Protecting White Matter from Stroke Injury

Dean Reinke
Deans' Stroke Musing

Sunday, January 6, 2013

This is something that needs more research if we are ever to objectively identify damage here and its resultant impacts. 26 pages at the link and 2 great diagrams in Protecting White Matter from Stroke Injury.

White matter (WM) exclusively contains axons and their glial cell partners including astrocytes, oligodendrocytes (myelinating and non-myelinating) and microglia. WM comprises about half of the forebrain volume of humans, a three to four-fold increase over rodents, the animals most used for neuroscience research.

1, 2 -- The low relative volume of WM in rodents led to neglect of this specialized brain area in studies of stroke pathophysiology and under-appreciation of the clinical importance of WM that has slowed progress to effective therapy. 

3 -- WM axons interconnect distant regions of the CNS and are metabolically independent of their cell bodies with regard to energy metabolism. Hence, proper propagation of electrical signals through WM axons demands a continuous supply of energy along their entire length and focal disruption of blood supply may compromise the viability of the whole axon. Yet, WM receives disproportionally less circulation than gray matter (GM) and is highly vulnerable to reduced blood supply exemplified by the frequency of pure WM strokes called lacunes’ or ‘lacunar infarcts’  

4 -- which can accumulate, sometimes silently, and produce vascular dementia. 

5 -- Damage of WM is a major cause of functional disability in cerebrovascular disease and the majority of ischemic strokes involve both WM and GM.2,  

6 -- Early animal studies indicate that WM can be damaged by even brief focal ischemia.7 Thus, after 30 min of arterial occlusion massive swelling of oligodendrocytes and astrocytes occurs, and about 3 hours later most oligodendrocytes die. These changes precede by several hours the appearance of necrotic neurons in ischemic regions. 

7 -- Other pathological changes in ischemic WM include segmental swelling of myelinated axons and the formation of spaces or vacuoles between the myelin sheath and axolemma (Figure 1). 

7, 8 -- These observations confirm that WM is vulnerable to ischemia and that this insult damages oligodendrocytes, myelin and axons in a manner that can proceed independently from neuronal perikaryal injury. In fact, up to 25% of ischemic strokes in humans are of the lacunar variety and are confined to WM areas such as the internal capsule. The clinical importance of WM ischemic injury increases as the most susceptible population, the elderly, constitutes a larger and larger fraction of world population. Some types of dementia may actually represent a chronic and stealthy form of ischemia exclusive to WM.

Stroke, therefore, produces disability not only as a result of dysfunction of neurons and synapses, but also by primary or secondary damage to WM axons and glia. This review summarizes current knowledge of the molecular mechanisms of ischemic injury to WM and discusses its translational implications for the treatment of stroke (Table 1).

See the original article:
      Protecting White Matter from Stroke Injury
      from Deans' Stroke Musing ?query= lacunar (about 10 hits)
      and   Deans' Stroke Musing