As a user on this homebrew issue utter's like a savant "package managers managing package managers rarely works out well."

First clean up your homebrew crap:

brew uninstall --force node
rm -rf ~/.npm
rm -rf ~/.node

Install NPM with the NVM install script

curl -o- | bash

The inital version installed with homebrew is ok, but updating node after installing via homebrew is impossible due to how homebrew handles linking. Using NPM makes upgrades and managing versions simpler.