Localization of pathological low frequency oscillation in stroke patients
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1
Elekta Oy, Finland
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2
Helsinki University Central Hospital, BioMag laboratory, Finland
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3
Helsinki University Central Hospital, Department of Neurology, Finland
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4
Helsinki University of Technology, Brain Research Unit, Low Temperature Laboratory, Finland
Brain lesions in patients with stroke, tumors or traumatic brain injury are sometimes associated with abnormal spontaneous low frequency oscillations of 1-4 Hz arising from the affected cortical area or its surroundings. As these oscillations can be detected by magnetoencephalography (MEG), it should be possible to localize the area producing this pathological activity from resting state MEG data. This would be particularly important in patients with functional deficits but no structural lesion in MRI [1]. This study presents a method to localize the pathological oscillation from a stroke patient. Three minutes of resting state MEG data were recorded from 12 first-ever stroke patients using the 306-channel whole head Elekta Neuromag MEG device, 2-7 days post stroke. The MEG data were first processed with the temporal signal space separation (tSSS) method to remove external and nearby disturbances. Thereafter, pathological low frequency oscillation was localized by L1-norm based minimum norm estimation (MCE) in frequency domain. The current distribution was estimated in source spaces including 1) evenly distributed points inside the cranial volume and 2) points constrained to cortical surface, drawn from the patient's MRI. The increased low frequency activity could be clearly observed in the sensor level spontaneous MEG data in 7 patients. Preliminary results from one patient show that the implemented method can be used to localize sources of spontaneous oscillatory activity. The study will be extended to include all the cases displaying clearly increased low frequency activity.
References
1. Huang et al., J Neurotrauma 2009 Apr. 22
Conference:
Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010.
Presentation Type:
Poster Presentation
Topic:
MEG: Clinical applications
Citation:
Helle
L,
Mäkelä
JP,
Forss
N,
Taulu
S,
Roiha
K and
Ahonen
A
(2010). Localization of pathological low frequency oscillation in stroke patients.
Front. Neurosci.
Conference Abstract:
Biomag 2010 - 17th International Conference on Biomagnetism .
doi: 10.3389/conf.fnins.2010.06.00291
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Received:
05 Apr 2010;
Published Online:
05 Apr 2010.
*
Correspondence:
Liisa Helle, Elekta Oy, Helsinki, Finland, liisa.helle@neuromag.fi