult↗
PubMed1985

Abnormal somatosensory evoked potentials in amyotrophic lateral sclerosis.

A patient with typical clinical and electromyographic features of amyotrophic lateral sclerosis (ALS) was found to have abnormal somatosensory evoked potentials (SEPs). Evoked responses are generally considered to be normal in ALS despite occasional pathological and clinical evidence of sensory involvement. Thus, abnormal SEPs are considered to argue against a diagnosis of ALS. Based on the present case and a review of the literature, we suggest that abnormal SEPs need not exclude a diagnosis of ALS.

Adult↗