Article
Normalisation of motor system excitability after bypass-surgery in patients with chronic cerebrovascular ischemia – a nTMS study
Die Erholung der Erregbarkeit des motorischen Systems bei Patienten mit chronischer hämodynamischer Ischämie nach Bypassanlage – eine nTMS-Studie
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Published: | June 4, 2021 |
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Objective: Recently we have introduced the concept of the “hibernating brain” in patients suffering from chronic hemodynamic ischemia. In the state of misery perfusion an adaptive reorganization of the cortical motor network consisting of a reduced cortico-cortical excitability, elevated inhibition and enlarged cortical motor area was detected. Surgical revascularization by EC/IC bypass led to a recovery of impaired cortical motor function. The aim this study now was to assess changes of corticospinal excitability and axonal integrity during chronic ischemia and following surgical revascularization.
Methods: In this study 53 Patients were examined before and 3-6 months after EC-IC bypass surgery using navigated transcranial magnetic stimulation (nTMS). We examined the cortical excitability by determining resting motor threshold (RMT) and motor area, corticospinal inhibition by cortical silent period (CSP) and axonal integrity by means of recruitment curve (RC) of both hemispheres.
Results: Hemispheres affected by cerebrovascular impairment presented with a lower cortico-cortical excitability (RMT 41,8 % ± 9,5% compared to 39,5 % ± 7,8 %, p <.05), higher corticospinal inhibition (CSP 172,4ms ± 46,2 compared to 136,7± 47,0, p <.05) and wider motor areas as compared to the unaffected hemispheres (3,3 ± 1,9 cm2 compared to 2,5 ± 1,3 cm2, p <.05). Following bypass surgery an improved corticospinal conductivity (RC 5,5 ± 2,1 compared to 8,9± 2,7, p < .05) and normalization of cortical excitability (RMT 40,7 % ± 7,8 5 compared to 38,8 % ± 8,3 %, p < .05) could be observed.
Conclusion: We demonstrated that the ischemic brain is, after revascularization, capable of reorganizing and restoring neuronal function as shown by a lower resting motor threshold and a change in neuronal recruitment. These findings suggest a “hibernation” of the brain, a condition of impairment capable of preserving functional integrity in chronic ischemia.