at the nape of the neck
Una pelota me pegó en la nuca mientras jugaba fútbol.
A ball hit me on the back of the neck while I was playing soccer.
Le pusieron una pistola en la nuca.
They put a gun to the back of his neck.
— Adiós a mi concubina (1993)
He has eyes in the back of his head.
Recibió un único disparo en la nuca.
He received a single shot in the back of the head.
I have eyes in the back of my head.