What Causes Weakness In Right Hand After Treatment For Chicken Pox?

my husband (61 years, now only 63 kgs, 6ft 1 inch) had an IV cannula inserted daily for six days while in hospital for chicken pox treatment last week. As a result his right forearm is bruised and painful still; but, what worries us more his right hand suddenly became very weak when the treatment began, and the weakness still persists. Is this something to worry about, such as a stroke?