  A simulation model for the spread and control of lesions in the brain is
constructed using a planar network (graph) representation for the Central
Nervous System (CNS). The model is inspired by the lesion structures observed
in the case of Multiple Sclerosis (MS), a chronic disease of the CNS. The
initial lesion site is at the center of a unit square and spreads outwards
based on the success rate in damaging edges (axons) of the network. The damaged
edges send out alarm signals which, at appropriate intensity levels, generate
programmed cell death. Depending on the extent and timing of the programmed
cell death, the lesion may get controlled or aggravated akin to the control of
wild fires by burning of peripheral vegetation. The parameter phase space of
the model shows smooth transition from uncontrolled situation to controlled
situation. The simulations show that the model is capable of generating a wide
variety of lesion growth and arrest scenarios.
