Aphasia,neglect and extinction are no prominent clinical signs in children and adolescents with acute surgical cerebellar lesions

The aim of the present study was to examine if clinically significant signs of aphasia, neglect or extinction, which have a well-known cerebral lateralization, are present in children and adolescents with acute focal lesions following tumour surgery in the cerebellum. Eight children and adolescents with cerebellar tumours were tested within days after tumour surgery. None of the children had received radiation or chemotherapy at the time of testing. Eleven age- and education-matched control subjects with major orthopedic surgery participated. High-resolution magnetic resonance images showed lesions of the right cerebellar hemisphere in three and of the left hemisphere in five children. Standard aphasia tests revealed no statistically significant difference comparing children with right- and left-sided lesions and controls. Mild signs of language disturbance, however, were present in single subjects with right-sided cerebellar lesions. Neglect and extinction tasks revealed minor abnormalities, which lacked consistent lateralization and were best explained by more unspecific attentional deficits and motor disorders in acute post-surgical stage. Acute right-sided cerebellar lesions can be followed by mild signs of language disturbances in single subjects. Clinically significant signs of neglect and extinction, however, are not observed in children and adolescents with acute surgical cerebellar lesions.     

Incorporating simulators in a standardized patient exam.

OBJECTIVE: Using simulated patients during a clinical skills exam that involves many students has the advantage of standardizing the delivery of historical data. One major disadvantage is the inability to standardize the physical exam findings. We designed a simulated patient exam that incorporates simulated abnormal physical exam findings. DESCRIPTION: The simulated patient exam case was divided into three separate stations: (1) the simulated patient's history, (2) the simulated physical exam, and (3) the presentation station. Dyspnea was chosen as the chief complaint because of the broad differential of possible cardiac and pulmonary auscultatory findings. In the first station, students obtained historical data from the standardized simulated patient. Students were graded on their ability to ask appropriate historical questions. Trained observers were used to verify the numbers of historical cues obtained by the students. The second station consisted of simulated physical exam findings. Students first measured the blood pressure on a commercially available blood pressure simulator arm from the Medical Plastics Laboratory, Inc., Gatesville, TX. Students then auscultated an abnormal digital heart sound and pulmonary sound from a small auscultation transducer developed by Andries Acoustics, Spicewood, TX. Students also palpated a simulated pulse from a newly developed pulse transducer. Digital cardiopulmonary sounds and pulse data were recorded onto a CD-ROM disc and transmitted to the small transducers via a CD-ROM disc player. Students used their own stethoscopes to auscultate cardiopulmonary sounds from the small transducers. The students were graded in the second station on their ability to accurately measure a blood pressure, identify abnormal cardiopulmonary digital sounds, and finally describe a peripheral pulse. In the third station, students presented the historical data and physical exam findings to a faculty member, and then provided a differential diagnosis list based on their key findings from the other two stations. A total of 171 students (n = 171) completed the simulated patient exam. Each student completed the exam in 45 minutes. DISCUSSION: In our simulated patient exam, students were evaluated not only on their data-gathering skills for key historical findings but also on the ability to correctly identify key physical exam findings such as abnormal cardiopulmonary sounds. Key physical exam findings were then integrated into the clinical decision-making process, which was presented in the faculty presentation station. Simulated patients with abnormal cardiopulmonary findings can be used for testing purposes. However, cardiac auscultatory abnormalities such as the ventricular S3 gallop are difficult to find and usually occur in a decompensated state such as heart failure. Other physical exam findings such as pulmonary crackles and wheezes also occur in decompensated conditions. Therefore, the use of simulators during a simulated patient exam offers the possibility of introducing several abnormal physical exam findings without having an unstable patient present in an exam setting. Further, the use of simulated physical exam findings allows for complete standardization of a clinical-simulated patient exam.     

Manual, semi-automated, and automated delineation of chronic brain lesions: a comparison of methods

The exact delineation of chronic brain lesions is a crucial step when investigating the relationship between brain structure and (dys-)function. For this, manual tracing, although very time-consuming, is still the gold standard. In order to assess the possible contributions from other methods, we compared manual tracing of lesion boundaries with a newly developed semi-automated and a fully automated approach for lesion definition in a sample of chronic stroke patients (n=11, 5m, median age 12, range 10-30years). Manual tracing requires substantially more human input (4.8-9.6h/subject) than semi-automated (24.9min/subject) and automated processing (1min/subject). When compared with manual tracing as the gold standard, both the semi-automated (tested with 4 different smoothing filters) and the automated approach towards lesion definition performed on an acceptable level, with an average Dice's similarity index of .53-.60 (semi-automated) and .49 (automated processing). In all semi-automated and automated approaches, larger lesions were identified with a significantly higher performance than smaller lesions, as were central versus peripheral voxels, indicating that the surface-to-volume ratio explains this trend. The automated approach failed to identify two lesions. In several cases, indirect lesion effects (such as enlarged ventricles) were detected using the semi-automated or the automated approach. We conclude that manual tracing remains the gold standard for exact lesion delineation, but that semi-automated and automated approaches may be alternatives for larger lesions and/or larger studies. The detection of indirect lesion effects may be another application of such approaches in the future.     

Pusher Syndrome – a frequent but little-known disturbance of body orientation perception

Abstract Disturbances of body orientation perception after brain lesions may specifically relate to only one dimension of space. Stroke patients with “pusher syndrome” suffer from a severe misperception of their body's orientation in the coronal (roll) plane. They experience their body as oriented ‘upright’ when it is in fact markedly tilted to one side. The patients use the unaffected arm or leg to actively push away from the unparalyzed side and resist any attempt to passively correct their tilted body posture. Although pusher patients are unable to correctly determine when their own body is oriented in an upright, vertical position, they seem to have no significant difficulty in determining the orientation of the surrounding visual world in relation to their own body. Pusher syndrome is a distinctive clinical disorder occurring characteristically after unilateral left or right brain lesions in the posterior thalamus and –less frequently– in the insula and postcentral gyrus. These structures thus seem to constitute crucial neural substrates controlling human (upright) body orientation in the coronal (roll) plane. A further disturbance of body orientation that predominantly affects a single dimension of space, namely the transverse (yaw) plane, is observed in stroke patients with spatial neglect. Apparently, our brain has evolved separate neural subsystems for perceiving and controlling body orientation in different dimensions of space.     

Cognitive functions in patients with MR-defined chronic focal cerebellar lesions

Abstract The aim of the present study was to examine cognitive functions in a group of chronic patients with focal cerebellar lesions. Both effects of localization (anterior vs. posterior lobe) and side (left vs. right cerebellar hemisphere) were of interest. Fourteen patients with infarctions within the territory of the posterior inferior cerebellar artery (PICA) and seven patients with infarctions within the territory of the superior cerebellar artery (SCA) participated. The affected lobules and nuclei were assessed based on 3D MR imaging. The right cerebellar hemisphere was affected in eight PICA and two SCA patients, the left hemisphere in six PICA and four SCA patients. One SCA patient revealed a bilateral lesion. In order to study possible lateralization of functions, subjects performed a language task as well as standard neglect and extinction tests. Moreover, two tests of executive functions were applied. There were no significant group differences apart from a verbal fluency task, in which all cerebellar patients – but especially those with right-sided lesions – were impaired. Voxel-based lesionsymptom mapping (VLSM) revealed that a lesion of the right hemispheric lobule Crus II was associated with impaired performance in the verbal fluency task. In sum, the results showed preserved cognitive abilities in chronic cerebellar patients apart from impairments of verbal fluency in patients with right-cerebellar lesions. The latter findings are in line with the assumption that the right posterolateral cerebellar hemisphere supports functions associated with verbal fluency.     

Objections against the view of visual extinction as an attentional disengagement deficit: the interaction between spatial position and temporal modulation

Visual extinction is a common consequence of brain injury where individuals fail to detect a contralesional target when it is presented with a competing ipsilesional target. This disorder is often seen as either a consequence of biased competitive interactions or as a consequence of an attentional disengagement deficit. A study of neurological patients by Rorden et al. (2008) found that extinction is maximal at stimulus simultaneity when the target stimuli straddle the central gaze fixation location, while it is maximal when the ipsilesional stimulus has a temporal lead on the contralesional stimulus when both target stimuli are presented in the ipsilesional visual field. The authors argued that these results are most parsimoniously explained as a consequence of low-level biased competitive interactions due to cortical magnification, but acknowledged that an attentional disengagement deficit could also accommodate the results. The present study set out to adjudicate between these models by examining the performance of neurologically healthy subjects who exhibit normal cortical magnification but do not have pathological attentional biases. We presented (a)synchronous double stimulation trials where both targets to be identified could straddle the central gaze fixation location or be presented in either the left or the right visual field. We found that in both the left and the right visual field target performance accuracy was poorest when the more peripheral stimulus led. This suggests that the findings from Rorden et al. can indeed be explained by a low-level physiological bias due to cortical magnification and argues against the notion that neurological extinction represents an attentional disengagement deficit.     

Saliency modulates global perception in simultanagnosia

Patients with parieto-occipital brain damage may show simultanagnosia, a selective impairment in the simultaneous perception and integration of multiple objects (global perception) with normal recognition of individual objects. Recent findings in patients with simultanagnosia indicate improved global perception at smaller spatial distances between local elements of hierarchical organized complex visual arrays. Global perception thus does not appear to be an all-or-nothing phenomenon but can be modified by the spatial relationship between local elements. The present study aimed to define characteristics of a general principle that accounts for improved global perception of hierarchically organized complex visual arrays in patients with simultanagnosia with respect to the spatial properties of local elements. In detail, we investigated the role of the number and size of the local elements as well as their relationship with each other for the global perception. The findings indicate that global perception increases independently of the size of the global object and depends on the spatial relationship between the local elements and the global object. The results further argue against the possibility of a restriction in the attended or perceived area in simultanagnosia, in the sense that the integration of local elements into a global scene is impaired if a certain spatial “field of view” is exceeded. A possible explanation for these observations might be a shift from global to local saliency in simultanagnosia.     

Assessment of vision-related quality of life in patients with homonymous visual field defects

BACKGROUND AND PURPOSE: Homonymous visual field defects (HVFDs) are among the most common disorders that occur in the elderly after vascular brain damage and can have a major impact on quality of life (QOL). Aims of this study were to describe the vision-targeted, health-related QOL in patients with HVFDs after cerebrovascular lesion, and to determine the relationship between patients' self-reported difficulties and the characteristics of HVFDs in the binocular visual field. METHODS: The German version of the 25-item National Eye Institute Visual Functioning Questionnaire (NEI-VFQ-25) was used. NEI-VFQ-25 scores for patients were compared to reference values of healthy German subjects from Franke (Z Med Psychol 7:178-184, 1999). Extent and location of absolute HVFDs were assessed by binocular semi-automated kinetic perimetry (SKP) within the 90 degrees visual field. Correlations of the NEI-VFQ-25 scores of patients with the area of sparing within the affected hemifield (A-SPAR) were estimated by Spearman's r (s). RESULTS: The mean NEI-VFQ-25 composite score for 33 patients (time span after brain injury at least 6 months) was 77.1, which was significantly lower (p < 0.0001) than the reference value for 360 healthy subjects (composite score = 90.6), and this was also the case for general vision, near activities, vision specific mental health, driving, colour, and peripheral vision. The score for general health was also significantly lower in patients than in reference subjects (p < 0.0001). A weak correlation of the composite score with A-SPAR (r (s) = 0.38) was observed. CONCLUSIONS: Our findings indicate that detectable decrements in vision-targeted, health-related QOL are observed in patients with homonymous visual field loss. A relationship of the perceived visual functioning with objective parameters is by definition difficult; however, understanding what components of visual function affect certain visual tasks, would help in developing more efficient, clinical assessment strategies. The results reveal a tendency for increasing QOL with advancing size of the area of sparing within the affected hemifield (A-SPAR). The lack of a strong correlation between NEI-VFQ-25 subscales and A-SPAR suggests that an assessment of the visual field may not accurately reflect patients' perceived difficulty in visual tasks. Additional consideration of visual exploration via eye and head movements may improve the correlation between visual function and its perception.