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Biomedical subjects

A Curt

Publications and source records attributed to A Curt.

At least 37 records · Page 2Linked to original sources
PubMed2002

Differential effect of spinal cord injury and functional impairment on human brain activation.

Reorganization of human brain function after spinal cord injury (SCI) has been shown in electrophysiological studies. However, it is less clear how far changes of brain activation in SCI patients are influenced by the extent of SCI (neuronal lesion) or the consequent functional impairment. Positron emission tomography ([15O]-H2O-PET) was performed during an unilateral hand movement in SCI patients and healthy subjects. SCI patients with paraplegia and normal hand function were compared to tetraplegic patients with impaired hand movements. Intergroup comparison between paraplegic patients and healthy subjects showed an increased activation of contralateral sensorimotor cortex (SMC), contralateral thalamus, ipsilateral superior parietal lobe, and bilateral cerebellum. In contrast to this, tetraplegic patients with impaired upper limb function revealed only a significant activation of supplementary motor area (SMA). Correlational analysis in the tetraplegic patients showed that the strength of hand movement was related to the activation of contralateral SMC. However, the severity of upper limb sensorimotor deficit was related to a reduced activation of contralateral SMA and ipsilateral cerebellum. The findings suggest that in paraplegic patients with normal hand function the spinal neuronal lesion itself induces a reorganization of brain activation unrelated to upper limb function. Compared to this, in tetraplegic patients changes of brain activation are related to the impaired upper limb function. Therefore, in patients with SCI a differential impact of spinal lesion and functional impairment on brain activation can be shown. The effect of impaired afferent feedback and/or increased compensatory use of non-impaired limbs in SCI patients needs further evaluation.

Adult↗
PubMed2001

Functional electrical stimulation for grasping and walking: indications and limitations.

This review describes the state of art in the field of Functional Electrical Stimulation (FES) and its impact on improving grasping and walking functions in acute and chronic Spinal Cord Injured (SCI) patients. It is argued that during the early rehabilitation period the FES systems with surface stimulation electrodes should be used to assist training of hand and leg movements in SCI patients. Our clinical trials have shown that a number of acute SCI patients with impaired walking and grasping functions could improve these functions due to training with an adjustable FES system to the point that they finally did not need the FES system to carry out these tasks. Other acute SCI patients, who did not recover the desired function, were enabled to perform either walking or grasping with the FES assistance. We believe that the subjects who can perform grasping or walking with the help of FES, and still use the neuroprosthesis 6 months after being subjected to the FES training, should consider the FES system as a prosthetic device in Activities of Daily Living (ADL). Despite the significant technical progress achieved in the last 10 to 15 years in the FES field, there is a general consensus that these systems are not sufficiently advanced and that they need further development. The limited acceptance of the FES technology can be in part explained by the fact that it is not completely mature and that the patients still require daily assistance to use the FES systems. Nevertheless the present FES treatments combined with conventional occupational and physical therapy still remain the most promising approach in rehabilitating SCI patients. In this review, advantages and limitations of different FES systems that are used to restore grasping and walking functions are discussed.

Electric Stimulation Therapy↗
PubMed2000

[Neurological diagnosis and prognosis: significance of neurophysiological findings in traumatic spinal cord lesions].

The clinical examination of patients with spinal cord injury can be supplemented by electrophysiological techniques (somatosensory evoked potentials [SSEP], motor evoked potentials [MEP], and electroneuromyographic recordings [ENMG]) to assess the extent and severity of a spinal cord injury. An essential advantage of these techniques in comparison with clinical examination is that they can also be reliably applied in uncooperative patients. These techniques allow early prognosis regarding the functional deficit in patients with acute spinal cord injury. Recordings of tibial nerve somatosensory evoked potentials and motor evoked potentials of the anterior tibial muscle serve to predict the outcome of ambulatory capacity, and pudendal nerve somatosensory evoked potentials that of bladder function. In tetraplegic patients median and ulnar nerve somatosensory evoked potentials and motor evoked potentials of the abductor digiti min. muscle may indicate the outcome of hand function at an early stage. The electroneuromyographic recordings make it possible to differentiate between the proportion of peripheral and central nervous lesion underlying a muscle paresis. This is of prognostic value in regard to the development of muscle tone and consequently for planning of 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 within the rehabilitation programme.

Electrodiagnosis↗
PubMed2000

From spinal shock to spasticity: neuronal adaptations to a spinal cord injury.

OBJECTIVE: To investigate the adaptational changes in excitability of spinal neuronal circuits below the level of lesion from spinal shock to spasticity in patients with spinal cord injury (SCI). METHODS: More than 6 months after an acute SCI, clinical follow-up examinations were paralleled by electrophysiologic recordings with tibial nerve stimulation (M-wave, F-wave, H-reflex, and flexor reflex). RESULTS: During spinal shock, the loss of tendon tap reflexes and flaccid muscle tone were associated with low persistence of F-waves and loss of flexor reflexes, whereas H-reflexes were already elicitable. During the transition to spasticity, the reappearance of tendon tap reflexes and muscle tone and the occurrence of spasms was associated with the recovery of F-waves and flexor reflex excitability, whereas the H-to-M ratio remained about stable over months. At later stages (2 to 6 months after SCI) when clinical signs of spasticity became established, the electrophysiologic measures showed little change. In paraplegic patients, in contrast to tetraplegic patients, M-wave and flexor reflex amplitudes even decreased. CONCLUSIONS: The late decrease in M-wave and flexor reflex amplitude in paraplegic patients suggests a secondary impairment/degeneration of premotoneuronal circuits and of motoneurons. The divergent course of clinical signs of spasticity and their probable neuronal correlates indicates the occurrence of non-neuronal changes contributing to spasticity.

Adaptation, Physiological↗
PubMed2000

[Differential diagnosis of acute spinal cord diseases].

We discuss the most important differential diagnosis in acute non traumatic spinal cord lesions. To therapy these patients, a large diagnostic and therapeutic spectrum must be considered. Nontraumatic spinal cord lesions include inflammatoric, immunologic, toxic-metabolic and physical reasons, tumours, bleedings, myelomalazies, neurodegenerative myelopathies and spinal deformities. The aimes of rehabilitation of these patients are almost similar to patients with tramatic spinal cord injured.

Acute Disease↗
PubMed2000

[Spinal compression syndrome and circulatory disorders].

Disorders due to spinal cord compression or ischemic spinal cord lesions represent the most relevant nontraumatic spinal cord injuries causing acute para- and tetraplegia. In acute spinal cord compression early diagnosis is most reasonable to indicate early operative intervention with decompression to prevent progressive neurological deficits. In patients suffering from malignant disorders the indication for operation is directed to maintain quality of life in an appropriate level (pain treatment, mobility by wheelchair). In chronic spinal cord compression operations are aimed to prevent the development or progression of neurological deficits, as the outcome of rehabilitation is very much dependent to the neurogenic damage. In ischemic spinal cord lesion therapy is restricted to prevent further cadiovascular complications which additionally induce spinal cord dysfunction.

Diagnosis, Differential↗
PubMed2000

[Neurologic diagnosis of spinal diseases].

The clinical assessment of neurological deficits using a standardized protocol in spinal cord disorders is most important for indicating further neuroradiological, neurophysiological and orthopedic examinations. By neurophysiological technics the clinical examinations can be supplemented not only in patients, who are not able to cooperate. Furthermore the latter technics are able to assess in how far findings in neuroradiological examinations can be related to clinically complained symptoms. The clinical examination should define the spinal level of lesion for motor and sensory function separately and use a semiquantitative scoring system of neurological deficits, which is most relevant for follow-up examinations. Performing motor evoked potentials (MEP), somato-sensory evoked potentials (SSEP) and electromyographic recordings allows to distinguish between lesions of the central and peripheral nervous system and to assess disturbances of spinal cord function.

Diagnosis, Differential↗
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

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

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

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

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↗
PubMed1998

Functional outcome following spinal cord injury: significance of motor-evoked potentials and ASIA scores.

OBJECTIVE: Prediction of outcome of ambulatory capacity and hand function in tetraplegic patients with spinal cord injury (SCI) using neurologic examination, according to the protocol of the American Spinal Injury Association (ASIA) and motor-evoked potentials (MEP). DESIGN: Correlation study on a prospective cohort. SETTING: SCI center, university hospital. PATIENTS: Thirty-six patients with acute and 34 with chronic SCI. OUTCOME MEASURES: (1) ASIA motor and sensory scores, (2) MEP recordings of upper and lower limb muscles, and (3) outcome of ambulatory capacity and hand function. RESULTS: In acute and chronic SCI, both the initial ASIA scores and the MEP recordings were significantly related (p < .0001) to the outcome of ambulatory capacity and hand function. In tetraplegic patients, the MEP of the abductor digiti minimi muscle (Spearman correlation coefficient, .75; p < .0001) and the ASIA motor score for the upper limbs (Spearman correlation coefficient, .83; p < .0001) were most related to the outcome of hand function. Ambulatory capacity could be predicted by the ASIA motor score of the lower limbs (Spearman correlation coefficient, .78; p < .0001) and by MEP recordings of the leg muscles (Spearman correlation coefficient, .77; p < .0001). In patients with acute SCI, for the period 6 months posttrauma, the ASIA motor score increased significantly (ANOVA, p < .05), whereas the ASIA sensory scores and MEP recordings were unchanged (ANOVA, p > 0.1). CONCLUSION: Both ASIA scores and MEP recordings are similarly related to the outcome of ambulatory capacity and hand function in patients with SCI. MEP recordings are of additional value to the clinical examination in uncooperative or incomprehensive patients. The combination of clinical examination and MEP recordings allows differentiation between the recovery of motor function (hand function, ambulatory capacity) and that of impulse transmission of descending motor tracts.

Activities of Daily Living↗
PubMed1998

Locomotor capacity and recovery of spinal cord function in paraplegic patients: a clinical and electrophysiological evaluation.

Recent studies have shown that a locomotor pattern can be induced and trained into paraplegic patients under conditions of body unloading using a moving treadmill. The present study investigated the behaviour of the locomotor pattern and also the relationship of its development to the spontaneous recovery of spinal cord function assessed by clinical and electrophysiological (tibial nerve somatosensory evoked potentials and motor evoked potentials) examinations. The earliest time that spinal locomotor activity could be induced was when signs of spinal shock had disappeared. This activity was distinct from spinal stretch reflex activity. In complete and incomplete paraplegic patients an increase of gastrocnemius electromyographic activity occurred during the stance phase of a step cycle with daily locomotor training over the whole training period of 12 weeks. This was coincident with a significant decrease in body unloading. In contrast to this, neither clinical nor electrophysiological examination scores improved after the onset of training in both patient groups. Only in incomplete paraplegic patients was there an insignificant increase in sensory and motor scores obtained in the neurological examination during the time period before onset of training. An improvement of locomotor function by training was also seen in patients with paraplegia due to a cauda lesion. Therefore, in patients with a spinal cord lesion training effects on muscles and tendons are present in addition to those on the spinal locomotor centres. The findings of this study may be relevant for future clinical treatment of paraplegic patients.

Adolescent↗
PubMed1998

Stumbling reactions in man: influence of corticospinal input.

The aim of this study was to evaluate the degree of contribution of supraspinal input to the generation of the compensatory leg muscle activation following stance perturbation. Therefore, evoked motor response (EMR) input-output relations of two different motor tasks were compared at 3 distinct periods: (1) the basic period of muscular activity during standing, i.e. when no additional cortical or spinal activity due to the different tasks is to be expected, (2) the pre-movement period with low background activity, when different spinal and cortical inputs to the motoneuronal pool can be assumed and (3) the period of plateau EMG activity of compensatory and voluntary motor task. Transcranial magnetic stimulation (TMS) just below the motor threshold was applied randomly at 19 different time-intervals before and during the onset of stance perturbation and for comparison during an equivalent voluntary foot-dorsiflexion task. Recordings of electromyographic (EMG) activity from the tibialis anterior (TA) and corresponding ankle-joint movements were made from both legs. Forward-directed displacements were induced by randomly-timed ramp impulses of constant acceleration upon a moveable platform. For comparison, leg muscle EMG was recorded during isometric foot dorsiflexion during stance while leaning back against a support. The stance perturbations were followed by a compensatory response (CR) in the TA with a mean onset time of 81 ms. During the basic period of muscular activity and the period of plateau EMG activity there was no significant difference of the input-output relation between stance perturbation and the voluntary motor task. However, in the voluntary task compared with the CR, there was significantly greater input-output relation (facilitation) of the EMR in the TA following TMS, which may be related to an increased cortical influence. In contrast to this result of the CR following stance perturbation, a facilitation of the EMR was described for hand muscles under corresponding conditions of automatic compensation for muscle stretch, suggesting a transcortical reflex loop. This difference in the results from upper and lower extremity muscles favors the assumption of a predominantly spinal generation of the TA-CR following stance perturbation.

Adult↗
PubMed1998

Locomotor pattern in paraplegic patients: training effects and recovery of spinal cord function.

Recent studies have shown that a locomotor pattern can be induced and utilized by paraplegic patients under conditions of body unloading using a moving treadmill. The present study investigated the behaviour of the locomotor pattern and also the relationship of its development to the spontaneous recovery of spinal cord function assessed by clinical and electrophysiological (tibial nerve somatosensory evoked potentials and motor evoked potentials) examinations. The earliest time that spinal locomotor activity could be induced was when signs of spinal shock had disappeared. This activity was distinct from spinal stretch reflex activity. In complete paraplegic patients the locomotor pattern improved spontaneously without training. This was coincident with both an increase of gastrocnemius electromyographic activity during the stance phase of gait and a decrease of body unloading. These effects reached a plateau after about 5 weeks. In complete and incomplete paraplegic patients a near linear increase of gastrocnemius electromyographic activity occurred during the stance phase of a step cycle with daily locomotor training over the whole training period of 12 weeks. This was also coincident with a significant decrease of body unloading. In contrast to this, neither clinical nor electrophysiological examination scores improved after the onset of training in both patient groups. Only in incomplete paraplegic patients was there recovery, albeit statistically insignificant, of spinal cord function according to the sensory and motor scores obtained in the neurological examination during the time period before onset of training. An improvement of locomotor function by training was also seen in patients with paraplegia due to a cauda lesion. Such training effects on muscles and tendons could be separated from those on the spinal locomotor centres. The findings of this study may be relevant for the future clinical treatment of paraplegic patients.

Adolescent↗