search
for
 About Bioline  All Journals  Testimonials  Membership  News


Neurology India
Medknow Publications on behalf of the Neurological Society of India
ISSN: 0028-3886 EISSN: 1998-4022
Vol. 57, Num. 4, 2009, pp. 501-504

Neurology India, Vol. 57, No. 4, July-August, 2009, pp. 501-504

Letter To Editor

Imaging of spontaneous neuromagnetic activity in a patient with internal carotid artery stenosis

Shinichi Sakamoto1,2, Naohiro Tsuyuguchi2, Wataru Ide1, Ikuo Hashimoto1, Hajime Kamada1, Hiroaki Tanaka3, Kensuke Sekihara4, Kenji Ohata2

1Departments of Neurosurgery, Hokuto Hospital, Obihiro,
2Osaka City University Graduate School of Medicine, Osaka,
3MEG Center, Yokogawa Electric Corporation, Kanazawa,
4Systems Design and Engineering, Tokyo Metropolitan University, Tokyo, Japan.

Correspondence Address: Department of Neurosurgery, Hokuto Hospital, Obihiro, Japan, s-sakamoto@med.osaka-cu.ac.jp

Date of Acceptance: 09-Jan-2009

Code Number: ni09142

PMID: 19770561

DOI: 10.4103/0028-3886.55584

Sir,

Magnetoencephalography (MEG) is beginning to be applied clinically because this technique allows direct capture of cerebral neural activity and resolves the problem associated with low spatial resolution of electroencephalography (EEG). The present study measured spontaneous cerebral magnetic fields using a whole-head-type MEG system, and used frequency analysis to attempt imaging of cerebral ischemic areas.

A 76-year-old man suffered a ischemic attack resulting in left hemiparesis, and brain magnetic resonance imaging (MRI) confirmed a small infarct in the watershed area of the right parieto-occipital region [Figure - 1]a. Cerebral angiography confirmed approximately 80% stenosis at the origin of the right internal carotid artery [Figure - 1]b. Positron emission tomography by the 15 O gas inhalation (steady-state) method ( 15 O gas PET) confirmed a decrease in cerebral blood flow (CBF) in the region of the right middle cerebral artery (right 36.2ml/100g /min; left 40.7ml/100g /min) [Figure - 2]a and increased oxygen extraction fraction (OEF) (right 45.2%; left 37.7%) [Figure - 2]b. The patient was thus diagnosed to have reduced CBF and metabolism reserve (misery perfusion) in the right middle cerebral artery region. Using a 160-channel whole-head-type gradiometer (MEG vision PQ1160C; Yokogawa, Kanazawa, Japan), [1] MEG was performed to measure spontaneous cerebral neuromagnetic activities. Slow-wave component analysis was performed using an adaptive beamformer, which provided a kind of spatial filtration. [2] At a sampling frequency of 500Hz, a DC-200Hz bandpass filter and a 50-Hz notch filter were used; 150-s data were analyzed in terms of δ waves (0.3-4Hz) and θ waves (4-8Hz). Asymmetrical slow-wave distributions in the cerebral cortex within 3 cm of the brain surface were superimposed onto preoperative cerebral MRI scans. MEG showed that the distribution of δ waves was broad from the right frontal area to the parietal area in the ipsilateral cerebral hemisphere corresponding to ischemic areas as confirmed by PET [Figure - 3]a, while the distribution of θ waves was relatively localized from the posterior temporal area to the parietal area in the ipsilateral cerebral hemisphere [Figure - 3]b.

Studies on slow-wave distributions as assessed by MEG have been previously conducted. [3,4] These studies surmised that δ wave distributions are seen around the cerebral infarction, while θ waves are in a relatively localized area irrespective of the extent of ischemia. However, in the past, slow-wave analysis was performed by comparing raw data or estimating equivalent current dipoles (ECDs), and such techniques are not suited to estimating ischemic areas beyond a certain volume in the brain, and imaging has not been necessarily clear. We addressed this problem by using the adaptive beamformer method, which allows reconstruction of cerebral activity sources with high spatial resolution without limits to numbers. [2]

The results of the present study suggest that cerebral magnetic field frequency analysis using MEG has the potential to identify the area of cerebral ischemia and may represent a useful technique for visualizing the ischemic penumbra. [5] Future investigations of differences between δ and θ wave distributions will be necessary in greater numbers of patients.

References

1.Higuchi M, Shimogawara M, Haruta Y, Uehara G, Kawai J, Ogata H, et al. System integration and trade-offs of SQUID system for biomagnetic applications. Appl Superconduct 1998;5:441-9.   Back to cited text no. 1    
2.Sekihara K, Nagarajan SS, Poeppel D, Marantz A, Miyashita Y. Reconstructing spatio-temporal activities of neural sources using an MEG vector beamformer technique. IEEE Trans Biomed Eng 2001;48:760-71.  Back to cited text no. 2    
3.Kamada K, Saguer M, Möller M, Wicklow K, Katenhäuser M, Kober H, et al. Functional and metabolic analysis of cerebral ischemia using magnetoencephalography and proton magnetic resonance spectroscopy. Ann Neurol 1997;42:554-63.  Back to cited text no. 3    
4.Seki S, Nakasato N, Ohtomo S, Kanno A, Shimizu H, Tominaga T. Neuromagnetic measurement of unilateral temporo-parietal theta rhythm in patients with internal carotid artery occlusive disease. Neuroimage 2005;25:502-10.  Back to cited text no. 4    
5.Astrup J, Siesjö BK, Symon L. Thresholds in cerebral ischemia - The ischemic penumbra. Stroke 1981;12:723-5.  Back to cited text no. 5    

Copyright 2009 - Neurology India

The following images related to this document are available:

Photo images

[ni09142f2.jpg] [ni09142f3.jpg] [ni09142f1.jpg]
Home Faq Resources Email Bioline
© Bioline International, 1989 - 2024, Site last up-dated on 01-Sep-2022.
Site created and maintained by the Reference Center on Environmental Information, CRIA, Brazil
System hosted by the Google Cloud Platform, GCP, Brazil