encephalogram vs pneumoencephalogram

encephalogram and pneumoencephalogram both are nouns.

Word	Noun	Adjective	Verb	Adverb
encephalogram	Yes	No	No	No
pneumoencephalogram	Yes	No	No	No

As nouns, encephalogram and pneumoencephalogram are synonyms defined as:

encephalogram and pneumoencephalogram: an X ray of the brain made by replacing spinal fluid with a gas (usually oxygen) to improve contrast

encephalogram (noun)	pneumoencephalogram (noun)
an X ray of the brain made by replacing spinal fluid with a gas (usually oxygen) to improve contrast	an X ray of the brain made by replacing spinal fluid with a gas (usually oxygen) to improve contrast
a graphical record of electrical activity of the brain; produced by an electroencephalograph