No, critical illness riders are limited to specified illnesses only. (securenow.in)
According to section 80 DDB, the expenses incurred towards treatment of specified illnesses for children can be deducted up to Rs 40,000. (policybazaar.com)
The one catch is that for most of these riders, the coverage is only for specified illnesses such as a heart attack, cancer, stroke and other forms of diseases described in the rider, and may vary from insurer to insurer. (abramsinc.com)