Why would all of a sudden your head/skull develop sunken spots?
Not Medical Advice: Possible causes of sunken soft spots on the head include dehydration, injury, abscess, cyst, or benign lipoma. A lipoma is a soft tissue benign tumor, usually painless, that is common in adults 40 to 60.
Most infants have soft spots on their heads called fontanelles. The fontanelle on the back closes in about 1 to 2 months, while the one on the top takes 7 to 19 months.