Hans W. Axelson

Human motor control consequences of thixotropic changes in muscular short-range stiffness.

1 The primary aim of the present study was to explore whether in healthy subjects the muscle contractions required for unrestrained voluntary wrist dorsiflexions are adjusted in strength to thixotropy‐dependent variations in the short‐range stiffness encountered in measurements of passive torque resistance to imposed wrist dorsiflexions. 2 After a period of rest, only the first movement in a series of passive wrist dorsiflexions of moderate amplitude exhibited clear signs of short‐range stiffness in the torque response. During analogous types of voluntary movements, the extensor EMG during the first movement after rest showed a steep initial rise of activity, which apparently served to compensate for the short‐range stiffness. 3 The passive torque resistance to minute repetitive wrist dorsiflexions (within the range of short‐range stiffness) was markedly reduced after various types of mechanical agitation. During analogous low‐amplitude voluntary wrist dorsiflexions the extensor EMG signals were weaker after than before agitation. 4 Mechanical agitation also led to enhancement of passive dorsiflexion movements induced by weak constant torque pulses. In an analogous way, the movement‐generating capacity of weak voluntary extensor activations (as determined by EMG recordings) was greatly enhanced by mechanical agitation. 5 The signals from a force transducer probe pressed against the wrist flexor tendons ‐ during passive wrist dorsiflexions ‐ revealed short‐range stiffness responses which highly resembled those observed in the torque measurements, suggesting that the latter to a large extent emanated from the stretched, relaxed flexor muscles. During repetitive stereotyped voluntary wrist dorsiflexions, a close correspondence was observed between the degree of short‐range stiffness as sensed by the wrist flexor tension transducer and the strength of the initial extensor activation required for movement generation. 6 The results provide evidence that the central nervous system in its control of voluntary movements takes account of and compensates for the history‐dependent degree of inherent short‐range stiffness of the muscles antagonistic to the prime movers.

Autologous haematopoietic stem cell transplantation: a viable treatment option for CIDP

Objective Only 70–80% of patients with chronic inflammatory demyelinating polyneuropathy (CIDP) respond satisfactorily to the established first-line immunomodulatory treatments. Autologous haematopoietic stem cell transplantation (AHSCT) has been performed as a last treatment resort in a few therapy-refractory cases with CIDP. We describe the results of AHSCT in 11 consecutive Swedish patients with therapy-refractory CIDP with a median follow-up time of 28 months. Method Case data were gathered retrospectively for AHSCT treatments in 11 patients with CIDP refractory to the first-line immunomodulatory treatments, intravenous high-dose immunoglobulin, corticosteroids and plasma exchange and to one or more second-line treatments used in 10 of the 11 patients. Results The median Inflammatory Neuropathy Cause and Treatment (INCAT) score within 1 month prior to AHSCT was 6 and the Rankin score 4. Total INCAT and Rankin scores improved significantly within 2–6 months after AHSCT and continued to do so at last follow-up. The motor action potential amplitudes (CMAP) improved already within 4 months (median) after AHSCT. Three of the 11 patients relapsed during the follow-up period, requiring retransplantation with AHSCT in one. Eight of the 11 patients maintained drug-free remission upon last follow-up. AHSCT was safe but on the short term associated with a risk of cytomegalovirus (CMV) and Epstein–Barr virus reactivation, CMV disease, haemorrhagic cystitis and pancreatitis. Conclusions Our results though hampered by the limited number of patients and the lack of a control group suggest AHSCT to be efficacious in therapy-refractory CIDP, with a manageable complication profile. Confirmation of these results is necessary through randomised controlled trials.

Successful repeated treatment with high dose cyclophosphamide and autologous blood stem cell transplantation in CIDP

Successful repeated treatment with high dose cyclophosphamide and autologous blood stem cell transplantation in CIDP

No benefit of treatment with cyclophosphamide and autologous blood stem cell transplantation in multifocal motor neuropathy

Introduction –  Patients with multifocal motor neuropathy (MMN) usually respond to intravenous immunoglobulin (IVIG), but because of the short‐lasting effect the treatment must be given repeatedly. Remission after treatment with high‐dose cyclophosphamide has recently been reported in one patient refractory to IVIG.

Microdialysis and electromyography of experimental muscle fatigue in healthy volunteers and patients with mitochondrial myopathy

Consecutive 60‐min microdialysis samples were taken from the tibial anterior muscle in 11 healthy subjects and 4 patients with mitochondrial myopathy before (2–3 samples) and after (3–4 samples, 2 controls and 1 patient excluded) sustained isometric foot dorsiflexions. Before exercise, mean concentrations of lactate, pyruvate, hypoxanthine, urate, aspartate, and glutamate did not significantly differ between controls and patients. After exercise, the controls showed significantly increased concentrations of lactate, pyruvate, and urate, decreased hypoxanthine, and no change in aspartate and glutamate. Similar findings were observed in the patients. Plasma lactate was unchanged. Exercise‐induced increase in integrated electromyogram amplitude and rated subjective fatigue were correlated to increased post‐exercise lactate concentrations, with no obvious difference between the groups. Microdialysis of skeletal muscle allows the detection and monitoring of biochemical changes in the interstitial space. With the exercise protocol used, however, it was not possible to demonstrate any biochemical difference between healthy controls and patients with mitochondrial myopathy.

Mathematical modeling and grey-box identification of the human smooth pursuit mechanism

A mathematical model of the human eye smooth pursuit mechanism was constructed by combining a fourth order nonlinear biomechanical model of the eye plant with a dynamic gain controller model. The biomechanical model was derived based on knowledge of the anatomical properties and characteristics of the extraocular motor system. The controller model structure was chosen empirically to agree with experimental data. With the parameters of the eye plant obtained from the literature, the controller parameters were estimated through grey-box identification. Randomly generated and smoothly moving visual stimuli projected on a computer monitor were used as input data while the output data were the resulting eye movements of test subjects tracking the stimuli. The model was evaluated in terms of accuracy in reproducing eye movements registered over time periods longer than 10 seconds, frequency characteristics and angular velocity step responses. It was found to perform better than earlier models for the extended time data sets used in this study.

Successful repeated treatment with high dose cyclophosphamide and autologous blood stem cell transplantation in CIDP.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is characterised by the occurrence of symmetrical weakness and sensory impairment in arms and legs. The course is relapsing or chronic and progressing. CIDP is considered to be an autoimmune disease, which is supported by the beneficial response to immunomodulating therapies in most patients. We report on a patient with CIDP who has been in remission for more than 3 years after treatment with high dose cyclophosphamide and autologous blood stem cell transplantation in CIDP on two occasions.

Diagnosis of Disorders of Consciousness : Evoked Potentials and Behavioural Assessment in clinical practice

Endogenous free radical production by NADPH oxidase 2 contributes to the secondary injury cascade after traumatic brain injury in miceAccepted Abstracts from the International Brain Injury Association’s Ninth World Congress on Brain InjuryObjectives: Studies have shown that occupational therapy interventions for clients with cognitive impairment following acquired brain injury (CIABI) have a positive effect on performance of activities of daily living, although the exact nature of the interventions are not clearly described. A better understanding of current practice is therefore needed to move further in the search for evidence based occupational therapy for clients with CIABI. Research on occupational therapists’ (OTs’) practice can play an important role to explore and describe current practice and furthermore define and evaluate the effectiveness of different components in OT interventions. The aim of this study was to survey Swedish OTs’ practice patterns for clients having CIABI.Methods: The study had a cross-sectional design using a questionnaire developed in two former studies. A stratified random sample was done with 250 OTs each from the following areas: regional care, somatic county care, primary care and municipal eldercare. The questionnaire was sent out using on-line survey software and 462 participants responded. Data is currently analyzed by descriptive and comparative statistics.Results: Preliminary results show that the interventions targeted a wide range of cognitive impairments and its consequences. Interventions were both remedial and compensatory with graded activity as the most common remediating intervention. To compensate for activity limitations prescription, or recommendation, of assistive devices (AD) as well as supporting clients in finding internal strategies were used extensively. The ADs used consisted of both high and low technology devices. Eighty-two percent also included different specific interventions to improve clients’ decreased self-awareness in their practice. A vast majority of the OTs (94%) preferred to use observations in daily activities to assess both activity limitations and cognitive impairment. Almost all participants also used interviews and sixty-two percent used tests on impairment level. To support practice general Occupational Therapy models were widely used while theories focusing on cognitive impairments specifically were used less. The participants’ answers reflected a client-centered attitude with collaborative goal-setting and feedback discussions after each session. Eighty- four percent felt dependent on relatives to reach a successful outcome and most of them worked deliberately to involve relatives in the rehabilitation. The OTs responses were evenly distributed over the spheres of activity. Ninety-two percent of the participants worked in team and the most common diagnoses were stroke and traumatic brain injury. There were some differences in responses between the spheres.Conclusions: Preliminary conclusions are that the OTs practice patterns included interventions targeting most cognitive impairments and their consequences in daily activities. The use of daily activities as a mean was preferred irrespective of whether the interventions were remediative or compensatory. Interventions targeting decreased self-awareness as well as the use of ADs were common. A client-centered approach was dominating including collaboration with relatives.For personalcentered approach was dominating including collaborationwith relatives.Diagnosis of Disorders of Consciousness : Evoked Potentials and Behavioural Assessment in clinical practice