Effects on the Brain and Central Nervous System.

Inflammation in the Brain. Encephalitis and meningitis, infections or inflammation in the central nervous systems, have occurred in a few varicella patients, both children and adults. This condition can be very dangerous, causing coma and even death. Fortunately, it is extremely rare. Symptoms vary. The patient may become over-agitated or may exhibit loss of coordination and poor balance.
Stroke. Although stroke in children is extremely rare, a condition called cerebral vasculitis, in which blood vessels in the brain become inflamed, has been associated with varicella-zoster. Varicella may be a factor in some cases of stroke in young adults.