**1. Introduction**

Computational Intelligence in Electromyography Analysis – 36 A Perspective on Current Applications and Future Challenges

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Since its commercial advent in 1985, transcranial magnetic stimulation (TMS), a technique for stimulating neurons in the cerebral cortex through the scalp, safely and with minimal discomfort, has captured the imaginations of scientists, clinicians and lay observers [Wassermann et al, 2012]. Initially a laboratory tool for neurophysiologists studying the human motor system, TMS now has a growing list of applications in clinical and basic neuroscience. At cortical level, the abnormal amplitudes of the motor evoked potentials (MEP) may be due to the damage of the motoneurons themselves; as well as to their reduced capacity for repetitive excitation; deficit of the intracortical synaptic transmission (transfer); activation of motoneuron inhibitors, etc. At subcortical level the causes may be demyelinization, remyelinization, activation of the long-latent corticofugal fibres, axonal damage, etc. [Komori et al, 1993].

The human brain possesses a remarkable ability to adapt in response to changing anatomical (e.g., aging) or environmental modifications. This form of neuroplasticity is important at all stages of life but is critical in neurological disorders such as amblyopia and stroke [Sharma, 2012]. When MEP are obtained in the acute phase of stroke, the functional recovery of the motor deficit, as a rule, is to occur [Nowak et al, 2010; Dimyan, 2010]. The initially registered normal MEP amplitudes have a predictive value in the view of the longterm functional outcome [Stinear, 2010; Dimyan et al, 2010;].

The TMS approach was also used in the investigation of patients with lacunar strokes. The central motor conduction time (CMCT) and the threshold intensities for eliciting MEPs in the relaxed muscles were significantly increased on the affected side. MEP amplitude abnormalities were related to pyramidal signs (though they could be observed also in a

patient without any motor impairment) and occurred independently of a specific clinical picture or a radiologically confirmed lacunar lesion [Abbruzzese et al, 1991; Hufnagel et al, 1990]. Earlier studies have shown that during the acute phase of the minor ischaemic stroke (MIS), MEP amplitudes can be registered in all investigated patients [Hadjipetrova et al, 1993]. To note, the increases in the latency of the M-response and CMCT have prognostic significance for early assessment of the outcome of ischaemic stroke [Stulin et al, 2003]. Earlier studies by Ferbert and collaborators [1992] have indicated that the MEP amplitudes are a more sensitive marker for the sublclinical damage of the pyramidal tract than CMCT. A significant correlation has also been reported among the recovery of muscle strength and the amplitude of MEP [Palliyath, 2000].

Modelling of Transcranial Magnetic Stimulation in

One-Year Follow-Up Study of Patients with Minor Ischaemic Stroke 39

**Figure 1.** CONSORT flow-chart of study screening, enrolment and analysis.

the analysis.

disease, cardiac conditions, cigarette smoking, educational background, etc.

Data were collected by instructed physicians and clinical (physical and neurological) examinations were conducted by study neurologists [Atanassova, Chalakova & Dimitrov, 2008a]. The assessments covered: hypertension, diabetes, dyslipidaemia, peripheral vascular

Initial stroke severity was assessed using the modified Rankin Scale [Bamford et al, 1990]. MIS diagnostic evaluations included CT or MRI of the brain and ultrasound evaluation and/or trans-thoracic or trans-oesophageal echocardiogram, as appropriate. A panel of stroke neurologists assessed every CV events subtype using standard diagnostic criteria and all available information for each patient. For this study, *MIS* was defined as a minor stroke if the score on the modified Rankin Scale was 1 at the first evaluation, or if the score was 0 or 1 at one-month follow-up (i.e., no symptoms, or minor symptoms that did not interfere with normal lifestyle) [Atanassova, 1998; Atanasova & Vukov, 1998; Atanassova, Voukov & Tchalakova, 2002]. In particular, acute onset was observed in 11 patients (20.4%). Extracranial ultrasound findings were recorded in 11 patients (20.4%). The main characteristics of the initial study cohort were as follows: 37 men (68.5%) and 17 women (31.5%), with male predominance in CV events (n=8 men) but with similar ages of 61.1±12.6 years in patients with CVE versus 62.2±9.2 years in patients without CVE (p>0.05). The mean follow-up time was 11.1±2.4 months with mean time to CV events of 5.8±2.7 months. For the purpose of this study, all MIS patients with subsequent stroke (n=8) as defined above, were excluded from

The aim of this study was to perform a *post-hoc* analysis of one-year follow-up data from 40 patients with MIS and to: (i) investigate the central motor conduction time (CMCT) and the amplitude of the motor evoked potential (MEP) during the acute phase of MIS; (ii) provide evidence for a subclinical damage of the pyramidal tract; and (iii) model and predict the outcome measures at month 12 after MIS as based on earlier changes in the acute phase.
