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Biomedical subjects

N Bohnen

Publications and source records attributed to N Bohnen.

At least 19 recordsLinked to original sources
PubMed1994

Early and midlife exposure to anesthesia and age of onset of Alzheimer's disease.

Patients with Alzheimer's disease (AD) who have a late onset of dementia may represent a subgroup of AD that has a unique multifactorial/genetic profile. It was hypothesized in the present study that if external factors interact with a biological or genetic susceptibility in at least some subsets of patients with AD, these factors may accelerate the manifestation of the disease. The cumulative exposure to different types of general and major regional anesthetics prior to the onset of dementia was calculated in a population-based study of incident cases of AD residing in Rochester, MN, for more than 40 years preceding the onset of dementia (N = 252). Correlational analysis revealed that age of onset was inversely related to cumulative exposure to general and spinal anesthesia before the age of 50, whereas there was no, or an expected positive, correlation for anesthetic exposure after 50 years. These findings may suggest that the manifestation of dementia in AD patients may be related to exposure to external factors at an earlier age.

Age Factors↗
PubMed1993

Water metabolism and postconcussional symptoms 5 weeks after mild head injury.

Posttraumatic diabetes insipidus has been reported as a sequela to head injury. It is unknown whether subclinical types of diabetes insipidus, or other types of water metabolism disorders, occur after mild head injury (MHI) and, if so, whether they are related to the persistence of postconcussional symptoms. MHI patients (n = 38) were screened for disturbances of water metabolism by comparing plasma and urine osmolalities at about 5 weeks after the trauma. Eight patients had evidence of an increased plasma osmolality together with a relatively decreased urine osmolality after an overnight fast. The presence of this disturbance was significantly related to the persistence of postconcussional symptoms. The results suggest that subclinical disturbances of water metabolism may, among other factors, be related to the persistence of symptoms after MHI.

Adolescent↗
PubMed1993

Persistent neuropsychological deficits in cervical whiplash patients without direct headstrike.

Persistent cognitive and neurasthenic complaints can be the consequence of a cervical whiplash injury. In contrast to otoneurological and orthopedic reports, neuropsychological studies on whiplash patients are scarce. We report disturbances of information processing and memory functions in two patients with a pure cervical whiplash injury with demonstrated central otoneurological abnormalities, whereas there was no evidence of intellectual deterioration or focal cortical deficits. The results suggest that the cognitive disturbances and neurasthenic symptoms may be part of one syndrome which appears to manifest itself under conditions of time pressure and distraction.

Adult↗
PubMed1992

Neurobehavioral aspects of postconcussive symptoms after mild head injury.

The sequelae of severe closed head injury have received much attention in the literature, but the effects of mild closed head injury (MHI) are less well established. There is a subgroup of patients who complain of persisting postconcussive symptoms (PCS) beyond the first weeks of recovery. Although the symptoms generally develop in the absence of clear neurological abnormalities, the condition of PCS can be chronic and disabling. It has been assumed that PCS result from an interaction between organic and psychological factors. Differentiating between the effect of primary neurological injury and secondary psychosocial problems is often difficult for clinicians and engenders controversy. Neuropsychological, neurophysiological, and neuroimaging measures can be helpful in selecting patients at risk of developing PCS. Assessment of the level of cognitive functioning, individual susceptibility to stress, and environmental demands may be beneficial in treating symptomatic patients. It is true that the vague and aspecific nature of the postconcussion syndrome may have given rise to the controversy over this entity, but the many methodological inconsistencies in the experimental approaches to the syndrome have certainly enhanced the confusion about this issue. The ensuing controversy surrounding research on the outcome of MHI and the postconcussion syndrome reflects ambiguities in definition, inconsistencies in criteria for patient selection, variation in procedures for neurobehavioral assessment, and difficulty in obtaining follow-up data.

Brain Concussion↗
PubMed1992

Performance in the Stroop color word test in relationship to the persistence of symptoms following mild head injury.

There is much controversy about whether the persistence of postconcussive symptoms (PCS) in mild head injured patients (MHI) is related to the presence of cognitive deficits. Most studies performed so far have relied on normal non-concussed control subjects rather than directly comparing patients with and without PCS following MHI. In addition, subtle cognitive deficits may be present in MHI patients that are demonstrable only with more demanding cognitive tasks. In the present study the Stroop Color Word Interference Test together with a more demanding modified interference subtask was administered to two groups of patients with uncomplicated MHI 10 days, 5 weeks and 3 months after the injury. Ten patients with persistent symptoms at 3 months were selected and individually matched with MHI patients who had initially reported symptoms but who had recovered by 3 months. The scores of the two retrospectively defined groups were compared at the different time points. Between-subjects analysis revealed overall differences for both the original and modified color word interference subtask. Within-subject analysis indicated that only the recovery rate in the modified interference subtask was significantly different between the two groups. The observation that there was a parallel trend between recovery and persistence of PCS and performance on the cognitive interference measures supports the notion that there is a functional relationship between these two phenomena.

Adult↗
PubMed1992

Recovery from visual and acoustic hyperaesthesia after mild head injury in relation to patterns of behavioural dysfunction.

Patients with head injuries frequently complain of a decreased ability to endure intense light and sound stimuli. The few psychophysical studies that have objectively studied this type of hyperaesthesia have not assessed to what extent patients recover from this hyperaesthesia after mild head injury (MHI). A computerised rating technique was used to assess tolerance to intense sound (95 dB) and light (1500 lux) stimuli in patients with an uncomplicated MHI. Patients were tested 10 days and five weeks after the injury. Although most patients substantially recovered from both visual and acoustic hyperaesthesia, 25% of the patients were still not able to endure intense stimuli by five weeks. Analysis of data obtained with two behavioural rating scales (one with post-concussive/cognitive complaints and a second with emotional/vegetative complaints) indicated that visual hyperaesthesia was specifically related to the post-concussive/cognitive complaints scale.

Adult↗
PubMed1992

Pitfalls in the measurement of plasma osmolality pertinent to research in vasopressin and water metabolism.

The reliability of measurements of plasma osmolality is known to be biased by technical artifacts, such as the anticoagulant and the osmometric technique used; the resulting measurement errors therefore may cause errors in interpretation of data. In assessing the potential biasing influence of procedural variables, we found that the temperature at which fresh plasma samples were stored, the duration of storage, and the freezing and thawing of samples appeared to significantly (P < 0.01) affect osmolality values around the narrow physiological range. These factors should be considered in the interpretation of studies on the osmoregulation of vasopressin secretion. In particular, the results suggest that data obtained for any but fresh samples, whether frozen-thawed samples or samples stored at room temperature, are unreliable.

Blood↗
PubMed1992

Neuropsychological deficits in patients with persistent symptoms six months after mild head injury.

There is much debate on the nature and duration of cognitive deficits and postconcussive symptoms (PCS) after mild head injury. Most studies performed so far have compared head-injured patients with subjects who had not suffered a concussion, instead of directly comparing patients with and without persistent PCS. The present study examined whether patients with PCS (n = 9) about 6 months after an uncomplicated mild head injury performed less well on selected neuropsychological tests than patients with mild head injuries who did not have PCS (n = 9) and healthy controls (n = 9). Patients with PCS were individually matched with controls for the time elapsed after the injury, age, sex, and education. We found that patients with PCS performed less well on tests of divided and selective attention than both patients without PCS and healthy controls. It is concluded that cognitive deficits may be present up to 6 months after mild head injury when symptoms persist. The findings indicate that patients with mild head injury and subjective symptoms may manifest demonstrable cognitive deficits.

Adult↗
PubMed1991

Tolerance for light and sound of patients with persistent post-concussional symptoms 6 months after mild head injury.

Patients with post-concussional symptoms (PCS) about 6 months after a mild head injury (MHI) were examined for tolerance of light and sound in comparison with concussed patients without PCS and non-concussed healthy controls. MHI patients with PCS were individually matched with subjects from the two control groups for the time elapsed from the injury, and for age and sex. Using a computerized rating technique, we assessed both the maximal and submaximal levels of lowered tolerance for light and sound over a wide range of stimuli. We found that the MHI patients with PCS 6 months after the trauma (n = 11) tolerated significantly less well stimuli of intensities of 71 dB and 500 lx than MHI patients without PCS (n = 11) and non-concussed controls (n = 11). There were no significant differences in tolerance for light and sound between MHI patients without PCS and the non-injured controls. Decreased tolerance for light and sound may contribute to the persistence of symptoms up to 6 months after a mild head injury. The psychophysical method provides an objective measure for the evaluation of the late persistent post-concussional syndrome.

Acoustic Stimulation↗
PubMed1991

Coping style, trait anxiety and cortisol reactivity during mental stress.

The present study examined whether salivary cortisol secretion as an index of stress reactivity to continuous mental task performance reflected individual differences in coping styles. During 4 hr of continuous mental tasks significantly higher cortisol levels were found in comparison with a control session. However, individual variability in the cortisol response was high. Correlational data indicate a significant negative relationship between the coping style 'comforting cognitions' and the individual cortisol response during mental stress. During this particular type of cognitive stress, where the subject has no control over the experimental situation, comforting and emotion-focused coping may be effective because of the subject's efforts of trying to reframe the inevitable situation in a positive and self-encouraging way. In contrast, there was no significant relationship between trait anxiety and individual glucocorticoid susceptibility to mental stress.

Adaptation, Psychological↗
PubMed1991

A psychophysical method for assessing visual and acoustic hyperaesthesia in patients with mild head injury.

Although it is well known that patients with mild head injury (MHI) are less able to endure intense light and sound stimuli than normal people, there are few psychophysical studies that have objectively measured this type of hyperaesthesia. In the present study, using a computerised rating scale technique, both the maximal and submaximal levels of reduced tolerance to light and sound were assessed for a wide range of stimuli. Three to six days after the trauma, 40 MHI patients were significantly less tolerant to stimuli of intensities over 71 dB and 500 lux levels than controls. These intensities are common, and MHI patients may suffer as a consequence.

Adult↗
PubMed1990

Cortisol reactivity and cognitive performance in a continuous mental task paradigm.

The after-effects of fatigue or stress on the performance of cognitive tests have been particularly difficult to demonstrate. In this study we examined whether salivary cortisol, used as an index of stress evoked by the continuous performance of mental tasks, reflected individual differences in cognitive performance. In a within-subject experiment in which 24 subjects were exposed to 4 hours of continuous mental activity and to a control session, significantly higher cortisol levels were found during the continuous task session. Cognitive performance was assessed before and after each session. The relevant test parameters involved aspects of verbal memory, concept shifting and divided attention. When subjects were divided into two groups based on the magnitude of individual cortisol responses to the continuous tasks, it was found that the subgroup with higher cortisol responses decreased in attention compared with their attention after the control session. In contrast, the performance of the subgroup with no or lower cortisol responses did not differ between the two sessions. There was no evidence of similar effects on verbal memory or concept shifting.

Adult↗
PubMed1989

Effects of an overnight fluid infusion on cognitive functions in preoperative patients.

The results of the present study show that subjects who received an overnight infusion of isotonic fluid did significantly less well at particular neuropsychological tests than controls who did not receive such an infusion. The relevant test parameters involved aspects of word list learning, and concept shifting on a complex speed task. Potentially biasing factors such as anxiety, disturbed sleep, education and age could be discarded. With respect to the physiological mechanism involved, the results suggest that a relatively expanded extracellular volume without dilutional hyponatremia might underlie the diminished performance. The experimental group did not lose weight overnight, and the hemoglobin and haematocrit level of the experimental group were significantly different from those of the control group; the blood pressure, plasma electrolytes and osmolality were not different. The present results provide evidence that disturbances in fluid homeostasis may affect cognitive performance.

Adult↗
PubMedDate not supplied

Coping styles, cortisol reactivity, and performance in a vigilance task of patients with persistent postconcussive symptoms after a mild head injury.

Some patients experience persistent postconcussive symptoms (PCS) after a mild head injury (MHI). According to the coping hypothesis, PCS result from the increased stress that head-injured patients experience when they are not able to cope with environmental demands. This study examined the coping ability and cortisol reactivity of MHI patients with and without PCS and in uninjured controls. Patients with PCS 12-34 months after injury were individually matched with MHI patients without PCS (N = 11) and healthy controls (N = 11) for the time elapsed since the injury, age, sex, education, and IQ. First, we found that patients with PCS reported being less able to cope with problems. These patients appeared to be inferior in active problem solving and had a more depressive attitude toward problems than subjects of the two control groups. Second, we found no differences between the three groups in the mean cortisol response during a vigilance task. These results only partly support the coping hypothesis. With respect to cognitive performance, we found that decrements in a vigilance task were related to an increased cortisol response during this task, especially in apparently "recovered" (asymptomatic) MHI patients. The latter finding may point to an increased cognitive vulnerability of apparently recovered MHI patients when exposed to a CNS stressor.

Adaptation, Psychological↗
PubMedDate not supplied

Post-traumatic and emotional symptoms in different subgroups of patients with mild head injury.

Post-concussional symptoms, such as headache, dizziness and irritability, are thought to result from the emotional stress associated with decreased cognitive performance after a head injury. A questionnaire-based investigation was carried out in 71 patients with mild head injury (MHI), using a heterogeneous item pool in order to study the interrelationships between traditional post-concussive complaints, cognitive problems, and more emotional and functional complaints. Factor analysis indicated that post-concussive symptoms loaded together with items on problems associated with decreased work performance and fatigability on a first factor, whereas psychovegetative and emotional complaints loaded together on a second factor. Two rating scales were constructed from the relevant items and were used to compare between subgroups of MHI patients and non-concussed controls. Patients with uncomplicated MHI had significantly higher scores than non-concussed subjects on the post-concussive-cognitive scale, but not on the emotional-vegetative scale. Patients with multiple head injuries or pre-existing emotional problems had higher scores on both the post-concussive-cognitive scale and the emotional-vegetative scale than MHI patients without a history of emotional problems. Reliable rating scales may be useful in multidiagnostic studies of MHI patients.

Adult↗
PubMedDate not supplied

Late outcome of mild head injury: results from a controlled postal survey.

There is insufficient information about the long-term sequelae of mild head injury (postconcussional symptoms, PCS). Therefore, a questionnaire-based investigation was carried out in patients 1-5 years after mild head injury (MHI) and in non-concussed subjects in order to study the nature of long-term complaints after MHI. A three-factor model of residual subjective and psychological complaints that contained a dysthymic factor, a vegetative/bodily complaints factor, and a cognitive performance factor were identified in the patient population. Three rating scales were constructed from the relevant items or factors, and were used to compare the MHI patients with non-concussed controls. It was found that the profile of distresses and discomforts mentioned by a population of MHI patients 1-5 years after the trauma was similar to that of a non-concussed control population. These symptoms were indistinguishable from those encountered in ordinary everyday life. These symptoms were significantly more severe in the MHI patients. Stepwise regression analysis in the patient population indicated that a number of parameters were statistically of predictive importance: comorbidity, sex, and neurological complication at the time of the trauma. The results support the hypothesis that MHI may not ever be completely reversible.

Adult↗