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Biomedical subjects

H C Sauerwein

Publications and source records attributed to H C Sauerwein.

6 recordsLinked to original sources
PubMed2000

Neuropsychology of childhood epilepsy: pre- and postsurgical assessment.

Childhood epilepsy is one of the most prevalent forms of chronic and disabling childhood disorders. Because it disrupts brain maturation, it has long been thought to produce non-specific consequences such as mental deficiency and behavioral problems. However, advances in medical knowledge have shown that childhood epilepsy should not be considered as a single disorder, and it is now becoming apparent that various clinical entities have different cognitive expressions that yet need to be specified. The purpose of this paper is to provide an up-to-date analysis of this multi-faceted pathology. The first section is devoted to the characterization of the neuropsychological profile that accompanies focal epilepsies, as defined by the site of the epileptic process. We report the first group study of children with frontal lobe epilepsy. The results indicate that frontal lobe epilepsy produces symptoms (deficits of planning, attention and motor dexterity) that are akin to those found in frontal-lesioned adults. Similarly, like in adults, temporal lobe epilepsy produces memory impairment in children as well as behavioral and academic disturbances. Occipito-parietal lobe epilepsy is rare in children and its effects still need to be specified. The second section deals with the neuropsychological techniques used in presurgical evaluation. Finally, the various neurosurgical procedures that are increasingly being used as part of the arsenal of epilepsy treatment are described along with the neuropsychological findings that are associated with these interventions. It can be concluded that the beneficial effects of epilepsy surgery (callosotomy, hemispherectomy, temporal and extra-temporal resections) by far outweigh the few cognitive deficits that are occasionally reported following these interventions.

Adult↗
PubMed1997

Neuropsychological alterations after split-brain surgery.

Neuropsychological changes following corpus callosotomy depend on the degree of the callosal section, the portion sectioned and the patient's age at the time of the surgery. Anterior section frequently results in transient hemiparesis of the non-dominant leg and temporary difficulties in initiating speech. Posterior section is followed by disconnection symptoms in the sensory modalities which can be demonstrated when input is lateralized and one hemisphere is denied access to the information received by the other. Visual and tactile stimuli presented to the non-dominant hemisphere are no longer verbally identified due to disconnection from the language-dominant hemisphere. Total callosotomy additionally interrupts interhemispheric communication between the motor regions. This results in deficits in bimanual coordination and apraxia of the non-dominant hand to verbal commands. Some of the symptoms subside, probably due to increased use of ipsilateral sensory and motor pathways. Others are permanent. However, they are not disabling since unrestricted scanning of the environment ensures bilateral representation of sensory experience. Cognitive functions are frequently improved, although preexisting lateralized deficits may be exacerbated. Learning of new material is difficult for some patients with lateralized temporal lobe dysfunction in whom interhemispheric compensation is abolished by the surgery. Language deficits are observed mainly in patients with crossed dominance. Studies in children reveal that callosotomy performed before puberty is not followed by permanent disconnection deficits. This may be attributable to the greater neural plasticity of the immature brain.

Child↗
PubMed1995

Extent and limits of callosal plasticity: presence of disconnection symptoms in callosal agenesis.

Although earlier studies have emphasized the absence of 'split-brain' symptoms in callosal agenesis patients, the notion of an 'asymptomatic' acallosal brain has lately been challenged. We report a number of findings that are indicative of an interruption of interhemispheric communication and integration in individuals lacking the corpus callosum. Several groups of patients with callosal pathology (acallosals, patients with commissurotomy or callosotomy, either complete or partial) were compared to matched controls. Interhemispheric transfer was tested in two different experiments involving pointing to a light source while maintaining central fixation. In the first experiment, a learning paradigm was used to measure transfer of a motor skill from the trained to the untrained hand. In the second experiment, subjects pointed to visual targets at different locations on a perimeter. Midline fusion, a recurrent theme when describing callosal function, was assessed using tasks which included depth perception with binocular and/or monocular cues, two-point discrimination thresholds and sound localization in the peri-central and lateral fields. Subjects with callosal pathology were impaired on all tasks involving transfer of motor and visuo-spatial skills and on some of the tasks requiring sensory integration of visual and tactile information across the body midline. We conclude that these functions require an intact corpus callosum since none of these deficits were seen in controls equated for IQ.

Adolescent↗
PubMed1994

Cognitive and sensori-motor functioning in the absence of the corpus callosum: neuropsychological studies in callosal agenesis and callosotomized patients.

The aim of the present study was to investigate the role of the corpus callosum in cognitive and sensori-motor functioning as measured by a neuropsychological test battery. After a brief review and analysis of the literature, we report our own studies in acallosal subjects (n = 9) and callosotomized patients (n = 25). The main instrument of evaluation was the Michigan Neuropsychological Test Battery. This battery was supplemented by age-appropriate intelligence tests. The performance of the acallosal group was compared to that of two matched control groups: one group consisting of children and adolescents that attended the same school as the acallosals and a second group of subjects recruited from regular schools. The callosotomized patients, tested pre- and post-operatively, served as their own controls. Taken together, the results of the reviewed and personal studies suggest that absence of the corpus callosum does not necessarily impede cognitive functioning. However, samples drawn from clinical populations tend to show a larger variability as to their mental abilities. In keeping with previous findings, our results indicate that the corpus callosum does play a role in bimanual motor coordination although other pathways (probably ipsilateral and/or subcortical) may provide adequate compensation in many cases. The data further suggest that the corpus callosum may be important for interhemispheric transfer of tactuo-motor learning when a spatial component is involved. Finally, our results are consistent with a facilitatory role of the corpus callosum in cognitive and sensori-motor functioning which allows for interhemispheric compensation as part of cerebral reorganization in the case of unilateral brain damage.

Adolescent↗
PubMed1992

Influence of anatomical factors and spatial compatibility on the stimulus-response relationship in the absence of the corpus callosum.

Simple and choice reaction times (RTs) to lateralized flashes of light were measured in two acallosal subjects, a callosotomized patient with sparing of the splenium, six IQ-matched controls and six controls with above average IQ. The aim of the study was to investigate the influence of stimulus-response factors on visuomotor integration in the absence of the corpus callosum. The results showed that simple-RTs are faster for all groups when sensory input and motor output are coordinated in the same hemisphere, regardless of the spatial relationship between stimulus (S) and response (R). The difference between ipsilateral and contralateral RTs, taken as a measure of interhemispheric transmission time (ITT), was more than three times longer in the patients lacking the corpus callosum than in the controls. In the choice-RT paradigm, the main determinant of the response speed was S-R spatial compatibility rather than the anatomical relationship between the neural structures receiving the visual input and those controlling the motor output. Spatially compatible S-R pairings were always faster than incompatible pairings. The compatibility effect was present in all subjects but it was significantly larger in the callosum-deprived patients and their IQ-matched controls with respect to the high-IQ controls. The latter finding suggests that cognitive factors may be involved in the production of the spatial compatibility effect.

Adult↗