hydrocephaly vs hydrocephalic

hydrocephaly is a noun but hydrocephalic is not a noun.

Word	Noun	Adjective	Verb	Adverb
hydrocephaly	Yes	No	No	No
hydrocephalic	No	Yes	No	No

hydrocephaly (noun)	hydrocephalic (noun)
an abnormal condition in which cerebrospinal fluid collects in the ventricles of the brain; in infants it can cause abnormally rapid growth of the head and bulging fontanelles and a small face; in adults the symptoms are primarily neurological

hydrocephaly (adjective)	hydrocephalic (adjective)
	relating to or characterized by or evidencing hydrocephalus