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Biomedical subjects

C W Erwin

Publications and source records attributed to C W Erwin.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1985

Evaluation of transducers for obtaining intraoperative short-latency auditory evoked potentials.

Operative monitoring of short-latency auditory evoked potentials during posterior fossa surgery requires audio transducers of small physical size so as to not interfere with the operative field. There are many relatively inexpensive transducers in the commercial audio hifi market of appropriate size. Some produce suitable biological responses and tolerate long term use without failure. The authors describe factors to consider and methods used in testing such transducers.

Evaluation Studies as Topic↗
PubMed1985

Limitations of brain stem auditory evoked potentials for intraoperative monitoring during a posterior fossa operation: case report and technical note.

We have encountered an example of the insensitivity of brain stem auditory evoked potentials (BAEPs) for monitoring the brain stem during a posterior fossa operation. The addition of somatosensory evoked potential recording to conventional BAEP protocols is readily accomplished and is likely to improve the sensitivity of intraoperative electrophysiological assessment of brain stem function.

Brain Stem↗
PubMed1984

A review of electroencephalographic features of normal sleep.

The electrographic features of sleep have been studied intensively using both routine electroencephalography and polysomnography. The two sections of this paper describe and illustrate the major characteristics of sleep physiology and associated clinical electroencephalography. In the first section, criteria for definition of sleep stages are presented and correlated with the phasic and tonic physiological events noted to occur as a function of sleep stage. The phylogeny and ontogeny of sleep are discussed as well as the neurophysiological mechanisms that may underlie sleep control. The second section presents a clinically oriented description of the patterns and events of the sleep electroencephalogram as seen in a normal adult and pediatric population.

Adolescent↗
PubMed1983

Evoked potential latency change with age suggests differential aging of primary somatosensory cortex.

The latencies of the first two cortical peaks in the somatosensory evoked potential were examined in subjects of various ages. Recent work on specialization of primary sensory cortex in primates implicates the cortical site of origin of the second cortical peak, P25, in the selective sensory losses of old age. The latency of the P25 peak changed significantly with age. The latency of the preceeding N20 peak, also of cortical origin but originating from a different site, showed no significant age-related change. Sex differences were present in both N20 and P25 latencies but were independent of the age effect in the latter. Our results provide electrophysiological evidence for differential aging of anatomically separate areas of somatosensory cortex.

Adult↗
PubMed1983

Psychomotor effects of diazepam in anxious patients and healthy volunteers.

Psychomotor effects of diazepam, 5 and 10 mg, were compared to placebo in 30 highly anxious, nonpsychotic outpatients and age and sex-matched healthy volunteers. Diazepam did not reduce anxiety according to psychiatrists' ratings, but 10 mg of diazepam three times a day reduced the scores of the self-rated visual analogue scale for anxiety compared to placebo. Diazepam, 5 mg, was devoid of adverse psychomotor effects, but diazepam, 10 mg, impaired tracking and divided attention task performance in patients and volunteers alike. Plasma, erythrocyte, and saliva diazepam and N-desmethyldiazepam concentrations did not correlate with the impairment of psychomotor skills over time.

Adult↗
PubMed1982

Efficacy and side effects of flunitrazepam and pentobarbital in severely insomniac patients.

One hundred thirty-seven current or prospective recipients of hypnotics were screened to obtain a sample of 12 severely insomniac patients for a study concerning efficacy and side effects of 2 mg flunitrazepam and 100 mg pentobarbital as hypnotics. During the baseline period, these 12 subjects showed wide intraindividual variability of sleep and performance. This variability was not reduced by the hypnotics, which on the average did not adversely affect performance. Flunitrazepam, but not pentobarbital, slightly reduced sleep latency. Neither hypnotic prolonged sleep duration or reduced the number of wakings. The generalizability of the results to the population of recipients of hypnotics is discussed.

Adult↗
PubMed1982

Ocular bobbing in metabolic encephalopathy: clinical, pathologic, and electrophysiologic study.

A patient with atypical ocular bobbing resulting from metabolic encephalopathy is described. Neurologic examination showed no signs of brainstem dysfunction, and postmortem examination failed to disclose any changes in sites associated with ocular bobbing in other reports. However, brainstem auditory evoked responses showed evidence of bilateral dysfunction of brainstem white matter. This is the first demonstration of functional disturbance in brainstem loci that are thought to be responsible for the infrequently observed ocular bobbing in metabolic encephalopathy.

Brain Diseases, Metabolic↗
PubMed1981

Effects of alcohol and flunitrazepam on mood and performance in healthy young men.

Alcohol and flunitrazepam did not have any pharmacokinetic interactions when ingested 30 minutes apart at night. Flunitrazepam, 2.0 mg, but not 0.8 Gm/kg alcohol had a strong deleterious effect on performance shortly after ingestion. The combination of flunitrazepam and alcohol impaired tracking in a divided attention task the following morning.

Adult↗
PubMed1981

Ethanol and menstrual cycle interactions in the visual evoked response.

Right and left hemisphere visual evoked responses from central locations were collected from 10 normal right-handed women in the follicular and luteal phases of their menstrual cycle. Subjects were tested sober and under 3 doses of ethanol. Amplitude and latency characteristics of the N120 and P180 components for each hemisphere were determined. Asymmetry between hemispheres for the various measurements was then calculated. The follicular phase was associated with a significant P180 latency asymmetry under baseline or placebo conditions. Virtually no asymmetry for P180 latency was present in the luteal phase. Ethanol eliminated the follicular P180 latency asymmetry and reduced the amplitude of both N120 and P180 in a dose-related fashion. The latency of the N120 component was prolonged by ethanol in a similar fashion. Interactions between menstrual cycle and ethanol occurred for both amplitude and latency of P180, but only for the response from the left hemisphere. These occurred at low or moderate doses of ethanol and illustrate the need to consider both the biphasic effects of low doses of ethanol and the possibility of lateralization of these effects to one cerebral hemisphere.

Adult↗