arachnoid cyst

[sinomum]

my son was diagnosed with arachnoid cyst..a huge left fronto temproparietal arachnoid cyst..it causes midline shift ..and compressing his left side of the brain..he did endoscopic cyst fenestration at 1 years old ..there was no increase in Intracranial pressure ..now 10 months after the operation the cyst is gradually decreasing but real slowly ..1/4 only of it dissapeared ..we did fundus examination it was good..the problem is  that my 1.10 years boy isnot talking yet ..he only says mama when he gets angry or says  No ..and is always babling or singing but i can't understand him..he can't understand my instructions..he did hearing assesement and dr said he hears perfectly..he runs to the door when his dad comes home ..hugs him but no talking ..what do u advise me to do am really worried