gms | German Medical Science

Objective: Patients with stenoocclusive cerebrovascular disease “Moyamoya Angiopathy” (MMA) often suffer from strokes. Extracranial-intracranial (EC-IC) bypass surgery is the therapy of choice to remedy hemodynamic compromise. As patients clinically improve after cerebral revascularization we hypothesize a recovery of cortical excitability in these patients. The aim of our study is to characterize the primary motor cortex electrophysiologically in MMA patients before and after EC-IC bypass surgery by navigated transcranial magnetic stimulation (nTMS).

Method: We prospectively recruited 33 patients with moyamoya angiopathy fulfilling the criteria for EC-IC bypass surgery. According to our protocol, the most affected hemisphere (leading hemisphere) would be operated first. Different electrophysiological parameters including resting motor threshold (RMT), cortical silent period (CSP), recruitment curve and paired pulse were obtained via nTMS preoperatively and 3 months after first surgery for both hemispheres. Finally we investigated the changes of the area of cortical representation of the first dorsal interosseus (FDI).

Results: We detected in the initial preoperative analysis a significantly larger motor area in the leading hemisphere in comparison to non-leading hemisphere (median= 316 mm² vs. 250 mm², respectively, p= 0,040), which was downsized 3 months after surgery. In paired pulse paradigms we observed in short stimulus interval of 3 ms (short interval cortical inhibition, SICI) a significant weaker inhibition of the leading hemisphere compared to non-leading hemisphere (p<0,03), which equalized 3 months after surgery.

Conclusions: Our preliminary data suggest that in case of a bilateral chronic ischemia a compensation between both hemispheres is existent before surgery and there is a partial normalization after surgery, which has to be analyzed more in detail.

Note: Thomas Picht and Peter Vajkoczy contributed equally.