Good question! Because neurons differ widely in location and function throughout your body, there are a number of possible outcomes depending on what exactly you mean by “all”. I’ve listed a few of those outcomes below!

Every neuron in your entire body: you die.

Every neuron in your body under conscious control: you die.

Every neuron in your Central Nervous System(brain and spinal cord): you die.

Every neuron in your brain: you die.

Every neuron in your brain that’s not in your hindbrain: you still die, but slightly slower and more agonizing.

Every neuron in your cerebrum: you die, but going from seconds to minutes here is progress!

Every neuron in your forebrain: you might conceivably survive this, albeit with severe personality changes and massive cognitive declines. Then again, it’s almost certainly going to trigger a massive seizure. In which case you just die.