Measurement of absolute cerebral haemoglobin concentration in adults and neonates.
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Adult↗
Biomedical subjects
V Dietz
Publications and source records attributed to V Dietz.
How to evaluate slow oxygenation changes to estimate absolute cerebral haemoglobin concentration by near infrared spectrophotometry in neonates.
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Brain↗
Corticospinal input in human gait: modulation of magnetically evoked motor responses.
Transcranial magnetic stimulation (TMS) of the motor cortex was applied during locomotion to investigate the significance of corticospinal input upon the gait pattern. Evoked motor responses (EMR) were studied in the electromyogram (EMG) of tibialis anterior (TA), gastrocnemius (GM) and, for reference, abductor digiti minimi (AD) muscles by applying below-threshold magnetic stimuli during treadmill walking in healthy adults. Averages of 15 stimuli introduced randomly at each of 16 phases of the stride cycle were analysed. Phase-dependent amplitude modulation of EMR was present in TA and GM which did not always parallel the gait-associated modulation of the EMG activity. No variation of onset latency of the EMR was observed. The net modulatory response was calculated by comparing EMR amplitudes during gait with EMR amplitudes obtained (at corresponding background EMG activities) during tonic voluntary muscle contraction. Large net responses in both muscles occurred prior to or during phasic changes of EMG activity in the locomotor pattern. This facilitation of EMR was significantly higher in leg flexor than extensor muscles, with maxima in TA prior to and during late swing phase. A comparison of this facilitation of TA EMR prior to swing phase and prior to a phasic voluntary foot dorsiflexion revealed a similar onset but an increased amount of early facilitation in the gait condition. The modulated facilitation of EMR during locomotion could in part be explained by spinal effects which are different under dynamic and static motor conditions. However, we suggest that changes in corticospinal excitability during gait are also reflected in this facilitation. This suggestion is based on: (1) the similar onset yet dissimilar size of facilitatory effects in TA EMR prior to the swing phase of the stride cycle and during a voluntary dynamic activation, (2) the inverse variation of EMR and EMG amplitudes during this phase, and (3) the occurrence of this inversion at stimulation strengths below motor threshold (motor threshold was determined during weak tonic contraction and EMR were facilitated during gait). It is hypothesized that the facilitation is phase linked to ensure postural stability and is most effective during the phases prior to and during rhythmical activation of the leg muscles resulting in anticipatory adjustment of the locomotor pattern.
Adult↗
[Prognosis of traumatic spinal cord lesions. Significance of clinical and electrophysiological findings].
The clinical examination of patients with spinal cord injury can be supplemented by electrophysiological techniques (somatosensory-evoked potentials (SSEP), motor-evoked potentials (MEP), electroneurography) to assess the extent and severity of a spinal cord injury. As essential advantage of these techniques in comparison with the clinical examination is that they can be reliably applied even in uncooperative patients. These techniques allow an early prognosis of the functional deficit in patients with acute spinal cord injury. Recordings of tibial nerve SSEP and MEP of the anterior tibial muscle allow to predict the outcome of ambulatory capacity, while recordings of pudendal nerve SSEP allow prognosis of the bladder function to be assessed. In tetraplegic patients median and ulnar nerve SSEP and MEP of the abductor digiti minimi muscle can indicate the development of hand function. Electroneurography allows to differentiate between the proportion of peripheral and central nervous lesions underlying the muscle paresis. This is of prognostic value with regard to the development of muscle tone and consequently for planning therapy. The electrophysiological examinations are of complementary value in the diagnostic assessment of spinal cord lesions, in the prediction of functional outcome, and in monitoring the course of neurological deficits. This is helpful for planning and selection of appropriate therapeutic approaches (e.g. functional electrical stimulation, application of botulinum toxin, splinting procedures) within the rehabilitation programme.
Activities of Daily Living↗
Ambulatory capacity in spinal cord injury: significance of somatosensory evoked potentials and ASIA protocol in predicting outcome.
OBJECTIVE: Prediction of outcome of ambulatory capacity in patients with acute spinal cord injury (SCI) by the American Spinal Injury Association (ASIA) protocol and somatosensory evoked potentials (SSEP). DESIGN: Correlational study on a prospective cohort. SETTING: Spinal cord injury center, university hospital. PATIENTS: Consecutively sampled, 70 acute and 34 chronic SCI patients. MAIN OUTCOME MEASURES: (1) ASIA motor and sensory scores; (2) tibial and pudendal SSEP graded in 5 categories, from normal to absent; (3) ambulatory capacity rated as no, therapeutic, functional, or full. The outcome of the ambulatory capacity was assessed after discharge from the rehabilitation program, at least 6 months after trauma. RESULTS: In acute SCI both the initial ASIA scores and the SSEP recordings are related (p < .001) to the outcome of ambulatory capacity. In acute tetraplegia the pudendal SSEP (spearman corr. coeff. .92; p < .001) and in acute paraplegia the ASIA motor score (spearman corr. coeff. .90; p < .001) were best related to the outcome of ambulatory capacity. In the early stage of acute SCI, ASIA scores and SSEP recordings can help to assess the outcome of ambulatory capacity and, therefore, can contribute to the selection of the appropriate therapeutic approaches during the rehabilitation program. In patients with acute SCI the ASIA motor score significantly increased (p < .05) in the 6 months after trauma, whereas the ASIA sensory scores and SSEP recordings did not change significantly during this same period. CONCLUSION: ASIA scores and SSEP are related to the outcome of ambulatory capacity in patients with acute spinal cord injury; in noncomprehensive or uncooperative patients the SSEP are of supplemental value to the clinical examination. Therefore, the combination of clinical and electrophysiological examinations can be of additional diagnostic value in the assessment of acute spinal cord injury.
Adult↗
Neurophysiology of gait disorders: present and future applications.
This article will review those electrophysiological investigations which have addressed the neuronal mechanisms underlying impaired gait. The aims of the review are to provide further insights to the underlying pathophysiology of impaired gait and also towards the selection of an appropriate treatment. From the patients' point of view the first indication of a central motor system lesion is an impairment of movement, most notably locomotion. These symptoms are characteristic in cases of spasticity, cerebellar lesion or Parkinson's disease. Clinical examination reveals typical changes in tendon tap reflexes and muscle tone which were believed to account for the movement disorder presented. However, we now know that there is only a weak relationship between the physical symptoms observed during clinical examination under passive motor conditions and the altered neuronal mechanisms underlying the impairment during active motion. By recording and analysing electrophysiological and biomechanical parameters during functional movements such as locomotion, the significance of impaired reflex behaviour or the pathophysiology of muscle tone and its contribution to the movement disorder can be reliably assessed. Consequently, the treatment should not be cosmetic, i.e. the correction of an isolated clinical parameter, but should be based on the pathophysiology and significance of those mechanisms underlying the impairment of the patients' movements. Data from electrophysiological and biomechanical investigations of locomotion of patients with spasticity, cerebellar disorder or Parkinson's disease are discussed in this review. The neuronal mechanisms, which are essentially central programs and afferent input, involved in disorders of gait are evaluated on the basis of their function in healthy subjects. The impact of this analysis in deciding an appropriate treatment are discussed with respect to the pathophysiology underlying the gait disorder (spasticity, cerebellar disorder or Parkinson's disease). At the present time we have only a basic understanding of the essential receptor systems, such as leg extensor load receptors, and their interaction with other systems involved in postural control. In the future, the knowledge gained from gait analysis may help in the selection of the appropriate pharmacological and physical treatment required even though the patient may only be at an early stage of motor impairment.
Ataxia↗
Locomotor recovery after spinal cord injury.
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Humans↗
Leg muscle activation during gait in Parkinson's disease: influence of body unloading.
The effect of body unloading (75, 50 and 25% of body weight) on upper and lower leg muscle activation during stepping on a treadmill was investigated in groups of patients with Parkinson's disease and age-matched healthy subjects. The aim of the study was to test the hypothesis that impaired extensor load receptor function exists in the patients. A strong load sensitivity was found for the gastrocnemius (GM) electromyographic (EMG) activity (i.e. EMG amplitude decreased with unloading during stepping in both groups of subjects). The change in the EMG amplitude of the rectus femoris was less dependent upon the load but was observed to be more pronounced in the patients. Upper and lower leg flexor muscles were relatively load-insensitive. The absolute GM EMG amplitude during the stance phase of stepping with normal body loading was significantly smaller in the patients than in the healthy subjects. It is suggested that the latter observation is due to a change in the threshold or bias of the extensor load reflex mechanism in the patients. The slope or gain of this reflex appears to be preserved.
Aged↗
Clinical value of F-wave recordings in traumatic cervical spinal cord injury.
F-waves and motor/sensory nerve conduction (NCS) of the median and ulnar nerves were examined in 66 patients with traumatic motoneurone lesion due to acute and chronic cervical spinal cord injury (SCI). The examinations were performed in parallel in chronic tetraplegics once and in acute tetraplegic patients monthly for the first 3 months, after 6 months and 1 year post-trauma. A pathological reduction of the compound muscle action potential (CMAP) (in 10% even a complete loss of the CMAP) was present in about 50% of the patients. The mean CMAP values of tetraplegic patients with either acute or chronic SCI were significantly (P < 0.001) reduced compared to normal subjects. Because sensory nerve conduction in these patients was normal, the reduction of CMAP should be due to damage of intramedullar motoneurones or anterior nerve roots. While in all chronic SCI patients with preserved CMAP F-waves could be elicited, 50% of the acute SCI patients showed a complete loss of F-waves of both nerves during the initial examination due to spinal shock. After 6 months all acute SCI patients with preserved motor potentials regained F-waves. Therefore, the excitability of F-waves is influenced by spinal shock in acute SCI. The mean F-wave latencies (Fmin-response, Fmin-M response) revealed no significant difference between healthy subjects and SCI patients. However, the frequency of F-wave production was related to the severity of the motoneurone lesion. Furthermore, while the F-wave latencies and CMAP values did not change significantly with time after acute SCI, the frequency of F-wave production increased, but remained reduced compared to normal subjects.
Action Potentials↗
Recovery of bladder function in patients with acute spinal cord injury: significance of ASIA scores and somatosensory evoked potentials.
The significance of the ASIA (American Spinal Injury Association) scores and SSEP (somatosensory evoked potentials) recordings in predicting the recovery of bladder function was evaluated in 70 patients with acute, traumatic spinal cord injury (SCI). The patients were examined following admission to the rehabilitation centre (mean 10 days post-trauma) both clinically by the ASIA scores and electrophysiologically by tibial and pudendal SSEP recordings. The results of the initial examinations were related to the degree of recovery of bladder function of the patients assessed by urodynamic examination at the end of the rehabilitation programme (at least 6 months post-trauma). The recovery of somatic nerve function (external urethral sphincter function) involved in bladder function was correlated to both the initial ASIA scores and SSEP recordings (Spearman correlation, P < 0.001). The latter parameters, however, were not related to the outcome of autonomic nerve function (eg detrusor vesicae function) (Spearman correlation, P = 0.1). Therefore, the initial clinical and electrophysiological examinations are of value in assessment of the degree to which the patient will recover somatic nervous control of bladder function. However, these examinations are not indicative of urodynamic impairment. Therefore, urodynamic examination should be mandatory for the diagnostic assessment and therapeutical approach of bladder dysfunction in patients with acute SCI.
Adult↗
Locomotion in patients with spinal cord injuries.
Following central motor lesions, two forms of reorganization can be observed that lead to improved mobility: (1) the development of increased muscle tone and (2) the activation of spinal locomotor centers induced by specific treadmill training. Tension development is different from normal during spastic gait and appears to be independent of exaggerated monosynaptic stretch reflexes. Exaggerated stretch reflexes are associated with an absence or reduction of functionally essential polysynaptic reflexes. Based on observations of the locomotor capacity of the spinal cat, recent studies have indicated that spinal locomotor centers can be activated and trained in patients with complete or incomplete paraplegia when the body is partially unloaded. The level of electromyographic activity in the gastrocnemius muscle, however, is considerably lower in patients with central motor lesions than in persons without neurological impairments. During the course of a daily locomotor training program, the amplitude of gastrocnemius muscle electromyographic activity increases during the stance phase and inappropriate tibialis anterior muscle activity decreases. Such training programs can improve the ability of patients with incomplete paraplegia to walk on stationary surfaces. This article reviews the pathophysiology and functional importance of increased muscle tone and the effects of treadmill training on the locomotor pattern underlying new attempts to improve the mobility of patients with paraplegia.
Animals↗
Influence of spinal cord injury on cerebral sensorimotor systems: a PET study.
OBJECTIVES: To assess the effect of a transverse spinal cord lesion on cerebral energy metabolism in view of sensorimotor reorganisation. METHODS: PET and 18F-fluorodeoxyglucose were used to study resting cerebral glucose metabolism in 11 patients with complete paraplegia or tetraplegia after spinal cord injury and 12 healthy subjects. Regions of interest analysis was performed to determine global glucose metabolism (CMRGlu). Statistical parametric mapping was applied to compare both groups on a pixel by pixel basis (significance level P = 0.001). RESULTS: Global absolute CMRGlu was lower in spinal cord injury (33.6 (6.6) mumol/100 ml/min (mean (SD)) than in controls (45.6 (6.2), Mann-Whitney P = 0.0026). Statistical parametric mapping analysis disclosed relatively increased glucose metabolism particularly in the supplementary motor area, anterior cingulate, and putamen. Relatively reduced glucose metabolism in patients with spinal cord injury was found in the midbrain, cerebellar hemispheres, and temporal cortex. CONCLUSIONS: It is assumed that cerebral deafferentiation due to reduction or loss of sensorimotor function results in the low level of absolute global CMRGlu found in patients with spinal cord injury. Relatively increased glucose metabolism in brain regions involved in attention and initiation of movement may be related to secondary disinhibition of these regions.
Adult↗
Assessment of autonomic dysreflexia in patients with spinal cord injury.
OBJECTIVES AND METHODS: To assess the impairment of supraspinal control over spinal sympathetic centres and the occurrence of autonomic dysreflexia in patients with spinal cord injury. Autonomic dysreflexia is caused by the disconnection of spinal sympathetic centres from supraspinal control and is characterised by paroxysmal hypertensive episodes caused by non-specific stimuli below the level of the lesion. Therefore, patients with spinal cord injury were examined clinically and by different techniques to assess the occurrence of autonomic dysreflexia and to relate disturbances of the sympathetic nervous system to episodes of autonomic dysreflexia. RESULTS: None of the paraplegic patients, but 59% (13/22) of tetraplegic patients (91% of the complete, 27% of the incomplete patients) presented signs of autonomic dysreflexia during urodynamic examination. Only 62% of the tetraplegic patients complained about symptoms of autonomic dysreflexia. Pathological sympathetic skin responses (SSRs) of the hands were related to signs of autonomic dysreflexia in 93% of cases. No patient with preserved SSR potentials of the hands and feet showed signs of autonomic dysreflexia, either clinically or during urodynamic examination. Ambulatory blood pressure measurements (ABPMs) indicated a loss of circadian blood pressure rhythm (sympathetic control) but preserved heart rate rhythm (parasympathetic regulation) only in patients with complete tetraplegia. Pathological ABPM recordings were seen in 70% of patients with symptoms of autonomic dysreflexia. CONCLUSIONS: The urodynamic examination was more sensitive in indicating signs of autonomic dysreflexia in patients with spinal cord injury, whereas SSR allowed the assessment of the degree of disconnection of the sympathetic spinal centres from supraspinal control. Using ABPM recordings the occurrence of episodes of autonomic dysreflexia over 24 hours and the effectiveness of therapeutical treatment can be assessed.
Adolescent↗
The use of mass campaigns in the expanded program on immunization: a review of reported advantages and disadvantages.
The use of mass immunization campaigns (MICs) has been and remains controversial. To evaluate these campaigns, the authors review the literature relating to their effectiveness, sustainability, and cost-effectiveness in controlling diseases and raising immunization coverage levels, and their impact on the subsequent development of routine immunization services. Well-conducted campaigns have increased vaccine coverage levels and decreased disease morbidity and mortality. Their use in the Americas has been associated with the apparent elimination of poliomyelitis. However, unless health care infrastructure is improved, or campaigns are repeated, gains in coverage levels may not be sustained. Studies suggest that MICs are often not as cost-effective for raising coverage as the delivery of vaccines through routine services, but the use of coverage as the only outcome measure is questionable. Mass immunization campaigns can increase awareness of vaccination and may be appropriate in situations where new programs are to be initiated, in refugee situations where people congregate into areas with little infrastructure, and in disease eradication efforts when specific time goals are set. Little information is available on whether MICs strengthen or interfere with the development of routine services. To be successful, MICs require a well-coordinated and planned effort on the part of national authorities with the identification of specific goals, intensive social promotion, and strong management. In addition, research is needed to clarify how MICs should be evaluated.
Adult↗
Factors affecting the immunogenicity and potency of tetanus toxoid: implications for the elimination of neonatal and non-neonatal tetanus as public health problems.
An estimated 400,000 deaths occur annually from neonatal tetanus (NT). In 1989 WHO adopted the goal of eliminating NT as a public health problem worldwide. To achieve this, and to control non-neonatal tetanus (non-NT), WHO recommends that newborns be passively protected at birth by the antepartum administration of at least two doses of tetanus toxoid (TT) to their mothers and that all children subsequently receive at least three doses of diphtheria-tetanus-pertussis (DTP) vaccine. For this strategy to be effective, the TT used must be immunogenic. Potential factors that may affect TT immunogenicity need to be evaluated if NT is to be eliminated and if non-NT is to be controlled. Although data are conflicting, concurrent malarial infection may decrease the immune response to TT; however, malarial chemoprophylaxis may enhance the immune response. Malnutrition does not appear to affect immunogenicity; nevertheless, one study suggests that vitamin A deficiency is associated with an impaired immune response. Although it has been postulated that placental transfer of tetanus antibody is impaired in African women, a survey of the published literature suggests that this is not the case. Freezing TT has been shown to decrease its potency, but its impact on immunogenicity needs more evaluation.
Adult↗
Effects of body immersion on postural adjustments to voluntary arm movements in humans: role of load receptor input.
1. The effect of body immersion on postural adjustments was studied in ten healthy subjects. Reaction times, for pushing or pulling a rigid handle, in response to a visual stimulus were measured. In addition EMG recordings were taken from upper arm and lower leg muscles during three levels of body immersion while standing on a platform (immersed to spinal levels: lumbar nerve root 2 (L2); thoracic nerve root 4 (T4); and cervical nerve root 7 (C7)), while floating and while standing or sitting out of water. 2. With increasing levels of body immersion there was a near linear reduction in the amplitude of the gastrocnemius (GM) EMG activity before (200 ms) the onset of a force signal from pulling, but immersion had a significantly weaker effect on the amplitude of the tibialis anterior (TA) EMG during pushing movements. There was no significant difference in the effect of body immersion on biceps femoris (BF) and rectus femoris (RF). Under free-floating conditions postural adjustments did not occur in response to pull or push movements. There were no adaptational changes of EMG adjustments during successive trials at a given immersion level. 3. Under non-immersed conditions reaction times were significantly shorter during sitting than during standing. This difference is assumed to be due to the postural adjustments required while standing before the onset of a voluntary arm movement. While standing, reaction times were significantly longer for pull compared with push movements. Under all conditions of body immersion the reaction times remained longer compared with the sitting condition, even when no leg muscle EMG adjustments were present. 4. It is assumed that the differential effect of body immersion on the antagonistic leg muscles is due to the differential neuronal control of antagonistic leg muscles with a strong influence from proprioceptive input (most probably from load receptors) on the leg extensors. The longer reaction times seen during body immersion, where no postural adjustments were evident, suggests that a supraspinal command to the leg muscles precedes the voluntary arm movement. However, because of the changed/decreased afferent input no postural adjustments are generated.
Arm↗
Significance of sympathetic skin response in the assessment of autonomic failure in patients with spinal cord injury.
As a result of spinal cord injury (SCI) descending spinal sympathetic pathways can be severed. Because of its clinical significance, the aim of this study was to assess the disturbance of the spinal sympathetic pathway by clinical and electrophysiological examinations. The sympathetic skin response (SSR) due to electrical stimulation of median nerve and transcranial magnetic stimulation was examined in 70 patients with complete and incomplete spinal cord injury. Clinical and neurological examinations were performed in these patients according to the protocol of the American Spinal Injury Association (ASIA). The SSR can be used to assess the integrity of the spinal sympathetic nervous system. In patients with complete tetraplegia and paraplegics with high thoracical lesions (up to level T3) SSRs of the hands and feet were absent. In patients with complete paraplegia and thoroacic lesions from level T4 up to T8 the SSRs could be evoked in the hands but not in the feet. However, in paraplegics with lumbal and thoracic lesions below level T8 SSRs of the hands and feet could be recorded. In about 50% of the patients with clinically incomplete SCI lesions SSR potentials were abolished, indicating that the spinal sympathetic system was severely affected. There was no patient with preserved SSR potentials who developed symptoms of autonomic dysreflexia (AD). However, all patients with episodes of AD showed abolished SSR at the hands and feet even in incomplete SCI patients. The results of the SSR recordings in SCI patients fit with the assumption that the development of AD is related to the disconnection of the spinal sympathetic centers from supraspinal control.
Adult↗
The impact of the standards for pediatric immunization practices on vaccination coverage levels.
OBJECTIVE: To assess the impact on clinic-specific vaccination coverage of implementing the Standards for Pediatric Immunization Practices. DESIGN: A nonrandomized intervention trial conducted for 1 year. SETTING: Two public health clinics in Albuquerque, NM: 1 intervention site and 1 control site, each serving 1 of 4 city quadrants. PARTICIPANTS: All children enrolled in the 2 city public health clinics. INTERVENTIONS: Implementation of the Standards for Pediatric Immunization Practices. OUTCOME MEASURES: Assessment of up-to-date vaccination coverage levels prior to and at the conclusion of the project. The impact on the proportion of children who dropped out of vaccination services after receiving 1 dose by 3 months of age. RESULTS: At the intervention site, up-to-date coverage at 12 months of age rose from 57.5% to 80.4%, while levels at the control site decreased from 42.1% to 41.9%. Before the intervention, 24% of children at the intervention site who received the first dose of diphtheria and tetanus toxoids and pertussis vaccine (DTP 1) by 3 months of age failed to receive the third dose of DTP (DTP 3) by 12 months of age vs 5% after the intervention. At the control site, the proportion of children who received DTP 1 by 3 months of age, but not DTP 3 by 12 months of age, increased from 39% to 51%. CONCLUSION: Implementation of the Standards for Pediatric Immunization Practices in a public health clinic was associated with important increases in vaccination coverage levels and a reduction in the proportion of children who dropped out of vaccination services.
Child↗