Measurement of ataxic symptoms with a graphic tablet: standard values in controls and validity in Multiple Sclerosis patients

Aim of our study was to find a specific measure for the intensity of upper limb tremor and other ataxic symptoms in Multiple Sclerosis (MS) patients, and to establish standard values and test quality parameters. Three hundred and forty-two consecutive patients with different symptoms in the upper limbs (upper motor neuron symptoms, cerebellar upper limb ataxia, and/or sensory deficits in the upper limbs) and 140 healthy controls took part in the study. All patients and controls had to trace over a 25 cm high figure '8' on a graphic tablet, to tap with the stylus on the tablet and to perform the nine-hole-peg test (9HPT). Patients were additionally examined using clinical standard scales to classify motor dysfunctions of the upper limbs. One hundred and eighty-nine patients and 27 controls were tested twice to investigate the test reliability. Kinematic analysis of the tablet data was performed by kernel estimators, oscillatory activity by spectral analysis. Total power in the 2--10 Hz band was very specific for ataxia versus other motor symptoms. Tapping and 9HPT could well distinguish patients from controls, and patients with predominant motor neuron or cerebellar symptoms from patients with predominant sensory dysfunctions. Mean drawing error did not differ between motor and sensory dysfunctions. The test--retest reliability was similarly high for both spectral analysis and 9HPT.

Day-to-day variability of maximum walking distance in MS patients can mislead to relevant changes in the Expanded Disability Status Scale (EDSS): average walking speed is a more constant parameter

In this preliminary study we measured maximum walking distance and walking time on four consecutive days in 29 patients with clinically stable multiple sclerosis (MS). Patients were included in the study if they could achieve a maximum unaided walking distance of 100 up to 500 m. Our results showed a certain day-to-day variability of maximum walking distance, in some cases meaning changes up to 1.5 points in the expanded disability status scale (EDSS), which could be misinterpreted as a progression of the disease. Simultaneous measurements of maximum walking time showed a similar variability, unlike the mean walking speed which turned out to be more stable. Our results therefore suggest that scoring of MS patients should not be based on one single measurement of the maximum walking distance. The more reliable parameter appears to be the mean walking speed.

Electrophysiological correlates of visual impairments after traumatic brain injury

Our aims were to investigate: (i) the VEP correlates of functional visual impairments following traumatic brain injury (TBI), in particular of the reduced spatial form perception; and (ii) the VEP correlates of visual sustained arousal in TBI patients. We used two approaches: (i) the analysis of latency and amplitude of the peaks; and (ii) the study of the correlations among the latencies of the peaks as a label of temporal synchronization. Thirty-five severe TBI outcome inpatients and 35 matching controls were studied. Pattern-reversal VEPs were recorded at Oz-Fz and Cz-A1, first without counting, then with counting of the reversals. Seven peaks of the waveform at Oz and eight peaks at Cz were measured. We found several differences in amplitude and latency between patients and controls, and between nocount/count. The temporal binding of the peaks within each channel and between the two channels was calculated by correlation matrices, and tested by factor analysis. Results indicated that the synchronization of the peaks within each channel did not differ between patients and controls. The temporal covariation between peaks occurring at Oz and Cz, however, was highly significantly altered in patients. This suggests that visual impairments in TBI patients may be due to a deranged synchronization of the activity of different brain regions.

Colonic sensitivity in irritable bowel syndrome and normal subjects according to their hemispheric preference and cognitive style

According to our earlier results, non-painful, weak afferent visceral signals may exert a steady influence on brain processes, including cognitive functions. In the present series colonic impulses of irritable bowel syndrome (IBS) subjects served as a model of chronic impact from the gut. Hemispheric preference, as well as cognitive style of information processing served as indicators of covert changes in brain functions. In twenty-one IBS patients and in ten control subjects of both sexes, the thresholds of minimal colonic distension sensitivity has been measured following the determination of hemispheric preference and of advantage in verbal or spatial information processing of the subjects. In IBS patients distension thresholds proved to be higher in verbals than in spatials, whereas in healthy controls the relationship of colonic thresholds and verbal versus spatial advantage was reversed. Among the normal controls with left hemisphere preference a significantly higher distension threshold has been observed than in those with right hemisphere preference, whereas in the IBS group such threshold-differences were not observable.

[Local ice application in therapy of kinetic limb ataxia. Clinical assessment of positive treatment effects in patients with multiple sclerosis]

Upper limb ataxia is one of the most disabling symptoms of patients with multiple sclerosis (MS). There are some clinically tested therapeutic strategies, especially with regard to cerebellar tremor. But most of the methods used for treatment of limb ataxia in physiotherapy and occupational therapy are not systematically evaluated, e.g. the effect of local ice applications, as reported by MS patients and therapists, respectively. We investigated 21 MS patients before and in several steps 1 up to 45 min after cooling the most affected forearm. We used a series of 6 tests, including parts of neurological status and activities of daily living as well. At each step skin temperature and nerve conduction velocity were recorded. All tests were documented by video for later offline analysis. Standardized evaluation was done by the investigators and separately by an independent second team, both of them using numeric scales for quality of performance. After local cooling all patients showed a positive effect, especially a reduction of intentional tremor. In most cases this effect lasted 45 min, in some patients even longer. We presume that a decrease in the proprioceptive afferent inflow-induced by cooling-may be the probable cause of this reduction of cerebellar tremor. Patients can use ice applications as a method of treating themselves when a short-time reduction of intention tremor is required, e.g. for typing, signing or self-catheterization.

Detection, discrimination and sensation of visceral stimuli

Afferent visceral signals serve mostly regulatory functions and produce vague, diffuse body sensations, which are not well reflected in experimental paradigms requiring distinct and localized 'visceral perceptions'. A series of studies is summarized which compared behavioral discrimination of gastrointestinal distension stimuli with subjective sensation ratings in relation to basic perceptual operations such as detection, localization, graduation, and identification. Results showed that detection of gastrointestinal stimuli is possible without the subject's awareness (discrimination without reportable sensation). This process does not depend on stimulus intensity at volumes below those sufficient for subjective sensation. The latter is necessary, however, for intensity discrimination (graduation). Contrary to exteroception (e.g. vision), conscious subjective sensation is also required for stimulus localization. These differences in processing could not be explained by simple differences in response criteria. An intensity-dependent two-process model of gastrointestinal interoception is derived which differs from standard models of somatosensory information processing.

Method and apparatus for pressure-controlled distension of the lower gastrointestinal tract

Despite the relevance of visceral perception in the lower gastrointestinal tract to clinical research, especially for diagnosis of functional diseases or neurological derangements of the bowel, precise techniques to evaluate these perceptual processes and mechanical properties of the bowel wall were lacking until recently. Such techniques must include the application of well-defined stimuli and the recording of physiological reactions. A probe was developed which causes minimal discomfort to the subject and is therefore suitable for psychophysical examinations. It can be easily modified for different applications. Stimuli are applied by inflating a balloon, which distends the colon or rectum wall. Prestretching of the balloon material before mounting it on the probe results in monotonic and flat pressure characteristics. Balloon volume is nearly independent from external pressure, within 5% under physiological conditions. Dynamic performance of the balloon is sufficient for studies on the influence of stimulus shape. A microcomputer-controlled pump-system presents precise stimuli within a wide range of volume and inflation rate. A stepping motor is the heart of this system and allows to define exact values for volume and pumping rate without the use of complicated controlling elements. Menu-driven programs allow complex stimulus shapes and sequences. The method and apparatus described above have been successfully used in clinical and basic psychophysiological studies.

Orocaecal transit-time by the H2 method: effects of definitions of caecal entry and test meal

The study compares common variants of the hydrogen breath test to measure oroceacal transit time under different conditions. Definition of caecal entry point rather than procedural parameters were found to be a main variable influencing the test results. Visual assessment still seemed to be the most reliable and valid technique. To overcome its subjectivity and evaluator-dependency, a comprehensive set of rules simulating implicit criteria of expert physicians was defined and compared with commonly used caecal entry assessment rules. Results indicated that: 1) using visual assessment, experts produce highly consistent CE points; 2) caecal entries by the new rule set correlate highly with them, while previously published caecal entry detection methods were poorly correlated with visual assessment; 3) using a semiliquid test meal reduced reliability of all methods, but the new method remained superior; 4) earlier caecal entry detection methods failed completely when early peaks or baseline fluctuations were present; 5) detection of H2 non-producers and of bacterial overgrowth was much more difficult with classical caecal entry definitions than with the new rule-set.