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George E. Carvell, PhD, PT   University of Pittsburgh
 
UPPER MOTOR NEURON SYNDROME: STROKE PATHOBIOLOGY II
LONGER TERM REACTIONS
  48-72 hours- microglia proliferate, macrophages appear & increase up to 3rd week, then decrease. Later softening of lesion (encephalomalacia) is followed by cyst formation.
  4-5 days- In penumbra, astrocytes proliferate and swell, peaking about 6 weeks, then a glial scar is formed.
  2 weeks- Surviving capillaries proliferate and take part in attempted repair. (see Benarroch et al p 81, 1999)
U. Dirnagl, C. Iadecola, and M.A. Moskowitz, Pathobiology of Ischaemic Stroke: An Integrated View. TINS 22: 391-397, 1999
Dirnagl et al Fig 1,2  p 393
Dirnagl et al Fig 3  p 394
The earliest response to injury involves cellular reactions in the core and penumbra. Excitotoxicity due primarily to unchecked depolarization has a major impact within the first hour. Cellular suicide (apoptosis) follows over the next several days.
Anoxia: RMP failure, release of Glutamate, depolarization of failing neurons & loss of active reuptake of Glutamate = excitotoxicity
Actual time may be expanded in human subjects