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Biomedical subjects

C G Matthews

Publications and source records attributed to C G Matthews.

At least 19 recordsLinked to original sources
PubMed1999

La Crosse and other forms of California encephalitis.

The California serogroup viruses are mosquito viruses that cause human infections on five continents. They are maintained and amplified in nature by a wide variety of mosquito vectors and mammalian hosts; they thrive in a remarkably wide variety of microclimates (eg, tropical, coastal temperate marshland, lowland river valleys, alpine valleys and highlands, high boreal deserts, and arctic steppes). In 1993, California serogroup viruses caused 71% of all cases of arboviral illness in the United States, principally La Crosse encephalitis. The 30 to 180 annual cases of La Crosse encephalitis represent 8% to 30% of all cases of encephalitis, rendering this illness the most common and important endemic mosquito-borne illness in the USA. Subclinical or mild infections are much more common. Methods and results acquired from intense study of California serogroup viruses have been applied, with benefit, to the study of the ecology and pathogenesis of many more serious human arboviral illnesses. The evolutionary potential of viruses, with particular reference to the development of more virulent strains, has been studied more closely in the California serogroup viruses than in almost any other agent of human disease.

Animals↗
PubMed1997

Sleep-disordered breathing and neuropsychological deficits. A population-based study.

The relationship of sleep-disordered breathing (SOB) to neuropsychological deficits was investigated with cross-sectional data from the Wisconsin Sleep Cohort Study, a population-based study of the natural history of SDB. A sample of 841 employed men and women ages 30 to 60 yr was studied by overnight polysomnography to assess the frequency of apneas and hypopneas per hour of sleep (apnea-hypopnea index, AHI). Prior to overnight polysomnography, the participants were given a battery of neuropsychological tests for functionally important capacities including motor skills, attention, concentration, information processing, and memory. Principal factor analysis of all the neuro-psychological test data revealed a psychomotor efficiency and a memory factor. Multiple regression analysis showed a significant negative association between logarithmically transformed AHI (LogAHI) and psychomotor efficiency score independent of age, gender, and educational status (p = 0.017). The relationship was not explained by self-reported sleepiness. No significant relationship was seen between LogAHI and memory score. In assessing the clinical significance of mild SDB, we estimate that an AHI of 15 is equivalent to the decrement in psychomotor efficiency associated with 5 additional yr of age, or to 50% of the decrement associated with hypnosedative use.

Adult↗
PubMed1992

The role of neuropsychology in the assessment and treatment of persons with epilepsy.

Several areas of current interest in the neuropsychology of epilepsy are briefly reviewed in this article. These include variables pertaining to seizures, seizure history, antiepileptic drugs, and methods of neuropsychological evaluation. It is apparent that epilepsy is a multifaceted area: Psychologists not only can be of great assistance to patients with this condition, but may also learn a great deal from this complex disorder.

Anticonvulsants↗
PubMed1991

Finger tremor after carbon disulfide-based pesticide exposures.

Index finger tremor accompanying voluntary movement was studied in 19 age-matched control subjects and in 19 grain industry employees chronically exposed to carbon disulfide-based fumigants. Visual judgments of tremor amplitude made by neurologists during clinical examinations equaled the sensitivity of computerized tremor amplitude measurements. Tremor frequency variations detectable only with computerized measurement were present in grain workers with and without increased tremor amplitudes. Frequency differences discriminated between normal subjects and 74% of the grain workers. The distribution of tremor frequency power in the grain workers was often sequestered at 5 to 7 Hz, reminiscent of tremor in idiopathic Parkinson's disease. These findings suggest that the measurement of subtle tremor frequency changes may provide an early indication of chronic carbon disulfide poisoning.

Adult↗
PubMed1990

Differences in frequency of finger tremor in otherwise asymptomatic mercury workers.

Tremor was measured from the index finger during low force, position holding in 18 control subjects and 18 battery workers with low level exposure to mercury. All workers were asymptomatic on clinical neurological examination. No differences were found in average tremor amplitudes between the groups, but statistically significant abnormalities in tremor frequency distribution existed. Tremor power spectra in the group of mercury workers were shifted toward the higher frequencies and compressed into narrow frequency peaks. These results suggest that measurements of finger tremor that evaluate the frequency distribution can produce a higher diagnostic yield than traditional visual clinical judgement. The findings also confirm other reports that currently permitted exposures to mercury are associated with subtle but distinctive differences in tremor accompanying voluntary movement.

Adult↗
PubMed1989

A comparison of the WAIS and WAIS-R using T-score conversions that correct for age, education, and sex.

A newly developed T score conversion system that corrects Wechsler Adult Intelligence Scale (WAIS) and Wechsler Adult Intelligence Scale-Revised (WAIS-R) subtest and IQ scores for appropriate demographic variables was used to compare subjects' performance on the two versions of the instrument. Using 428 pairs of subjects matched on age, education, and sex, with one person in each pair having taken the WAIS and the other the WAIS-R, we found no significant differences in level or pattern of performance when analyses were performed on the T scores. This was in contrast to highly significant differences when uncorrected scaled scores and IQ values were compared. Therefore, the T score system appears to provide a tool which may help clinicians make more direct comparisons between the results obtained on the WAIS and WAIS-R.

Adult↗
PubMed1988

Extrapyramidal and other neurologic manifestations associated with carbon disulfide fumigant exposure.

Three groups of pesticide-exposed grain workers from three different work facilities experienced chronic central and peripheral nervous system dysfunction that appeared to be exposure related. The grain inspectors, malt laboratory workers, and grain elevator workers displayed higher prevalence rates of atypical parkinsonism, cerebellar signs, hearing loss, and sensory changes than would be expected in a nonneurologic control population. The 21 self-selected patients included in this report exhibited cogwheel rigidity in 80% (17/21), decreased associated movements in 71% (15/21), distal sensory shading in 62% (13/21), intention tremulousness in 52% (11/21), resting tremulousness in 48% (10/21), and nerve conduction abnormalities in 44% (7/16). Carbon disulfide, a major component of the fumigant mixtures used, has been associated in the rayon industry, since the 1930s, with similar neurologic symptoms.

Adult↗
PubMed1986

Synergistic neurotoxicity of carbon tetrachloride/carbon disulfide (80/20 fumigants) and other pesticides in grain storage workers.

Neurophysiologic, neurobehavioral, and neuropsychologic profiles in 17 grain storage workers, 1 grain inspector, and 4 malting laboratory workers are described. The effects of CS2 toxicity as seen in viscose rayon workers as well as in experimental animals is remarkably similar to the clinical profile of our grain storage workers. CS2 use explains the dysfunction of peripheral axons, auditory nerve, the optic nerve, and the extrapyramidal system, as well as altered behavior and cognition changes. The signs and symptoms in these workers seem to be dose-related and we note that workers separated out from the areas where fumigation took place reported improvement not seen by fellow workers who continued the fumigant treatment routine. Likewise, malting laboratory workers exposed only to the grain dust from 3 to 7 years showed only minimal symptoms. Though a number of mechanism have been suggested for the alteration of neuropsychological function, the chelating ability of DDC derived from CS2 and its ability to markedly increase copper and zinc within the central nervous system suggests a mechanism of toxicity analogous to copper intoxication as in Wilson's Disease and may explain the production of extrapyramidal symptoms in these patients. Chelation of copper might prove therapeutic in CS2 poisoning. It is obvious that both basic and clinical research will be necessary to sort out the questions raised. We applaud the EPA's decision to ban the use of 80/20 fumigants and also methyl bromide, and trust that similar toxic substances be carefully studied before their selection for replacing these previous toxic agents. We further decry the technique of re-introducing grain dust into the food chain rather than destroying it, since the dust contains very high residues of fumigant material. We speculate on the possible role of CS2 and other pesticides in the food chain and the incidence of Parkinsonian symptoms in these patients and the general public.

Adult↗
PubMed1985

Use of demographic variables to predict full scale IQ: a replication and extension.

The evaluation of current level of neuropsychological functioning is handicapped by the lack of validated actuarial methods for estimating premorbid intellectual functioning. The present study cross-validated and attempted to improve the one existing method of using demographic variables in a systematic way to predict WAIS Full Scale IQ (Wilson et al., 1978). A sample of 491 neurologically normal subjects was used. The results generally supported the IQ prediction equation, but did reveal systematic differences in accuracy of prediction and direction of prediction error for IQs in the high and low ranges. Also, a simpler IQ prediction formula that uses only years of education was developed and compared with the 5-variable Wilson et al. formula.

Adolescent↗
PubMed1984

18F positron emission computed tomography in closed head injury.

Locus and extent of cerebral dysfunction in five closed head injured patients as inferred from positron emission tomography (PET) and computed tomography (CT) scan studies were compared with locus and extent inferences made in the same five patients using three additional independent sources of data. These data included: (1) clinical neurologic examination findings, (2) an extensive battery of neuropsychologic tests (including WAIS, Wechsler Memory, Halstead Reitan procedures), and (3) a comprehensive speech and language assessment battery (including the Boston Diagnostic Aphasia Examination (BDAE) and the Token Test). Neurologic, psychologic, and speech examinations were conducted within one week of the PET and CT studies. Three patients were studied at three months, one patient at six months, and one patient at two years after head injury. Follow-up CT scans were done 14 months later on four of five patients. This study supported the following major conclusions: the PET findings closely correspond with the site and extent of cerebral dysfunction inferences derived from the neurologic and behaviorial examinations but the CT findings did not; the follow-up CT scans, however, showed structural abnormalities (ie, encephalomalacia and atrophy) that were consistent with the PET, neurologic examination, and behavioral assessment findings; the study strongly supports the validity and predictive utility of neurobehavioral data which are directly pertinent to rehabilitation planning/programming in patients with closed head injury.

Brain↗
PubMed1982

Carbon disulfide-induced neuropsychiatric changes in grain storage workers.

The clinical and neuropsychiatric features of seven workers from the grain storage industry are described. All were exposed to fumigants, especially carbon disulfide and malathion. Clinical manifestations included cogwheel rigidity, resting and action tremor, peripheral neuropathy, pyramidal tract signs, an EEG pattern of sleep apnea, and characteristic measurable neurobehavioral dysfunction. Similar signs and symptoms due to carbon disulfide exposure in the viscose rayon industry strongly supported the conclusion that these grain storage workers were suffering from carbon disulfide poisoning. Malathion exposure probably had a contributing role. We conclude that exposure to these fumigants poses a serious occupational risk to the nervous system.

Aged↗
PubMed1979

The effect of symptom duration on cognitive and motor performance in parkinsonism.

Neuropsychologic test performance was examined in a normal control group and in three groups of Parkinson disease patients, with symptoms for 2 years or less, for 3 to 5 years, or for 6 to 15 years. On a test battery sampling a wide variety of cognitive and motor abilities, significant intergroup differences occurred primarily on tasks with a primary motor component, although mild intergroup cognitive impairment was also demonstrated. The results suggested that maximal deterioration occurred during the first 5 years of symptoms, with few significant additional changes after that.

Attention↗
PubMed1978

Hyperkinesis and food additives: testing the Feingold hypothesis.

Teacher ratings, objective classroom and laboratory observational data, attention-concentration, and other psychological measures obtained on 36 school-age, hyperactive boys under experimental and control diet conditions yielded no support for the Feingold hypothesis. Parental ratings revealed positive behavioral changes for the experimental diet; however, they seemed primarily attributable to one diet sequence. Parents' behavioral ratings on ten hyperactive, preschool boys indicated a positive response to the experimental diet; again, laboratory observations showed no diet effect.

Child↗