Biomedical subjects

G Kerkhoff

Publications and source records attributed to G Kerkhoff.

33 records · Page 2Linked to original sources

PubMed1999

Multimodal spatial orientation deficits in left-sided visual neglect.

Patients with right-sided temporo-parietal lesions often show contralesional neglect. However, neglect patients may also show spatial-perceptual deficits beyond the bisection and space exploration deficits frequently assessed in the horizontal plane, that is, deficits in the judgment of the subjective visual vertical or horizontal. In a recent study (Kerkhoff, G. & Zoelch, C.. Disorders of visuo-spatial orientation in the frontal plane in patients with visual neglect following right or left parietal lesions. Exp. Brain Res., 1998;122:108-120) we found significant perturbations in the perception of these three visual spatial axes in patients with contralesional neglect from right or left parietal lesions. To examine if this finding extends also to another modality we investigated how neglect patients perform tasks of visual- and tactile-spatial judgments of axis-orientation in the frontal plane. Visual-spatial and tactile-spatial judgments of the subjective vertical, horizontal and a right oblique orientation were obtained from patients with and without neglect as well as from normal subjects. Patients with left neglect showed a significant, contraversive tilt of all three visual-spatial axes (+5.6 degrees to +9.5 degrees, counterclockwise), and of the three tactile-spatial axes as well (+5.2 degrees to +10.5 degrees, counterclockwise). In contrast, right and left hemisphere lesioned control patients without neglect and normal control subjects showed unimpaired visual and tactile-spatial judgments (constant errors: < 1.0 degree). Difference thresholds in the visual-spatial tasks and unsigned errors in the tactile-spatial tasks were selectively elevated in the neglect group in contrast to all other subject groups. Spatial orientation deficits were significantly associated with the severity of clinical neglect (r = 0.55-0.88), and with the patients' ambulation performance (r = 0.45-0.70). Furthermore, crossmodal axis orientation tests in two neglect patients showed a similar counterclockwise tilt of +5 degrees to +15 degrees, suggesting a similar spatial deficit in both modalities. Orientation judgments were significantly aggravated by a 25 degree-tilt of the head to the left, as tested in one neglect patient, while a comparable rightward head-tilt improved spatial judgments in both modalities. This suggests that spatial orientation judgments are significantly modulated by gravitational input in neglect patients. Together these results are interpreted as evidence for multisensory spatial orientation deficits in neglect patients which are modulated by head-position and are related to their accompanying postural impairment.

Adult↗

PubMed1999

Restorative and compensatory therapy approaches in cerebral blindness - a review.

In the first part of this review, different types of homonymous Visual Field Disorders (VFDs) and their resulting visual disabilities are analyzed in 313 patients with VFDs and 141 patients without VFDs from a neurorehabilitation centre for adults. Homonymous hemianopia was the most frequent visual field loss (54.7 %), followed by hemiamblyopia (23.3 %), quadrantanopia (15.3 %) and paracentral scotomata (6.7 %). About 70 % of all VFD patients had a visual field sparing of 5 degrees or less (macula or foveal sparing). Patients with VFDs frequently showed two types of disabilities: hemianopic alexia was subjectively reported and objectively found in 50-90 % of all patients, and visual exploration deficits in the scotoma were complained and found in 17-70 % of the VFD patients. While hemianopic alexia was related to parafoveal visual field sparing, and additionally to visual acuity in patients with bilateral VFDs, visual exploration deficits were correlated to the size of the area in the scotoma in which the patient searched for a stimulus with saccadic eye movements (search field). The size of the search field in the intact hemifield was not related to visual exploration deficits in unilateral VFDs. As a third disability, visual-spatial deficits in VFD patients are summarized. In the second part, restorative and compensatory treatment approaches for postchiasmatic VFDs are reviewed. Partial restitution of blind regions in the visual field is achieved in the majority of patients treated with purely restorative methods including saccadic localization or light detection in the scotoma. However, the amount of the visual field recovered is limited to 5-12 degrees (mean) in 90 % of these patients. Compensatory treatments seek to improve the substitution of the lost field region by large-scale saccadic eye movements to the scotoma, spatially organized search strategies in both visual hemifields, and by training small-scale eye movements required for reading. Significant improvements in these areas are achieved in 95 % of all VFD patients with these treatment techniques, with documented transfer to visually related activities of daily living. Furthermore, a significant though limited visual field increase of 5-7 degrees is achieved in 30-50 % of patients treated in this way. In the final section, promising approaches that might lead to new treatment techniques for VFDs are reviewed. Among these are the gaze-dependant modulation of scotomata, training-dependant enlargement of the useful field of view, a nd t he uncovering of residual visuomotor capacities to visual stimuli in a scotoma.

Journal Article↗

PubMed1998

Disorders of visuospatial orientation in the frontal plane in patients with visual neglect following right or left parietal lesions.

Current models of spatial neglect focus on deficits in the patients' horizontal or midsagittal plane. However, other evidence suggests that patients with temporo-parietal lesions centered on the parieto-insular-vestibular cortex show disturbed spatial perception of the subjective visual vertical and oblique orientation discrimination in another spatial plane, the frontal plane. As the relationship between neglect and spatial orientation deficits is unclear, we examined how patients with and without visual neglect perform visuospatial tasks in the roll plane and how their performance is related to neglect. Thirteen patients with predominantly right parietal lesions and left-sided neglect, 14 control patients without neglect after right-hemispheric cerebral lesions (RBD-controls), 11 patients without neglect after left-hemispheric lesions (LBD-controls), 3 patients with right-sided neglect after left parietal lesions, and 12 normal subjects were investigated. Constant errors and difference thresholds were measured with a PC-based system when the subjects had to adjust a luminous line to their subjective visual vertical, subjective visual horizontal, and in relation to an obliquely oriented reference line. Subjects were oriented with their head and body earth-vertical while sitting in a chair in total darkness. Patients with left-sided as well as those with right-sided neglect showed a significant, in most cases contraversive, tilt of the three spatial orientations (about 5 degrees counterclockwise in the left neglect group and 5.5 degrees-8.5 degrees clockwise in the right neglect group). In contrast, the two patient groups without neglect as well as the normal subjects showed nearly perfect visuospatial judgements with constant errors of less than 0.8 degrees . Difference thresholds were significantly elevated in patients with left neglect and in two of three patients with right-sided neglect, whereas normal control subjects and both control patient groups without neglect performed indistinguishably, having thresholds of one-tenth of those of the neglect patients. Tilt of all three spatial axes was significantly related to the severity of neglect (mean r for unsigned errors, 0.74; for difference thresholds, 0.40), indicating a significant contribution to the symptomatology of left and right spatial neglect. These results indicate a close although not necessarily causal link between spatial orientation deficits in the frontal plane and hemispatial neglect in patients with left or right parietal lesions, surpassing the well-documented impairments of these patients in the horizontal plane.

Adult↗

PubMed1998

Effects of beta-carotene, retinal, riboflavin, alpha-tocopherol and vitamins C and K1 on sister-chromatid exchanges induced by 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and cyclophosphamide in human lymphocyte cultures.

The vitamins and related compounds cited in the title were investigated for their abilities to modulate sister-chromatid exchanges (SCEs) induced by Trp-P-2 or cyclophosphamide (CP) in human peripheral lymphocyte cultures in the presence of an exogenous metabolizing system from rat liver. When inducer and test substances were given simultaneously, beta-carotene, retinal and alpha-tocopherol caused a dose-dependent decrease of SCE frequencies induced by Trp-P-2 and CP. Vitamin K1, however, brought about an identical effect with Trp-P-2 only, while with CP an initial decrease of SCEs was followed by a statistically significant re-increase at higher concentrations. Vitamin C was ineffective against Trp-P-2, but caused an overall increase of SCEs induced by CP. When blood cultures were preincubated with vitamins before the addition of CP or Trp-P-2, basically identical effects were observed with beta-carotene, retinal, alpha-tocopherol, vitamin K1 and vitamin C. Riboflavin decreased SCEs induced by Trp-P-2 in all treatment schedules, although statistically confirmed minima were observed in the dose-response curves, except in post-treatment experiments. On the other hand, riboflavin only reduced SCEs induced by CP when it was preincubated with lymphocytes. When vitamins were applied in a post-treatment schedule after removal of Trp-P-2 or CP, again, basically identical results against both genotoxins were observed with beta-carotene, retinal and alpha-tocopherol with vitamin K1, however, only with respect to Trp-P-2, and with vitamin C only with respect to CP. In the post-treatment schedule, vitamin K1 caused a decrease of SCE frequencies induced by CP, and vitamin C a decrease of SCEs induced by Trp-P-2.

Animals↗

PubMed1997

Head and trunk orientation modulate visual neglect.

Five patients with left visual neglect after right hemisphere lesions were examined with a line bisection and a reading task under five different conditions: head and trunk straight ahead, head or trunk oriented 20 degrees to the left and head or trunk oriented 20 degrees to the right. Fixation was always straight ahead. Five patients with right hemisphere lesions but without neglect and five normal subjects served as controls. In all neglect patients, turning the head or trunk to the left reduced line bisection and reading errors significantly as compared with the other three conditions and with the control groups. The modulation of neglect behaviour by trunk as well as head position supports the hypothesis of a disturbed egocentric coordinate system leading to neglect.

Attention↗

PubMed1997

[Hemi-neglect versus hemianopia. Differential diagnosis].

Neglect and hemianopia represent frequent disorders in brain damaged patients. Differential diagnosis of both disorders may be difficult since both may present in diagnostic tests and daily life as a failure to perceive or react to stimuli in the contralesional hemispace or hemifield. The present paper summarizes several useful techniques in order to achieve a correct distinction. After a short review of the clinical phenomenology of hemianopia and -neglect the following topics are described: (1) subjective complaints and awareness of deficits (2) aetiology and lesion localisation, (3) uni-versus multimodal deficits; (4) extinction, (5) drawing from memory; (6) visual-spatial disorders; (7) line bisection, (8) effectiveness of attentional "cueing" strategies; (9) specific perimetric techniques; (10) visual evoked potentials and eye movement registration. The differences between hemianopia and -neglect are contrasted for all these topics. Taken all these possible features together the association and/or dissociation of hemineglect and postchiasmatic scotomata can efficiently be diagnosed. The results are summarized in a table at the end of the paper.

Cognition Disorders↗

PubMed1995

VS--a new computer program for detailed offline analysis of visual-spatial perception.

A new IBM-AT-compatible software program, VS, for the analysis of visual-spatial (VS) perception in humans, especially brain-damaged patients, is described. VS is suitable for analysis of the following visual-spatial tests: (1) subjective visual vertical (SVV), (2) subjective visual horizontal (SVH), and (3) orientation, length, distance, form and position discrimination, as well as line/bar bisection. The program allows manipulation of a wide range of experimental tasks by varying relevant parameters, e.g., length, width, color, movement direction, step width, and position on screen of the stimuli. Psychophysical parameters are computed (methods of limits) and stored in dBASE files which can be retrieved for further data analysis with commercial statistics or graphics software. VS has a versatile text editor, with two macro languages which enables the user to define their own experimental configurations and realize individual graphic plots on screen or laser printer. VS incorporates two standard examinations together with normative data of control subjects and standard plots of the subject's performance. The results of separate investigations show highly stable results in normal control subjects in repeated examinations as well as good retest-reliability of these standard examinations in brain-damaged patients (rtt = 0.77). Representative case reports of a patient with left-sided visual neglect, a patient with Balint's syndrome as well as a patient with visual-spatial deficits subsequent to a left parietal brain lesion demonstrate the sensitivity and specificity of the program.

Adult↗

PubMed1994

Neurovisual rehabilitation in cerebral blindness.

OBJECTIVE: The efficacy of a systematic training of saccadic eye movements was evaluated in hemianopic patients with three main objectives: (1) to determine the role of visual field recovery, (2) to assess the transfer of treatment gains to functional outcome measures, and (3) to evaluate the patients' subjective experience throughout therapy. DESIGN: Within-subject repeated measures design. The mean follow-up interval was 3 months (range, 1 to 10 months). SETTING: Outpatients of a day clinic for the treatment of neuropsychological disorders that is associated with a city hospital. PATIENTS: A consecutive sample of 22 hemianopic patients without neglect after unilateral stroke. Follow-up was possible in all cases. INTERVENTIONS: Saccadic eye movement strategies were treated regularly (30-minute daily sessions 5 days per week; 25 to 27 total treatment sessions). MAIN OUTCOME MEASURES: Visual perimetry results, visual search field within the scotoma, visual search on projected slides with wide eccentricity, search times for identifying objects visually on a table (table test), and standardized rating of the degree of subjective visual impairment due to the field defect. All outcome measures were planned before initiation of the study. RESULTS: (1) Increase in visual search field size (mean, 30 degrees). (2) Training-related visual field increases in 12 (54%) of 22 patients (mean increase, 6.7 degrees; range, 2 degrees to 24 degrees). (3) Transfer of treatment gains to functional measures (table test) and improvement after training in patients' subjective rating of their visual impairments. (4) Stability of improvements at the 3-month follow-up visit. (5) Return to part-time work in 20 (91%) of 22 patients. All mentioned results were significant (nonparametric tests; alpha level, .05; two-sided; adjusted for the number of tests). CONCLUSIONS: Training of compensatory eye movement strategies restores oculomotor functions, improves performance in functional visual activities, and reintegrates hemianopic patients into vocational life.

Activities of Daily Living↗

PubMed1994

[Treatment of fusional disorders in patients with brain damage].

BACKGROUND: We trained fusional convergence systematically using 3 orthoptic devices (fusion trainer, prisms, cheiroscope) in brain damaged patients with a severe deficit of convergent fusion. PATIENTS AND METHODS: 12 patients were selected, 6 with vascular cerebral lesions and 6 with traumatic brain damage. The chronicity (time since lesion) was 15.8 months (range: 2-108). Near and far visual acuity, accommodation, convergent fusional range, stereopsis (Titmus and TNO test), maximal reading duration and subjective complaints (e.g. eye strain, headache) were evaluated. To separate improvements during treatment from spontaneous recovery of function or measurement artefacts we performed repeated measurements before treatment (baseline period) during a time span of 4-6 weeks. Follow-up measurements could be performed in 9 of 9 patients 10 months after cessation of treatment. RESULTS: No improvements were seen during the baseline period. 11 of 12 patients showed a significant recovery of fusional range during training which remained stable during the 10-month follow-up period. 10 of 11 patients showed significant improvements of local stereopsis (Titmus test) and 4 of 5 patients of global stereopsis (TNO test). All patients showed a significant increase of near visual acuity of about 10% (decimal visual acuity), improved reading ability and a reduction of subjective symptoms resulting from fusional deficiency, e.g. eye strain, headache. CONCLUSIONS: These results suggest a considerable potential for recovery of oculomotor and visual functions in brain damaged patients after training.

Accommodation, Ocular↗

PubMed1994

Recovery of fusional convergence after systematic practice.

Fusional convergence was trained systematically with orthoptic devices in three patients with a severe deficit in convergent fusion resulting from vascular (one case) or traumatic (two cases) brain damage. Within a single-subject baseline design two of the three patients showed a significant, and the third patient a moderate, recovery of fusional range. All patients showed a significant improvement in visual acuity for objects close by, improved reading performance and an increase in stereo acuity (two cases). The results suggest a considerable potential for recovery of oculomotor functions in brain-damaged patients when appropriate treatment methods are applied.

Accommodation, Ocular↗

PubMed1994

[Standardized analysis of visuospatial perception. Studies of objectivity, reliability and validity].

Retest reliability and validity of a computational method (VS, [19]) for the analysis of visual spatial perception in brain damaged patients was investigated. Retest reliability was tested in 20 patients (retest interval: 1 week; range: 1-3) and varied from r = 0.65-0.95 for the different subtests for the "point of subjective equality" and r = 0.39-0.89 for the "interval of uncertainty". In the several investigations concerning the validity of VS. 234 patients and 10 normal subjects participated. In the first place, we found significant relationships of some of the subtests of VS to similar visual-spatial tests, but no relationship to tests of visual object perception. Secondly, we found significant relationships to certain tasks which approximated daily functioning. In summary, the present results demonstrate the objectivity, retest-reliability and validity of VS in brain damaged patients.

Adolescent↗

PubMed1993

Displacement of the egocentric visual midline in altitudinal postchiasmatic scotomata.

Vertical and horizontal bar bisection was assessed in six patients with homonymous altitudinal scotomata, four of whom had additional hemianopic scotomas. Analysis of performance showed a small but significant deviation of the bisection midline ("egocentric midline") to the upper field in four patients with blindness of the upper hemifield and a more pronounced deviation to the inferior hemifield in two patients with lower altitudinal field defects. In addition, horizontal bar bisection showed a shift of the egocentric midline towards the scotoma in all four patients with left- or right-sided homonymous hemianopia. Hence, location of the scotoma predicted direction of the shift of the egocentric midline but not degree of shift.

Adult↗

PubMed1993

[Standardized analysis of visual spatial perception. Construction of the procedure and applications].

Assessment of visuo-spatial perception (VS) in brain-damaged patients. So far, no comprehensive methods for reliable assessment of visuo-spatial deficits after brain damage have been described. The tests usually applied are subtests of intelligence tests, paper-pencil tests or visual-constructive tests which also require motor and planning abilities. Almost all these methods are unsuitable for measuring therapeutic changes and do not reveal specific impairments. The computational method presented here (VS) is suitable for the quantitative assessment of visuo-spatial functions, e.g. subjective visual vertical and horizontal; orientation, length, distance, form and position discrimination as well as line bisection. It can easily be installed on an IBM compatible PC. A clinical standard examination can be performed within 20-30 minutes including numerical and graphical analysis of the results. The method is sensitive for measuring therapeutic changes. Moreover, it offers a wide range of experimental task manipulations for more sophisticated experimental tests.

Attention↗

PubMed1990

[Anamnesis of brain-originated vision disorders].

A questionnaire for the subjective assessment of cerebral visual disorders was administered to 269 brain damaged patients. The patients' subjective complaints were correlated with the outcome of objective diagnostic procedures (visual perimetry, visual search, spatial contrast sensitivity, visual evoked potentials, depth perception, light- and dark-adaptation, reading, colour vision). A significant correlation was found between subjective complaints and objective diagnostic results for all fields. The prediction of visual impairments on the basis of subjective complaints and verified by objective tests was correct in 80 to 98% of the brain damaged patients tested. Interrater reliability was about 0.84. Thus, the questionnaire is suitable for the assessment of cerebral visual disorders because of its simplicity, short administration time (10-15 min) and high predictive value.

Accommodation, Ocular↗

PubMed1988

The influence of homonymous visual field disorders on colour sorting performance in the FM 100-hue test.

An influence of visual field disorders on sorting performance in the FM 100-hue test is reported. Patients with left-sided field disorders performed worse in the conventional testing direction, i.e. from left to right, compared with patients with right-sided defects. Reversing the direction of sorting led, however, to a similar impairment in patients with right-sided field defects. Observations in normals tested under different conditions of hue sorting support the view that the difference obtained cannot be accounted for by a hemisphere difference in colour processing but by the strategy adopted by subjects.

Adolescent↗