Non linear analysis of magnetoencephalographic signals as a tool for assessing malignant lesions of the brain: First results

Background and purpose: Non linear signal analysis is a powerful technique that reveals qualitative and quantitative differentiations between different dynamical systems (biological or otherwise). Presented here are the first results of a work in progress to investigate the Magnetoencephalograms (MEG) from patients with malignant CNS lesions and from healthy volunteers. Methods: We present MEG recordings of 10 patients diagnosed with malignant CNS lesions and the corresponding ones from 10 healthy volunteers. A 122-channel SQUID biomagnetometer in an electromagnetically shielded room was used to record the MEG signals and the Grassberger-Procaccia method for the estimation of the correlation dimension was applied on the phase space reconstruction of the recorded signal from each patient. Results: Evidence linking MEG signal characteristics (existence of low dimensionality chaotic dynamics) with the existence of the tumour was found from this analysis. Conclusion: The obtained results substantiate our hypothesis of a relation between tumours of the brain and the mathematically chaotic nature of the neural dynamics derived from their MEG recordings.