Klinische Neurophysiologie 2010; 41 - ID46
DOI: 10.1055/s-0030-1250875

Focal cortical plasticity in patients with high-grade stenosis of the internal carotid artery

J List 1, E Wilbers 1, J Kürten 1, J Albers 1, A Schwindt 2, A Flöel 3
  • 1Uniklinik Münster, Neurologie, Münster, Deutschland
  • 2Universitätsklinik Münster, Gefäßchirurgie, Münster, Deutschland
  • 3Charité-Universitätsmedizin, Neurologie, Berlin, Deutschland

Introduction: Beside increased risk of ipsihemispherical stroke, severe stenosis of the internal carotid artery (ICA) has shown mild decline of cognitive functions in some studies (1). Here we investigated the influence of severe ICA-stenosis on motor cortex plasticity. Cortical plasticity was measured with the well established protocol of paired associative stimulation (PASN20) using transcranial magnetic stimulation (TMS) and peripheral electrical stimulation (2). PASN20 can induce long-term-potentiation (LTP)-like plasticity in the primary motor cortex. Previous studies could show that motor learning is mediated via LTP-like mechanisms (3). Furthermore, relations between LTP-induction due to PAS and learning-relevant genetic polymorphisms were found (4).

Methods: 10 patients (62±8 years, 5 women) with high-grade stenosis of the ICA, who came to Münster University Hospital for carotid endarterectomy (CEA) were investigated with PASN20-protocol on the hemisphere of the stenosis, and nine age-matched controls (63±8 years). 3 of the patients had minor strokes on the side of the stenosis, without substantial motor-deficits of the contralateral hand. The other patients showed no focal neurological deficit. Resting motor threshold (RMT) was determined, then the subjects underwent PASN20-protocol (2). Motor-evoked potentials (MEP) were measured 0, 15 and 30 Minutes after PAS.

Results: RMT was 41%±8% of maximal stimulator output in patients with ICA-stenosis and 46%±4% in healthy controls (diff. n.s.). On average, healthy controls showed the expected LTP-like induction 0 to 30 minutes after PAS, whereas patients with ICA-stenosis showed no significant change of MEP size after PAS (Fig).

Conclusions: In this study we found reduced LTP-induction in patients with ICA-stenosis compared with healthy controls. Patients with severe ICA-stenosis will be re-investigated 6 months after CEA to see if changes in cortical plasticity occur as a result of operative revascularisation. Previous studies could show some improvement of cognitive function after CEA (5). Our study will show for the first time, if a neurophysiological correlate, that is, increased motor cortex plasticity, can be found in the affected hemisphere.

Literature: [1] Bakker, JF et al (2000). J Neurol.247: 669–676. [2] Stefan, K et al (2000). Brain.123: 572–584. [3] Ziemann, U et al (2004). J Neurosci.24:1666–1672. [4] Cheeran, B et al. (2008). J Physiol.586.23: 5717–5725. [5] Gremigni, P et al (2009). J Neurol.72: 91–97.

Fig.1: LTP-induction in patients with severe ICA-stenosis