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Axelson, Hans
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Publications (10 of 22) Show all publications
Amandusson, Å. (2017). Comparison between adaptive and fixed stimulus paired-pulsetranscranial magnetic stimulation (ppTMS) in normal subjects. Clinical Neurophysiology Practice, 91-97
Open this publication in new window or tab >>Comparison between adaptive and fixed stimulus paired-pulsetranscranial magnetic stimulation (ppTMS) in normal subjects
2017 (English)In: Clinical Neurophysiology Practice, ISSN 2467-981X, p. 91-97Article in journal (Refereed) Published
Abstract [en]

Objectives

Paired-pulse TMS (ppTMS) examines cortical excitability but may require lengthy test procedures and fine tuning of stimulus parameters due to the inherent variability of the elicited motor evoked potentials (MEPs) and their tendency to exhibit a ‘ceiling/floor effects’ in inhibition trials. Aiming to overcome some of these limitations, we implemented an ‘adaptive’ ppTMS protocol and compared the obtained excitability indices with those from ‘conventional’ fixed-stimulus ppTMS.

Methods

Short- and long interval intracortical inhibition (SICI and LICI) as well as intracortical facilitation (ICF) were examined in 20 healthy subjects by adaptive ppTMS and fixed-stimulus ppTMS. The test stimulus intensity was either adapted to produce 500 μV MEPs (by a maximum likelihood strategy in combination with parameter estimation by sequential testing) or fixed to 120% of resting motor threshold (rMT). The conditioning stimulus was 80% rMT for SICI and ICF and 120% MT for LICI in both tests.

Results

There were significant (p < 0.05) intraindividual correlations between the two methods for all excitability measures. There was a clustering of SICI and LICI indices near maximal inhibition (‘ceiling effect’) in fixed-stimulus ppTMS which was not observed for adaptive SICI and LICI.

Conclusions

Adaptive ppTMS excitability data correlates to those acquired from fixed-stimulus ppTMS.

Significance

Adaptive ppTMS is easy to implement and may serve as a more sensitive method to detect changes in cortical inhibition than fixed stimulus ppTMS. Whether equally confident data are produced by less stimuli with our adaptive approach (as already confirmed for motor threshold estimation) remains to be explored.

National Category
Neurosciences
Identifiers
urn:nbn:se:uu:diva-342567 (URN)10.1016/j.cnp.2017.04.001 (DOI)
Available from: 2018-02-22 Created: 2018-02-22 Last updated: 2018-03-15Bibliographically approved
Jansson, D., Medvedev, A., Axelson, H. & Nyholm, D. (2015). Stochastic anomaly detection in eye-tracking data for quantification of motor symptoms in Parkinson's disease. In: Signal and Image Analysis for Biomedical and Life Sciences: (pp. 63-82). Springer
Open this publication in new window or tab >>Stochastic anomaly detection in eye-tracking data for quantification of motor symptoms in Parkinson's disease
2015 (English)In: Signal and Image Analysis for Biomedical and Life Sciences, Springer, 2015, p. 63-82Chapter in book (Refereed)
Abstract [en]

Two methods for distinguishing between healthy controls and patients diagnosed with Parkinson's disease by means of recorded smooth pursuit eye movements are presented and evaluated. Both methods are based on the principles of stochastic anomaly detection and make use of orthogonal series approximation for probability distribution estimation. The first method relies on the identification of a Wiener model of the smooth pursuit system and attempts to find statistically significant differences between the estimated parameters in healthy controls and patients with Parkinson's disease. The second method applies the same statistical method to distinguish between the gaze trajectories of healthy and Parkinson subjects tracking visual stimuli. Both methods show promising results, where healthy controls and patients with Parkinson's disease are effectively separated in terms of the considered metric. The results are preliminary because of the small number of participating test subjects, but they are indicative of the potential of the presented methods as diagnosing or staging tools for Parkinson's disease.

Place, publisher, year, edition, pages
Springer, 2015
Series
Advances in Experimental Medicine and Biology, ISSN 0065-2598 ; 823
National Category
Control Engineering Neurology
Identifiers
urn:nbn:se:uu:diva-244824 (URN)10.1007/978-3-319-10984-8_4 (DOI)000350427300005 ()25381102 (PubMedID)978-3-319-10983-1 (ISBN)
Available from: 2014-10-13 Created: 2015-02-20 Last updated: 2015-04-16Bibliographically approved
Press, R., Askmark, H., Svenningsson, A., Andersen, O., Axelson, H. W., Strömberg, U., . . . Hägglund, H. (2014). Autologous haematopoietic stem cell transplantation: a viable treatment option for CIDP. Journal of Neurology, Neurosurgery and Psychiatry, 85(6), 618-624
Open this publication in new window or tab >>Autologous haematopoietic stem cell transplantation: a viable treatment option for CIDP
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2014 (English)In: Journal of Neurology, Neurosurgery and Psychiatry, ISSN 0022-3050, E-ISSN 1468-330X, Vol. 85, no 6, p. 618-624Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Medical and Health Sciences Neurology
Identifiers
urn:nbn:se:uu:diva-223064 (URN)10.1136/jnnp-2013-306014 (DOI)000336124400009 ()24262917 (PubMedID)
Available from: 2014-04-16 Created: 2014-04-16 Last updated: 2017-12-05Bibliographically approved
Franck-Larsson, K., Graf, W., Edebol Eeg-Olofsson, K., Axelson, H. W. & Rönnblom, A. (2014). Physiological and structural anorectal abnormalities in patients with systemic sclerosis and fecal incontinence. Scandinavian Journal of Gastroenterology, 49(9), 1073-1083
Open this publication in new window or tab >>Physiological and structural anorectal abnormalities in patients with systemic sclerosis and fecal incontinence
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2014 (English)In: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 49, no 9, p. 1073-1083Article in journal (Refereed) Published
Abstract [en]

Objective

Fecal incontinence is common in systemic sclerosis (SSc), but the underlying mechanisms are not fully understood. The objectives of this study were to characterize anorectal physiological and morphological defects in SSc patients and to correlate the results with incontinence symptoms.

Materials and methods

Twenty-five SSc patients underwent anorectal neurophysiological investigations, anal manometry, and ultrasound.

Results

Eleven patients (44%) reported incontinence to solid or liquid feces, but no patient reported diarrhea. Increased fiber density (FD) was recorded in 78% of patients with and in 86% of patients without fecal incontinence not significant (NS). Incontinent patients had lower squeeze pressure (SP; median 49.5 mm Hg) in the high-pressure zone (HPZ) than continent patients (median 72 mm Hg; p = 0.01). In two of the incontinent patients, sonographic abnormalities of the internal anal sphincter (IAS) and the external anal sphincter (EAS) were present, whereas in another two patients isolated IAS abnormalities were seen. These four individuals had lower resting pressure at 1 cm and in the HPZ, and lower SP at 2 cm than patients with normal anorectal sonographic findings (p < 0.05).

Conclusion

Lower voluntary SP in incontinent patients and EAS sonographic abnormalities only in patients with incontinence suggest that the EAS is more important in maintaining fecal continence in SSc patients than has previously been reported. The finding of increased FD in most patients further supports involvement of the EAS function in SSc and could indicate previous nerve injury with consequent incomplete reinnervation.

National Category
Rheumatology and Autoimmunity Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-224114 (URN)10.3109/00365521.2014.913188 (DOI)000340829900007 ()24786727 (PubMedID)
Available from: 2014-05-04 Created: 2014-05-04 Last updated: 2017-12-05Bibliographically approved
Axelson, H. W., Isberg, M., Flink, R. & Amandusson, Å. (2014). Trigeminal Nerve Stimulation Does Not Acutely Affect Cortical Excitability in Healthy Subjects. Brain Stimulation, 7(4), 613-617
Open this publication in new window or tab >>Trigeminal Nerve Stimulation Does Not Acutely Affect Cortical Excitability in Healthy Subjects
2014 (English)In: Brain Stimulation, ISSN 1935-861X, E-ISSN 1876-4754, Vol. 7, no 4, p. 613-617Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Trigeminal nerve stimulation (TNS) has recently emerged as a new therapeutic option for patients with drug-resistant epilepsy but its potential mechanisms of action are not known. Since other antiepileptic treatments have been shown to alter cortical excitability, thereby reducing the liability to seizures, it has been suggested that cranial nerve stimulation such as TNS may act in the same way.

OBJECTIVE: To study whether TNS has the potential to alter cortical excitability in healthy subjects.

METHODS: An adaptive paired-pulse transcranial magnetic stimulation protocol stimulating the dominant hand motor area was used to measure resting motor threshold (rMT), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF) and long-interval intracortical inhibition (LICI) before, during, and after 40 min of 120 Hz bilateral external continuous trigeminal nerve stimulation. Neuronavigation was used for guidance.

RESULTS: TNS was well tolerated by all subjects. No significant changes were seen in the parameters studied.

CONCLUSION: Unlike for example anti-epileptic drugs and the ketogenic diet, trigeminal nerve stimulation does not seem to alter cortical excitability in healthy subjects. This is the first study on cortical excitability in relation to continuous trigeminal nerve stimulation. It still remains to be proven that TNS has the prerequisites to effectively counteract epileptic events in humans.

National Category
Neurology
Identifiers
urn:nbn:se:uu:diva-225861 (URN)10.1016/j.brs.2014.04.010 (DOI)000339984300017 ()24852898 (PubMedID)
Available from: 2014-06-09 Created: 2014-06-09 Last updated: 2017-12-05Bibliographically approved
Alm, P. A., Karlsson, R., Sundberg, M. & Axelson, H. W. (2013). Hemispheric Lateralization of Motor Thresholds in Relation to Stuttering. PLoS ONE, 8(10), e76824
Open this publication in new window or tab >>Hemispheric Lateralization of Motor Thresholds in Relation to Stuttering
2013 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 10, p. e76824-Article in journal (Refereed) Published
Abstract [en]

Stuttering is a complex speech disorder. Previous studies indicate a tendency towards elevated motor threshold for the left hemisphere, as measured using transcranial magnetic stimulation (TMS). This may reflect a monohemispheric motor system impairment. The purpose of the study was to investigate the relative side-to-side difference (asymmetry) and the absolute levels of motor threshold for the hand area, using TMS in adults who stutter (n = 15) and in controls (n = 15). In accordance with the hypothesis, the groups differed significantly regarding the relative side-to-side difference of finger motor threshold (p = 0.0026), with the stuttering group showing higher motor threshold of the left hemisphere in relation to the right. Also the absolute level of the finger motor threshold for the left hemisphere differed between the groups (p = 0.049). The obtained results, together with previous investigations, provide support for the hypothesis that stuttering tends to be related to left hemisphere motor impairment, and possibly to a dysfunctional state of bilateral speech motor control.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-211798 (URN)10.1371/journal.pone.0076824 (DOI)000325819400084 ()
Available from: 2013-12-02 Created: 2013-12-02 Last updated: 2017-12-06Bibliographically approved
Axelson, H. W., Johansson, E. & Bill-Axelson, A. (2013). Intraoperative Cavernous Nerve Stimulation and Laser-Doppler Flowmetry during Radical Prostatectomy. Journal of Sexual Medicine, 10(11), 2842-2848
Open this publication in new window or tab >>Intraoperative Cavernous Nerve Stimulation and Laser-Doppler Flowmetry during Radical Prostatectomy
2013 (English)In: Journal of Sexual Medicine, ISSN 1743-6095, E-ISSN 1743-6109, Vol. 10, no 11, p. 2842-2848Article in journal (Refereed) Published
Abstract [en]

Introduction. 

Erectile dysfunction is a common side effect following radical prostatectomy mainly due to damage of the pelvic autonomic nerve fibers (cavernous nerves). Intraoperative electrical stimulation of the cavernous nerves while measuring changes in penile girth has previously been shown to provide the surgeon with feedback of nerve integrity.

Aim. 

To test the feasibility of recording changes in glans penis blood flow by Laser Doppler flowmetry from cavernous nerve stimulation.

Methods. 

Fifteen patients with localized prostate cancer undergoing radical prostatectomy had electrical stimulation of the proximal and distal parts of the neurovascular bundles after prostate removal. The stimulation consisted of 30-40 seconds biphasic constant current (10-30 mA) with 0.5 millisecond pulse duration.

Main Outcome Measures. 

Stimulus induced changes in penile blood flow was recorded from a Laser Doppler probe attached to the glans penis. Changes in penile girth were simultaneously recorded from a mercury-in rubber strain gauge. Erectile function was evaluated three months after surgery.

Results. 

Ten patients had stimulus induced increase in Laser Doppler flow unilaterally (N = 7) or bilaterally (N = 3). Out of 10 patients, 6 reported some preserved erectile function postoperatively at 3 months follow-up (indicating 6 true and 4 false positives). Three patients had no Doppler response from stimulation and had no postoperative erectile function postoperatively (indicating three true negatives). Two patients were excluded from the study due to bad signal quality in the Laser Doppler signal. In the majority of patients, stimulation produced increase in penile girth sensed by the strain gauge.

Conclusion. 

This preliminary report provides evidence that Laser Doppler Flowmetry is able to detect increased penile blood flow from intraoperative electrical stimulation of the neurovascular bundles. However, further improvement in the recording technique is required. Laser Doppler Flowmetry may also be feasible to confirm autonomic nerve sparing in women undergoing pelvic surgery.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-181770 (URN)10.1111/j.1743-6109.2012.02892.x (DOI)000326465900024 ()22909402 (PubMedID)
Available from: 2012-09-28 Created: 2012-09-28 Last updated: 2019-04-09Bibliographically approved
Axelson, H., Winkler, T., Flygt, J., Djupsjö, A., Hånell, A. & Marklund, N. (2013). Plasticity of the contralateral motor cortex following focal traumatic brain injury in the rat. Restorative Neurology and Neuroscience, 31(1), 73-85
Open this publication in new window or tab >>Plasticity of the contralateral motor cortex following focal traumatic brain injury in the rat
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2013 (English)In: Restorative Neurology and Neuroscience, ISSN 0922-6028, E-ISSN 1878-3627, Vol. 31, no 1, p. 73-85Article in journal (Refereed) Published
Abstract [en]

Purpose: Recovery is limited following traumatic brain injury (TBI) since injured axons regenerate poorly and replacement of lost cells is minimal. Behavioral improvements could instead be due to plasticity of uninjured brain regions. We hypothesized that plasticity of the uninjured hemisphere occurs contralateral to a focal TBI in the adult rat. Thus, we performed cortical mapping of the cortex contralateral to the TBI using intracortical microstimulation (ICMS). Methods: A focal TBI was induced using the weight-drop technique (n = 5) and sham-injured animals were used as controls (n = 4). At five weeks post-injury, ICMS was used to map the motor area contralateral to the injury. Motor responses were detected by visual inspection and electromyography (EMG). Results: In sham- and brain-injured animals, numerous fore- and hindlimb motor responses contralateral to the stimulation (ipsilateral to the injury) were obtained. Compared to sham-injured controls, there was a markedly increased (p < 0.05) number of fore- and hindlimb responses ipsilateral to the stimulation after TBI. Conclusion: Following focal TBI in the rat, our data suggest reorganization of cortical and/or subcortical regions in the uninjured hemisphere contralateral to a focal TBI leading to an altered responsiveness to ICMS. Although we cannot exclude that these changes are maladaptive, it is plausible that this plasticity process positively influences motor recovery after TBI.

National Category
Neurosciences
Identifiers
urn:nbn:se:uu:diva-188332 (URN)10.3233/RNN-2012-120242 (DOI)000313740500007 ()23047494 (PubMedID)
Available from: 2012-12-15 Created: 2012-12-15 Last updated: 2018-01-11Bibliographically approved
Jansson, D., Medvedev, A., Axelson, H. & Nyholm, D. (2013). Stochastic anomaly detection in eye-tracking data for quantification of motor symptoms in Parkinson's disease. In: International Symposium on Computational Models for Life Sciences: CMLS 2013. Paper presented at CMLS 2013, November 27-29, Sydney, Australia (pp. 98-107). Melville, NY: American Institute of Physics (AIP)
Open this publication in new window or tab >>Stochastic anomaly detection in eye-tracking data for quantification of motor symptoms in Parkinson's disease
2013 (English)In: International Symposium on Computational Models for Life Sciences: CMLS 2013, Melville, NY: American Institute of Physics (AIP), 2013, p. 98-107Conference paper, Published paper (Refereed)
Abstract [en]

Two methods for distinguishing between healthy controls and patients diagnosed with Parkinson's disease by means of recorded smooth pursuit eye movements are presented and evaluated. Both methods are based on the principles of stochastic anomaly detection and make use of orthogonal series approximation for probability distribution estimation. The first method relies on the identification of a Wiener-type model of the smooth pursuit system and attempts to find statistically significant differences between the estimated parameters in healthy controls and patientts with Parkinson's disease. The second method applies the same statistical method to distinguish between the gaze trajectories of healthy and Parkinson subjects attempting to track visual stimuli. Both methods show promising results, where healthy controls and patients with Parkinson's disease are effectively separated in terms of the considered metric. The results are preliminary because of the small number of participating test subjects, but they are indicative of the potential of the presented methods as diagnosing or staging tools for Parkinson's disease.

Place, publisher, year, edition, pages
Melville, NY: American Institute of Physics (AIP), 2013
Series
AIP Conference Proceedings ; 1559
Keywords
Smooth pursuit, Anomaly detection, Modeling biomedical systems, Parkinson's Disease
National Category
Neurosciences Control Engineering
Identifiers
urn:nbn:se:uu:diva-221215 (URN)10.1063/1.4825001 (DOI)000331467600013 ()978-0-7354-1187-6 (ISBN)
Conference
CMLS 2013, November 27-29, Sydney, Australia
Available from: 2013-10-09 Created: 2014-03-26 Last updated: 2018-01-11Bibliographically approved
Axelson, H. W. (2012). Compound Motor Action Potential Interexaminer Variability in Photoguided Placement of the Recording Electrodes. Journal of clinical neurophysiology, 29(3), 256-259
Open this publication in new window or tab >>Compound Motor Action Potential Interexaminer Variability in Photoguided Placement of the Recording Electrodes
2012 (English)In: Journal of clinical neurophysiology, ISSN 0736-0258, E-ISSN 1537-1603, Vol. 29, no 3, p. 256-259Article in journal (Refereed) Published
Abstract [en]

Interpretation of neurographic data in follow-up studies of patients with neuromuscular disease is sometimes challenging because of the expected variability in repeated tests. In this study, we explored whether the interexaminer variability of the compound motor action potential (CMAP) amplitude is reduced if the examiner is guided by the previously taken photographs of the position of the recording electrodes. The CMAPs were recorded from 20 subjects by unilateral distal stimulation of the median, ulnar, peroneal, and tibial nerve by 4 different technicians. All the subjects were examined on 2 occasions (similar to 1 week apart). On the first occasion, the technicians recorded the CMAP values according to routine protocols. On the second occasion, the technicians had additional guidance from photographs displaying the recording electrode positions from the first study. The CMAP coefficient of variation (CoV) was calculated for each nerve examined by the four technicians. Differences in CoV between the two types of tests (i.e., with or without photographs) were evaluated. When the examiners were guided by the photographs during electrode application, the CMAP CoV for the tibial innervated abductor hallucis (AH) muscle was reduced (P = 0.02) from 18.5% to 13%. There were, however, no significant reductions in CoV for the abductor pollicis brevis (APB, P = 0.23, median nerve), abductor digiti minimi (P = 0.37, ulnar nerve), or extensor digitorum brevis (EDB, P = 0.15, peroneal nerve) muscles. Photographic documentation of the CMAP recording electrodes seems to have a limited overall effect on interexaminer variability in a subsequent study.

Keywords
neurography, CMAP, reliability
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-177239 (URN)10.1097/WNP.0b013e3182570f6e (DOI)000304811600009 ()
Available from: 2012-07-05 Created: 2012-07-04 Last updated: 2017-12-07Bibliographically approved
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