What does 'dead from the neck up' mean?

English Language Tests, Intermediate level

ESL/EFL Test #330 [color=blue]“English Slang Idioms (51)”, question 6

I don’t know why Jay doesn’t fire Ted. That guy is dead from the up. He can’t even get the simplest tasks done.

(a) ground
(b) pick
© brain
(d) neck

English Language Tests, Intermediate level

ESL/EFL Test #330 [color=blue]“English Slang Idioms (51)”, answer 6

I don’t know why Jay doesn’t fire Ted. That guy is dead from the neck up. He can’t even get the simplest tasks done.

Correct answer: (d) neck

Your answer was: [color=green]correct
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Hi,
May I know what does" be dead from the neck up" mean?
Thank you.

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Stupid.
.