Are Wobbling Legs And Headache In A Child Normal While Having Chicken Pox?

my 5 year old son has chicken pox. he was complaining of head aches recently, over the last couple of days and this morning he was very wobbly on his legs and complaining his body wouldnt let him walk straight. its been hours since then and hes still very unsteady on his feet. he isnt complaining of any thing else but keeps complaining his legs wobble. any ideas