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Biomedical subjects

V Dietz

Publications and source records attributed to V Dietz.

At least 73 records · Page 4Linked to original sources
PubMed2000

Diagnostic and prognostic value of compound motor action potential of lower limbs in acute paraplegic patients.

OBJECTIVES: To evaluate the diagnostic and prognostic contribution of motor nerve conduction studies (NCS) in addition to neurological examination in patients with acute paraplegia. METHODS: In 79 patients with acute onset of paraplegia due to traumatic or ischaemic damage of the conus medullaris/cauda equina (conus/cauda) or lesion of the mid-thoracic spinal cord (epiconal) neurological (initial and follow-up clinical motor and sensory scores; outcome of ambulatory capacity determined at least 6 months post-trauma) and electrophysiological examinations (motor nerve conduction velocity (MNCV) and compound motor action potential (CMAP) of tibial and peroneal nerves) were performed in parallel. RESULTS: Severe axonal motor neuropathies were significantly caused by conus/cauda lesions (loss of tibial CMAP in 71% and of peroneal CMAP in 68%) compared to patients with epiconal lesion (no loss of tibial CMAP and abolished peroneal CMAP in 14%). The CMAPs were deemed acutely pathological 4 - 14 days post-trauma and were indicative of the severity of conus/cauda lesion while the MNCV remained normal. Follow-up recordings (up to 1 year post trauma) revealed no significant change in the CMAP values. The clinical examination according to the American Spinal Injury Association (ASIA protocol) in contrast to the CMAP values was significantly related to the outcome of ambulatory capacity. CONCLUSIONS: In contrast to patients with an epiconal SCI almost all patients with damage of the conus/cauda present a severe axonal neuropathy of the tibial and peroneal nerves. Pathological CMAPs develop as early as 1 - 2 weeks after onset of acute paraplegia. They allow, at an early stage, to differentiate between conus/cauda or epiconal lesion and to assess the severity of conus/cauda lesion. Thereafter follow-up examinations remain stable and a developing worsening of peripheral nerve or spinal cord function, eg due to post-traumatic syringomyelia, may be indicated by a secondary deterioration of CMAP values. The clinical examination, according to the ASIA protocol, in acute paraplegia patients, in contrast to the motor nerve conduction studies, is of prognostic value in predicting the outcome of ambulatory capacity.

Action Potentials↗
PubMed2000

Spastic movement disorder.

This review deals with the neuronal mechanisms underlying spastic movement disorder, assessed by electrophysiological means with the aim of first, a better understanding of the underlying pathophysiology and second, the selection of an adequate treatment. For the patient usually one of the first symptoms of a lesion within the central motor system represents the movement disorder, which is most characteristic during locomotion in patients with spasticity. The clinical examination reveals exaggerated tendon tap reflexes and increased muscle tone typical of the spastic movement disorder. However, today we know that there exists only a weak relationship between the physical signs obtained during the clinical examination in a passive motor condition and the impaired neuronal mechanisms being in operation during an active movement. By the recording and analysis of electrophysiological and biomechanical parameters during a functional movement such as locomotion, the significance of, for example, impaired reflex behaviour or pathophysiology of muscle tone and its contribution to the movement disorder can reliably be assessed. Consequently, an adequate treatment should not be restricted to the cosmetic therapy and correction of an isolated clinical parameter but should be based on the pathophysiology and significance of the mechanisms underlying the disorder of functional movement which impairs the patient.

Humans↗
PubMed2000

Tissue oxygen saturation measured by near infrared spectrophotometry correlates with arterial oxygen saturation during induced oxygenation changes in neonates.

The aim of this study was to compare quantitatively the changes in tissue oxygen saturation (TOS), determined by two algorithms (TOSc and TOSa) based on near-infrared spectrophotometry, to the changes in arterial oxygen saturation (SaO2) measured by pulse oximetry. TOSc is an algorithm derived by the manufacturer (Critikon) based on a modified Beer-Lambert law; TOSa, our own algorithm, uses the diffusion approximation of light transport for the semi-infinite boundary condition. Slow changes of more than 3% in SaO2 were carried out in 20 mechanically ventilated neonates by altering the inspired oxygen fraction. For each change the regression lines of TOSc versus SaO2, TOSa versus SaO2 and TOSc versus TOSa were calculatcd. For each infant the mcan slope, intercept and r2 of these lines were determined. In 18 preterm infants we obtained median 9.5 (range one to 13) measurements corresponding to a total of 166 measurements. The mean SaO2 was 91.6 (SD 2.3)%, TOSc was 64.7 (SD 7.2)% and TOSa was 71.4 (SD 11.0)%. Changes in TOSc and TOSa were strongly correlated to changes in SaO2 (r2 = 0.86 and r2 = 0.87). TOSc considerably but systematically underestimated the size of the change: delta TOSc = 0.49 delta SaO2. TOSa quantified changes reasonably correctly: delta TOSa = 0.90 delta SaO2. Changes in TOSc and TOSa were highly correlated (r2 = 0.98). These results are promising, but the large inter-individual variation requires further work.

Algorithms↗
PubMed2000

Validation of the weight-drop contusion model in rats: a comparative study of human spinal cord injury.

Animal models are widely used for studying the pathophysiology as well as treatment strategies for injuries of the central nervous system. However, it is still unclear in how far the rat model of spinal cord injury (SCI) is valid for human SCI. Therefore, comparisons were made among functional, electrophysiological, and morphological outcome parameters following SCI in rats and humans. Contusion of the mid-thoracic spinal cord in 27 adult rats was induced by a weight-drop, leading to severe deficits in open field locomotion at a chronic stage. The data of 85 human patients with chronic SCI were collected and compared with the rat data. In electrophysiological recordings, prolonged latencies and reduced amplitudes in both motor evoked potentials (MEP) and somatosensory evoked potentials (SSEP) were closely correlated to the impairment of locomotor capacity of lower limbs in rats and humans. The morphological parameters assessed by high-resolution magnetic resonance imaging (MRI) in both species indicated that the lesion length and spinal cord atrophy were significantly related to the electrophysiological and functional outcome parameters. In rats, histological analysis was performed and showed, in addition to the MRI, a close relationship between spared white matter and locomotor capacity. Our results suggest an analogous relationship in rats and humans with respect to functional, electrophysiological, and morphological outcomes. Thus, the techniques for evaluating the extent and severity of SCI in humans and rats are of comparable value. This indicates that the rat can serve as an adequate animal model for research on functional and morphological changes after SCI and the effects of new treatment strategies.

Adolescent↗
PubMed2000

Longitudinal changes in bone in men with spinal cord injury.

INTRODUCTION: Quantitative bone assessment today is primarily based on the analysis of bone mineral density (BMD). The geometric and structural properties of bone, which are important parameters for skeletal strength, are generally not considered in the routine clinical assessment of spinal cord injury-related osteopenia. OBJECTIVE: To study changes in structural and geometric properties of tibia bone longitudinally by means of peripheral quantitative computerized tomography and a biomechanical test method (bone stiffness measurement device Swing) in 12 subjects with spinal cord injury. DESIGN: Measurements were conducted in the 5th week and around the 104th week after the spinal cord injury in a university hospital. RESULTS: Paired Student's t-tests showed a significant decrease in trabecular (p < 0.05) and cortical bone (p < 0.05), as well as a significant decrease in geometric properties of tibia bone (p < 0.05) within two years after the spinal cord injury. Phase velocity propagation changed in three subjects within two years following the spinal cord injury. CONCLUSIONS: This study indicates that beside changes in tissue composition, changes in bone geometric indices and in structural properties occur in the lower extremity after a spinal cord injury. In the tibia, consideration of geometric and biomechanical parameters of bone combined with bone mineral density measurements could result in an improved screening for spinal cord injury-related osteopenia and the prediction of fracture risk in spinal cord injury.

Adult↗
PubMed2000

Active, multisite, laboratory-based surveillance for Cryptosporidium parvum.

Cryptosporidium parvum leaped to the attention of the United States following the 1993 outbreak in Milwaukee, Wisconsin, which sickened 400,000 people. Other outbreaks in the United States have been associated with drinking and recreational water, consumption of contaminated foods, contact with animals, and childcare attendance. Despite its public health importance, the number of people who become infected each year is not known. In 1997, active surveillance for C. parvum was added to the Foodborne Diseases Active Surveillance Network (FoodNet), a collaborative effort among the Centers for Disease Control and Prevention, selected state health departments, the U.S. Departments of Agriculture and Food and Drug Administration. During the first 2 years of surveillance, 1,023 laboratory-confirmed cases of cryptosporidiosis were detected in FoodNet (Connecticut, Minnesota, Oregon, and selected counties in California, Georgia, Maryland, and New York). The annual rate per 100,000 persons was 2.3. Sixteen percent of case-patients were hospitalized. A seasonal increase in case detection was noted in late summer among persons less than 15 years of age. These data represent the first active multistate ascertainment of laboratory-confirmed cryptosporidiosis cases and provide useful information on the burden of disease in the United States.

Adolescent↗
PubMed2000

Bladder neck incompetence in patients with spinal cord injury: significance of sympathetic skin response.

PURPOSE: We investigated whether recording the perineal sympathetic skin response, which reflects the sympathetic function of the thoracolumbar spinal cord, represents a reliable and accurate diagnostic tool for assessing bladder neck competence and incompetence. MATERIALS AND METHODS: We compared the sympathetic skin response recorded from the hand, foot and perineal skin with urodynamic findings in 90 patients with neurogenic bladder dysfunction, including 66 with spinal cord injury and 24 with cauda equina lesions. RESULTS: Video urodynamics revealed an incompetent bladder neck in 11 of 32 patients (34%) with complete and 7 of 34 (21%) with incomplete spinal cord injury but in only 1 of 24 (4%) with the conus-cauda equina syndrome. This association significantly correlated with the lesion level at T10 to L2 in 12 of 26 cases (46%) as well as with the loss of perineal but preserved hand and foot sympathetic skin response in 13 of 18 (72%). CONCLUSIONS: Recording the perineal sympathetic skin response in addition to that of the hand and foot represents a sensitive diagnostic tool for assessing sympathetic nerve function within the thoracolumbar spinal cord. It is of diagnostic value for evaluating neurogenic bladder neck incompetence in spinal cord injured patients.

Adult↗
PubMed1999

Voluntary control of human gait: conditioning of magnetically evoked motor responses in a precision stepping task.

The aim of this study was to investigate visuomotor control during human gait. It was assumed that visual input should modulate transcranially evoked motor potentials (EMPs) during walking. The effect of transcranial magnetic stimulation (TMS) in a visually guided precision stepping task was compared with that during normal gait. EMPs were studied in tibialis anterior (TA), gastrocnemius (GM), and abductor digiti minimi (AD) muscles during treadmill walking. In both stepping tasks, a facilitation of EMPs was observed prior to activation of the respective leg muscle. EMP facilitation proved to be modulated throughout the stride cycle when normalising EMP with respect to the underlying electromyogram (EMG). Facilitation was strongest in TA prior to the swing phase. Significant differences of EMP facilitation between the visual and control tasks were present. In the visual task, maximal facilitation of TA EMPs prior to and during the swing phase was decreased compared to the control task. Conversely, there was increased facilitation of GM EMPs during swing phase of the visual task, prior to the heel strike and prior to the plantarflexion, which was the moment when the target was hit. Thus, the effect of visual input upon EMPs in TA and GM was differential and reciprocal according to the respective functional state. The results support the hypothesis of a conditioning effect of visual or, alternatively volitional, drive on EMPs during stepping.

Adult↗
PubMed1999

Level of spinal cord lesion determines locomotor activity in spinal man.

Recent studies have demonstrated that coordinated stepping movements can be induced in patients with complete para-/tetraplegia, when they were standing on a moving treadmill with their body weight partially unloaded and external assistance. The aim of this study was to determine which part of the spinal cord generated the locomotor pattern. In patients with complete paraplegia due to lesions at different levels of the spinal cord, the locomotor pattern was compared with that of healthy subjects. Any similarities in electromyographic (EMG) activity of gastrocnemius and tibialis anterior muscles between the patients and healthy subjects were reflected by the analysis of the variation ratio and amplitudes of the EMG activity. It was found that the higher the level of spinal cord lesion the more "normal" was the locomotor pattern. This suggests that neuronal circuits underlying locomotor "pattern generation" in man are not restricted to any specific level(s) of the spinal cord, but that an intricate neuronal network contributing to bipedal locomotion extends from thoracolumbal to cervical levels.

Adult↗
PubMed1999

Changes of tibia bone properties after spinal cord injury: effects of early intervention.

OBJECTIVE: To evaluate the effectiveness of an early intervention program for attenuating bone mineral density loss after acute spinal cord injury (SCI) and to estimate the usefulness of a multimodality approach in diagnosing osteoporosis in SCI. DESIGN: A single-case, experimental, multiple-baseline design. SETTING: An SCI center in a university hospital. METHODS: Early loading intervention with weight-bearing by standing and treadmill walking. PATIENTS: Nineteen patients with acute SCI. OUTCOME MEASURES: (1) Bone density by peripheral computed tomography and (2) flexural wave propagation velocity with a biomechanical testing method. RESULTS: Analysis of the bone density data revealed a marked decrease of trabecular bone in the nonintervention subjects, whereas early mobilized subjects showed no or insignificant loss of trabecular bone. A significant change was observed in 3 of 10 subjects for maximal and minimal area moment of inertia. Measurements in 19 subjects 5 weeks postinjury revealed a significant correlation between the calculated bending stiffness of the tibia and the maximal and minimal area moment of inertia, respectively. CONCLUSION: A controlled, single-case, experimental design can contribute to an efficient tracing of the natural history of bone mineral density and can provide relevant information concerning the efficacy of early loading intervention in SCI. The combination of bone density and structural analysis could, in the long term, provide improved fracture risk prediction in patients with SCI and a refined understanding of the bone remodeling processes during initial immobilization after injury.

Adult↗
PubMed1999

Cyclical fluctuations in blood pressure, heart rate and cerebral blood volume in preterm infants.

Many recently published papers describe cyclical changes of cerebral circulatory variables, mainly in cerebral blood flow velocity (CBFV) performed with Doppler sonography. In this paper we focus on another important variable of cerebral circulation: on cerebral blood volume (CBV) measured by near infrared spectrophotometry (NIRS). In a retrospective analysis of NIRS measurements in 20 preterm infants (median 27 3/7 weeks of gestation), the dominating frequencies and prevalence of cyclical changes of CBV and its possible correlation with peripheral circulatory variables (mean arterial pressure and heart rate) was examined. In 19 out of the 20 infants cyclical changes of CBV were found within a frequency range of 2-4.7 cycles/min which is comparable to the results of the Doppler studies describing fluctuations in CBFV. A dominating frequency of heart rate (HR), was found only in 12 out of 20 infants, and it was with 2.1-3.8 cycles/min in a similar range compared to CBV. In mean arterial blood pressure (MABP), however we detected cycles with longer periods every 1-2.5 min in 14 out of 20 infants. There was a significant coherence between MABP/CBV and HR/CBV. The area under the coherence curve, however, was significantly larger between MABP and CBV as compared to HR and CBV (P = 0.0007, Wilcoxon signed-rank test).

Blood Pressure↗
PubMed1999

Electrophysiological recordings in patients with spinal cord injury: significance for predicting outcome.

The clinical assessment of the level, extent and severity of spinal cord injury (SCI) can be supplemented by electrophysiological recordings. These techniques also provide an early diagnosis of neurological deficits in patients with acute SCI and are of prognostic value even in uncooperative patients. Electrophysiological recordings (motor evoked potentials (MEP) and somato-sensory evoked potentials (SSEP)) are of similar significance in predicting functional outcome of ambulatory capacity, hand- and bladder function as the clinical examination according to the ASIA standards. EMG, neurographic and reflex recordings of acute SCI patients within spinal shock are even more sensitive in assessing an associated damage of the peripheral motor pathways (ie of motoneurones and nerve roots) than the clinical examination and allow the possibility of predicting the development of muscle tone or muscle atrophy. The evaluation of impairment of the autonomic nervous system after SCI by clinical examination is restricted. In contrast, recordings of the sympathetic skin response (SSR) can provide information about the extent and level of lesions of the spinal sympathetic nervous system which are related to autonomic dysfunction. Therefore, electrophysiological recordings supplementary to the clinical examination are helpful for planning and selecting the appropriate therapeutical approaches within the rehabilitation programme. Furthermore, they allow the prediction of functional outcome and the objective assessment of recovery of specific parts of the spinal and peripheral fibre tracts.

Electromyography↗
PubMed1999

The influence of a clear layer on near-infrared spectrophotometry measurements using a liquid neonatal head phantom.

It is difficult to test near-infrared spectrophotometry instruments in vivo. Therefore we constructed a liquid phantom which mimics the neonatal head. It consists of a spherical 3.5 mm thick layer of silicone rubber simulating skin and bone and a 0.5 mm thick clear layer of polypropylene imitating cerebrospinal fluid. It acts as container for a liquid solution with Intralipid, 60 micromol l(-1) haemoglobin and yeast. The solution was oxygenated using oxygen and then deoxygenated by the yeast. From the instrumental (Critikon 2020) algorithm, we found that with increasing scattering (0.5%, 1%, 1.5% and 2% Intralipid concentration) the reading was increasingly offset from the expected value of 0 micromol l(-1) by 55.7, 68.6, 76.5 and 80.4 micromol l(-1) (oxyhaemoglobin) and 16.0, 24.4, 29.6 and 31.7 micromol l(-1) (deoxyhaemoglobin). This reduced the range of the oxygen saturation reading from the expected 100% to 31.5, 21.1, 14.3 and 11.5%. Haemoglobin concentration changes were increasingly underestimated by a factor of two to four. For a second algorithm based on the diffusion approximation the offsets were smaller: oxyhaemoglobin 11.4, 17.8, 22.5 and 25.1 micromol l(-1) and deoxyhaemoglobin 1.3, 3.4, 5.2 and 6.0 micromol l(-1). The range of the oxygen saturation reading was higher: 41.3, 29.2, 23.4 and 16.6%. Concentration changes were underestimated by a factor of six to ten. This study demonstrates the need to develop algorithms which take into consideration anatomical structures.

Algorithms↗
PubMed1999

Impaired modulation of quadriceps tendon jerk reflex during spastic gait: differences between spinal and cerebral lesions.

In healthy subjects, functionally appropriate modulation of short latency leg muscle reflexes occurs during gait. This modulation has been ascribed, in part, to changes in presynaptic inhibition of Ia afferents. The changes in modulation of quadriceps tendon jerk reflexes during gait of healthy subjects were compared with those of hemi- or paraparetic spastic patients. The spasticity was due to unilateral cerebral infarction or traumatic spinal cord injury, respectively. The modulation of the quadriceps femoris tendon jerk reflex at 16 phases of the step cycle was studied. The reflex responses obtained during treadmill walking were compared with control values obtained during gait-mimicking standing postures with corresponding levels of voluntary muscle contraction and knee angles. In healthy subjects the size of the reflexes was profoundly modulated and was generally depressed throughout the step cycle. In patients with spinal lesion the reflex depression during gait was almost removed and was associated with weak or no modulation during the step cycle. In patients with cerebral lesion there was less depression of the reflex size associated with a reduced reflex modulation on the affected side compared with healthy subjects. On the 'unaffected' side of these patients reflex modulation was similar to that of healthy subjects, but the reflex size during gait was not significantly different from standing control values. These observations suggest that the mechanisms responsible for the depression of reflex size and the modulation normally seen during gait in healthy subjects are impaired to different extents in spasticity of spinal or cerebral origin, possibly due to the unilateral preservation of fibre tracts in hemiparesis.

Adolescent↗
PubMed1999

Prognosis and recovery in ischaemic and traumatic spinal cord injury: clinical and electrophysiological evaluation.

OBJECTIVES: To compare prognostic factors and functional recovery between paraplegic patients with either ischaemic (28 patients) or traumatic (39 patients) spinal cord injury (SCI). METHODS: On admission to the spinal injury centre and 6 months later the patients underwent clinical (following the guidelines set down by the American Spinal Injury Association) and electrophysiological (tibial and pudendal somatosensory evoked potentials) examinations in parallel. The degree of ambulatory capacity was assessed after discharge from the rehabilitation programme or at least 6 months after trauma. RESULTS: At the acute stage of either ischaemic or traumatic SCI similar motor and sensory deficits and pathological SSEP recordings were present. Both patient groups recovered to similar degrees with respect to motor, sensory, and ambulatory capacity. The clinical examination in both patient groups was the most sensitive prognostic factor of functional recovery irrespective of the aetiology of the SCI. In the ischaemic patients only the tibial SSEP whereas in the traumatic patients both the pudendal and tibial SSEP were of value in predicting recovery. CONCLUSIONS: Although the two patient groups are pathophysiologically different, the severity and extent of neurological deficits and rate of recovery are quite similar. In both ischaemic and traumatic SCI clinical and electrophysiological examinations are of prognostic value for the functional recovery.

Adult↗