In 2010, had dengue with encephalitis. The only abnormality in CSF was WBC 20c/mm3 with 100% lymp. Need to retest now or does the CNS infection heal?

No need to test. No one really knows what causes the CNS symptoms / signs in dengue. But no lab work will be as helpful as simply asking, "how do you feel?" i would urge you to stop troubling yourself and get on with your life, glad for your recovery.