Transhemispheric diaschisis. A review and comment.

Area of Science:

• Neuroscience
• Cerebrovascular Biology
• Systems Neuroscience

Background:

• Unilateral cerebral ischemia triggers complex responses in the contralateral hemisphere, a phenomenon known as transhemispheric diaschisis.
• Previous research has explored alterations in electrical activity, blood flow, and metabolism in the non-affected hemisphere following stroke.
• The temporal dynamics and underlying mechanisms of these remote effects remain incompletely understood.

Purpose of the Study:

• To systematically review and analyze the literature on contralateral hemisphere responses to unilateral cerebral ischemia in animal models and humans.
• To elucidate the time course of transhemispheric diaschisis, focusing on changes in electrical activity, blood flow, and metabolism.
• To investigate whether diaschisis represents a loss of remote inhibition or facilitation.

Main Methods:

• Comprehensive literature review of studies investigating unilateral cerebral ischemia.
• Analysis of data categorized by time elapsed since initial ischemic injury.
• Examination of contralateral electrical activity (e.g., evoked potentials), blood flow, and metabolism.

Main Results:

• Contralateral electrical activity shows increased amplitude in late stages post-infarction; acute phase data are inconclusive.
• Contralateral blood flow changes correlate with ischemic injury magnitude, with larger insults causing decreases not seen in smaller ones.
• Contralateral metabolism generally mirrors blood flow patterns, showing an initial decrease followed by gradual recovery.

Conclusions:

• Transhemispheric diaschisis involves dynamic changes in contralateral electrical activity, blood flow, and metabolism over time.
• The nature of diaschisis may involve loss of remote inhibition, challenging traditional views.
• Further investigation into early contralateral changes is crucial for understanding brain defense mechanisms post-ischemia.