Ischemia causes anoxic cell depolarizations and it is this increase in membrane potential at the presynaptic cell that triggers the release of glutamate, an excitatory neurotransmitter.Glucose deprivation in the brain for any amount of time has the potential to pose serious consequences, and the amount of time the brain spends under these anoxic conditions is directly related to accumulation of irreversible damage to protein biosynthesis pathways. Protein synthesis all over the body is severely inhibited and essentially comes to a standstill while the brain is suffering from acute oxygen deprivation. Once oxygen sufficiently saturates the tissues again, protein biosynthesis returns to normal in non-vulnerable areas but remains at below normal levels in other areas. Insufficient protein synthesis in the brain is especially troubling in the fetal brain given the amount of growth and development that normally occurs. Areas particularly vulnerable to the damaging effects of hypoxic episodes include: the superior brainstem, the cerebellum, white matter and subcortical structures supplied by the branches of deep and superficial penetrating blood vessels. Vulnerable areas where protein synthesis is interrupted usually indicate impending cell death in neurons. When oxygen levels return, oxygen radicals, nitric oxide and an imbalance of neurotransmitters cause further damage and lead to cellular death through apoptosis. Neuron cell death is responsible for gliosis and results in the mushroom appearance of areas and is characteristic of ulegyria. Cerebral hemorrhage
A cerebral hemorrhage is the result of immature blood vessels of a brain lesion bursting.
In the neuromuscular junction there is a vital pathway that maintains synaptic structure and results in the aggregation and localization of AChR on the postsynaptic folds. This pathway consists of agrin, muscle-specific tyrosine kinase (MuSK), acetylcholine receptors (AChRs) and the AChR-clustering protein rapsyn, encoded by the RAPSN gene. The vast majority of mutations causing CMS are found in the AChR subunits and rapsyn genes.Out of all mutations associated with CMS, more than half are mutations in one of the four genes encoding the adult acetylcholine receptor (AChR) subunits. Mutations of the AChR often result in endplate deficiency. Most of the mutations of the AChR are mutations of the CHRNE gene. The CHRNE gene codes for the epsilon subunit of the AChR. Most mutations are autosomal recessive loss-of-function mutations and as a result there is endplate AChR deficiency. CHRNE is associated with changing the kinetic properties of the AChR. One type of mutation of the epsilon subunit of the AChR introduces an Arginine into the binding site at the α/ε subunit interface of the receptor. The addition of a cationic Arg into the anionic environment of the AChR binding site greatly reduces the kinetic properties of the receptor. The result of the newly introduced Arg is a 30-fold reduction of agonist affinity, 75-fold reduction of gating efficiency, and an extremely weakened channel opening probability. This type of mutation results in an extremely fatal form of CMS.Another common underlying mechanism of CMS is the mutation of the rapsyn protein, coded by the RAPSN gene.