Automated localization of magnetoencephalographic interictal spikes by adaptive spatial filtering

• Published in: Clinical neurophysiology Vol. 117; no. 10; pp. 2264 - 2271
• Main Authors: Kirsch, H.E., Robinson, S.E., Mantle, M., Nagarajan, S.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ireland Ltd 01.10.2006; Elsevier
• Subjects: Adaptive spatial filtering; Algorithms; Automated spike localization; Biological and medical sciences; Electrodiagnosis. Electric activity recording; Epilepsy; Epilepsy - physiopathology; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Humans; Investigative techniques, diagnostic techniques (general aspects); Magnetocardiography; Medical sciences; MEG; Nervous system; Nervous system (semeiology, syndromes); Neurology; Reproducibility of Results; Software; Automated spike localization; Epilepsy; MEG; Adaptive spatial filtering; Waveform; Human; Spike; Nervous system diseases; Magnetoencephalography; Equivalent current; Adaptive filtering; Algorithm; Cerebral disorder; Software tool; Sensitivity; Specificity; Central nervous system disease; Technique; Localization; Signal to noise ratio
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2006.06.708

Automated adaptive spatial filtering techniques can be applied to magnetoencephalographic (MEG) data collected from people with epilepsy. Source waveforms estimated by these methods have higher signal-to-noise ratio (SNR) than spontaneous MEG data, allowing identification and location of interictal spikes. The software tool SAM( g 2) provides an adaptive spatial filtering algorithm for MEG data that yields source images of excess kurtosis and provides source time-courses in voxels exhibiting high excess kurtosis. The sensitivity and specificity of SAM( g 2) in epilepsy is unknown. Interictal MEG data from 36 patients with intractable epilepsy were analyzed using SAM( g 2), and results compared with equivalent current dipole (ECD) fit procedures. When SNR of interictal spikes was high (compared to background) with a clear single focus, in most cases there was good agreement between ECD and SAM( g 2). With multiple foci, there was typically overlap but imperfect concordance between results of ECD and SAM( g 2). SAM( g 2) may in some cases be equivalent to manual ECD fit for localizing interictal spikes with single locus and good SNR. Further studies are required to validate SAM( g 2) with multiple foci or poor SNR. In some cases, SAM( g 2) might eventually assist or replace manual ECD analysis of MEG data.